git commit --gpg-sign =< key-id>`时，什么数据正在签名？ [英] What data is being signed when you `git commit --gpg-sign=<key-id>`?

问题描述

我试图弄清楚如何手动签署/验证提交，但我无法弄清楚签署什么数据来创建签名。换句话说，我无法弄清楚 gpg中的< data> --verify< commit-sig> < data> 需要。

以下是相关的git源代码： https://github.com/git/git/blob/master/commit.c#L1047-L1231 但我是对于C也是新的。

---

以下是一些示例数据：

在一个新的git仓库中，我创建了一个文件 ledger.txt ，并提交了一个签名的提交：

  git config --global user.signingkey 7E482429 
 git init 
 echoEAC5-531F-38E8-9670-81AE-4E77-C7AA -5FC3-7E48-2429 1 \\\
> ledger.txt 
 git add ledger.txt 
 git commit -m初始提交--gpg-sign = 7E482429 
  

这里是在日志中：

$ b

  git日志--show-signature 
 
 commit 876793da21833b5b8197b08462523fd6aad3e5ba 
 gpg：使用RSA密钥ID签署5月9日20:01:55 2014 CDT签名7E482429 
 gpg：Dan Neumann< [e-mail]> 
作者：Dan Neumann< [e-mail]> 
日期：星期五5月9日20:01:55 2014 -0500 
 
初始提交
  

以下是漂亮的提交对象（位于 .git / objects / 87 / 6793da21833b5b8197b08462523fd6aad3e5ba 中）：

git cat-file -p 876793da21833b5b8197b08462523fd6aad3e5ba

tree 70e7c184c3a89c749174b4987830c287fd78952d
作者Dan Neumann< danrodneu @ gmail .COM> 1399683715 -0500
提交者Dan Neumann< [e-mail]> 1399683715 -0500
gpgsig ----- BEGIN PGP SIGNATURE -----
版本：GnuPG v1

iQEcBAABAgAGBQJTbXqDAAoJEMeqX8N + SCQpTBIH / 3zCpf0w0 + xp8hkwz7dTV9Bw
ercZp4UpxKV1HgqCxu2r / nGIuZyabLwTis1rcwXOVC4DgRxO0f2BiP0xnyL3OhJu
CKh8l + HZvvGqVH3Dopm0D / kOxDAWHcjokbyzWBbYJX6WhvT8OI7SSYmwuF4r610h
hkZ1xgjo4p1x9WegY296PzA1wEe6yy9BvvdIpJHoqBVKClgFrZvtE5PidbrAyLGF
吉隆坡/ 2f0K3peBdo6XP0Zaml8NyQlFmAlCV831hHgUmZsBSRpgh / WNvrDSNILTlFJgY
BOPb2yPP + tiJOXYB66MsjQY9GlX7n43miu5wMtdk1AGqh + 26OExbSrZcYVFLk4w =
= SREE
----- END PGP SIGNATURE -----

初始提交


这里是提交对象文件的实际内容：

  hexdump .git / objects / 87 / 6793da21833b5b8197b08462523fd6aad3e5ba | \ 
 zlib-decompress | \ 
 bin-to-ascii 
 
 commit 671\tree 70e7c184c3a89c749174b4987830c287fd78952d\\\
author Dan Neumann< [e-mail]> 1399683715 -0500 \ ncommitter Dan Neumann< [e-mail]> 1399683715 -0500\\\
gpgsig ----- BEGIN PGP SIGNATURE ----- \\\
版本：GnuPG的v1\\\
 \\\
 iQEcBAABAgAGBQJTbXqDAAoJEMeqX8N + SCQpTBIH / 3zCpf0w0 + xp8hkwz7dTV9Bw\\\
 ercZp4UpxKV1HgqCxu2r / nGIuZyabLwTis1rcwXOVC4DgRxO0f2BiP0xnyL3OhJu\\\
 CKh8l + HZvvGqVH3Dopm0D / kOxDAWHcjokbyzWBbYJX6WhvT8OI7SSYmwuF4r610h\\\
 hkZ1xgjo4p1x9WegY296PzA1wEe6yy9BvvdIpJHoqBVKClgFrZvtE5PidbrAyLGF\\\
吉隆坡/ 2f0K3peBdo6XP0Zaml8NyQlFmAlCV831hHgUmZsBSRpgh / WNvrDSNILTlFJgY\\\
 BOPb2yPP + tiJOXYB66MsjQY9GlX7n43miu5wMtdk1AGqh + 26OExbSrZcYVFLk4w = \\\
 = sRee\\\
 ----- END PGP SIGNATURE ----- \\\
\ nInitial commit\\\
 
  

解决方案

strong> commit_tree_extended ，似乎用于签名的数据是从树到注释结尾的部分，当然不包括签名。在你的例子中，它应该是：
$ b

  tree 70e7c184c3a89c749174b49 87830c287fd78952d 
作者Dan Neumann< [e-mail]> 1399683715 -0500 
提交者Dan Neumann< [e-mail]> 1399683715 -0500 
初始提交
  

来自git源码：

初始化缓冲区：

  strbuf_init（& buffer，8192）; / *应该避免为头文件重新分配* / 
 strbuf_addf（& buffer，tree％s \ n，sha1_to_hex（tree））; 
  

父提交遍历：

  / * 
 *注意！这种排序意味着，如果一切都保持不变，那么与父母的
 *不同顺序合并的相同的确切树会是一个_different_变更集，甚至是
 *。 
 * / 
 while（parents）{
 struct commit_list * next = parents-> next; 
 struct commit * parent = parents-> item; 
 
 strbuf_addf（& buffer，parent％s \ n，
 sha1_to_hex（parent-> object.sha1））; 
免费（父母）; 
父母=下一个; 
 
  

个人/日期信息：

  if（！author）
 author = git_author_info（IDENT_STRICT）; 
 strbuf_addf（& buffer，author％s \ n，author）; 
 strbuf_addf（& buffer，committer％s \\\
，git_committer_info（IDENT_STRICT））; 
 if（！encoding_is_utf8）
 strbuf_addf（& buffer，encoding％s\\\
，git_commit_encoding）; 
 
 while（extra）{
 add_extra_header（& buffer，extra）; 
 extra = extra-> next; 
} 
 strbuf_addch（& buffer，'\\\
'）; 
  

评论&编码检查：

  / *并添加注释* / 
 strbuf_addbuf（& buffer，msg）;如果（encoding_is_utf8&&！verify_utf8（& buffer））
 fprintf（stderr，commit_utf8_warn）;则检查编码* / 
; 
  

这就是签名发生的地方。
$ b

  if（sign_commit&& do_sign_commit（& buffer，sign_commit））
返回-1; 
  

如果您的提交有一些信息，也会有父母信息。

I'm trying to figure out how to sign/verify commits by hand, but I can't figure out what data is being signed to create the signature. In other words, I can't figure out what <data> in gpg --verify <commit-sig> <data> needs to be.

Here's the relevant bit of git's source code: https://github.com/git/git/blob/master/commit.c#L1047-L1231 but I'm also new to C.

---

Here's some example data:

In a fresh git repo, I create a file ledger.txt and commit it with a signed commit:

git config --global user.signingkey 7E482429
git init
echo "EAC5-531F-38E8-9670-81AE-4E77-C7AA-5FC3-7E48-2429 1\n" > ledger.txt
git add ledger.txt
git commit -m "Initial commit" --gpg-sign=7E482429

And here it is in the log:

git log --show-signature

    commit 876793da21833b5b8197b08462523fd6aad3e5ba
    gpg: Signature made Fri May  9 20:01:55 2014 CDT using RSA key ID 7E482429
    gpg: Good signature from "Dan Neumann <[e-mail]>"
    Author: Dan Neumann <[e-mail]>
    Date:   Fri May 9 20:01:55 2014 -0500

        Initial commit

Here's the pretty-printed commit object (which lives in .git/objects/87/6793da21833b5b8197b08462523fd6aad3e5ba):

git cat-file -p 876793da21833b5b8197b08462523fd6aad3e5ba

tree 70e7c184c3a89c749174b4987830c287fd78952d
author Dan Neumann <[e-mail]> 1399683715 -0500
committer Dan Neumann <[e-mail]> 1399683715 -0500
gpgsig -----BEGIN PGP SIGNATURE-----
 Version: GnuPG v1

 iQEcBAABAgAGBQJTbXqDAAoJEMeqX8N+SCQpTBIH/3zCpf0w0+xp8hkwz7dTV9Bw
 ercZp4UpxKV1HgqCxu2r/nGIuZyabLwTis1rcwXOVC4DgRxO0f2BiP0xnyL3OhJu
 CKh8l+HZvvGqVH3Dopm0D/kOxDAWHcjokbyzWBbYJX6WhvT8OI7SSYmwuF4r610h
 hkZ1xgjo4p1x9WegY296PzA1wEe6yy9BvvdIpJHoqBVKClgFrZvtE5PidbrAyLGF
 Kl/2f0K3peBdo6XP0Zaml8NyQlFmAlCV831hHgUmZsBSRpgh/WNvrDSNILTlFJgY
 BOPb2yPP+tiJOXYB66MsjQY9GlX7n43miu5wMtdk1AGqh+26OExbSrZcYVFLk4w=
 =sRee
 -----END PGP SIGNATURE-----

Initial commit

And here are the actual contents of the commit object file:

hexdump .git/objects/87/6793da21833b5b8197b08462523fd6aad3e5ba | \
zlib-decompress | \
bin-to-ascii

commit 671\0tree 70e7c184c3a89c749174b4987830c287fd78952d\nauthor Dan Neumann <[e-mail]> 1399683715 -0500\ncommitter Dan Neumann <[e-mail]> 1399683715 -0500\ngpgsig -----BEGIN PGP SIGNATURE-----\n Version: GnuPG v1\n \n iQEcBAABAgAGBQJTbXqDAAoJEMeqX8N+SCQpTBIH/3zCpf0w0+xp8hkwz7dTV9Bw\n ercZp4UpxKV1HgqCxu2r/nGIuZyabLwTis1rcwXOVC4DgRxO0f2BiP0xnyL3OhJu\n CKh8l+HZvvGqVH3Dopm0D/kOxDAWHcjokbyzWBbYJX6WhvT8OI7SSYmwuF4r610h\n hkZ1xgjo4p1x9WegY296PzA1wEe6yy9BvvdIpJHoqBVKClgFrZvtE5PidbrAyLGF\n Kl/2f0K3peBdo6XP0Zaml8NyQlFmAlCV831hHgUmZsBSRpgh/WNvrDSNILTlFJgY\n BOPb2yPP+tiJOXYB66MsjQY9GlX7n43miu5wMtdk1AGqh+26OExbSrZcYVFLk4w=\n =sRee\n -----END PGP SIGNATURE-----\n\nInitial commit\n

解决方案

After reading the code in commit_tree_extended, it seems the data used to sign is the part from "tree" to the end of the comment, of course excluding the signature.

In your example, it should be:

tree 70e7c184c3a89c749174b4987830c287fd78952d
author Dan Neumann <[e-mail]> 1399683715 -0500
committer Dan Neumann <[e-mail]> 1399683715 -0500
Initial commit

From the git source:

Init of buffer:

strbuf_init(&buffer, 8192); /* should avoid reallocs for the headers */
strbuf_addf(&buffer, "tree %s\n", sha1_to_hex(tree));

Parent commits traversing:

/*
* NOTE! This ordering means that the same exact tree merged with a
* different order of parents will be a _different_ changeset even
* if everything else stays the same.
*/
while (parents) {
    struct commit_list *next = parents->next;
    struct commit *parent = parents->item;

    strbuf_addf(&buffer, "parent %s\n",
    sha1_to_hex(parent->object.sha1));
    free(parents);
    parents = next;
}

Person/date information:

if (!author)
    author = git_author_info(IDENT_STRICT);
strbuf_addf(&buffer, "author %s\n", author);
strbuf_addf(&buffer, "committer %s\n", git_committer_info(IDENT_STRICT));
if (!encoding_is_utf8)
    strbuf_addf(&buffer, "encoding %s\n", git_commit_encoding);

while (extra) {
    add_extra_header(&buffer, extra);
    extra = extra->next;
}
strbuf_addch(&buffer, '\n');

The comment & encoding check:

/* And add the comment */
strbuf_addbuf(&buffer, msg);

/* And check the encoding */
if (encoding_is_utf8 && !verify_utf8(&buffer))
    fprintf(stderr, commit_utf8_warn);

That's where the signing happens. Signature will be added after the header.

if (sign_commit && do_sign_commit(&buffer, sign_commit))
    return -1;

There would be parent information too if your commit had some.

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