6393c956f4
If valid-before/after dates are configured for this signatures key in the
allowedSigners file then the verification should check if the key was valid at
the time the commit was made. This allows for graceful key rollover and
revoking keys without invalidating all previous commits.
This feature needs openssh > 8.8. Older ssh-keygen versions will simply
ignore this flag and use the current time.
Strictly speaking this feature is available in 8.7, but since 8.7 has a
bug that makes it unusable in another needed call we require 8.8.
Timestamp information is present on most invocations of check_signature.
However signer ident is not. We will need the signer email / name to be able
to implement "Trust on first use" functionality later.
Since the payload contains all necessary information we can parse it
from there. The caller only needs to provide us some info about the
payload by setting payload_type in the signature_check struct.
- Add payload_type field & enum and payload_timestamp to struct
signature_check
- Populate the timestamp when not already set if we know about the
payload type
- Pass -Overify-time={payload_timestamp} in the users timezone to all
ssh-keygen verification calls
- Set the payload type when verifying commits
- Add tests for expired, not yet valid and keys having a commit date
outside of key validity as well as within
Signed-off-by: Fabian Stelzer <fs@gigacodes.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
80 lines
3.7 KiB
Plaintext
80 lines
3.7 KiB
Plaintext
gpg.program::
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Use this custom program instead of "`gpg`" found on `$PATH` when
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making or verifying a PGP signature. The program must support the
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same command-line interface as GPG, namely, to verify a detached
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signature, "`gpg --verify $signature - <$file`" is run, and the
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program is expected to signal a good signature by exiting with
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code 0, and to generate an ASCII-armored detached signature, the
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standard input of "`gpg -bsau $key`" is fed with the contents to be
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signed, and the program is expected to send the result to its
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standard output.
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gpg.format::
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Specifies which key format to use when signing with `--gpg-sign`.
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Default is "openpgp". Other possible values are "x509", "ssh".
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gpg.<format>.program::
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Use this to customize the program used for the signing format you
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chose. (see `gpg.program` and `gpg.format`) `gpg.program` can still
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be used as a legacy synonym for `gpg.openpgp.program`. The default
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value for `gpg.x509.program` is "gpgsm" and `gpg.ssh.program` is "ssh-keygen".
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gpg.minTrustLevel::
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Specifies a minimum trust level for signature verification. If
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this option is unset, then signature verification for merge
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operations require a key with at least `marginal` trust. Other
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operations that perform signature verification require a key
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with at least `undefined` trust. Setting this option overrides
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the required trust-level for all operations. Supported values,
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in increasing order of significance:
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+
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* `undefined`
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* `never`
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* `marginal`
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* `fully`
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* `ultimate`
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gpg.ssh.defaultKeyCommand:
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This command that will be run when user.signingkey is not set and a ssh
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signature is requested. On successful exit a valid ssh public key is
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expected in the first line of its output. To automatically use the first
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available key from your ssh-agent set this to "ssh-add -L".
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gpg.ssh.allowedSignersFile::
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A file containing ssh public keys which you are willing to trust.
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The file consists of one or more lines of principals followed by an ssh
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public key.
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e.g.: user1@example.com,user2@example.com ssh-rsa AAAAX1...
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See ssh-keygen(1) "ALLOWED SIGNERS" for details.
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The principal is only used to identify the key and is available when
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verifying a signature.
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+
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SSH has no concept of trust levels like gpg does. To be able to differentiate
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between valid signatures and trusted signatures the trust level of a signature
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verification is set to `fully` when the public key is present in the allowedSignersFile.
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Otherwise the trust level is `undefined` and git verify-commit/tag will fail.
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+
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This file can be set to a location outside of the repository and every developer
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maintains their own trust store. A central repository server could generate this
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file automatically from ssh keys with push access to verify the code against.
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In a corporate setting this file is probably generated at a global location
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from automation that already handles developer ssh keys.
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+
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A repository that only allows signed commits can store the file
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in the repository itself using a path relative to the top-level of the working tree.
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This way only committers with an already valid key can add or change keys in the keyring.
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+
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Since OpensSSH 8.8 this file allows specifying a key lifetime using valid-after &
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valid-before options. Git will mark signatures as valid if the signing key was
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valid at the time of the signatures creation. This allows users to change a
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signing key without invalidating all previously made signatures.
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+
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Using a SSH CA key with the cert-authority option
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(see ssh-keygen(1) "CERTIFICATES") is also valid.
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gpg.ssh.revocationFile::
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Either a SSH KRL or a list of revoked public keys (without the principal prefix).
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See ssh-keygen(1) for details.
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If a public key is found in this file then it will always be treated
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as having trust level "never" and signatures will show as invalid.
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