copy bcrypt autotune from encrypt(1) and expose via crypt_newhash

ok deraadt miod

2 files changed, 43 insertions, 5 deletions

diff --git a/src/lib/libc/crypt/bcrypt.c b/src/lib/libc/crypt/bcrypt.c
index 94758ca40b..abcbe138ca 100644
--- a/src/lib/libc/crypt/bcrypt.c
+++ b/src/lib/libc/crypt/bcrypt.c
@@ -1,4 +1,4 @@
-/*      $OpenBSD: bcrypt.c,v 1.46 2014/11/24 22:47:01 tedu Exp $        */
+/*      $OpenBSD: bcrypt.c,v 1.47 2014/12/30 10:27:24 tedu Exp $        */
 
 /*
  * Copyright (c) 2014 Ted Unangst <tedu@openbsd.org>
@@ -225,6 +225,38 @@ bcrypt_checkpass(const char *pass, const char *goodhash)
 }
 
 /*
+ * Measure this system's performance by measuring the time for 8 rounds.
+ * We are aiming for something that takes between 0.25 and 0.5 seconds.
+ */
+int
+bcrypt_autorounds(void)
+{
+        clock_t before, after;
+        int r = 8;
+        char buf[_PASSWORD_LEN];
+        int duration;
+
+        before = clock();
+        bcrypt_newhash("testpassword", r, buf, sizeof(buf));
+        after = clock();
+
+        duration = after - before;
+
+        /* too quick? slow it down. */
+        while (r < 16 && duration <= CLOCKS_PER_SEC / 4) {
+                r += 1;
+                duration *= 2;
+        }
+        /* too slow? speed it up. */
+        while (r > 4 && duration > CLOCKS_PER_SEC / 2) {
+                r -= 1;
+                duration /= 2;
+        }
+
+        return r;
+}
+
+/*
  * internal utilities
  */
 static const u_int8_t Base64Code[] =
diff --git a/src/lib/libc/crypt/cryptutil.c b/src/lib/libc/crypt/cryptutil.c
index f101240524..7e93dad3c8 100644
--- a/src/lib/libc/crypt/cryptutil.c
+++ b/src/lib/libc/crypt/cryptutil.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: cryptutil.c,v 1.6 2014/12/24 22:10:34 tedu Exp $ */
+/* $OpenBSD: cryptutil.c,v 1.7 2014/12/30 10:27:24 tedu Exp $ */
 /*
  * Copyright (c) 2014 Ted Unangst <tedu@openbsd.org>
  *
@@ -21,6 +21,8 @@
 #include <login_cap.h>
 #include <errno.h>
 
+int bcrypt_autorounds(void);
+
 int
 crypt_checkpass(const char *pass, const char *goodhash)
 {
@@ -64,9 +66,13 @@ crypt_newhash(const char *pass, const char *pref, char *hash, size_t hashlen)
                 errno = EINVAL;
                 goto err;
         }
-        rounds = strtonum(pref + 9, 4, 31, &errstr);
-        if (errstr)
-                goto err;
+        if (strcmp(pref + 9, "a") == 0) {
+                rounds = bcrypt_autorounds();
+        } else {
+                rounds = strtonum(pref + 9, 4, 31, &errstr);
+                if (errstr)
+                        goto err;
+        }
         rv = bcrypt_newhash(pass, rounds, hash, hashlen);
 
 err: