Re: [PATCH 2/4] write_sha1_file_prepare: fix buffer overrun with extra-long object type
- From
Junio C Hamano <gitster@pobox.com>
- Date
- May 5, 2015, 17:30 UTC
- Message-ID
- <xmqqvbg7dja6.fsf@gitster.dls.corp.google.com>
- In-Reply-To
- <CAPig+cS3f2XggxqbvX6Z2Da24QKLOg915Bf-bTVa+4oVzfhA1A@mail.gmail.com>
Eric Sunshine <sunshine@sunshineco.com> writes:
Show 7 quoted lines
> On Mon, May 4, 2015 at 5:37 PM, Junio C Hamano <gitster@pobox.com> wrote: >> From: Eric Sunshine <sunshine@sunshineco.com> > > Thanks for re-rerolling this series. Considering that the only bits > left from me are the diagnosis and the (mostly intact) commit message, > perhaps the authorship should be changed, or at the very least a big > "Helped-by: Junio" added? Anyhow, a few minor comments below...
I am a bit too lazy to take the ownership, so I decided only to take the blame ;-)
Here is a replacement; all the other patches stay the same.
-- >8 -- From: Eric Sunshine <sunshine@sunshineco.com> Date: Mon, 4 May 2015 03:25:15 -0400 Subject: [PATCH] hash-object --literally: fix buffer overrun with extra-long object type
"hash-object" learned in 5ba9a93 (hash-object: add --literally option, 2014-09-11) to allow crafting 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). Introduce a custom helper to allow arbitrarily long typenames just for "hash-object --literally".
[jc: Eric's original used a strbuf in the more common codepaths, and I rewrote it to avoid penalizing the non-literally code. Bugs are mine]
Signed-off-by: Eric Sunshine <sunshine@sunshineco.com> Signed-off-by: Junio C Hamano <gitster@pobox.com> --- builtin/hash-object.c | 4 +--- cache.h | 1 + sha1_file.c | 21 +++++++++++++++++++++ 3 files changed, 23 insertions(+), 3 deletions(-)
diff --git a/builtin/hash-object.c b/builtin/hash-object.c index 6158363..17e8bfdc 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.buf, buf.len, type, sha1, flags); strbuf_release(&buf); return ret; } diff --git a/cache.h b/cache.h index dfa1a56..e037cad 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(const void *buf, unsigned long len, const char *type, unsigned char *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..dc940e6 100644 --- a/sha1_file.c +++ b/sha1_file.c @@ -2962,6 +2962,27 @@ 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(const void *buf, unsigned long len, const char *type, + unsigned char *sha1, unsigned flags) +{ + char *header; + int hdrlen, status = 0; + + /* type string, SP, %lu of the length plus NUL must fit this */ + header = xmalloc(strlen(type) + 32); + write_sha1_file_prepare(buf, len, type, sha1, header, &hdrlen); + + if (!(flags & HASH_WRITE_OBJECT)) + goto cleanup; + if (has_sha1_file(sha1)) + goto cleanup; + status = write_loose_object(sha1, header, hdrlen, buf, len, 0); + +cleanup: + free(header); + return status; +} + int force_object_loose(const unsigned char *sha1, time_t mtime) { void *buf;
-- 2.4.0-311-gf1d9b8d