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Date: Fri, 10 Aug 2012 17:41:36 +0200
From: Szabolcs Nagy <nsz@...t70.net>
To: musl@...ts.openwall.com
Subject: wcsstr is broken
naive_wcsstr is wrong, h can overrun in the inner loop
as reported in irc:
16:36 < dkl> with certain input, it appears to be overrunning
16:36 < dkl> for example: wcsstr(L"ab", L"ac");
...
16:41 < dkl> in this case the inner one keeps increasing the "h" pointer past the null terminator
16:44 < dkl> I had a go at a patch too: http://jafile.com/uploads/dkl/0001-wcsstr-fix-buffer-overrun.patch
see patch below
>>From 2b635da731496e037d1b18118d874acbad5f351a Mon Sep 17 00:00:00 2001
>From: dkl <daniel.c.klauer@....de>
Date: Fri, 10 Aug 2012 05:32:44 +0200
Subject: [PATCH] wcsstr(): fix buffer overrun
A wcsstr() call such as:
wcsstr(L"ab", L"ac");
causes naive_wcsstr() to be used. For this input however, it would overrun
the first input string, due to the inner loop continuing to increase h
past the null terminator.
The same problem existed in the naive_strstr() function for strstr(),
which however was commented out and thus not used anyways.
---
src/string/strstr.c | 10 ----------
src/string/wcsstr.c | 16 +++++++++++++---
2 files changed, 13 insertions(+), 13 deletions(-)
diff --git a/src/string/strstr.c b/src/string/strstr.c
index 683cdd0..0649174 100644
--- a/src/string/strstr.c
+++ b/src/string/strstr.c
@@ -25,16 +25,6 @@ static char *fourbyte_strstr(const unsigned char *h, const unsigned char *n)
return *h ? (char *)h-3 : 0;
}
-#if 0
-static char *naive_strstr(const char *h, const char *n)
-{
- size_t i;
- for (i=0; n[i] && h[i]; i++)
- for ( ; n[i] != h[i]; h++, i=0);
- return n[i] ? 0 : (char *)h;
-}
-#endif
-
#define MAX(a,b) ((a)>(b)?(a):(b))
#define MIN(a,b) ((a)<(b)?(a):(b))
diff --git a/src/string/wcsstr.c b/src/string/wcsstr.c
index 966174f..6196a02 100644
--- a/src/string/wcsstr.c
+++ b/src/string/wcsstr.c
@@ -6,9 +6,19 @@
static wchar_t *naive_wcsstr(const wchar_t *h, const wchar_t *n)
{
size_t i;
- for (i=0; n[i] && h[i]; i++)
- for ( ; n[i] != h[i]; h++, i=0);
- return n[i] ? 0 : (wchar_t *)h;
+
+ for ( ; *h; h++) {
+ /* check for needle starting from here */
+ i = 0;
+ while (1) {
+ if (!n[i]) return (wchar_t *)h; /* matched whole n */
+ if (!h[i]) return 0; /* end of h, can't match anymore */
+ if (h[i] != n[i]) break;
+ i++;
+ }
+ }
+
+ return 0;
}
#define MAX(a,b) ((a)>(b)?(a):(b))
--
1.7.9.5
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