Documentation/technical/signature-format.txt

   1 Git signature format
   2 ====================
   3
   4 == Overview
   5
   6 Git uses cryptographic signatures in various places, currently objects (tags,
   7 commits, mergetags) and transactions (pushes). In every case, the command which
   8 is about to create an object or transaction determines a payload from that,
   9 calls gpg to obtain a detached signature for the payload (`gpg -bsa`) and
  10 embeds the signature into the object or transaction.
  11
  12 Signatures always begin with `-----BEGIN PGP SIGNATURE-----`
  13 and end with `-----END PGP SIGNATURE-----`, unless gpg is told to
  14 produce RFC1991 signatures which use `MESSAGE` instead of `SIGNATURE`.
  15
  16 The signed payload and the way the signature is embedded depends
  17 on the type of the object resp. transaction.
  18
  19 == Tag signatures
  20
  21 - created by: `git tag -s`
  22 - payload: annotated tag object
  23 - embedding: append the signature to the unsigned tag object
  24 - example: tag `signedtag` with subject `signed tag`
  25
  26 ----
  27 object 04b871796dc0420f8e7561a895b52484b701d51a
  28 type commit
  29 tag signedtag
  30 tagger C O Mitter <committer@example.com> 1465981006 +0000
  31
  32 signed tag
  33
  34 signed tag message body
  35 -----BEGIN PGP SIGNATURE-----
  36 Version: GnuPG v1
  37
  38 iQEcBAABAgAGBQJXYRhOAAoJEGEJLoW3InGJklkIAIcnhL7RwEb/+QeX9enkXhxn
  39 rxfdqrvWd1K80sl2TOt8Bg/NYwrUBw/RWJ+sg/hhHp4WtvE1HDGHlkEz3y11Lkuh
  40 8tSxS3qKTxXUGozyPGuE90sJfExhZlW4knIQ1wt/yWqM+33E9pN4hzPqLwyrdods
  41 q8FWEqPPUbSJXoMbRPw04S5jrLtZSsUWbRYjmJCHzlhSfFWW4eFd37uquIaLUBS0
  42 rkC3Jrx7420jkIpgFcTI2s60uhSQLzgcCwdA2ukSYIRnjg/zDkj8+3h/GaROJ72x
  43 lZyI6HWixKJkWw8lE9aAOD9TmTW9sFJwcVAzmAuFX2kUreDUKMZduGcoRYGpD7E=
  44 =jpXa
  45 -----END PGP SIGNATURE-----
  46 ----
  47
  48 - verify with: `git verify-tag [-v]` or `git tag -v`
  49
  50 ----
  51 gpg: Signature made Wed Jun 15 10:56:46 2016 CEST using RSA key ID B7227189
  52 gpg: Good signature from "Eris Discordia <discord@example.net>"
  53 gpg: WARNING: This key is not certified with a trusted signature!
  54 gpg:          There is no indication that the signature belongs to the owner.
  55 Primary key fingerprint: D4BE 2231 1AD3 131E 5EDA  29A4 6109 2E85 B722 7189
  56 object 04b871796dc0420f8e7561a895b52484b701d51a
  57 type commit
  58 tag signedtag
  59 tagger C O Mitter <committer@example.com> 1465981006 +0000
  60
  61 signed tag
  62
  63 signed tag message body
  64 ----
  65
  66 == Commit signatures
  67
  68 - created by: `git commit -S`
  69 - payload: commit object
  70 - embedding: header entry `gpgsig`
  71   (content is preceded by a space)
  72 - example: commit with subject `signed commit`
  73
  74 ----
  75 tree eebfed94e75e7760540d1485c740902590a00332
  76 parent 04b871796dc0420f8e7561a895b52484b701d51a
  77 author A U Thor <author@example.com> 1465981137 +0000
  78 committer C O Mitter <committer@example.com> 1465981137 +0000
  79 gpgsig -----BEGIN PGP SIGNATURE-----
  80  Version: GnuPG v1
  81
  82  iQEcBAABAgAGBQJXYRjRAAoJEGEJLoW3InGJ3IwIAIY4SA6GxY3BjL60YyvsJPh/
  83  HRCJwH+w7wt3Yc/9/bW2F+gF72kdHOOs2jfv+OZhq0q4OAN6fvVSczISY/82LpS7
  84  DVdMQj2/YcHDT4xrDNBnXnviDO9G7am/9OE77kEbXrp7QPxvhjkicHNwy2rEflAA
  85  zn075rtEERDHr8nRYiDh8eVrefSO7D+bdQ7gv+7GsYMsd2auJWi1dHOSfTr9HIF4
  86  HJhWXT9d2f8W+diRYXGh4X0wYiGg6na/soXc+vdtDYBzIxanRqjg8jCAeo1eOTk1
  87  EdTwhcTZlI0x5pvJ3H0+4hA2jtldVtmPM4OTB0cTrEWBad7XV6YgiyuII73Ve3I=
  88  =jKHM
  89  -----END PGP SIGNATURE-----
  90
  91 signed commit
  92
  93 signed commit message body
  94 ----
  95
  96 - verify with: `git verify-commit [-v]` (or `git show --show-signature`)
  97
  98 ----
  99 gpg: Signature made Wed Jun 15 10:58:57 2016 CEST using RSA key ID B7227189
 100 gpg: Good signature from "Eris Discordia <discord@example.net>"
 101 gpg: WARNING: This key is not certified with a trusted signature!
 102 gpg:          There is no indication that the signature belongs to the owner.
 103 Primary key fingerprint: D4BE 2231 1AD3 131E 5EDA  29A4 6109 2E85 B722 7189
 104 tree eebfed94e75e7760540d1485c740902590a00332
 105 parent 04b871796dc0420f8e7561a895b52484b701d51a
 106 author A U Thor <author@example.com> 1465981137 +0000
 107 committer C O Mitter <committer@example.com> 1465981137 +0000
 108
 109 signed commit
 110
 111 signed commit message body
 112 ----
 113
 114 == Mergetag signatures
 115
 116 - created by: `git merge` on signed tag
 117 - payload/embedding: the whole signed tag object is embedded into
 118   the (merge) commit object as header entry `mergetag`
 119 - example: merge of the signed tag `signedtag` as above
 120
 121 ----
 122 tree c7b1cff039a93f3600a1d18b82d26688668c7dea
 123 parent c33429be94b5f2d3ee9b0adad223f877f174b05d
 124 parent 04b871796dc0420f8e7561a895b52484b701d51a
 125 author A U Thor <author@example.com> 1465982009 +0000
 126 committer C O Mitter <committer@example.com> 1465982009 +0000
 127 mergetag object 04b871796dc0420f8e7561a895b52484b701d51a
 128  type commit
 129  tag signedtag
 130  tagger C O Mitter <committer@example.com> 1465981006 +0000
 131
 132  signed tag
 133
 134  signed tag message body
 135  -----BEGIN PGP SIGNATURE-----
 136  Version: GnuPG v1
 137
 138  iQEcBAABAgAGBQJXYRhOAAoJEGEJLoW3InGJklkIAIcnhL7RwEb/+QeX9enkXhxn
 139  rxfdqrvWd1K80sl2TOt8Bg/NYwrUBw/RWJ+sg/hhHp4WtvE1HDGHlkEz3y11Lkuh
 140  8tSxS3qKTxXUGozyPGuE90sJfExhZlW4knIQ1wt/yWqM+33E9pN4hzPqLwyrdods
 141  q8FWEqPPUbSJXoMbRPw04S5jrLtZSsUWbRYjmJCHzlhSfFWW4eFd37uquIaLUBS0
 142  rkC3Jrx7420jkIpgFcTI2s60uhSQLzgcCwdA2ukSYIRnjg/zDkj8+3h/GaROJ72x
 143  lZyI6HWixKJkWw8lE9aAOD9TmTW9sFJwcVAzmAuFX2kUreDUKMZduGcoRYGpD7E=
 144  =jpXa
 145  -----END PGP SIGNATURE-----
 146
 147 Merge tag 'signedtag' into downstream
 148
 149 signed tag
 150
 151 signed tag message body
 152
 153 # gpg: Signature made Wed Jun 15 08:56:46 2016 UTC using RSA key ID B7227189
 154 # gpg: Good signature from "Eris Discordia <discord@example.net>"
 155 # gpg: WARNING: This key is not certified with a trusted signature!
 156 # gpg:          There is no indication that the signature belongs to the owner.
 157 # Primary key fingerprint: D4BE 2231 1AD3 131E 5EDA  29A4 6109 2E85 B722 7189
 158 ----
 159
 160 - verify with: verification is embedded in merge commit message by default,
 161   alternatively with `git show --show-signature`:
 162
 163 ----
 164 commit 9863f0c76ff78712b6800e199a46aa56afbcbd49
 165 merged tag 'signedtag'
 166 gpg: Signature made Wed Jun 15 10:56:46 2016 CEST using RSA key ID B7227189
 167 gpg: Good signature from "Eris Discordia <discord@example.net>"
 168 gpg: WARNING: This key is not certified with a trusted signature!
 169 gpg:          There is no indication that the signature belongs to the owner.
 170 Primary key fingerprint: D4BE 2231 1AD3 131E 5EDA  29A4 6109 2E85 B722 7189
 171 Merge: c33429b 04b8717
 172 Author: A U Thor <author@example.com>
 173 Date:   Wed Jun 15 09:13:29 2016 +0000
 174
 175     Merge tag 'signedtag' into downstream
 176
 177     signed tag
 178
 179     signed tag message body
 180
 181     # gpg: Signature made Wed Jun 15 08:56:46 2016 UTC using RSA key ID B7227189
 182     # gpg: Good signature from "Eris Discordia <discord@example.net>"
 183     # gpg: WARNING: This key is not certified with a trusted signature!
 184     # gpg:          There is no indication that the signature belongs to the owner.
 185     # Primary key fingerprint: D4BE 2231 1AD3 131E 5EDA  29A4 6109 2E85 B722 7189
 186 ----