Protect against small overread in SASLprep validation

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 <[email protected]>
Reviewed-by: Daniel Gustafsson <[email protected]>
Discussion: https://postgr.es/m/CAOYmi+mTnmM172g=_+Yvc47hzzeAsYPy2C4UBY3HK9p-AXNV0g@mail.gmail.com

diff --git a/src/common/saslprep.c b/src/common/saslprep.c
index 315ccacd7ce45d51483129381d37f5ecd2f687c9..78f6fcbd8051b0fd3500baab302827f892f699fc 100644 (file)
--- 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++;
    }