dsdb:password_hash.c: restrict crypt hash to proper forms

Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Jennifer Sutton <jennifersutton@catalyst.net.nz>

diff --git a/source4/dsdb/samdb/ldb_modules/password_hash.c b/source4/dsdb/samdb/ldb_modules/password_hash.c
index ee4aae6d10a336c80fd173271ace567d7ae830a1..b7a0c5066a70ad7299c62ee281a0b208d7cdbc01 100644 (file)
--- a/source4/dsdb/samdb/ldb_modules/password_hash.c
+++ b/source4/dsdb/samdb/ldb_modules/password_hash.c
@@ -1562,6 +1562,9 @@ static bool parse_scheme(const char *scheme, int *algorithm, int *rounds) {
                   == 0) {
                *algorithm = SHA_512_ALGORITHM_ID;
        } else {
+               DBG_ERR("user password scheme '%s' is not SHA_256 or SHA_512 "
+                       "('$5$' or '$6$')\n",
+                       scheme);
                return false;
        }
 
@@ -1577,6 +1580,27 @@ static bool parse_scheme(const char *scheme, int *algorithm, int *rounds) {
        }
        digits[i] = '\0';
        *rounds = atoi(digits);
+       /*
+        * According to https://www.akkadia.org/drepper/SHA-crypt.txt
+        * SHA_256 and SHA_512 crypt rounds are restricted to the range
+        * [1000, 999_999_999]. (thus it is OK to use int and atoi).
+        *
+        * As specified crypt() itself will clamp to these values and
+        * continue, but that leads to confusing situations, like the
+        * salt not matching.
+        *
+        * Rather than let that happen, we complain and bail out. This
+        * is from smb.conf ("password hash userPassword schemes"),
+        * and we want to let the admin know it's wrong.
+        */
+       if (*rounds < 1000 || *rounds > 999999999) {
+               DBG_ERR("user password scheme '%s' specifies a non-standard "
+                       "number of rounds (%d)\n",
+                       scheme,
+                       *rounds);
+               return false;
+       }
+
        return true;
 }