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| author | shejialuo <shejialuo@gmail.com> | 2025-02-28 00:07:00 +0800 |
|---|---|---|
| committer | Junio C Hamano <gitster@pobox.com> | 2025-02-27 14:03:08 -0800 |
| commit | 5637d5542021294e81cf0d8344fe140368117296 (patch) | |
| tree | 5a7220372947d809cd175661b2cc47234bc0c700 /refs | |
| parent | c92e7e156e6b406e7555fb5df058d18758a0b3f0 (diff) | |
| download | git-5637d5542021294e81cf0d8344fe140368117296.tar.gz | |
packed-backend: check whether the refname contains NUL characters
"packed-backend.c::next_record" will use "check_refname_format" to check
the consistency of the refname. If it is not OK, the program will die.
However, it is reported in [1], we cannot catch some corruption. But we
already have the code path and we must miss out something.
We use the following code to get the refname:
strbuf_add(&iter->refname_buf, p, eol - p);
iter->base.refname = iter->refname_buf.buf
In the above code, `p` is the start pointer of the refname and `eol` is
the next newline pointer. We calculate the length of the refname by
subtracting the two pointers. Then we add the memory range between `p`
and `eol` to get the refname.
However, if there are some NUL characters in the memory range between `p`
and `eol`, we will see the refname as a valid ref name as long as the
memory range between `p` and first occurred NUL character is valid.
In order to catch above corruption, create a new function
"refname_contains_nul" by searching the first NUL character. If it is
not at the end of the string, there must be some NUL characters in the
refname.
Use this function in "next_record" function to die the program if
"refname_contains_nul" returns true.
[1] https://lore.kernel.org/git/6cfee0e4-3285-4f18-91ff-d097da9de737@rd10.de/
Reported-by: R. Diez <rdiez-temp3@rd10.de>
Mentored-by: Patrick Steinhardt <ps@pks.im>
Mentored-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: shejialuo <shejialuo@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'refs')
| -rw-r--r-- | refs/packed-backend.c | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/refs/packed-backend.c b/refs/packed-backend.c index 07154bccae..9a90c52f70 100644 --- a/refs/packed-backend.c +++ b/refs/packed-backend.c @@ -494,6 +494,21 @@ static void verify_buffer_safe(struct snapshot *snapshot) last_line, eof - last_line); } +/* + * When parsing the "packed-refs" file, we will parse it line by line. + * Because we know the start pointer of the refname and the next + * newline pointer, we could calculate the length of the refname by + * subtracting the two pointers. However, there is a corner case where + * the refname contains corrupted embedded NUL characters. And + * `check_refname_format()` will not catch this when the truncated + * refname is still a valid refname. To prevent this, we need to check + * whether the refname contains the NUL characters. + */ +static int refname_contains_nul(struct strbuf *refname) +{ + return !!memchr(refname->buf, '\0', refname->len); +} + #define SMALL_FILE_SIZE (32*1024) /* @@ -895,6 +910,9 @@ static int next_record(struct packed_ref_iterator *iter) strbuf_add(&iter->refname_buf, p, eol - p); iter->base.refname = iter->refname_buf.buf; + if (refname_contains_nul(&iter->refname_buf)) + die("packed refname contains embedded NULL: %s", iter->base.refname); + if (check_refname_format(iter->base.refname, REFNAME_ALLOW_ONELEVEL)) { if (!refname_is_safe(iter->base.refname)) die("packed refname is dangerous: %s", |