thodg/libgit2

2018-10-19T10:29:19

commit: fix reading out of bounds when parsing encoding The commit message encoding is currently being parsed by the `git__prefixcmp` function. As this function does not accept a buffer length, it will happily skip over a buffer's end if it is not `NUL` terminated. Fix the issue by using `git__prefixncmp` instead. Add a test that verifies that we are unable to parse the encoding field if it's cut off by the supplied buffer length. (cherry picked from commit 7655b2d89e8275853d9921dd903dcdad9b3d4a7b)

diff --git a/src/commit.c b/src/commit.c
index 838688b..8972c07 100644
--- a/src/commit.c
+++ b/src/commit.c
@@ -443,7 +443,7 @@ int git_commit__parse(void *_commit, git_odb_object *odb_obj)
 		while (eoln < buffer_end && *eoln != '\n')
 			++eoln;
 
-		if (git__prefixcmp(buffer, "encoding ") == 0) {
+		if (git__prefixncmp(buffer, buffer_end - buffer, "encoding ") == 0) {
 			buffer += strlen("encoding ");
 
 			commit->message_encoding = git__strndup(buffer, eoln - buffer);