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hash-object --literally: fix buffer overrun with extra-long object type

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"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>
This commit is contained in:
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
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@ -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;
}