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diff --git a/Documentation/technical/signature-format.txt b/Documentation/technical/signature-format.txt new file mode 100644 index 000000000000..2c9406a56a88 --- /dev/null +++ b/Documentation/technical/signature-format.txt @@ -0,0 +1,186 @@ +Git signature format +==================== + +== Overview + +Git uses cryptographic signatures in various places, currently objects (tags, +commits, mergetags) and transactions (pushes). In every case, the command which +is about to create an object or transaction determines a payload from that, +calls gpg to obtain a detached signature for the payload (`gpg -bsa`) and +embeds the signature into the object or transaction. + +Signatures always begin with `-----BEGIN PGP SIGNATURE-----` +and end with `-----END PGP SIGNATURE-----`, unless gpg is told to +produce RFC1991 signatures which use `MESSAGE` instead of `SIGNATURE`. + +The signed payload and the way the signature is embedded depends +on the type of the object resp. transaction. + +== Tag signatures + +- created by: `git tag -s` +- payload: annotated tag object +- embedding: append the signature to the unsigned tag object +- example: tag `signedtag` with subject `signed tag` + +---- +object 04b871796dc0420f8e7561a895b52484b701d51a +type commit +tag signedtag +tagger C O Mitter <committer@example.com> 1465981006 +0000 + +signed tag + +signed tag message body +-----BEGIN PGP SIGNATURE----- +Version: GnuPG v1 + +iQEcBAABAgAGBQJXYRhOAAoJEGEJLoW3InGJklkIAIcnhL7RwEb/+QeX9enkXhxn +rxfdqrvWd1K80sl2TOt8Bg/NYwrUBw/RWJ+sg/hhHp4WtvE1HDGHlkEz3y11Lkuh +8tSxS3qKTxXUGozyPGuE90sJfExhZlW4knIQ1wt/yWqM+33E9pN4hzPqLwyrdods +q8FWEqPPUbSJXoMbRPw04S5jrLtZSsUWbRYjmJCHzlhSfFWW4eFd37uquIaLUBS0 +rkC3Jrx7420jkIpgFcTI2s60uhSQLzgcCwdA2ukSYIRnjg/zDkj8+3h/GaROJ72x +lZyI6HWixKJkWw8lE9aAOD9TmTW9sFJwcVAzmAuFX2kUreDUKMZduGcoRYGpD7E= +=jpXa +-----END PGP SIGNATURE----- +---- + +- verify with: `git verify-tag [-v]` or `git tag -v` + +---- +gpg: Signature made Wed Jun 15 10:56:46 2016 CEST using RSA key ID B7227189 +gpg: Good signature from "Eris Discordia <discord@example.net>" +gpg: WARNING: This key is not certified with a trusted signature! +gpg: There is no indication that the signature belongs to the owner. +Primary key fingerprint: D4BE 2231 1AD3 131E 5EDA 29A4 6109 2E85 B722 7189 +object 04b871796dc0420f8e7561a895b52484b701d51a +type commit +tag signedtag +tagger C O Mitter <committer@example.com> 1465981006 +0000 + +signed tag + +signed tag message body +---- + +== Commit signatures + +- created by: `git commit -S` +- payload: commit object +- embedding: header entry `gpgsig` + (content is preceded by a space) +- example: commit with subject `signed commit` + +---- +tree eebfed94e75e7760540d1485c740902590a00332 +parent 04b871796dc0420f8e7561a895b52484b701d51a +author A U Thor <author@example.com> 1465981137 +0000 +committer C O Mitter <committer@example.com> 1465981137 +0000 +gpgsig -----BEGIN PGP SIGNATURE----- + Version: GnuPG v1 + + iQEcBAABAgAGBQJXYRjRAAoJEGEJLoW3InGJ3IwIAIY4SA6GxY3BjL60YyvsJPh/ + HRCJwH+w7wt3Yc/9/bW2F+gF72kdHOOs2jfv+OZhq0q4OAN6fvVSczISY/82LpS7 + DVdMQj2/YcHDT4xrDNBnXnviDO9G7am/9OE77kEbXrp7QPxvhjkicHNwy2rEflAA + zn075rtEERDHr8nRYiDh8eVrefSO7D+bdQ7gv+7GsYMsd2auJWi1dHOSfTr9HIF4 + HJhWXT9d2f8W+diRYXGh4X0wYiGg6na/soXc+vdtDYBzIxanRqjg8jCAeo1eOTk1 + EdTwhcTZlI0x5pvJ3H0+4hA2jtldVtmPM4OTB0cTrEWBad7XV6YgiyuII73Ve3I= + =jKHM + -----END PGP SIGNATURE----- + +signed commit + +signed commit message body +---- + +- verify with: `git verify-commit [-v]` (or `git show --show-signature`) + +---- +gpg: Signature made Wed Jun 15 10:58:57 2016 CEST using RSA key ID B7227189 +gpg: Good signature from "Eris Discordia <discord@example.net>" +gpg: WARNING: This key is not certified with a trusted signature! +gpg: There is no indication that the signature belongs to the owner. +Primary key fingerprint: D4BE 2231 1AD3 131E 5EDA 29A4 6109 2E85 B722 7189 +tree eebfed94e75e7760540d1485c740902590a00332 +parent 04b871796dc0420f8e7561a895b52484b701d51a +author A U Thor <author@example.com> 1465981137 +0000 +committer C O Mitter <committer@example.com> 1465981137 +0000 + +signed commit + +signed commit message body +---- + +== Mergetag signatures + +- created by: `git merge` on signed tag +- payload/embedding: the whole signed tag object is embedded into + the (merge) commit object as header entry `mergetag` +- example: merge of the signed tag `signedtag` as above + +---- +tree c7b1cff039a93f3600a1d18b82d26688668c7dea +parent c33429be94b5f2d3ee9b0adad223f877f174b05d +parent 04b871796dc0420f8e7561a895b52484b701d51a +author A U Thor <author@example.com> 1465982009 +0000 +committer C O Mitter <committer@example.com> 1465982009 +0000 +mergetag object 04b871796dc0420f8e7561a895b52484b701d51a + type commit + tag signedtag + tagger C O Mitter <committer@example.com> 1465981006 +0000 + + signed tag + + signed tag message body + -----BEGIN PGP SIGNATURE----- + Version: GnuPG v1 + + iQEcBAABAgAGBQJXYRhOAAoJEGEJLoW3InGJklkIAIcnhL7RwEb/+QeX9enkXhxn + rxfdqrvWd1K80sl2TOt8Bg/NYwrUBw/RWJ+sg/hhHp4WtvE1HDGHlkEz3y11Lkuh + 8tSxS3qKTxXUGozyPGuE90sJfExhZlW4knIQ1wt/yWqM+33E9pN4hzPqLwyrdods + q8FWEqPPUbSJXoMbRPw04S5jrLtZSsUWbRYjmJCHzlhSfFWW4eFd37uquIaLUBS0 + rkC3Jrx7420jkIpgFcTI2s60uhSQLzgcCwdA2ukSYIRnjg/zDkj8+3h/GaROJ72x + lZyI6HWixKJkWw8lE9aAOD9TmTW9sFJwcVAzmAuFX2kUreDUKMZduGcoRYGpD7E= + =jpXa + -----END PGP SIGNATURE----- + +Merge tag 'signedtag' into downstream + +signed tag + +signed tag message body + +# gpg: Signature made Wed Jun 15 08:56:46 2016 UTC using RSA key ID B7227189 +# gpg: Good signature from "Eris Discordia <discord@example.net>" +# gpg: WARNING: This key is not certified with a trusted signature! +# gpg: There is no indication that the signature belongs to the owner. +# Primary key fingerprint: D4BE 2231 1AD3 131E 5EDA 29A4 6109 2E85 B722 7189 +---- + +- verify with: verification is embedded in merge commit message by default, + alternatively with `git show --show-signature`: + +---- +commit 9863f0c76ff78712b6800e199a46aa56afbcbd49 +merged tag 'signedtag' +gpg: Signature made Wed Jun 15 10:56:46 2016 CEST using RSA key ID B7227189 +gpg: Good signature from "Eris Discordia <discord@example.net>" +gpg: WARNING: This key is not certified with a trusted signature! +gpg: There is no indication that the signature belongs to the owner. +Primary key fingerprint: D4BE 2231 1AD3 131E 5EDA 29A4 6109 2E85 B722 7189 +Merge: c33429b 04b8717 +Author: A U Thor <author@example.com> +Date: Wed Jun 15 09:13:29 2016 +0000 + + Merge tag 'signedtag' into downstream + + signed tag + + signed tag message body + + # gpg: Signature made Wed Jun 15 08:56:46 2016 UTC using RSA key ID B7227189 + # gpg: Good signature from "Eris Discordia <discord@example.net>" + # gpg: WARNING: This key is not certified with a trusted signature! + # gpg: There is no indication that the signature belongs to the owner. + # Primary key fingerprint: D4BE 2231 1AD3 131E 5EDA 29A4 6109 2E85 B722 7189 +---- |