Internet DRAFT - draft-hallambaker-mesh-app-ssh
draft-hallambaker-mesh-app-ssh
Network Working Group P. Hallam-Baker
Internet-Draft Comodo Group Inc.
Intended status: Informational August 18, 2017
Expires: February 19, 2018
Mathematical Mesh: SSH Application
draft-hallambaker-mesh-app-ssh-01
Abstract
Mesh/SSH
The use of the Mathematical Mesh to manage OpenSSH Keys is described.
This document is also available online at
http://prismproof.org/Documents/draft-hallambaker-mesh-app-ssh.html .
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This Internet-Draft will expire on February 19, 2018.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2.2. Related Specifications . . . . . . . . . . . . . . . . . 3
2.3. Defined Terms . . . . . . . . . . . . . . . . . . . . . . 3
2.4. Implementation Status . . . . . . . . . . . . . . . . . . 4
3. User Experience . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Initial profile creation . . . . . . . . . . . . . . . . 4
3.2. Configuring SSH for machine X . . . . . . . . . . . . . . 4
3.3. Configuring SSH for machine Y . . . . . . . . . . . . . . 4
3.4. Configuring SSH for machine Z . . . . . . . . . . . . . . 5
3.5. Deleting a Device . . . . . . . . . . . . . . . . . . . . 5
3.6. Future directions . . . . . . . . . . . . . . . . . . . . 5
3.6.1. Native Mesh support in SSH . . . . . . . . . . . . . 5
3.6.2. Update Daemon . . . . . . . . . . . . . . . . . . . . 5
3.6.3. Batched Connection Requests . . . . . . . . . . . . . 6
3.6.4. Enhanced administration . . . . . . . . . . . . . . . 6
4. Platform Bindings . . . . . . . . . . . . . . . . . . . . . . 6
4.1. OpenSSH Files . . . . . . . . . . . . . . . . . . . . . . 6
5. Application Profile . . . . . . . . . . . . . . . . . . . . . 6
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
7. Security Considerations . . . . . . . . . . . . . . . . . . . 6
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
9.1. Normative References . . . . . . . . . . . . . . . . . . 7
9.2. Informative References . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
The Secure Shell (SSH) transport layer protocol [!RFC4253] is widely
used as a mechanism for securing access to remote hosts. In addition
to providing a terminal connection to a remote host, SSH also
supports file transfer and remote access (VPN) functionality. It is
also used to provide remote procedure call (RPC) capabilities in
applications such as Git.
While SSH permits a high level of security to be achieved, achieving
a high security configuration requires a considerable degree of
attention to detail. Numerous ?how to? guides found on the Internet
advise the user to engage in many unsafe practices. These include:
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Using a single private key for authentication for every machine to be
used as a client.
Emailing a copy of the authentication key to yourself to transfer it
to a new machine. (Alternatively use of insecure FTP, copying the
data to /temp, etc.)
Of equal concern was the fact that none of the guides mentioned any
form of maintenance activity such as deleting authentication keys for
a decommissioned device or performing a rekey operation in the case
that a device is compromised.
Configuring SSH securely is a non-trivial task because SSH is the
tool through which the administrator will be connecting to secure
their system. This is a bootstrap problem: It is easy to solve the
problem of SSH configuration once we have SSH configured for use. To
enable SSH access to a
The Mathematical Mesh provides an infrastructure for single touch
administration of all the devices a user has connected to their Mesh
profile. Managing SSH configuration with the Mesh guides the user
towards use of a maximally secure configuration. Once the
configuration is achieved, it is maintained automatically.
2. Definitions
This section presents the related specifications and standard, the
terms that are used as terms of art within the documents and the
terms used as requirements language.
2.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119] [RFC2119] .
2.2. Related Specifications
The related specifications are described in the Mesh Architecture
specification [draft-hallambaker-mesh-architecture]
[draft-hallambaker-mesh-architecture]
2.3. Defined Terms
No terms of art are defined.
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2.4. Implementation Status
The implementation status of the reference code base is described in
the companion document [draft-hallambaker-mesh-developer]
[draft-hallambaker-mesh-developer] .
3. User Experience
Alice is a user of three machines, X, Y and Z. Machines X and Y are
configured with monitors and keyboards enabling their use as an SSH
client. Machine Z is to be configured as a headless machine (no
monitor). When finished, Alice wants to be able to connect to
machines X, Y or Z from machine X or Y.
Since SSH is a tool principally used on UNIX based systems and
machines configured to provide similar behavior, this guide assumes
machines X, Y and Z are all UNIX systems when describing the files to
be modified. When used on a Windows machine, the Mesh tools
configure the equivalent Windows files.
3.1. Initial profile creation
If this is the first time Alice has used the Mesh, she creates a
personal profile for herself on machine X:
X> meshman /personal alice@mesh.prismproof.org
3.2. Configuring SSH for machine X
To configure SSH on machine X, Alice adds it to her profile.
X> meshman /ssh
Note that the meshman tool only performs the
At this point, Alice has a new private key that is unique to machine
X and the corresponding public key has been added to her profile
3.3. Configuring SSH for machine Y
To configure the second machine, Alice first requests adding it to
her profile:
Y>
This request must be accepted on machine X:
X>
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Alice now adds the SSH profile to machine Y:
Y> meshman /ssh
At this point machines X and Y both have a unique private key and
both the corresponding public keys have been added to the authorized
key files on Y. The authorized key file on X will be updated by a
mesh profile manager running periodically.
3.4. Configuring SSH for machine Z
Configuration of machine Z begins in exactly the same way as for
machine Y. The only difference is that when she creates the SSH
profile for the device, she requests it be a host only profile:
Z> meshman /ssh /host
3.5. Deleting a Device
3.6. Future directions
3.6.1. Native Mesh support in SSH
The chief weakness in this user experience is that the machines
cannot update themselves automatically or even know when an update is
required. The only approach that is available is for the host
devices to periodically poll the Mesh portal and request updates for
the registered profiles.
This delay can be avoided if the SSH protocol and implementations
were updated to support direct use of Mesh profiles. This allows a
client to push the updated profile data to the server when making the
connection attempt.
3.6.2. Update Daemon
Native support allows the process of adding devices to be automated
but does not guarantee timely processing of deletion requests. It
also requires action by third parties who may not be interested in
providing Mesh support.
A better approach would be to run a daemon on each machine that could
receive update notifications from the portal whenever a significant
event (profile addition/deletion) had occurred.
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3.6.3. Batched Connection Requests
The existing management tools require a device to be connected to a
profile before use of applications are enabled on the device.
3.6.4. Enhanced administration
While this approach is functional, it does not meet the requirement
for complete mediation of the log in request. While the system
administrator has the ability to permit or deny remote access
capabilities to a user, these are the only options that the
administration tools currently supported by most SSH configurations
provide. The administrator cannot control the types of credentials
used by specific users.
The Mesh could be employed to permit a closer level of control.
Storing the user?s profile fingerprint in the password database
(/etc/passwd or /etc/shadow) would allow every application and system
utility to refer to a single root of trust for authenticating every
credential presented by a user.
4. Platform Bindings
Since SSH is an application program
4.1. OpenSSH Files
Contains a list of all the keys that are authorized to access the
corresponding account. This is a list of Mesh SSH per device
application keys.
Default name for the user?s RSA public key
Default name for the user?s RSA private key
List of host keys known to this user.
5. Application Profile
6. Acknowledgements
7. Security Considerations
[This is just a sketch for the present.]
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8. IANA Considerations
[TBS list out all the code points that require an IANA registration]
9. References
9.1. Normative References
[draft-hallambaker-mesh-architecture]
Hallam-Baker, P., "Mathematical Mesh: Architecture",
draft-hallambaker-mesh-architecture-03 (work in progress),
May 2017.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997.
9.2. Informative References
[draft-hallambaker-mesh-developer]
Hallam-Baker, P., "Mathematical Mesh: Developer's Guide",
draft-hallambaker-mesh-developer-02 (work in progress),
September 2016.
Author's Address
Phillip Hallam-Baker
Comodo Group Inc.
Email: philliph@comodo.com
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