git-commit-vandalism/Documentation/config/gpg.txt
Fabian Stelzer 9fb391bff9 ssh signing: clarify trustlevel usage in docs
facca53ac added verification for ssh signatures but incorrectly
described the usage of gpg.minTrustLevel. While the verifications
trustlevel is stil set to fully or undefined depending on if the key is
known or not it has no effect on the verification result. Unknown keys
will always fail verification. This commit updates the docs to match
this behaviour.

Signed-off-by: Fabian Stelzer <fs@gigacodes.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2021-10-13 10:02:27 -07:00

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gpg.program::
Use this custom program instead of "`gpg`" found on `$PATH` when
making or verifying a PGP signature. The program must support the
same command-line interface as GPG, namely, to verify a detached
signature, "`gpg --verify $signature - <$file`" is run, and the
program is expected to signal a good signature by exiting with
code 0, and to generate an ASCII-armored detached signature, the
standard input of "`gpg -bsau $key`" is fed with the contents to be
signed, and the program is expected to send the result to its
standard output.
gpg.format::
Specifies which key format to use when signing with `--gpg-sign`.
Default is "openpgp". Other possible values are "x509", "ssh".
gpg.<format>.program::
Use this to customize the program used for the signing format you
chose. (see `gpg.program` and `gpg.format`) `gpg.program` can still
be used as a legacy synonym for `gpg.openpgp.program`. The default
value for `gpg.x509.program` is "gpgsm" and `gpg.ssh.program` is "ssh-keygen".
gpg.minTrustLevel::
Specifies a minimum trust level for signature verification. If
this option is unset, then signature verification for merge
operations require a key with at least `marginal` trust. Other
operations that perform signature verification require a key
with at least `undefined` trust. Setting this option overrides
the required trust-level for all operations. Supported values,
in increasing order of significance:
+
* `undefined`
* `never`
* `marginal`
* `fully`
* `ultimate`
gpg.ssh.defaultKeyCommand:
This command that will be run when user.signingkey is not set and a ssh
signature is requested. On successful exit a valid ssh public key is
expected in the first line of its output. To automatically use the first
available key from your ssh-agent set this to "ssh-add -L".
gpg.ssh.allowedSignersFile::
A file containing ssh public keys which you are willing to trust.
The file consists of one or more lines of principals followed by an ssh
public key.
e.g.: user1@example.com,user2@example.com ssh-rsa AAAAX1...
See ssh-keygen(1) "ALLOWED SIGNERS" for details.
The principal is only used to identify the key and is available when
verifying a signature.
+
SSH has no concept of trust levels like gpg does. To be able to differentiate
between valid signatures and trusted signatures the trust level of a signature
verification is set to `fully` when the public key is present in the allowedSignersFile.
Otherwise the trust level is `undefined` and git verify-commit/tag will fail.
+
This file can be set to a location outside of the repository and every developer
maintains their own trust store. A central repository server could generate this
file automatically from ssh keys with push access to verify the code against.
In a corporate setting this file is probably generated at a global location
from automation that already handles developer ssh keys.
+
A repository that only allows signed commits can store the file
in the repository itself using a path relative to the top-level of the working tree.
This way only committers with an already valid key can add or change keys in the keyring.
+
Using a SSH CA key with the cert-authority option
(see ssh-keygen(1) "CERTIFICATES") is also valid.
gpg.ssh.revocationFile::
Either a SSH KRL or a list of revoked public keys (without the principal prefix).
See ssh-keygen(1) for details.
If a public key is found in this file then it will always be treated
as having trust level "never" and signatures will show as invalid.