gpg

gpg.program
Pathname of the program to use instead of “gpg” 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. 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".

See linkgit:gitformat-signature[5] for the signature format, which differs based on the selected gpg.format.

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 requires 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 will be run when user.signingkey is not set and a ssh signature is requested. On successful exit a valid ssh public key prefixed with key:: is expected in the first line of its output. This allows for a script doing a dynamic lookup of the correct public key when it is impractical to statically configure user.signingKey. For example when keys or SSH Certificates are rotated frequently or selection of the right key depends on external factors unknown to git.

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.

Since OpensSSH 8.8 this file allows specifying a key lifetime using valid-after & valid-before options. Git will mark signatures as valid if the signing key was valid at the time of the signature’s creation. This allows users to change a signing key without invalidating all previously made signatures.

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.