diff options
author | Corinna Vinschen <corinna@vinschen.de> | 2020-07-06 14:17:53 +0300 |
---|---|---|
committer | Corinna Vinschen <corinna@vinschen.de> | 2020-07-06 14:17:53 +0300 |
commit | bb96bd03b0b9be5ed63127771687ac4877092ef8 (patch) | |
tree | c74823d22d8f7b9b96dd4e442f442b92a3503301 /winsup/cygwin/strfuncs.cc | |
parent | f095752167343ac10eeeba9007a84d51151aad3d (diff) |
Cygwin: fix buffer overrun in cygwin_strcasecmp
sys_mbstowcs is called with the destination buffer length
set to MaximumLength from the receiving UNICODE_STRING buffer.
This is twice as much as the actual size of the buffer in
wchar_t units, which is the unit expected by sys_mbstowcs.
sys_mbstowcs always attaches a NUL, within the destination
buffersize given. But if the string is exactly one wchar_t
less than the actual buffer, and the buffersize is given too
large, sys_mbstowcs writes a NUL one wchar_t beyond the buffer.
This has only been exposed with Cygwin 3.1.5 because alloca
on newer gcc 9 apparently allocates more tightly. The alloca
buffer here is requested with 16 bytes, which is exactly the
number of bytes required for the string L"cmd.exe". Older gcc
apparently allocated a few more bytes on the stack, while gcc 9
allocates in 16 byte granularity...
Fix this by giving the correct destination buffer size to
sys_mbstowcs.
Fixes: https://cygwin.com/pipermail/cygwin/2020-June/245226.html
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
Diffstat (limited to 'winsup/cygwin/strfuncs.cc')
-rw-r--r-- | winsup/cygwin/strfuncs.cc | 34 |
1 files changed, 20 insertions, 14 deletions
diff --git a/winsup/cygwin/strfuncs.cc b/winsup/cygwin/strfuncs.cc index e0a4c7182..604d7611c 100644 --- a/winsup/cygwin/strfuncs.cc +++ b/winsup/cygwin/strfuncs.cc @@ -635,7 +635,7 @@ sys_cp_mbstowcs (mbtowc_p f_mbtowc, wchar_t *dst, size_t dlen, /* The technique is based on a discussion here: http://www.mail-archive.com/linux-utf8@nl.linux.org/msg00080.html - Invalid bytes in a multibyte secuence are converted to + Invalid bytes in a multibyte sequence are converted to the private use area which is already used to store ASCII chars invalid in Windows filenames. This technque allows to store them in a symmetric way. */ @@ -801,14 +801,18 @@ extern "C" int __stdcall cygwin_strcasecmp (const char *cs, const char *ct) { UNICODE_STRING us, ut; - ULONG len; - - len = (strlen (cs) + 1) * sizeof (WCHAR); - RtlInitEmptyUnicodeString (&us, (PWCHAR) alloca (len), len); - us.Length = sys_mbstowcs (us.Buffer, us.MaximumLength, cs) * sizeof (WCHAR); - len = (strlen (ct) + 1) * sizeof (WCHAR); - RtlInitEmptyUnicodeString (&ut, (PWCHAR) alloca (len), len); - ut.Length = sys_mbstowcs (ut.Buffer, ut.MaximumLength, ct) * sizeof (WCHAR); + ULONG len, ulen; + + len = strlen (cs) + 1; + ulen = len * sizeof (WCHAR); + RtlInitEmptyUnicodeString (&us, (PWCHAR) alloca (ulen), ulen); + us.Length = sys_mbstowcs (us.Buffer, len, cs) * sizeof (WCHAR); + + len = strlen (ct) + 1; + ulen = len * sizeof (WCHAR); + RtlInitEmptyUnicodeString (&ut, (PWCHAR) alloca (ulen), ulen); + ut.Length = sys_mbstowcs (ut.Buffer, len, ct) * sizeof (WCHAR); + return RtlCompareUnicodeString (&us, &ut, TRUE); } @@ -816,19 +820,21 @@ extern "C" int __stdcall cygwin_strncasecmp (const char *cs, const char *ct, size_t n) { UNICODE_STRING us, ut; - ULONG len; + ULONG ulen; size_t ls = 0, lt = 0; while (cs[ls] && ls < n) ++ls; - len = (ls + 1) * sizeof (WCHAR); - RtlInitEmptyUnicodeString (&us, (PWCHAR) alloca (len), len); + ulen = (ls + 1) * sizeof (WCHAR); + RtlInitEmptyUnicodeString (&us, (PWCHAR) alloca (ulen), ulen); us.Length = sys_mbstowcs (us.Buffer, ls + 1, cs, ls) * sizeof (WCHAR); + while (ct[lt] && lt < n) ++lt; - len = (lt + 1) * sizeof (WCHAR); - RtlInitEmptyUnicodeString (&ut, (PWCHAR) alloca (len), len); + ulen = (lt + 1) * sizeof (WCHAR); + RtlInitEmptyUnicodeString (&ut, (PWCHAR) alloca (ulen), ulen); ut.Length = sys_mbstowcs (ut.Buffer, lt + 1, ct, lt) * sizeof (WCHAR); + return RtlCompareUnicodeString (&us, &ut, TRUE); } |