38a52bd3b5
Release notes are available at https://www.openssh.com/txt/release-9.1 9.1 contains fixes for three minor memory safety problems; these have lready been merged to the copy of OpenSSH 9.0 that is in the FreeBSD base system. Some highlights copied from the release notes: Potentially-incompatible changes -------------------------------- * ssh(1), sshd(8): SetEnv directives in ssh_config and sshd_config are now first-match-wins to match other directives. Previously if an environment variable was multiply specified the last set value would have been used. bz3438 * ssh-keygen(8): ssh-keygen -A (generate all default host key types) will no longer generate DSA keys, as these are insecure and have not been used by default for some years. New features ------------ * ssh(1), sshd(8): add a RequiredRSASize directive to set a minimum RSA key length. Keys below this length will be ignored for user authentication and for host authentication in sshd(8). * sftp-server(8): add a "users-groups-by-id@openssh.com" extension request that allows the client to obtain user/group names that correspond to a set of uids/gids. * sftp(1): use "users-groups-by-id@openssh.com" sftp-server extension (when available) to fill in user/group names for directory listings. * sftp-server(8): support the "home-directory" extension request defined in draft-ietf-secsh-filexfer-extensions-00. This overlaps a bit with the existing "expand-path@openssh.com", but some other clients support it. * ssh-keygen(1), sshd(8): allow certificate validity intervals, sshsig verification times and authorized_keys expiry-time options to accept dates in the UTC time zone in addition to the default of interpreting them in the system time zone. YYYYMMDD and YYMMDDHHMM[SS] dates/times will be interpreted as UTC if suffixed with a 'Z' character. Also allow certificate validity intervals to be specified in raw seconds-since-epoch as hex value, e.g. -V 0x1234:0x4567890. This is intended for use by regress tests and other tools that call ssh-keygen as part of a CA workflow. bz3468 * sftp(1): allow arguments to the sftp -D option, e.g. sftp -D "/usr/libexec/sftp-server -el debug3" * ssh-keygen(1): allow the existing -U (use agent) flag to work with "-Y sign" operations, where it will be interpreted to require that the private keys is hosted in an agent; bz3429 MFC after: 2 weeks Relnotes: Yes Sponsored by: The FreeBSD Foundation
85 lines
3.0 KiB
Plaintext
85 lines
3.0 KiB
Plaintext
The SSH agent protocol is described in
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https://tools.ietf.org/html/draft-miller-ssh-agent-04
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This file documents OpenSSH's extensions to the agent protocol.
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1. session-bind@openssh.com extension
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This extension allows a ssh client to bind an agent connection to a
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particular SSH session identifier as derived from the initial key
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exchange (as per RFC4253 section 7.2) and the host key used for that
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exchange. This binding is verifiable at the agent by including the
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initial KEX signature made by the host key.
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The message format is:
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byte SSH_AGENTC_EXTENSION (0x1b)
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string session-bind@openssh.com
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string hostkey
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string session identifier
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string signature
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bool is_forwarding
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Where 'hostkey' is the encoded server host public key, 'session
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identifier' is the exchange hash derived from the initial key
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exchange, 'signature' is the server's signature of the session
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identifier using the private hostkey, as sent in the final
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SSH2_MSG_KEXDH_REPLY/SSH2_MSG_KEXECDH_REPLY message of the initial key
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exchange. 'is_forwarding' is a flag indicating whether this connection
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should be bound for user authentication or forwarding.
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When an agent received this message, it will verify the signature and
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check the consistency of its contents, including refusing to accept
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a duplicate session identifier, or any attempt to bind a connection
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previously bound for authentication. It will then then record the
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binding for the life of the connection for use later in testing per-key
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destination constraints.
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2. restrict-destination-v00@openssh.com key constraint extension
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The key constraint extension supports destination- and forwarding path-
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restricted keys. It may be attached as a constraint when keys or
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smartcard keys are added to an agent.
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byte SSH_AGENT_CONSTRAIN_EXTENSION (0xff)
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string restrict-destination-v00@openssh.com
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constraint[] constraints
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Where a constraint consists of:
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string from_username (must be empty)
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string from_hostname
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keyspec[] from_hostkeys
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string to_username
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string to_hostname
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keyspec[] to_hostkeys
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And a keyspec consists of:
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string keyblob
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bool is_ca
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When receiving this message, the agent will ensure that the
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'from_username' field is empty, and that 'to_hostname' and 'to_hostkeys'
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have been supplied (empty 'from_hostname' and 'from_hostkeys' are valid
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and signify the initial hop from the host running ssh-agent). The agent
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will then record the constraint against the key.
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Subsequent operations on this key including add/remove/request
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identities and, in particular, signature requests will check the key
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constraints against the session-bind@openssh.com bindings recorded for
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the agent connection over which they were received.
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3. SSH_AGENT_CONSTRAIN_MAXSIGN key constraint
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This key constraint allows communication to an agent of the maximum
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number of signatures that may be made with an XMSS key. The format of
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the constraint is:
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byte SSH_AGENT_CONSTRAIN_MAXSIGN (0x03)
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uint32 max_signatures
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This option is only valid for XMSS keys.
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$OpenBSD: PROTOCOL.agent,v 1.18 2022/09/21 22:26:50 dtucker Exp $
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