Changeset ddcf491f

Timestamp:

2008-03-16T14:18:22Z (17 years ago)

Author:

Wilmer van der Gaast <wilmer@…>

Branches:

master

Children:

e960a52

Parents:

d07c3a8

Message:

Adding padding to encrypted IM-passwords so the exact password length can't
be guessed from the encrypted data anymore.

Files:

• lib/arc.c (modified) (2 diffs)
• lib/arc.h (modified) (1 diff)
• storage_xml.c (modified) (1 diff)
• tests/check_arc.c (modified) (5 diffs)

lib/arc.c

@@ -131 +131 @@
    
    Both functions return the number of bytes in the result string.
+   
+   Note that if you use the pad_to argument, you will need zero-termi-
+   nation to find back the original string length after decryption. So
+   it shouldn't be used if your string contains \0s by itself!
 */
 
-int arc_encode( char *clear, int clear_len, unsigned char **crypt, char *password )
+int arc_encode( char *clear, int clear_len, unsigned char **crypt, char *password, int pad_to )
 {
         struct arc_state *st;
         unsigned char *key;
-        int key_len, i;
+        char *padded = NULL;
+        int key_len, i, padded_len;
         
         key_len = strlen( password ) + ARC_IV_LEN;
         if( clear_len <= 0 )
                 clear_len = strlen( clear );
+        
+        /* Pad the string to the closest multiple of pad_to. This makes it
+           impossible to see the exact length of the password. */
+        if( pad_to > 0 && ( clear_len % pad_to ) > 0 )
+        {
+                padded_len = clear_len + pad_to - ( clear_len % pad_to );
+                padded = g_malloc( padded_len );
+                memcpy( padded, clear, clear_len );
+                
+                /* First a \0 and then random data, so we don't have to do
+                   anything special when decrypting. */
+                padded[clear_len] = 0;
+                random_bytes( (unsigned char*) padded + clear_len + 1, padded_len - clear_len - 1 );
+                
+                clear = padded;
+                clear_len = padded_len;
+        }
         
         /* Prepare buffers and the key + IV */
@@ -161 +183 @@
         
         g_free( st );
+        g_free( padded );
         
         return clear_len + ARC_IV_LEN;

lib/arc.h

@@ -31 +31 @@
 };
 
-struct arc_state *arc_keymaker( unsigned char *key, int kl, int cycles );
+G_GNUC_MALLOC struct arc_state *arc_keymaker( unsigned char *key, int kl, int cycles );
 unsigned char arc_getbyte( struct arc_state *st );
-int arc_encode( char *clear, int clear_len, unsigned char **crypt, char *password );
+int arc_encode( char *clear, int clear_len, unsigned char **crypt, char *password, int pad_to );
 int arc_decode( unsigned char *crypt, int crypt_len, char **clear, char *password );

storage_xml.c

@@ -428 +428 @@
                 int pass_len;
                 
-                pass_len = arc_encode( acc->pass, strlen( acc->pass ), (unsigned char**) &pass_cr, irc->password );
+                pass_len = arc_encode( acc->pass, strlen( acc->pass ), (unsigned char**) &pass_cr, irc->password, 12 );
                 pass_b64 = base64_encode( pass_cr, pass_len );
                 g_free( pass_cr );

tests/check_arc.c

@@ -7 +7 @@
 #include "arc.h"
 
-char *password = "TotT";
+char *password = "ArcVier";
 
 char *clear_tests[] =
@@ -14 +14 @@
         "ItllBeBitlBee",
         "One more boring password",
+        "Hoi hoi",
         NULL
 };
@@ -28 +29 @@
                 int len;
                 
-                len = arc_encode( clear_tests[i], 0, &crypted, password );
+                len = arc_encode( clear_tests[i], 0, &crypted, password, 12 );
                 len = arc_decode( crypted, len, &decrypted, password );
                 
@@ -41 +42 @@
 struct
 {
-        unsigned char crypted[24];
+        unsigned char crypted[30];
         int len;
         char *decrypted;
 } decrypt_tests[] = {
+        /* One block with padding. */
         {
                 {
-                        0xc3, 0x0d, 0x43, 0xc3, 0xee, 0x80, 0xe2, 0x8c, 0x0b, 0x29, 0x32, 0x7e,
-                        0x38, 0x05, 0x82, 0x10, 0x21, 0x1c, 0x4a, 0x00, 0x2c
-                }, 21, "Debugging sucks"
+                        0x3f, 0x79, 0xb0, 0xf5, 0x91, 0x56, 0xd2, 0x1b, 0xd1, 0x4b, 0x67, 0xac,
+                        0xb1, 0x31, 0xc9, 0xdb, 0xf9, 0xaa
+                }, 18, "short pass"
         },
+        
+        /* Two blocks with padding. */
         {
                 {
-                        0xb0, 0x00, 0x57, 0x0d, 0x0d, 0x0d, 0x70, 0xe1, 0xc0, 0x00, 0xa4, 0x25,
-                        0x7d, 0xbe, 0x03, 0xcc, 0x24, 0xd1, 0x0c
-                }, 19, "Testing rocks"
+                        0xf9, 0xa6, 0xec, 0x5d, 0xc7, 0x06, 0xb8, 0x6b, 0x63, 0x9f, 0x2d, 0xb5,
+                        0x7d, 0xaa, 0x32, 0xbb, 0xd8, 0x08, 0xfd, 0x81, 0x2e, 0xca, 0xb4, 0xd7,
+                        0x2f, 0x36, 0x9c, 0xac, 0xa0, 0xbc
+                }, 30, "longer password"
         },
+
+        /* This string is exactly two "blocks" long, to make sure unpadded strings also decrypt
+           properly. */
         {
                 {
-                        0xb6, 0x92, 0x59, 0xe4, 0xf9, 0xc1, 0x7a, 0xf6, 0xf3, 0x18, 0xea, 0x28,
-                        0x73, 0x6d, 0xb3, 0x0a, 0x6f, 0x0a, 0x2b, 0x43, 0x57, 0xe9, 0x3e, 0x63
-                }, 24, "OSCAR is creepy..."
+                        0x95, 0x4d, 0xcf, 0x4d, 0x5e, 0x6c, 0xcf, 0xef, 0xb9, 0x80, 0x00, 0xef,
+                        0x25, 0xe9, 0x17, 0xf6, 0x29, 0x6a, 0x82, 0x79, 0x1c, 0xca, 0x68, 0xb5,
+                        0x4e, 0xd0, 0xc1, 0x41, 0x8e, 0xe6
+                }, 30, "OSCAR is really creepy.."
         },
         { "", 0, NULL }
@@ -80 +89 @@
                 
                 fail_if( strcmp( decrypt_tests[i].decrypted, decrypted ) != 0,
-                         "%s didn't decrypt properly", clear_tests[i] );
+                         "`%s' didn't decrypt properly", decrypt_tests[i].decrypted );
                 
                 g_free( decrypted );