diff options
| author | aszlig <aszlig@redmoonstudios.org> | 2015-01-02 03:27:39 +0100 |
|---|---|---|
| committer | Eelco Dolstra <eelco.dolstra@logicblox.com> | 2015-01-02 12:53:42 +0100 |
| commit | bbd45ac80fa8ab80acd317ed8d5cc8b3448f7387 (patch) | |
| tree | 802f5a1f05916dcd31bcdd4421a9027f6972071b /src/libutil | |
| parent | 411b237ee55012b0f7b790ed509f4f4102a811ae (diff) | |
libutil: Improve errmsg on readLink size mismatch.
A message like "error: reading symbolic link `...' : Success" really is
quite confusing, so let's not indicate "success" but rather point out
the real issue.
We could also limit the check of this to just check for non-negative
values, but this would introduce a race condition between stat() and
readlink() if the link target changes between those two calls, thus
leading to a buffer overflow vulnerability.
Reported by @Ericson2314 on IRC. Happened due to a possible ntfs-3g bug
where a relative symlink returned the absolute path (st_)size in stat()
while readlink() returned the relative size.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
Tested-by: John Ericson <Ericson2314@Yahoo.com>
Diffstat (limited to 'src/libutil')
| -rw-r--r-- | src/libutil/util.cc | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/src/libutil/util.cc b/src/libutil/util.cc index dcdb438e0..879f9fb5f 100644 --- a/src/libutil/util.cc +++ b/src/libutil/util.cc @@ -193,8 +193,12 @@ Path readLink(const Path & path) if (!S_ISLNK(st.st_mode)) throw Error(format("‘%1%’ is not a symlink") % path); char buf[st.st_size]; - if (readlink(path.c_str(), buf, st.st_size) != st.st_size) + ssize_t rlsize = readlink(path.c_str(), buf, st.st_size); + if (rlsize == -1) throw SysError(format("reading symbolic link ‘%1%’") % path); + else if (rlsize != st.st_size) + throw Error(format("symbolic link ‘%1%’ size mismatch %2% != %3%") + % path % rlsize % st.st_size); return string(buf, st.st_size); } |