Object parsing hardening #3956
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Object parsing hardening #3956
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When parsing tree entries from raw object data, we do not verify that the tree entry actually has a filename as well as a valid object ID. Fix this by asserting that the filename length is non-zero as well as asserting that there are at least `GIT_OID_RAWSZ` bytes left when parsing the OID.
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By the way: is there some test logic for directly parsing raw objects? I didn't spot any while skimming the tests, but obviously it would be nice to have these fixes backed by some tests. |
| @@ -462,6 +462,9 @@ int git_commit__parse(void *_commit, git_odb_object *odb_obj) | |||
| if (buffer <= buffer_end) { | |||
| commit->raw_message = git__strndup(buffer, buffer_end - buffer); | |||
| GITERR_CHECK_ALLOC(commit->raw_message); | |||
| } else { | |||
| commit->raw_message = git__strdup(""); | |||
| GITERR_CHECK_ALLOC(commit->raw_message); | |||
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Tiny nitpick: This line could be moved beneath the if/else blocks.
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Yeah, agreed, realized the same after posting this PR. Will change
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Fixed. Thanks for your careful eyes
When parsing a commit, we will treat all bytes left after parsing the headers as the commit message. When no bytes are left, we leave the commit's message uninitialized. While uncommon to have a commit without message, this is the right behavior as Git unfortunately allows for empty commit messages. Given that this scenario is so uncommon, most programs acting on the commit message will never check if the message is actually set, which may lead to errors. To work around the error and not lay the burden of checking for empty commit messages to the developer, initialize the commit message with an empty string when no commit message is given.
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Thanks! |
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See the commit messages for more info. These commits fix #3936 and #3937. I bet there are more issues around here which I'd like to find. I think I'll try some more fuzzing with AFL around the object-parsing logic sometimes soon.