Protect against small overread in SASLprep validation

danielgustafsson · danielgustafsson · commit 390b3cbbb2af · 2024-09-10T11:02:28.000+02:00
In case of torn UTF8 in the input data we might end up going past the end of the string since we don't account for length. While validation won't be performed on a sequence with a NULL byte it's better to avoid going past the end to beging with. Fix by taking the length into consideration. Author: Jacob Champion <jacob.champion@enterprisedb.com> Reviewed-by: Daniel Gustafsson <daniel@yesql.se> Discussion: https://postgr.es/m/CAOYmi+mTnmM172g=_+Yvc47hzzeAsYPy2C4UBY3HK9p-AXNV0g@mail.gmail.com
diff --git a/src/common/saslprep.c b/src/common/saslprep.c
@@ -1004,15 +1004,17 @@ pg_utf8_string_len(const char *source)
 	const unsigned char *p = (const unsigned char *) source;
 	int			l;
 	int			num_chars = 0;
+	size_t		len = strlen(source);
 
-	while (*p)
+	while (len)
 	{
 		l = pg_utf_mblen(p);
 
-		if (!pg_utf8_islegal(p, l))
+		if (len < l || !pg_utf8_islegal(p, l))
 			return -1;
 
 		p += l;
+		len -= l;
 		num_chars++;
 	}
 
