Update NSS to 3.41

1 files changed, 42 insertions, 19 deletions

diff --git a/security/nss/lib/freebl/mpi/mpi.c b/security/nss/lib/freebl/mpi/mpi.c
index 8c893fb5f..401eac51d 100644
--- a/security/nss/lib/freebl/mpi/mpi.c
+++ b/security/nss/lib/freebl/mpi/mpi.c
@@ -4775,38 +4775,61 @@ mp_to_signed_octets(const mp_int *mp, unsigned char *str, mp_size maxlen)
 /* }}} */
 
 /* {{{ mp_to_fixlen_octets(mp, str) */
-/* output a buffer of big endian octets exactly as long as requested. */
+/* output a buffer of big endian octets exactly as long as requested.
+   constant time on the value of mp. */
 mp_err
 mp_to_fixlen_octets(const mp_int *mp, unsigned char *str, mp_size length)
 {
-    int ix, pos = 0;
+    int ix, jx;
     unsigned int bytes;
 
-    ARGCHK(mp != NULL && str != NULL && !SIGN(mp), MP_BADARG);
-
-    bytes = mp_unsigned_octet_size(mp);
-    ARGCHK(bytes <= length, MP_BADARG);
+    ARGCHK(mp != NULL, MP_BADARG);
+    ARGCHK(str != NULL, MP_BADARG);
+    ARGCHK(!SIGN(mp), MP_BADARG);
+    ARGCHK(length > 0, MP_BADARG);
+
+    /* Constant time on the value of mp.  Don't use mp_unsigned_octet_size. */
+    bytes = USED(mp) * MP_DIGIT_SIZE;
+
+    /* If the output is shorter than the native size of mp, then check that any
+     * bytes not written have zero values.  This check isn't constant time on
+     * the assumption that timing-sensitive callers can guarantee that mp fits
+     * in the allocated space. */
+    ix = USED(mp) - 1;
+    if (bytes > length) {
+        unsigned int zeros = bytes - length;
+
+        while (zeros >= MP_DIGIT_SIZE) {
+            ARGCHK(DIGIT(mp, ix) == 0, MP_BADARG);
+            zeros -= MP_DIGIT_SIZE;
+            ix--;
+        }
 
-    /* place any needed leading zeros */
-    for (; length > bytes; --length) {
-        *str++ = 0;
+        if (zeros > 0) {
+            mp_digit d = DIGIT(mp, ix);
+            mp_digit m = ~0ULL << ((MP_DIGIT_SIZE - zeros) * CHAR_BIT);
+            ARGCHK((d & m) == 0, MP_BADARG);
+            for (jx = MP_DIGIT_SIZE - zeros - 1; jx >= 0; jx--) {
+                *str++ = d >> (jx * CHAR_BIT);
+            }
+            ix--;
+        }
+    } else if (bytes < length) {
+        /* Place any needed leading zeros. */
+        unsigned int zeros = length - bytes;
+        memset(str, 0, zeros);
+        str += zeros;
     }
 
-    /* Iterate over each digit... */
-    for (ix = USED(mp) - 1; ix >= 0; ix--) {
+    /* Iterate over each whole digit... */
+    for (; ix >= 0; ix--) {
         mp_digit d = DIGIT(mp, ix);
-        int jx;
 
         /* Unpack digit bytes, high order first */
-        for (jx = sizeof(mp_digit) - 1; jx >= 0; jx--) {
-            unsigned char x = (unsigned char)(d >> (jx * CHAR_BIT));
-            if (!pos && !x) /* suppress leading zeros */
-                continue;
-            str[pos++] = x;
+        for (jx = MP_DIGIT_SIZE - 1; jx >= 0; jx--) {
+            *str++ = d >> (jx * CHAR_BIT);
         }
     }
-    if (!pos)
-        str[pos++] = 0;
     return MP_OKAY;
 } /* end mp_to_fixlen_octets() */
 /* }}} */