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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>
maint
Eric Sunshine 2015-05-04 03:25:15 -04:00 committed by Junio C Hamano
parent 83115ac4a8
commit 0c3db67cc8
3 changed files with 23 additions and 3 deletions
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4
builtin/hash-object.c
View File

@ -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;
}

1
cache.h
View File

@ -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);

21
sha1_file.c
View File

@ -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;