[src/trunk]: src/lib/libcrypt Provide a safer salting method that does not tu...

[christos <christos%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/4bd0ac0e6f9c
branches:  trunk
changeset: 772261:4bd0ac0e6f9c
user:      christos <christos%NetBSD.org@localhost>
date:      Mon Dec 26 22:58:45 2011 +0000

description:
Provide a safer salting method that does not turn invalid salts to '.'.
Be more sensitive to bad salts and counts. From:
http://cvsweb.openwall.com/cgi/cvsweb.cgi/Owl/packages/glibc/crypt_freesec.c
>From Solar Designer

diffstat:

 lib/libcrypt/crypt.c |  66 ++++++++++++++++++++++++++++++++++++---------------
 1 files changed, 46 insertions(+), 20 deletions(-)

diffs (127 lines):

diff -r e9a51191bb16 -r 4bd0ac0e6f9c lib/libcrypt/crypt.c
--- a/lib/libcrypt/crypt.c      Mon Dec 26 22:04:35 2011 +0000
+++ b/lib/libcrypt/crypt.c      Mon Dec 26 22:58:45 2011 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: crypt.c,v 1.29 2011/12/26 16:03:42 christos Exp $      */
+/*     $NetBSD: crypt.c,v 1.30 2011/12/26 22:58:45 christos Exp $      */
 
 /*
  * Copyright (c) 1989, 1993
@@ -37,7 +37,7 @@
 #if 0
 static char sccsid[] = "@(#)crypt.c    8.1.1.1 (Berkeley) 8/18/93";
 #else
-__RCSID("$NetBSD: crypt.c,v 1.29 2011/12/26 16:03:42 christos Exp $");
+__RCSID("$NetBSD: crypt.c,v 1.30 2011/12/26 22:58:45 christos Exp $");
 #endif
 #endif /* not lint */
 
@@ -445,8 +445,6 @@
 /* =====  Tables that are initialized at run time  ==================== */
 
 
-static unsigned char a64toi[128];      /* ascii-64 => 0..63 */
-
 /* Initial key schedule permutation */
 static C_block PC1ROT[64/CHUNKBITS][1<<CHUNKBITS];
 
@@ -469,6 +467,35 @@
 static C_block constdatablock;                 /* encryption constant */
 static char    cryptresult[1+4+4+11+1];        /* encrypted result */
 
+/*
+ * We match the behavior of UFC-crypt on systems where "char" is signed by
+ * default (the majority), regardless of char's signedness on our system.
+ */
+static inline int
+ascii_to_bin(char ch)
+{
+       signed char sch = ch;
+       int retval;
+
+       if (sch >= 'a')
+               retval = sch - ('a' - 38);
+       else if (sch >= 'A') 
+               retval = sch - ('A' - 12);
+       else
+               retval = sch - '.';
+
+       return retval & 0x3f;
+}
+#include <stdio.h>
+/*
+ * When we choose to "support" invalid salts, nevertheless disallow those
+ * containing characters that would violate the passwd file format.
+ */
+static inline int
+ascii_is_unsafe(char ch)
+{
+       return !ch || ch == '\n' || ch == ':';
+}
 
 /*
  * Return a pointer to static data consisting of the "setting"
@@ -502,7 +529,7 @@
                        key++;
                keyblock.b[i] = t;
        }
-       if (des_setkey((char *)keyblock.b))     /* also initializes "a64toi" */
+       if (des_setkey((char *)keyblock.b))
                return (NULL);
 
        encp = &cryptresult[0];
@@ -529,12 +556,14 @@
                /* get iteration count */
                num_iter = 0;
                for (i = 4; --i >= 0; ) {
-                       if ((t = (unsigned char)setting[i]) == '\0')
-                               t = '.';
-                       encp[i] = t;
-                       num_iter = (num_iter << 6) |
-                           a64toi[t & (sizeof(a64toi) - 1)];
+                       int value = ascii_to_bin(setting[i]);
+                       if (itoa64[value] != setting[i])
+                               return NULL;
+                       encp[i] = setting[i];
+                       num_iter = (num_iter << 6) | value;
                }
+               if (num_iter == 0)
+                       return NULL;
                setting += 4;
                encp += 4;
                salt_size = 4;
@@ -542,14 +571,17 @@
        default:
                num_iter = 25;
                salt_size = 2;
+               if (ascii_is_unsafe(setting[0]) || ascii_is_unsafe(setting[1]))
+                       return NULL;
        }
 
        salt = 0;
        for (i = salt_size; --i >= 0; ) {
-               if ((t = (unsigned char)setting[i]) == '\0')
-                       t = '.';
-               encp[i] = t;
-               salt = (salt<<6) | a64toi[t & (sizeof(a64toi) - 1)];
+               int value = ascii_to_bin(setting[i]);
+               if (salt_size == 4 && itoa64[value] != setting[i])
+                       return NULL;
+               encp[i] = setting[i];
+               salt = (salt << 6) | value;
        }
        encp += salt_size;
        if (des_cipher((char *)(void *)&constdatablock,
@@ -752,12 +784,6 @@
        static unsigned char perm[64], tmp32[32];       /* "static" for speed */
 
        /*
-        * table that converts chars "./0-9A-Za-z"to integers 0-63.
-        */
-       for (i = 0; i < 64; i++)
-               a64toi[itoa64[i]] = i;
-
-       /*
         * PC1ROT - bit reverse, then PC1, then Rotate, then PC2.
         */
        for (i = 0; i < 64; i++)