1 /* 2 * Trivially encode strings to protect them from innocent eyes (i.e., 3 * inadvertent password compromises, like a network administrator 4 * who's watching packets for legitimate reasons and accidentally sees 5 * the password protocol go by). 6 * 7 * This is NOT secure encryption. 8 * 9 * It would be tempting to encode the password according to username 10 * and repository, so that the same password would encode to a 11 * different string when used with different usernames and/or 12 * repositories. However, then users would not be able to cut and 13 * paste passwords around. They're not supposed to anyway, but we all 14 * know they will, and there's no reason to make it harder for them if 15 * we're not trying to provide real security anyway. 16 */ 17 18 /* Set this to test as a standalone program. */ 19 /* #define DIAGNOSTIC */ 20 21 #ifndef DIAGNOSTIC 22 #include "cvs.h" 23 #else /* ! DIAGNOSTIC */ 24 /* cvs.h won't define this for us */ 25 #define AUTH_CLIENT_SUPPORT 26 #define xmalloc malloc 27 /* Use "gcc -fwritable-strings". */ 28 #include <stdio.h> 29 #include <stdio.h> 30 #include <string.h> 31 #endif /* ! DIAGNOSTIC */ 32 33 #if defined(AUTH_CLIENT_SUPPORT) || defined(AUTH_SERVER_SUPPORT) 34 35 /* Map characters to each other randomly and symmetrically, A <--> B. 36 * 37 * We divide the ASCII character set into 3 domains: control chars (0 38 * thru 31), printing chars (32 through 126), and "meta"-chars (127 39 * through 255). The control chars map _to_ themselves, the printing 40 * chars map _among_ themselves, and the meta chars map _among_ 41 * themselves. Why is this thus? 42 * 43 * No character in any of these domains maps to a character in another 44 * domain, because I'm not sure what characters are valid in 45 * passwords, or what tools people are likely to use to cut and paste 46 * them. It seems prudent not to introduce control or meta chars, 47 * unless the user introduced them first. And having the control 48 * chars all map to themselves insures that newline and 49 * carriage-return are safely handled. 50 */ 51 52 static unsigned char 53 shifts[] = { 54 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 55 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 56 114,120, 53, 79, 96,109, 72,108, 70, 64, 76, 67,116, 74, 68, 87, 57 111, 52, 75,119, 49, 34, 82, 81, 95, 65,112, 86,118,110,122,105, 58 41, 57, 83, 43, 46,102, 40, 89, 38,103, 45, 50, 42,123, 91, 35, 59 125, 55, 54, 66,124,126, 59, 47, 92, 71,115, 78, 88,107,106, 56, 60 36,121,117,104,101,100, 69, 73, 99, 63, 94, 93, 39, 37, 61, 48, 61 58,113, 32, 90, 44, 98, 60, 51, 33, 97, 62, 77, 84, 80, 85,223, 62 225,216,187,166,229,189,222,188,141,249,148,200,184,136,248,190, 63 199,170,181,204,138,232,218,183,255,234,220,247,213,203,226,193, 64 174,172,228,252,217,201,131,230,197,211,145,238,161,179,160,212, 65 207,221,254,173,202,146,224,151,140,196,205,130,135,133,143,246, 66 192,159,244,239,185,168,215,144,139,165,180,157,147,186,214,176, 67 227,231,219,169,175,156,206,198,129,164,150,210,154,177,134,127, 68 182,128,158,208,162,132,167,209,149,241,153,251,237,236,171,195, 69 243,233,253,240,194,250,191,155,142,137,245,235,163,242,178,152 }; 70 71 72 /* SCRAMBLE and DESCRAMBLE work like this: 73 * 74 * scramble(STR) returns SCRM, a scrambled copy of STR. SCRM[0] is a 75 * single letter indicating the scrambling method. As of this 76 * writing, the only valid method is 'A', but check the code for more 77 * up-to-date information. The copy will have been allocated with 78 * xmalloc(). 79 * 80 * descramble(SCRM) returns STR, again in its own xmalloc'd space. 81 * descramble() uses SCRM[0] to determine which method of unscrambling 82 * to use. If it does not recognize the method, it dies with error. 83 */ 84 85 /* Return a xmalloc'd, scrambled version of STR. */ 86 char * 87 scramble (char *str) 88 { 89 int i; 90 char *s; 91 92 /* +2 to hold the 'A' prefix that indicates which version of 93 scrambling this is (the first, obviously, since we only do one 94 kind of scrambling so far), and then the '\0' of course. */ 95 s = (char *) xmalloc (strlen (str) + 2); 96 97 /* Scramble (TM) version prefix. */ 98 s[0] = 'A'; 99 strcpy (s + 1, str); 100 101 for (i = 1; s[i]; i++) 102 s[i] = shifts[(unsigned char)(s[i])]; 103 104 return s; 105 } 106 107 /* Decode the string in place. */ 108 char * 109 descramble (char *str) 110 { 111 char *s; 112 int i; 113 114 /* For now we can only handle one kind of scrambling. In the future 115 there may be other kinds, and this `if' will become a `switch'. */ 116 if (str[0] != 'A') 117 #ifndef DIAGNOSTIC 118 error (1, 0, "descramble: unknown scrambling method"); 119 #else /* DIAGNOSTIC */ 120 { 121 fprintf (stderr, "descramble: unknown scrambling method\n", str); 122 fflush (stderr); 123 exit (EXIT_FAILURE); 124 } 125 #endif /* DIAGNOSTIC */ 126 127 /* Method `A' is symmetrical, so scramble again to decrypt. */ 128 s = scramble (str + 1); 129 130 /* Shift the whole string one char to the left, pushing the unwanted 131 'A' off the left end. Safe, because s is null-terminated. */ 132 for (i = 0; s[i]; i++) 133 s[i] = s[i + 1]; 134 135 return s; 136 } 137 138 #endif /* (AUTH_CLIENT_SUPPORT || AUTH_SERVER_SUPPORT) from top of file */ 139 140 #ifdef DIAGNOSTIC 141 int 142 main( int argc, char **argv ) 143 { 144 int i; 145 char *e, *m, biggie[256]; 146 147 char *cleartexts[5]; 148 cleartexts[0] = "first"; 149 cleartexts[1] = "the second"; 150 cleartexts[2] = "this is the third"; 151 cleartexts[3] = "$#% !!\\3"; 152 cleartexts[4] = biggie; 153 154 /* Set up the most important test string: */ 155 /* Can't have a real ASCII zero in the string, because we want to 156 use printf, so we substitute the character zero. */ 157 biggie[0] = '0'; 158 /* The rest of the string gets straight ascending ASCII. */ 159 for (i = 1; i < 256; i++) 160 biggie[i] = i; 161 162 /* Test all the strings. */ 163 for (i = 0; i < 5; i++) 164 { 165 printf ("clear%d: %s\n", i, cleartexts[i]); 166 e = scramble (cleartexts[i]); 167 printf ("scram%d: %s\n", i, e); 168 m = descramble (e); 169 free (e); 170 printf ("clear%d: %s\n\n", i, m); 171 free (m); 172 } 173 174 fflush (stdout); 175 return 0; 176 } 177 #endif /* DIAGNOSTIC */ 178 179 /* 180 * ;;; The Emacs Lisp that did the dirty work ;;; 181 * (progn 182 * 183 * ;; Helper func. 184 * (defun random-elt (lst) 185 * (let* ((len (length lst)) 186 * (rnd (random len))) 187 * (nth rnd lst))) 188 * 189 * ;; A list of all characters under 127, each appearing once. 190 * (setq non-meta-chars 191 * (let ((i 0) 192 * (l nil)) 193 * (while (< i 127) 194 * (setq l (cons i l) 195 * i (1+ i))) 196 * l)) 197 * 198 * ;; A list of all characters 127 and above, each appearing once. 199 * (setq meta-chars 200 * (let ((i 127) 201 * (l nil)) 202 * (while (< i 256) 203 * (setq l (cons i l) 204 * i (1+ i))) 205 * l)) 206 * 207 * ;; A vector that will hold the chars in a random order. 208 * (setq scrambled-chars (make-vector 256 0)) 209 * 210 * ;; These characters should map to themselves. 211 * (let ((i 0)) 212 * (while (< i 32) 213 * (aset scrambled-chars i i) 214 * (setq non-meta-chars (delete i non-meta-chars) 215 * i (1+ i)))) 216 * 217 * ;; Assign random (but unique) values, within the non-meta chars. 218 * (let ((i 32)) 219 * (while (< i 127) 220 * (let ((ch (random-elt non-meta-chars))) 221 * (if (= 0 (aref scrambled-chars i)) 222 * (progn 223 * (aset scrambled-chars i ch) 224 * (aset scrambled-chars ch i) 225 * (setq non-meta-chars (delete ch non-meta-chars) 226 * non-meta-chars (delete i non-meta-chars)))) 227 * (setq i (1+ i))))) 228 * 229 * ;; Assign random (but unique) values, within the non-meta chars. 230 * (let ((i 127)) 231 * (while (< i 256) 232 * (let ((ch (random-elt meta-chars))) 233 * (if (= 0 (aref scrambled-chars i)) 234 * (progn 235 * (aset scrambled-chars i ch) 236 * (aset scrambled-chars ch i) 237 * (setq meta-chars (delete ch meta-chars) 238 * meta-chars (delete i meta-chars)))) 239 * (setq i (1+ i))))) 240 * 241 * ;; Now use the `scrambled-chars' vector to get your C array. 242 * ) 243 */ 244