| NETCONF Working Group | K. Watsen |
| Internet-Draft | Juniper Networks |
| Intended status: Standards Track | M. Abrahamsson |
| Expires: December 21, 2017 | T-Systems |
| I. Farrer | |
| Deutsche Telekom AG | |
| June 19, 2017 |
Zero Touch Provisioning for NETCONF or RESTCONF based Management
draft-ietf-netconf-zerotouch-14
This draft presents a secure technique for establishing a NETCONF or RESTCONF connection between a newly deployed device, configured with just its factory default settings, and its deployment specific network management system (NMS).
This draft contains many placeholder values that need to be replaced with finalized values at the time of publication. This note summarizes all of the substitutions that are needed. Please note that no other RFC Editor instructions are specified anywhere else in this document.
Artwork in the IANA Considerations section contains placeholder values for DHCP options pending IANA assignment. Please apply the following replacements:
Artwork in this document contains shorthand references to drafts in progress. Please apply the following replacements:
Artwork in this document contains placeholder values for the date of publication of this draft. Please apply the following replacement:
Please update the following references to reflect their final RFC assignments:
The following one Appendix section is to be removed prior to publication:
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A fundamental business requirement for any network operator is to reduce costs where possible. For network operators, deploying devices to many locations can be a significant cost, as sending trained specialists to each site for installations is both cost prohibitive and does not scale.
This document defines a bootstrapping strategy enabling devices to securely obtain bootstrapping data with no installer action beyond physical placement and connecting network and power cables. The ultimate goal of this document is to enable a secure NETCONF [RFC6241] or RESTCONF [RFC8040] connection to a deployment specific network management system (NMS).
This document uses the following terms (sorted by name):
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.
A simplified graphical representation of the data models is used in this document. The meaning of the symbols in these diagrams is as follows:
This document defines two types of information that devices access during the bootstrapping process. These information types are described in this section. Examples are provided in Section 8.2
Redirect information redirects a device to another bootstrap server. Redirect information encodes a list of bootstrap servers, each defined by its hostname or IP address, an optional port, and an optional trust anchor certificate.
Redirect information is YANG modeled data formally defined by the "redirect-information" container in the YANG module presented in Section 8.3. This container has the tree diagram shown below. Please see Section 1.4 for tree diagram notation.
+--:(redirect-information)
+--ro redirect-information
+--ro bootstrap-server* [address]
+--ro address inet:host
+--ro port? inet:port-number
+--ro trust-anchor? binary
Redirect information MAY be trusted or untrusted. The redirect information is trusted whenever it is obtained via a secure connection to a trusted bootstrap server, or whenever it is signed by the device's owner. In all other cases, the redirect information is untrusted.
Trusted redirect information is useful for enabling a device to establish a secure connection to a bootstrap server, which is possible when the redirect information includes the bootstrap server's trust anchor certificate. When a device is able to establish a secure connection to a bootstrap server, the data is implicitly trusted, and does not need to be signed.
Untrusted redirect information is useful for directing a device to a bootstrap server where signed data has been staged for it to obtain. When the redirect information is untrusted, the device MUST discard any potentially included trust anchor certificates and SHOULD establish a provisional connection (by blindly accepting the TLS certificate) to any of the specified bootstrap servers. In this case, the device MUST NOT trust the bootstrap server, and data provided by the bootstrap server MUST be signed for it to be of any use to the device.
How devices process redirect information is described more formally in Section 7.5.
Bootstrap information provides all the data necessary for a device to bootstrap itself, in order to be considered ready to be managed (e.g., by an NMS). As defined in this document, this data includes information about a boot image the device MUST be running, an initial configuration the device MUST commit, and optional scripts that, if specified, the device MUST successfully execute.
Bootstrap information is YANG modeled data formally defined by the "onboarding-information" container in the YANG module presented in Section 8.3. This container has the tree diagram shown below. Please see Section 1.4 for tree diagram notation.
+--:(onboarding-information)
+--ro onboarding-information
+--ro boot-image
| +--ro name string
| +--ro (hash-algorithm)
| | +--:(sha256)
| | +--ro sha256? string
| +--ro uri* inet:uri
+--ro configuration-handling enumeration
+--ro pre-configuration-script? script
+--ro configuration?
+--ro post-configuration-script? script
Bootstrap information MUST be trusted for it to be of any use to a device. There is no option for a device to process untrusted onboarding information.
Bootstrap information is trusted whenever it is obtained via a secure connection to a trusted bootstrap server, or whenever it is signed by the device's owner. In all other cases, the onboarding information is untrusted.
How devices process onboarding information is described more formally in Section 7.6.
This document defines the following three artifacts that can be made available to devices while they are bootstrapping. As will be seen in Section 5, each source of bootstrapping information specifies a means for providing each of the artifacts defined in this section.
The zero touch information artifact encodes the essential bootstrapping data for the device. This artifact is used to encode the redirect information and onboarding information types discussed in Section 2.
The zero touch information artifact is a PKCS#7 SignedData structure, as specified by Section 9.1 of [RFC2315], encoded using ASN.1 distinguished encoding rules (DER), as specified in ITU-T X.690. The PKCS#7 structure MUST contain JSON-encoded content conforming to the YANG module specified in Section 8.3.
In order for the zero touch information artifact to be trusted when conveyed over an untrusted transport, the PKCS#7 structure MUST also contain a 'signerInfo' structure, as described in Section 9.1 of [RFC2315], containing a signature generated over the content using the private key associated with the owner certificate (Section 3.2).
The owner certificate artifact is a certificate that is used to identify an 'owner' (e.g., an organization), as known to a trusted certificate authority. The owner certificate is signed by a trusted certificate authority (CA), whose certificate is placed into the ownership voucher (Section 3.3).
The owner certificate is used by a device to verify the signature attached to the zero touch information artifact (Section 3.1) that the device SHOULD have also received, as described in Section 4. In particular, the device verifies signature using the public key in the owner certificate over the content contained within the zero touch information artifact.
In order to validate the owner certificate, a device MUST verify that the owner certificate's certificate-chain includes the certificate specified by the ownership voucher (Section 3.3) that the device SHOULD have also received, as described in Section 4, and the device MUST verify that owner certificate contains an identifier matching the one specified in the voucher and, for devices that verify certificate revocation status, the device MUST also verify that the certificate has neither expired nor been revoked.
The owner certificate artifact is formally an unsigned PKCS #7 SignedData structure as specified by Section 9.1 in [RFC2315], encoded using ASN.1 distinguished encoding rules (DER), as specified in ITU-T X.690.
The owner certificate PKCS#7 structure MUST contain the owner certificate itself, as well as all intermediate certificates leading up to the trust anchor certificate specified in the ownership voucher. The owner certificate artifact MAY optionally include the trust anchor certificate.
Additionally, in order to support devices deployed on private networks, the owner certificate PKCS#7 structure MAY also contain suitably fresh CRLs [RFC5280] and/or OCSP Responses [RFC6960]. Having these revocation objects stapled to the owner certificate precludes the need for the device to have to download them dynamically using the CRL distribution point or an OCSP responder specified in the associated certificates.
The ownership voucher artifact is used to securely identify a device's owner, as it is known to the manufacturer. The ownership voucher is signed by the device's manufacturer or delegate.
More specifically, the ownership voucher is used to verify the owner certificate (Section 3.2) that the device SHOULD have also received, as described in Section 4. In particular, the device verifies that the owner certificate has a chain of trust leading to the trusted certificate included in the ownership voucher, even if it is itself (e.g., self-signed certificate).
In order to validate the ownership voucher, a device MUST perform a number of checks. The device MUST verify that the voucher specifies the device's serial number. The device MUST verify that the ownership voucher has a chain of trust to a trusted certificate known to the device (Section 7.1). If the ownership voucher contains an expiration date, the device MUST also verify that the ownership voucher has not expired.
The ownership voucher artifact, including its encoding, is formally defined in [I-D.ietf-anima-voucher].
Section 3 lists all the possible bootstrapping artifacts, but only certain groupings of these artifacts make sense to return in the various bootstrapping situations described in this document. The remainder of this section identifies these groupings to further clarify how the artifacts are used.
The first grouping of artifacts is for unsigned information. That is, when the zero touch information artifact (Section 3.1) has not been signed.
Unsigned information is useful for cases when transport level security can be used to convey trust (e.g., HTTPS), or when the information can be processed in a provisional manner (i.e. unsigned redirect information).
Conveying unsigned information entails communicating just one of the three artifacts listed in Section 3 as follows:
List of artifacts included in this grouping: - zero touch information (with no embedded signature)
The second grouping of artifacts is for when the zero touch information artifact (Section 3.1) has been signed, but without any revocation information, because the device is expected to download the revocation information dynamically (e.g., using the CRL distribution point or OCSP Responder listed in the owner certificate and and the pinned domain certificate specified in the ownership voucher).
Signed information is needed when the information is obtained from an untrusted source of bootstrapping data (Section 5), in order for the device to be able to trust the information.
Revocation information may not need to be provided because, for instance, the device only uses revocation information obtained dynamically from Internet based resources. Another possible reason may be because the device does not have a reliable clock, and therefore the manufacturer decides to never revoke information (e.g., ownership assignments are forever).
Conveying signed information without revocation information entails communicating all three of the artifacts listed in Section 3 as follows:
List of artifacts included in this grouping: - zero touch information (with an embedded signature) - owner certificate (with no stapled revocation objects) - ownership voucher (with no stapled revocation objects)
The third grouping of artifacts is for when the zero touch information artifact (Section 3.1) has been signed and also includes revocation information.
Signed information, as described above, is needed when the information is obtained from an untrusted source of bootstrapping data (Section 5), in order for the device be able to trust the information.
Revocation information may need to be provided because, for instance, the device is deployed on a private network and therefore unable to obtain the revocation information from Internet based resources.
Conveying signed information with revocation information entails communicating all three of the artifacts listed in Section 3 as follows:
List of artifacts included in this grouping: - zero touch information (with an embedded signature) - owner certificate (with stapled revocation objects) - ownership voucher (with stapled revocation objects)
This section defines some sources for zero touch bootstrapping data that a device can access. The list of sources defined here is not meant to be exhaustive. It is left to future documents to define additional sources for obtaining zero touch bootstrapping data.
For each source defined in this section, details are given for how each of the three artifacts listed in Section 3 is provided.
A directly attached removable storage device (e.g., a USB flash drive) MAY be used as a source of zero touch bootstrapping data.
To use a removable storage device as a source of bootstrapping data, a device need only detect if the removable storage device is plugged in and mount its filesystem.
Use of a removable storage device is compelling, as it doesn't require any external infrastructure to work. It is notable that the raw boot image file can be located on the removable storage device, enabling a removable storage device to be a fully self-standing bootstrapping solution.
A removable storage device is an untrusted source of bootstrapping data. This means that the information stored on the removable storage device either MUST be signed, or it MUST be information that can be processed provisionally (e.g., unsigned redirect information).
From an artifact perspective, since a removable storage device presents itself as a filesystem, the bootstrapping artifacts need to be presented as files. The three artifacts defined in Section 3 are mapped to files below.
Artifact to File Mapping:
The format of the removable storage device's filesystem and the naming of the files are outside the scope of this document. However, in order to facilitate interoperability, it is RECOMMENDED devices support open and/or standards based filesystems. It is also RECOMMENDED that devices assume a file naming convention that enables more than one instance of bootstrapping data to exist on a removable storage device. The file naming convention SHOULD be unique to the manufacturer, in order to enable bootstrapping data from multiple manufacturers to exist on a removable storage device.
A DNS server MAY be used as a source of zero touch bootstrapping data.
Using a DNS server may be a compelling option for deployments having existing DNS infrastructure, as it enables a touchless bootstrapping option that does not entail utilizing an Internet based resource hosted by a 3rd-party.
To use a DNS server as a source of bootstrapping data, a device MAY perform a multicast DNS [RFC6762] query searching for the service "_zerotouch._tcp.local.". Alternatively the device MAY perform DNS-SD [RFC6763] via normal DNS operation, using the domain returned to it from the DHCP server; for example, searching for the service "_zerotouch._tcp.example.com".
Unsigned DNS records (e.g., not using DNSSEC as described in [RFC6698]) are an untrusted source of bootstrapping data. This means that the information stored in the DNS records either MUST be signed, or it MUST be information that can be processed provisionally (e.g., unsigned redirect information).
From an artifact perspective, since a DNS server presents resource records (Section 3.2.1 of [RFC1035]), the bootstrapping artifacts need to be presented as resource records. The three artifacts defined in Section 3 are mapped to resource records below.
Artifact to Resource Record Mapping:
TXT records have an upper size limit of 65535 bytes (Section 3.2.1 in RFC1035), since 'RDLENGTH' is a 16-bit field. Please see Section 3.1.3 in RFC4408 for how a TXT record can achieve this size. Due to this size limitation, some zero touch information artifacts may not fit. In particular, onboarding information could hit this upper bound, depending on the size of the included configuration and scripts.
When onboarding information (not redirect information) is provided, it is notable that the URL for the boot-image the device can download would have to point to another server (e.g., http://, ftp://, etc.), as DNS servers do not themselves distribute files.
A DHCP server MAY be used as a source of zero touch bootstrapping data.
Using a DHCP server may be a compelling option for deployments having existing DHCP infrastructure, as it enables a touchless bootstrapping option that does not entail utilizing an Internet based resource hosted by a 3rd-party.
A DHCP server is an untrusted source of bootstrapping data. Thus the information stored on the DHCP server either MUST be signed, or it MUST be information that can be processed provisionally (e.g., unsigned redirect information).
However, unlike other sources of bootstrapping data described in this document, the DHCP protocol (especially DHCP for IPv4) is limited in the amount of data that can be conveyed, to the extent that signed data cannot be communicated. This means only unsigned redirect information can be conveyed. Since the redirect information is unsigned, it SHOULD NOT include the optional trust anchor certificate, as the device would have to discard it anyway.
From an artifact perspective, the three artifacts defined in Section 3 are mapped to the DHCP fields specified in Section 10 as follows:
A bootstrap server MAY be used as a source of zero touch bootstrapping data. A bootstrap server is defined as a RESTCONF [RFC8040] server implementing the YANG module provided in Section 9.
Unlike any other source of bootstrap data described in this document, a bootstrap server is not only a source of data, but it can also receive data from devices using the YANG-defined "notification" action statement defined in the YANG module (Section 9.3). The data sent from devices both enables visibility into the bootstrapping process (e.g., warnings and errors) as well as provides potentially useful completion status information (e.g., the device's SSH host-keys).
To use a bootstrap server as a source of bootstrapping data, a device MUST use the RESTCONF protocol to access the YANG container node /device, passing its own serial number in the URL as the key to the 'device' list.
Using a bootstrap server as a source of bootstrapping data is a compelling option as it MAY use transport-level security, in lieu of signed data, which may be easier to deploy in some situations. Additionally, the bootstrap server is able to receive notifications from devices, which may be critical to some deployments (e.g., the passing of the device's SSH host keys).
A bootstrap server may be trusted or an untrusted source of bootstrapping data, depending on how the device learned about the bootstrap server's trust anchor from a trusted source. When a bootstrap server is trusted, the information returned from it MAY be signed. However, when the server is untrusted, in order for its information to be of any use to the device, the bootstrap information MUST either be signed or be information that can be processed provisionally (e.g., unsigned redirect information).
When a device is able to trust a bootstrap server, it MUST send its IDevID certificate in the form of a TLS client certificate, and it MUST send notifications to the bootstrap server. When a device is not able to trust a bootstrap server, it MUST NOT send its IDevID certificate in the form of a TLS client certificate, and it MUST NOT send any notifications to the bootstrap server.
From an artifact perspective, since a bootstrap server presents data as a YANG-modeled data, the bootstrapping artifacts need to be mapped to nodes in the YANG module. The three artifacts defined in Section 3 are mapped to bootstrap server nodes defined in Section 9.3 below.
Artifact to Bootstrap Server Node Mapping:
While RESTCONF servers typically support a nested hierarchy of resources, zero touch bootstrap servers only need to support the paths /device and /device/notification. The device processing instructions provided in Section 7.3 only uses these two URLs.
The zero touch solution presented in this document is conceptualized to be composed of the workflows described in this section. Implementations MAY vary in details. Each diagram is followed by a detailed description of the steps presented in the diagram, with further explanation on how implementations may vary.
The following diagram illustrates key interactions that may occur from when a prospective owner enrolls in a manufacturer's zero touch program to when the manufacturer ships devices for an order placed by the prospective owner.
+-----------+
+------------+ |Prospective| +---+
|Manufacturer| | Owner | |NMS|
+------------+ +-----------+ +---+
| | |
| | |
| 1. initiate enrollment | |
#<-----------------------------| |
# | |
# | |
# IDevID trust anchor | |
#-----------------------------># set IDevID trust anchor |
# #--------------------------->|
# | |
# bootstrap server | |
# account credentials | |
#-----------------------------># set credentials |
| #--------------------------->|
| | |
| | |
| 2. set owner certificate trust anchor |
|<----------------------------------------------------------|
| | |
| | |
| 3. place device order | |
|<-----------------------------# model devices |
| #--------------------------->|
| | |
| 4. ship devices and send | |
| device identifiers and | |
| ownership vouchers | |
|-----------------------------># set device identifiers |
| # and ownership vouchers |
| #--------------------------->|
| | |
Each numbered item below corresponds to a numbered item in the diagram above.
The following diagram illustrates how an owner might stage the network for bootstrapping devices.
+----------+ +------------+
|Deployment| |Manufacturer| +------+ +------+
| Specific | | Hosted | | Local| | Local| +---------+
+---+ |Bootstrap | | Bootstrap | | DNS | | DHCP | |Removable|
|NMS| | Server | | Server | |Server| |Server| | Storage |
+---+ +----------+ +------------+ +------+ +------+ +---------+
| | | | | |
activate | | | | | |
modeled | | | | | |
1. device | | | | | |
----------->| | | | | |
| 2. (optional) | | | |
| configure | | | |
| bootstrap | | | |
| server | | | |
|------->| | | | |
| | | | | |
| 3. (optional) configure | | |
| bootstrap server | | | |
|--------------------->| | | |
| | | | | |
| | | | | |
| 4. (optional) configure DNS server| | |
|---------------------------------->| | |
| | | | | |
| | | | | |
| 5. (optional) configure DHCP server | |
|------------------------------------------->| |
| | | | | |
| | | | | |
| 6. (optional) store bootstrapping artifacts on media |
|----------------------------------------------------->|
| | | | | |
| | | | | |
Each numbered item below corresponds to a numbered item in the diagram above.
+----------+
+-----------+ |Deployment|
| Source of | | Specific |
+------+ | Bootstrap | |Bootstrap | +---+
|Device| | Data | | Server | |NMS|
+------+ +-----------+ +----------+ +---+
| | | |
| | | |
| 1. if running a modified (not | | |
| factory default) configuration, | | |
| then exit. | | |
| | | |
| 2. for each source supported, check | | |
|------------------------------------->| | |
| | | |
| 3. if onboarding-information found, | | |
| initialize self and, only if | | |
| source is a bootstrap server, | | |
| send notifications | | |
|-------------------------------------># | |
| # webhook | |
| #----------------------->|
| | |
| 4. else if redirect-information found, for | |
| each bootstrap server specified, check | |
|-+-------------------------------------------------->| |
| | | |
| | if more redirect-information is found, recurse | |
| | (not depicted), else if onboarding-information | |
| | found, initialize self and post notifications | |
| +--------------------------------------------------># |
| # webhook |
| #-------->|
|
| 5. retry sources and/or wait for manual provisioning.
|
The following diagram illustrates the sequence of activities that occur when a device powers on.
The interactions in the above diagram are described below.
If the device is ever able to complete the bootstrapping process successfully (i.e., no longer running its factory default configuration), it exits the bootstrapping logic without considering any additional sources of bootstrapping data.
Devices supporting the bootstrapping strategy described in this document MUST have the preconfigured factory default state and bootstrapping logic described in the following sections.
+------------------------------------------------------------------+ | <device> | | | | +----------------------------------------------------------+ | | | <read-only storage> | | | | | | | | 1. IDevID cert & associated intermediate certificate(s) | | | | 2. list of trusted Internet based bootstrap servers | | | | 3. list of trust anchor certs for bootstrap servers | | | | 4. trust anchor cert for verifying ownership vouchers | | | +----------------------------------------------------------+ | | | | +----------------------+ | | | <secure storage> | | | | | | | | 5. private key | | | +----------------------+ | | | +------------------------------------------------------------------+
Each numbered item below corresponds to a numbered item in the diagram above.
A device claiming to support the bootstrapping strategy defined in this document MUST support the boot sequence described in this section.
Power On
|
v No
1. Running default config? --------> Boot normally
|
| Yes
v
2. For each supported source of bootstrapping data,
try to load bootstrapping data from the source
|
|
v Yes
3. Able to bootstrap off any source? -----> Run with new configuration
|
| No
v
4. Loop and/or wait for manual provisioning.
Each numbered item below corresponds to a numbered item in the diagram above.
This section describes a recursive algorithm that devices can use to, ultimately, obtain onboarding information. The algorithm is recursive only because sources of bootstrapping data MAY return redirect information, which causes the algorithm to run again, for the newly discovered sources of information. To be clear, an expression that captures all possible combinations is "(redirect information)* onboarding information". That is, zero or more redirect information responses, followed by one bootstrap information response.
Untrusted Source Trusted Source
Kind of Bootstrapping Data Can Provide? Can Provide?
Unsigned Redirect Info : Yes+ Yes
Signed Redirect Info : Yes Yes*
Unsigned Bootstrap Info : No Yes
Signed Bootstrap Info : Yes Yes*
The '+' above denotes that the source redirected to MUST
return signed data, or more unsigned redirect information.
The '*' above denotes that, while possible, it is generally
unnecessary for a trusted source to return signed data. In
fact, it's only needed when the '+' case occurs.
An important aspect of the algorithm is knowing when data needs to be signed or not. The following figure provides a summary of options:
As an example, imagine a device initially obtains unsigned redirect information, which redirects it to an [untrusted] bootstrap server where it obtains more unsigned redirect information, which redirects it to another [untrusted] bootstrap server where it obtains signed redirect information, which redirects it to a [trusted] bootstrap server where it obtains redirect information (signed or unsigned doesn't matter, its trusted either way), but without an included trust anchor certificate, which is unexpected but possible, so the device can't trust the server it's redirected to, and so on, until finally the device obtains some onboarding information.
To support this behavior, this recursive algorithm uses a conceptually global-scoped variable algorithm variable called "trust-state". The trust-state variable is initialized to FALSE. The ultimate goal of this algorithm is for the device to process onboarding information (Section 2.2) while the trust-state variable is TRUE.
If the data source is a bootstrap server, the only source of bootstrapping data defined in this document that can be trusted via transport level security, and the device is able to authenticate the server using X.509 certificate path validation ([RFC6125], Section 6) to one of the device's preconfigured trust anchors, or to a trust anchor that it learned from a previous step, then the device MUST set trust-state to TRUE.
If trust-state is TRUE, when connecting to the bootstrap server, the device MUST use its IDevID certificate for client certificate based authentication and MUST POST progress notifications using the bootstrap server's "notification" action. Otherwise, if trust-state is FALSE, when connecting to the bootstrap server, the device MUST NOT use its IDevID certificate for a client certificate based authentication and MUST NOT POST progress notifications using the bootstrap server's "notification" action.
When accessing a bootstrap server, the device SHOULD only access its top-level resource, to obtain all the data staged for it in a single GET request.
For any source of bootstrapping data (e.g., Section 5), if the data is signed and the device is able to validate the signed data using the algorithm described in Section 7.4, then the device MUST set trust-state to TRUE, else the device MUST set trust-state to FALSE. Note, this is worded to cover the special case when signed data is returned even from a trusted bootstrap server.
If the data is onboarding information (not redirect information), and trust-state is FALSE, the device MUST exit the recursive algorithm (as this is not allowed, per the figure above), returning to the state machine described in Section 7.2. Otherwise, the device MUST attempt to process the onboarding information as described in Section 7.6. In either case, success or failure, the device MUST exit the recursive algorithm, returning to the state machine described in Section 7.2, the only difference being in how it responds to the "Able to bootstrap off any source?" conditional described in the figure in the section.
If the data is redirect information, the device MUST process the redirect information as described in Section 7.5. This is the recursion step, it will cause to device to reenter this algorithm, but this time the data source will most definitely be a bootstrap server, as that is all redirect information is able to redirect a device to.
Whenever a device is presented signed data from an untrusted source, it MUST validate the signed data as described in this section. If the signed data is provided by a trusted source, a redundant trust case, the device MAY skip verifying the signature.
Whenever there is signed data, the device MUST also be provided an ownership voucher and an owner certificate. Depending on circumstances, the device MAY also be provided certificate revocations. How all the needed artifacts are provided for each source of bootstrapping data is defined in Section 5.
The device MUST first authenticate the ownership voucher by validating the signature on it to one of its preconfigured trust anchors (see Section 7.1) and verify that the ownership voucher contains the device's serial number. If the ownership voucher contains an expiration timestamp, the device MUST also verify that the ownership voucher has not expired. If the authentication of the ownership voucher is successful, the device extracts from it information that can be used to verify the owner certificate in the next step.
Next the device MUST authenticate the owner certificate by performing X.509 certificate path verification to the trusted certificate provided in the voucher. If the device insists on verifying revocation status, it MUST also verify that none of the certificates in the chain of certificates have been revoked or expired. If the authentication of the owner certificate is successful, the device extracts the owner's public key from the owner certificate for use in the next step.
Finally the device MUST verify the signature over information artifact was generated by the private key matching the public key extracted from the owner certificate in the previous step.
If any of these steps fail, then the device MUST mark the data as invalid and not perform any of the subsequent steps.
In order to process redirect information (Section 2.1), the device MUST follow the steps presented in this section.
Processing redirect information is straightforward. The device sequentially steps through the list of provided bootstrap servers until it can find one it can bootstrap off of.
If a hostname is provided, and the hostname's DNS resolution is to more than one IP address, the device MUST attempt to connect to all of the DNS resolved addresses at least once, before moving on to the next bootstrap server. If the device is able to obtain bootstrapping data from any of the DNS resolved addresses, it MUST immediately process that data, without attempting to connect to any of the other DNS resolved addresses.
If the redirect information is trusted (e.g., trust-state is TRUE), and the bootstrap server entry contains a trust anchor certificate, then the device MUST authenticate the bootstrap server using X.509 certificate path validation ([RFC6125], Section 6) to the specified trust anchor. If the device is unable to authenticate the bootstrap server to the specified trust anchor, the device MUST NOT attempt a provisional connection to the bootstrap server (i.e., by blindly accepting its server certificate).
If the redirect information is untrusted (e.g., trust-state is FALSE), the device MUST discard any trust anchors provided by the redirect information and establish a provisional connection to the bootstrap server (i.e., by blindly accepting its TLS server certificate).
In order to process onboarding information (Section 2.2), the device MUST follow the steps presented in this section.
When processing onboarding information, the device MUST first process the boot image information, then execute the pre-configuration script (if any), then commit the initial configuration, and then execute the script (if any), in that order. If the device encounters an error at any step, it MUST NOT proceed to the next step.
First the device MUST determine if the image it is running satisfies the specified boot image criteria (e.g., name or fingerprint match). If it does not, the device MUST download (using the supplied URI), verify, and install the specified boot image, and then reboot. To verify the boot image, the device MUST check that the boot image file matches the fingerprint (e.g., sha256) supplied by the bootstrapping information. Upon rebooting, the device MUST still be in its factory default state, causing the bootstrapping process to run again, which will eventually come to this very point, but this time the device's running image will satisfy the specified criteria, and thus the device will move to processing the next step.
Next, for devices that support executing scripts, if a pre-configuration script has been specified, the device MUST execute the script and check its exit status code to determine if had any warnings or errors. In the case of errors, the device MUST reset itself in such a way that force the reinstallation of its boot image, thereby wiping out any bad state the script might have left behind.
Next the device commits the provided initial configuration. Assuming no errors, the device moves to processing the next step.
Again, for devices that support executing scripts, if a post-configuration script has been specified, the device MUST execute the script and check its exit status code to determine if it had any warnings or errors. In the case of errors, the device MUST reset itself in such a way that force the reinstallation of its boot image, thereby wiping out any bad state the script might have left behind.
At this point, the device has completely processed the bootstrapping data and is ready to be managed. If the device obtained the bootstrap information from a trusted bootstrap server, the device MUST send the 'bootstrap-complete' notification now.
At this point the device is configured and no longer running its factory default configuration. Notably, if the onboarding information configured the device it initiate a call home connection, the device would proceed to do so now.
This section defines a YANG [RFC6020] module that is used to define the data model for the zero touch information artifact described in Section 3.1. Examples illustrating this artifact in use are provided in Section 8.2.
The following tree diagram provides an overview of the data model for the zero touch information artifact. The syntax used for this tree diagram is described in Section 1.4.
module: ietf-zerotouch-information
+---- (information-type)
+--:(redirect-information)
| +---- redirect-information
| +---- bootstrap-server* [address]
| +---- address inet:host
| +---- port? inet:port-number
| +---- trust-anchor? binary
+--:(onboarding-information)
+---- onboarding-information
+---- boot-image
| +---- name string
| +---- (hash-algorithm)
| | +--:(sha256)
| | +---- sha256? string
| +---- uri* inet:uri
+---- configuration-handling? enumeration
+---- pre-configuration-script? script
+---- configuration? <anydata>
+---- post-configuration-script? script
This section presents examples for how the zero touch information artifact (Section 3.1) can be encoded into a document that can be distributed outside the bootstrap server's RESTCONF API.
The following example illustrates how redirect information can be encoded into an artifact.
<redirect-information
xmlns="urn:ietf:params:xml:ns:yang:ietf-zerotouch-information">
<bootstrap-server>
<address>phs1.example.com</address>
<port>8443</port>
<trust-anchor>Base64-encoded X.50 </trust-anchor>
</bootstrap-server>
<bootstrap-server>
<address>phs2.example.com</address>
<port>8443</port>
<trust-anchor>Base64-encoded X.50 </trust-anchor>
</bootstrap-server>
<bootstrap-server>
<address>phs3.example.com</address>
<port>8443</port>
<trust-anchor>Base64-encoded X.50 </trust-anchor>
</bootstrap-server>
</redirect-information>
The following example illustrates how onboarding information can be encoded into an artifact. This example uses data models from [RFC7317] and [I-D.ietf-netconf-netconf-client-server].
<-- '\' line wrapping added for formatting purposes only -->
<onboarding-information
xmlns="urn:ietf:params:xml:ns:yang:ietf-zerotouch-information">
<boot-image>
<name>boot-image-v3.2R1.6.img</name>
<sha256>Hex-encoded SHA256 hash</sha256>
<uri>file:///some/path/to/raw/file </uri>
</boot-image>
<configuration-handling>merge</configuration-handling>
<configuration>
<!-- from ietf-system.yang -->
<system xmlns="urn:ietf:params:xml:ns:yang:ietf-system">
<authentication>
<user>
<name>admin</name>
<authorized-key>
<name>admin's rsa ssh host-key</name>
<algorithm>ssh-rsa</algorithm>
<key-data>AAAAB3NzaC1yc2EAAAADAQABAAABAQDeJMV8zrtsi8CgEsRC\
jCzfve2m6zD3awSBPrh7ICggLQvHVbPL89eHLuecStKL3HrEgXaI/O2Mwj\
E1lG9YxLzeS5p2ngzK61vikUSqfMukeBohFTrDZ8bUtrF+HMLlTRnoCVcC\
WAw1lOr9IDGDAuww6G45gLcHalHMmBtQxKnZdzU9kx/fL3ZS5G76Fy6sA5\
vg7SLqQFPjXXft2CAhin8xwYRZy6r/2N9PMJ2Dnepvq4H2DKqBIe340jWq\
EIuA7LvEJYql4unq4Iog+/+CiumTkmQIWRgIoj4FCzYkO9NvRE6fOSLLf6\
gakWVOZZgQ8929uWjCWlGlqn2mPibp2Go1</key-data>
</authorized-key>
</user>
</authentication>
</system>
<!-- from ietf-netconf-server.yang -->
<netconf-server
xmlns="urn:ietf:params:xml:ns:yang:ietf-netconf-server">
<call-home>
<netconf-client>
<name>config-mgr</name>
<ssh>
<endpoints>
<endpoint>
<name>east-data-center</name>
<address>11.22.33.44</address>
</endpoint>
<endpoint>
<name>west-data-center</name>
<address>55.66.77.88</address>
</endpoint>
</endpoints>
<host-keys>
<host-key>
<name>certificate</name>
<certificate>builtin-idevid-cert</certificate>
</host-key>
</host-keys>
<client-cert-auth>
<trusted-ca-certs>deployment-specific-ca-certs</trusted-ca-certs>
<trusted-client-certs>explicitly-trusted-client-certs</trusted-client-certs>
</client-cert-auth>
</ssh>
<connection-type>
<periodic>
<idle-timeout>300</idle-timeout>
<reconnect-timeout>60</reconnect-timeout>
</periodic>
</connection-type>
<reconnect-strategy>
<start-with>last-connected</start-with>
<max-attempts>3</max-attempts>
</reconnect-strategy>
</netconf-client>
</call-home>
</netconf-server>
</configuration>
</onboarding-information>
The zero touch information artifact is normatively defined by the YANG module defined in this section.
Note: the module defined herein uses data types defined in [RFC5280], [RFC6234], and [RFC6991].
<CODE BEGINS> file "ietf-zerotouch-information@2017-06-19.yang"
module ietf-zerotouch-information {
yang-version "1.1";
namespace "urn:ietf:params:xml:ns:yang:ietf-zerotouch-information";
prefix "zti";
import ietf-inet-types {
prefix inet;
reference "RFC 6991: Common YANG Data Types";
}
import ietf-restconf {
prefix rc;
description
"This import statement is only present to access
the yang-data extension defined in RFC 8040.";
reference "RFC 8040: RESTCONF Protocol";
}
organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web: http://tools.ietf.org/wg/netconf
WG List: <mailto:netconf@ietf.org>
Author: Kent Watsen <mailto:kwatsen@juniper.net>";
description
"This module defines the data model for the Zero Touch Information
artifact defined by RFC XXXX: Zero Touch Provisioning for NETCONF
or RESTCONF based Management.
Copyright (c) 2014 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, is permitted pursuant to, and subject to the license
terms contained in, the Simplified BSD License set forth in Section
4.c of the IETF Trust's Legal Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX; see the RFC
itself for full legal notices.";
revision "2017-06-19" {
description
"Initial version";
reference
"RFC XXXX: Zero Touch Provisioning for NETCONF or RESTCONF based
Management";
}
rc:yang-data zerotouch-information {
choice information-type {
mandatory true;
description
"This choice statement ensures the response only contains
redirect-information or onboarding-information. Note that
this is the only mandatory true node, as the other nodes
are not needed when the device trusts the bootstrap server,
in which case the data does not need to be signed.";
container redirect-information {
description
"This is redirect information, as described in Section 2.1
in RFC XXXX. Its purpose is to redirect a device to another
bootstrap server.";
reference
"RFC XXXX: Zero Touch Provisioning for NETCONF or RESTCONF
based Management";
list bootstrap-server {
key address;
description
"A bootstrap server entry.";
leaf address {
type inet:host;
mandatory true;
description
"The IP address or hostname of the bootstrap server the
device should redirect to.";
}
leaf port {
type inet:port-number;
default 443;
description
"The port number the bootstrap server listens on.";
}
leaf trust-anchor { //should there be two fields like voucher?
type binary;
description
"An X.509 v3 certificate structure as specified by RFC
5280, Section 4, encoded using ASN.1 distinguished
encoding rules (DER), as specified in ITU-T X.690. A
certificate that a device can use as a trust anchor
to authenticate the bootstrap server it is being
redirected to.";
reference
"RFC 5280:
Internet X.509 Public Key Infrastructure Certificate
and Certificate Revocation List (CRL) Profile.
ITU-T X.690:
Information technology – ASN.1 encoding rules:
Specification of Basic Encoding Rules (BER),
Canonical Encoding Rules (CER) and Distinguished
Encoding Rules (DER).";
}
}
}
container onboarding-information {
description
"This is bootstrap information, as described in Section 2.2 in
RFC XXXX. Its purpose is to provide the device everything it
needs to bootstrap itself.";
reference
"RFC XXXX: Zero Touch Provisioning for NETCONF or RESTCONF
based Management";
container boot-image {
description
"Specifies criteria for the boot image the device MUST
be running.";
leaf name { // maybe this should be a regex?
type string;
mandatory true;
description
"The name of a software image that the device MUST
be running in order to process the remaining nodes.";
}
choice hash-algorithm {
mandatory true;
description
"Identifies the hash algorithm used.";
leaf sha256 {
type string;
description
"The hex-encoded SHA-256 hash over the boot
image file. This is used by the device to
verify a downloaded boot image file.";
reference
"RFC 6234: US Secure Hash Algorithms.";
}
}
leaf-list uri {
type inet:uri;
min-elements 1;
description
"An ordered list of URIs to where the boot-image file MAY
be obtained. Deployments MUST know in which URI schemes
(http, ftp, etc.) a device supports. If a secure scheme
(e.g., https) is provided, a device MAY establish a
provisional connection to the server, by blindly
accepting the server's credentials (e.g., its TLS
certificate)";
}
}
leaf configuration-handling {
type enumeration {
enum merge {
description
"Merge configuration into existing running configuration.";
}
enum replace {
description
"Replace existing running configuration with the passed
configuration.";
}
}
description
"This enumeration indicates how the server should process
the provided configuration. When not specified, the device
MAY determine how to process the configuration using other
means (e.g., vendor-specific metadata).";
}
leaf pre-configuration-script {
type script;
description
"A script that, when present, is executed before the
configuration has been processed.";
}
anydata configuration {
must "../configuration-handling";
description
"Any configuration data model known to the device. It may
contain manufacturer-specific and/or standards-based data
models.";
}
leaf post-configuration-script {
type script;
description
"A script that, when present, is executed after the
configuration has been processed.";
}
}
}
}
typedef script {
type binary;
description
"A device specific script that enables the execution of commands
to perform actions not possible thru configuration alone.
No attempt is made to standardize the contents, running context,
or programming language of the script. The contents of the
script are considered specific to the vendor, product line,
and/or model of the device.
If a script is erroneously provided to a device that does not
support the execution of scripts, the device SHOULD send a
'script-warning' notification message, but otherwise continue
processing the bootstrapping data as if the script had not
been present.
The script returns exit status code '0' on success and non-zero
on error, with accompanying stderr/stdout for logging purposes.
In the case of an error, the exit status code will specify what
the device should do.
If the exit status code is greater than zero, then the device
should assume that the script had a soft error, which the
script believes does not affect manageability. If the device
obtained the bootstrap information from a bootstrap server,
it SHOULD send a 'script-warning' notification message.
If the exit status code is less than zero, the device should
assume the script had a hard error, which the script believes
will affect manageability. In this case, the device SHOULD
send a 'script-error' notification message followed by a
reset that will force a new boot-image install (wiping out
anything the script may have done) and restart the entire
bootstrapping process again.";
}
}
<CODE ENDS>
This section defines a YANG [RFC6020] module that is used to define the RESTCONF [RFC8040] API used by the bootstrap server defined in Section 5.4. Examples illustrating this API in use are provided in Section 9.2.
The following tree diagram provides an overview for the bootstrap server RESTCONF API. The syntax used for this tree diagram is described in Section 1.4.
module: ietf-zerotouch-bootstrap-server
+--ro device* [unique-id]
+--ro unique-id string
+--ro zerotouch-information pkcs7
+--ro owner-certificate? pkcs7
+--ro ownership-voucher? pkcs7
+---x notification
+---w input
+---w notification-type enumeration
+---w message? string
+---w ssh-host-keys
| +---w ssh-host-key*
| +---w format enumeration
| +---w key-data string
+---w trust-anchors
+---w trust-anchor*
+---w protocol* enumeration
+---w certificate pkcs7
In the above diagram, notice that all of the protocol accessible nodes are read-only, to assert that devices can only pull data from the bootstrap server.
Also notice that the module defines an action statement, which devices use to provide progress notifications to the bootstrap server.
This section presents some examples illustrating the bootstrap server's API. Two examples are provided, one illustrating a device fetching bootstrapping data from the server, and the other illustrating a data posting a progress notification to the server.
The following example illustrates a device using the API to fetch its bootstrapping data from the bootstrap server. In this example, the device receives a signed response; an unsigned response would look similar except the last two fields (owner-certificate and ownership-voucher) would be absent in the response.
REQUEST ------- ['\' line wrapping added for formatting only] GET https://example.com/restconf/data/ietf-zerotouch-bootstrap-server:\ device=123456 HTTP/1.1 HOST: example.com Accept: application/yang.data+xml RESPONSE -------- HTTP/1.1 200 OK Date: Sat, 31 Oct 2015 17:02:40 GMT Server: example-server Content-Type: application/yang.data+xml <!-- '\' line wrapping added for formatting purposes only --> <device xmlns="urn:ietf:params:xml:ns:yang:ietf-zerotouch-bootstrap-server"> <unique-id>123456789</unique-id> <zerotouch-information>Base64-encoded PKCS#7<zerotouch-information> <owner-certificate>Base64-encoded PKCS#7</owner-certificate> <ownership-voucher>Base64-encoded PKCS#7</ownership-voucher> </device>
The following example illustrates a device using the API to post a notification to a bootstrap server. Illustrated below is the 'bootstrap-complete' message, but the device may send other notifications to the server while bootstrapping (e.g., to provide status updates). In this message, the device is sending both its SSH host keys and TLS server certificate, which the bootstrap server may, for example, pass to an NMS, as discussed in Section 6.3.
Note that devices that are able to present an IDevID certificate [Std-802.1AR-2009] when establishing SSH or TLS connections do not need to include its DevID certificate in the bootstrap-complete message. It is unnecessary to send the DevID certificate in this case because the IDevID certificate does not need to be pinned by an NMS in order to be trusted.
Note that the bootstrap server MUST NOT process a notification from a device without first authenticating the device. This is in contrast to when a device is fetching data from the server, a read-only operation, in which case device authentication is not strictly required (e.g., when sending signed information).
REQUEST
-------
['\' line wrapping added for formatting only]
POST https://example.com/restconf/data/ietf-zerotouch:\
device=123456/notification HTTP/1.1
HOST: example.com
Content-Type: application/yang.data+xml
<!-- '\' line wrapping added for formatting purposes only -->
<input
xmlns="urn:ietf:params:xml:ns:yang:ietf-zerotouch-bootstrap-server">
<notification-type>bootstrap-complete</notification-type>
<message>example message</message>
<ssh-host-keys>
<ssh-host-key>
<format>ssh-rsa</format>
<key-data>Base64-encoded SSH RSA Public Key</key-data>
</ssh-host-key>
<ssh-host-key>
<format>ssh-dsa</format>
<key-data>Base64-encoded SSH DSA Public Key</key-data>
</ssh-host-key>
</ssh-host-keys>
<trust-anchors>
<trust-anchor>
<protocol>netconf-ssh</protocol>
<protocol>netconf-tls</protocol>
<protocol>restconf-tls</protocol>
<protocol>netconf-ch-ssh</protocol>
<protocol>netconf-ch-tls</protocol>
<protocol>restconf-ch-tls</protocol>
<certificate>Base64-encoded X.509</certificate>
</trust-anchor>
</trust-anchors>
</input>
RESPONSE
--------
HTTP/1.1 204 No Content
Date: Sat, 31 Oct 2015 17:02:40 GMT
Server: example-server
The bootstrap server's device-facing API is normatively defined by the YANG module defined in this section.
Note: the module defined herein uses data types defined in [RFC2315], [RFC5280], and [I-D.ietf-anima-voucher].
<CODE BEGINS> file "ietf-zerotouch-bootstrap-server@2017-06-19.yang"
module ietf-zerotouch-bootstrap-server {
yang-version "1.1";
namespace
"urn:ietf:params:xml:ns:yang:ietf-zerotouch-bootstrap-server";
prefix "ztbs";
organization
"IETF NETCONF (Network Configuration) Working Group";
contact
"WG Web: <http://tools.ietf.org/wg/netconf/>
WG List: <mailto:netconf@ietf.org>
Author: Kent Watsen
<mailto:kwatsen@juniper.net>";
description
"This module defines an interface for bootstrap servers, as defined
by RFC XXXX: Zero Touch Provisioning for NETCONF or RESTCONF based
Management.
Copyright (c) 2014 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, is permitted pursuant to, and subject to the license
terms contained in, the Simplified BSD License set forth in Section
4.c of the IETF Trust's Legal Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX; see the RFC
itself for full legal notices.";
revision "2017-06-19" {
description
"Initial version";
reference
"RFC XXXX: Zero Touch Provisioning for NETCONF or RESTCONF based
Management";
}
// typedefs
typedef pkcs7 {
type binary;
description
"A PKCS #7 SignedData structure, as specified by Section 9.1
in RFC 2315, encoded using ASN.1 distinguished encoding rules
(DER), as specified in ITU-T X.690.";
reference
"RFC 2315:
PKCS #7: Cryptographic Message Syntax Version 1.5.
ITU-T X.690:
Information technology – ASN.1 encoding rules:
Specification of Basic Encoding Rules (BER),
Canonical Encoding Rules (CER) and Distinguished
Encoding Rules (DER).";
}
// protocol accessible node
list device {
key unique-id;
config false;
description
"A device's record entry. This is the only RESTCONF resource
that a device will GET, as described in Section 8.2 in RFC XXXX.
Getting just this top-level node provides a device with all the
data it needs in a single request.";
reference
"RFC XXXX: Zero Touch Provisioning for NETCONF or
RESTCONF based Management";
leaf unique-id {
type string;
description
"A unique identifier for the device (e.g., serial number).
Each device accesses its bootstrapping record by its unique
identifier.";
}
leaf zerotouch-information {
type pkcs7;
mandatory true;
description
"A 'zerotouch-information' artifact, as described in Section
4.1 of RFC XXXX. When conveyed over an untrusted transport, in
order to be processed by a device, this PKCS#7 SignedData
structure MUST contain a 'signerInfo' structure, described
in Section 9.1 of RFC 2315, containing a signature generated
using the owner's private key.";
reference
"RFC XXXX: Zero Touch Provisioning for NETCONF or
RESTCONF based Management.
RFC 2315:
PKCS #7: Cryptographic Message Syntax Version 1.5";
}
leaf owner-certificate {
type pkcs7;
description
"An unsigned PKCS #7 SignedData structure, as specified by
Section 9.1 in RFC 2315, encoded using ASN.1 distinguished
encoding rules (DER), as specified in ITU-T X.690.
This structure MUST contain the owner certificate and all
intermediate certificates leading up to at least the trust
anchor certificate specified in the ownership voucher.
Additionally, if needed by the device, this structure MAY
also contain suitably fresh CRL and or OCSP Responses.
X.509 certificates and CRLs are described in RFC 5280.
OCSP Responses are described in RFC 6960.";
reference
"RFC 2315:
PKCS #7: Cryptographic Message Syntax Version 1.5.
RFC 5280:
Internet X.509 Public Key Infrastructure Certificate
and Certificate Revocation List (CRL) Profile.
RFC 6960:
X.509 Internet Public Key Infrastructure Online
Certificate Status Protocol - OCSP.
ITU-T X.690:
Information technology – ASN.1 encoding rules:
Specification of Basic Encoding Rules (BER),
Canonical Encoding Rules (CER) and Distinguished
Encoding Rules (DER).";
}
leaf ownership-voucher {
type pkcs7;
must "../owner-certificate" {
description
"An owner certificate must be present whenever an ownership
voucher is presented.";
}
description
"A 'voucher' artifact, as described in Section 5 of
I-D.ietf-anima-voucher. The voucher informs the device
who it's 'owner' is. The voucher encodes the device's
serial number, so that the device can be ensured that
the voucher applies to it. The voucher is signed by
the device's manufacturer or delagate.";
reference
"I-D.etf-anima-voucher:
Voucher and Voucher Revocation Profiles for Bootstrapping
Protocols";
}
action notification {
input {
leaf notification-type {
type enumeration {
enum bootstrap-initiated {
description
"Indicates that the device has just accessed the
bootstrap server. The 'message' field below MAY
contain any additional information that the
manufacturer thinks might be useful.";
}
enum parsing-warning {
description
"Indicates that the device had a non-fatal error when
parsing the response from the bootstrap server. The
'message' field below SHOULD indicate the specific
warning that occurred.";
}
enum parsing-error {
description
"Indicates that the device encountered a fatal error
when parsing the response from the bootstrap server.
For instance, this could be due to malformed encoding,
the device expecting signed data when only unsigned
data is provided, because the ownership voucher didn't
include the device's unique identifier, or because the
signature didn't match. The 'message' field below
SHOULD indicate the specific error. This notification
also indicates that the device has abandoned trying to
bootstrap off this bootstrap server.";
}
enum boot-image-warning {
description
"Indicates that the device encountered a non-fatal
error condition when trying to install a boot-image.
A possible reason might include a need to reformat a
partition causing loss of data. The 'message' field
below SHOULD indicate any warning messages that were
generated.";
}
enum boot-image-error {
description
"Indicates that the device encountered an error when
trying to install a boot-image, which could be for
reasons such as a file server being unreachable,
file not found, signature mismatch, etc. The
'message' field SHOULD indicate the specific error
that occurred. This notification also indicates
that the device has abandoned trying to bootstrap
off this bootstrap server.";
}
enum pre-script-warning {
description
"Indicates that the device obtained a greater than
zero exit status code from the script when it was
executed. The 'message' field below SHOULD indicate
both the resulting exit status code, as well as
capture any stdout/stderr messages the script may
have produced.";
}
enum pre-script-error {
description
"Indicates that the device obtained a less than zero
exit status code from the script when it was executed.
The 'message' field below SHOULD indicate both the
resulting exit status code, as well as capture any
stdout/stderr messages the script may have produced.
This notification also indicates that the device has
abandoned trying to bootstrap off this bootstrap
server.";
}
enum config-warning {
description
"Indicates that the device obtained warning messages
when it committed the initial configuration. The
'message' field below SHOULD indicate any warning
messages that were generated.";
}
enum config-error {
description
"Indicates that the device obtained error messages
when it committed the initial configuration. The
'message' field below SHOULD indicate the error
messages that were generated. This notification
also indicates that the device has abandoned trying
to bootstrap off this bootstrap server.";
}
enum post-script-warning {
description
"Indicates that the device obtained a greater than
zero exit status code from the script when it was
executed. The 'message' field below SHOULD indicate
both the resulting exit status code, as well as
capture any stdout/stderr messages the script may
have produced.";
}
enum post-script-error {
description
"Indicates that the device obtained a less than zero
exit status code from the script when it was executed.
The 'message' field below SHOULD indicate both the
resulting exit status code, as well as capture any
stdout/stderr messages the script may have produced.
This notification also indicates that the device has
abandoned trying to bootstrap off this bootstrap
server.";
}
enum bootstrap-complete {
description
"Indicates that the device successfully processed the
all the bootstrapping data and that it is ready to be
managed. The 'message' field below MAY contain any
additional information that the manufacturer thinks
might be useful. After sending this notification,
the device is not expected to access the bootstrap
server again.";
}
enum informational {
description
"Indicates any additional information not captured by
any of the other notification-type. For instance, a
message indicating that the device is about to reboot
after having installed a boot-image could be provided.
The 'message' field below SHOULD contain information
that the manufacturer thinks might be useful.";
}
}
mandatory true;
description
"The type of notification provided.";
}
leaf message {
type string;
description
"An optional human-readable value.";
}
container ssh-host-keys {
when "../notification-type = 'bootstrap-complete'" {
description
"SSH host keys are only sent when the notification
type is 'bootstrap-complete'.";
}
description
"A list of SSH host keys an NMS may use to authenticate
a NETCONF connection to the device with.";
list ssh-host-key {
description
"An SSH host-key";
leaf format {
type enumeration {
enum ssh-dss { description "ssh-dss"; }
enum ssh-rsa { description "ssh-rsa"; }
}
mandatory true;
description
"The format of the SSH host key.";
}
leaf key-data {
type string;
mandatory true;
description
"The key data for the SSH host key";
}
}
}
container trust-anchors {
when "../notification-type = 'bootstrap-complete'" {
description
"Trust anchors are only sent when the notification
type is 'bootstrap-complete'.";
}
description
"A list of trust anchor certificates an NMS may use to
authenticate a NETCONF or RESTCONF connection to the
device with.";
list trust-anchor {
description
"A list of trust anchor certificates an NMS may use to
authenticate a NETCONF or RESTCONF connection to the
device with.";
leaf-list protocol {
type enumeration {
enum netconf-ssh { description "netconf-ssh"; }
enum netconf-tls { description "netconf-tls"; }
enum restconf-tls { description "restconf-tls"; }
enum netconf-ch-ssh { description "netconf-ch-ssh"; }
enum netconf-ch-tls { description "netconf-ch-tls"; }
enum restconf-ch-tls { description "restconf-ch-tls"; }
}
min-elements 1;
description
"The protocols that this trust anchor secures.";
}
leaf certificate {
type pkcs7;
mandatory true;
description
"An X.509 v3 certificate structure, as specified by
Section 4 in RFC5280, encoded using ASN.1 distinguished
encoding rules (DER), as specified in ITU-T X.690.";
reference
"RFC 5280:
Internet X.509 Public Key Infrastructure Certificate
and Certificate Revocation List (CRL) Profile.
ITU-T X.690:
Information technology – ASN.1 encoding rules:
Specification of Basic Encoding Rules (BER),
Canonical Encoding Rules (CER) and Distinguished
Encoding Rules (DER).";
}
}
}
}
} // end action
} // end device
}
<CODE ENDS>
This section defines two DHCP options, one for DHCPv4 and one for DHCPv6. These two options are semantically the same, though syntactically different.
The DHCPv4 Zero Touch Option is used to provision the client with one or more URIs for bootstrap servers that can be contacted to attempt further configuration.
DHCPv4 Zero Touch Redirect Option
0 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| option-code (TBD) | option-length |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
. .
. bootstrap-server-list (variable length) .
. .
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
o option-code: OPTION_V4_ZEROTOUCH_REDIRECT (TBD)
o option-length: The option length in octets
o bootstrap-server-list: A list of servers for the
client to attempt contacting, in order to obtain
further bootstrapping data, in the format shown
in [common-field-encoding].
DHCPv4 Client Behavior
Clients MAY request the OPTION_V4_ZEROTOUCH_REDIRECT by including its option code in the Parameter Request List (55) in DHCP request messages.
On receipt of a DHCPv4 Reply message which contains the OPTION_V4_ZEROTOUCH_REDIRECT, the client performs the following steps:
Any invalid URI entries received in the uri-data field are ignored by the client. If OPTION_V4_ZEROTOUCH_REDIRECT does not contain at least one valid URI entry in the uri-data field, then the client MUST discard the option.
DHCPv4 Server Behavior
The DHCPv4 server MAY include a single instance of Option OPTION_V4_ZEROTOUCH_REDIRECT in DHCP messages it sends. Servers MUST NOT send more than one instance of the OPTION_V4_ZEROTOUCH_REDIRECT option.
The DHCPv6 Zero Touch Option is used to provision the client with one or more URIs for bootstrap servers that can be contacted to attempt further configuration.
DHCPv6 Zero Touch Redirect Option
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| option-code (TBD) | option-length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. bootstrap-server-list (variable length) .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o option-code: OPTION_V6_ZEROTOUCH_REDIRECT (TBD)
o option-length: The option length in octets
o bootstrap-server-list: A list of servers for the client to
attempt contacting, in order to obtain further bootstrapping
data, in the format shown in [common-field-encoding].
DHCPv6 Client Behavior
Clients MAY request the OPTION_V6_ZEROTOUCH_REDIRECT option, as defined in [RFC3315], Sections 17.1.1, 18.1.1, 18.1.3, 18.1.4, 18.1.5, and 22.7. As a convenience to the reader, we mention here that the client includes requested option codes in the Option Request Option.
On receipt of a DHCPv6 reply message which contains the OPTION_V6_ZEROTOUCH_REDIRECT, the client performs the following steps:
Any invalid URI entries received in the uri-data field are ignored by the client. If OPTION_V6_ZEROTOUCH_REDIRECT does not contain at least one valid URI entry in the uri-data field, then the client MUST discard the option.
DHCPv6 Server Behavior
Sections 17.2.2 and 18.2 of [RFC3315] govern server operation in regard to option assignment. As a convenience to the reader, we mention here that the server will send a particular option code only if configured with specific values for that option code and if the client requested it.
Option OPTION_V6_ZEROTOUCH_REDIRECT is a singleton. Servers MUST NOT send more than one instance of the OPTION_V6_ZEROTOUCH_REDIRECT option.
Both of the DHCPv4 and DHCPv6 options defined in this section encode a list of bootstrap server URIs. The 'URI' structure is an option that can contain multiple URIs (see [RFC7227], Section 5.7).
bootstrap-server-list:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+-+-+-+-+-+
| uri-length | URI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...-+-+-+-+-+-+-+
o uri-length: variable, in octets.
o URI: URI of Netconf zerotouch bootstrap server, using the HTTPS URI
scheme defined in Section 2.7.2 of RFC7230.
Devices MUST ensure that all their trust anchor certificates, including those for connecting to bootstrap servers and verifying ownership vouchers, are protected from external modification.
It may be necessary to update these certificates over time (e.g., the manufacturer wants to delegate trust to a new CA). It is therefore expected that devices MAY update these trust anchors when needed through a verifiable process, such as a software upgrade using signed software images.
The solution in this document relies on TLS certificates, owner certificates, and ownership vouchers, all of which require an accurate clock in order to be processed correctly (e.g., to test validity dates and revocation status). Implementations MUST ensure devices have an accurate clock when shipped from manufacturing facilities, and take steps to prevent clock tampering.
If it is not possible to ensure clock accuracy, it is RECOMMENDED that implementations disable the aspects of the solution having clock sensitivity. In particular, such implementations should assume that TLS certificates and owner certificates are not revokable. In real-world terms, this means that manufacturers SHOULD only issue a single ownership voucher for the lifetime of some devices.
It is important to note that implementations SHOULD NOT rely on NTP for time, as it is not a secure protocol.
This document allows a device to blindly authenticate a bootstrap server's TLS certificate. It does so to allow for cases where the redirect information may be obtained in an unsecured manner, which is desirable to support in some cases.
To compensate for this, this document requires that devices, when connected to an untrusted bootstrap server, do not send their IDevID certificate for client authentication, and they do not POST any progress notifications, and they assert that data downloaded from the server is signed.
Section 7.2.7.2 of the IEEE Std 802.1AR-2009 standard says that IDevID certificate should never expire (i.e. having the notAfter value 99991231235959Z). Given the long-lived nature of these certificates, it is paramount to use a strong key length (e.g., 512-bit ECC).
This draft uses the device's serial number both in the IDevID certificate as well as in the bootstrap server API. Serial numbers are are ubiquitous and prominently contained in invoices and on labels affixed to devices and their packaging. That said, serial numbers many times encode revealing information, such as the device's model number, manufacture date, and/or sequence number. Knowledge of this information may provide an adversary with details needed to launch an attack.
For devices supporting more than one source for bootstrapping data, no particular sequencing order has to be observed for security reasons, as the solution for each source is considered equally secure. However, from a privacy perspective, it is RECOMMENDED that devices access local sources before accessing remote sources.
TBD for OPTION_V4_ZEROTOUCH_REDIRECT
IANA is kindly requested to allocate a new option code from the "BOOTP Manufacturer Extensions and DHCP Options" registry maintained at http://www.iana.org/assignments/bootp-dhcp-parameters:
TBD for OPTION_V6_ZEROTOUCH_REDIRECT
And a new option code from the "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)" registry maintained at http://www.iana.org/assignments/dhcpv6-parameters:
This document registers two URIs in the IETF XML registry [RFC3688]. Following the format in [RFC3688], the following registrations are requested:
URI: urn:ietf:params:xml:ns:yang:ietf-zerotouch-information Registrant Contact: The NETCONF WG of the IETF. XML: N/A, the requested URI is an XML namespace. URI: urn:ietf:params:xml:ns:yang:ietf-zerotouch-bootstrap-server Registrant Contact: The NETCONF WG of the IETF. XML: N/A, the requested URI is an XML namespace.
This document registers two YANG modules in the YANG Module Names registry [RFC6020]. Following the format defined in [RFC6020], the the following registrations are requested:
name: ietf-zerotouch-information namespace: urn:ietf:params:xml:ns:yang:ietf-zerotouch-information prefix: zt reference: RFC XXXX name: ietf-zerotouch-bootstrap-server namespace: urn:ietf:params:xml:ns:yang:ietf-zerotouch-bootstrap-server prefix: zt reference: RFC XXXX
Both this document and [I-D.ietf-anima-bootstrapping-keyinfra] define bootstrapping mechanisms. The authors have collaborated on both solutions and believe that each solution has merit and, in fact, can work together. That is, it is possible for a device to support both solutions simultaneously.
The authors would like to thank for following for lively discussions on list and in the halls (ordered by last name): David Harrington, Michael Behringer, Dean Bogdanovic, Martin Bjorklund, Joe Clarke, Toerless Eckert, Stephen Farrell, Stephen Hanna, Wes Hardaker, Russ Mundy, Reinaldo Penno, Randy Presuhn, Max Pritikin, Michael Richardson, Phil Shafer, Juergen Schoenwaelder.
Special thanks goes to Steve Hanna, Russ Mundy, and Wes Hardaker for brainstorming the original I-D's solution during the IETF 87 meeting in Berlin.