[PATCH 2/4] write_sha1_file_prepare: fix buffer overrun with extra-long object type
- From
Junio C Hamano <gitster@pobox.com>
- Date
- May 4, 2015, 21:37 UTC
- Message-ID
- <1430775451-31130-3-git-send-email-gitster@pobox.com>
- In-Reply-To
- <1430775451-31130-1-git-send-email-gitster@pobox.com>
From: Eric Sunshine <sunshine@sunshineco.com>
git-hash-object learned --literally in 5ba9a93 (hash-object: add --literally option, 2014-09-11) which can be used to craft a corrupt/broken object of unknown type.
When the user-provided type is particularly long, however, it can overflow the relatively small stack-based character array handed to write_sha1_file_prepare() by hash_sha1_file() and write_sha1_file(), leading to stack corruption (and crash).
Signed-off-by: Eric Sunshine <sunshine@sunshineco.com> Signed-off-by: Junio C Hamano <gitster@pobox.com> ---
* Tweaked and backported directly on top of 5ba9a93b (hash-object: add --literally option, 2014-09-11) which is v2.2.0-rc0~88^2
builtin/hash-object.c | 4 +--- cache.h | 1 + sha1_file.c | 27 ++++++++++++++++++++++++++- 3 files changed, 28 insertions(+), 4 deletions(-)
diff --git a/builtin/hash-object.c b/builtin/hash-object.c index 6158363..887a8ea 100644 --- a/builtin/hash-object.c +++ b/builtin/hash-object.c @@ -22,10 +22,8 @@ static int hash_literally(unsigned char *sha1, int fd, const char *type, unsigne if (strbuf_read(&buf, fd, 4096) < 0) ret = -1; - else if (flags & HASH_WRITE_OBJECT) - ret = write_sha1_file(buf.buf, buf.len, type, sha1); else - ret = hash_sha1_file(buf.buf, buf.len, type, sha1); + ret = hash_sha1_file_literally(&buf, type, sha1, flags); strbuf_release(&buf); return ret; } diff --git a/cache.h b/cache.h index dfa1a56..2da7740 100644 --- a/cache.h +++ b/cache.h @@ -888,6 +888,7 @@ static inline const unsigned char *lookup_replace_object_extended(const unsigned extern int sha1_object_info(const unsigned char *, unsigned long *); extern int hash_sha1_file(const void *buf, unsigned long len, const char *type, unsigned char *sha1); extern int write_sha1_file(const void *buf, unsigned long len, const char *type, unsigned char *return_sha1); +extern int hash_sha1_file_literally(struct strbuf *buf, const char *type, unsigned char *return_sha1, unsigned flags); extern int pretend_sha1_file(void *, unsigned long, enum object_type, unsigned char *); extern int force_object_loose(const unsigned char *sha1, time_t mtime); extern int git_open_noatime(const char *name); diff --git a/sha1_file.c b/sha1_file.c index c08c0cb..0fe3f29 100644 --- a/sha1_file.c +++ b/sha1_file.c @@ -2962,6 +2962,31 @@ int write_sha1_file(const void *buf, unsigned long len, const char *type, unsign return write_loose_object(sha1, hdr, hdrlen, buf, len, 0); } +int hash_sha1_file_literally(struct strbuf *buf, const char *type, + unsigned char *sha1, unsigned flags) +{ + struct strbuf header = STRBUF_INIT; + int hdrlen, status = 0; + + /* type string, SP, %lu of the length plus NUL must fit this */ + strbuf_grow(&header, strlen(type) + 20); + + write_sha1_file_prepare(buf->buf, buf->len, type, sha1, + header.buf, &hdrlen); + + if (!(flags & HASH_WRITE_OBJECT)) + goto cleanup; + + if (has_sha1_file(sha1)) + goto cleanup; + status = write_loose_object(sha1, header.buf, hdrlen, + buf->buf, buf->len, 0); + +cleanup: + strbuf_release(&header); + return status; +} + int force_object_loose(const unsigned char *sha1, time_t mtime) { void *buf;
-- 2.4.0-302-g6743426