358 lines
8.3 KiB
C
358 lines
8.3 KiB
C
/* pwdauth 2.0 - check a shadow password Author: Kees J. Bot
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* 7 Feb 1994
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*
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* This program gets as input the key and salt arguments of the crypt(3)
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* function as two null terminated strings. The crypt result is output as
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* one null terminated string. Input and output must be <= 1024 characters.
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* The exit code will be 1 on any error.
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*
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* If the key has the form '##name' then the key will be encrypted and the
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* result checked to be equal to the encrypted password in the shadow password
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* file. If equal than '##name' will be returned, otherwise exit code 2.
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*
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* Otherwise the key will be encrypted normally and the result returned.
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*
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* As a special case, anything matches a null encrypted password to allow
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* a no-password login.
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*/
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#define nil 0
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#define crypt CRYPT /* The true crypt is included here. */
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#include <sys/types.h>
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#include <pwd.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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#include <unistd.h>
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#define LEN 1024
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char SHADOW[] = "/etc/shadow";
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int main(int argc, char **argv)
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{
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char key[LEN];
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char *salt;
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struct passwd *pw;
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int n;
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/* Read input data. Check if there are exactly two null terminated
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* strings.
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*/
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n= read(0, key, LEN);
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if (n < 0) return 1;
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salt = key + n;
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n = 0;
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while (salt > key) if (*--salt == 0) n++;
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if (n != 2) return 1;
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salt = key + strlen(key) + 1;
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if (salt[0] == '#' && salt[1] == '#') {
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/* Get the encrypted password from the shadow password file,
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* encrypt key and compare.
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*/
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setpwfile(SHADOW);
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if ((pw= getpwnam(salt + 2)) == nil) return 2;
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/* A null encrypted password matches a null key, otherwise
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* do the normal crypt(3) authentication check.
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*/
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if (*pw->pw_passwd == 0 && *key == 0) {
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/* fine */
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} else
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if (strcmp(crypt(key, pw->pw_passwd), pw->pw_passwd) != 0) {
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return 2;
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}
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} else {
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/* Normal encryption. */
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if (*salt == 0 && *key == 0) {
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/* fine */
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} else {
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salt= crypt(key, salt);
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}
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}
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/* Return the (possibly new) salt to the caller. */
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if (write(1, salt, strlen(salt) + 1) < 0) return 1;
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return 0;
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}
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/* The one and only crypt(3) function. */
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/* From Andy Tanenbaum's book "Computer Networks",
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rewritten in C
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*/
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struct block {
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unsigned char b_data[64];
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};
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struct ordering {
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unsigned char o_data[64];
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};
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static struct block key;
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static struct ordering InitialTr = {
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58,50,42,34,26,18,10, 2,60,52,44,36,28,20,12, 4,
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62,54,46,38,30,22,14, 6,64,56,48,40,32,24,16, 8,
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57,49,41,33,25,17, 9, 1,59,51,43,35,27,19,11, 3,
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61,53,45,37,29,21,13, 5,63,55,47,39,31,23,15, 7,
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};
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static struct ordering FinalTr = {
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40, 8,48,16,56,24,64,32,39, 7,47,15,55,23,63,31,
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38, 6,46,14,54,22,62,30,37, 5,45,13,53,21,61,29,
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36, 4,44,12,52,20,60,28,35, 3,43,11,51,19,59,27,
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34, 2,42,10,50,18,58,26,33, 1,41, 9,49,17,57,25,
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};
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static struct ordering swap = {
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33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,
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49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,
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1, 2, 3, 4, 5, 6, 7, 8, 9,10,11,12,13,14,15,16,
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17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,
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};
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static struct ordering KeyTr1 = {
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57,49,41,33,25,17, 9, 1,58,50,42,34,26,18,
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10, 2,59,51,43,35,27,19,11, 3,60,52,44,36,
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63,55,47,39,31,23,15, 7,62,54,46,38,30,22,
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14, 6,61,53,45,37,29,21,13, 5,28,20,12, 4,
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};
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static struct ordering KeyTr2 = {
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14,17,11,24, 1, 5, 3,28,15, 6,21,10,
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23,19,12, 4,26, 8,16, 7,27,20,13, 2,
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41,52,31,37,47,55,30,40,51,45,33,48,
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44,49,39,56,34,53,46,42,50,36,29,32,
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};
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static struct ordering etr = {
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32, 1, 2, 3, 4, 5, 4, 5, 6, 7, 8, 9,
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8, 9,10,11,12,13,12,13,14,15,16,17,
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16,17,18,19,20,21,20,21,22,23,24,25,
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24,25,26,27,28,29,28,29,30,31,32, 1,
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};
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static struct ordering ptr = {
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16, 7,20,21,29,12,28,17, 1,15,23,26, 5,18,31,10,
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2, 8,24,14,32,27, 3, 9,19,13,30, 6,22,11, 4,25,
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};
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static unsigned char s_boxes[8][64] = {
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{ 14, 4,13, 1, 2,15,11, 8, 3,10, 6,12, 5, 9, 0, 7,
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0,15, 7, 4,14, 2,13, 1,10, 6,12,11, 9, 5, 3, 8,
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4, 1,14, 8,13, 6, 2,11,15,12, 9, 7, 3,10, 5, 0,
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15,12, 8, 2, 4, 9, 1, 7, 5,11, 3,14,10, 0, 6,13,
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},
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{ 15, 1, 8,14, 6,11, 3, 4, 9, 7, 2,13,12, 0, 5,10,
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3,13, 4, 7,15, 2, 8,14,12, 0, 1,10, 6, 9,11, 5,
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0,14, 7,11,10, 4,13, 1, 5, 8,12, 6, 9, 3, 2,15,
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13, 8,10, 1, 3,15, 4, 2,11, 6, 7,12, 0, 5,14, 9,
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},
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{ 10, 0, 9,14, 6, 3,15, 5, 1,13,12, 7,11, 4, 2, 8,
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13, 7, 0, 9, 3, 4, 6,10, 2, 8, 5,14,12,11,15, 1,
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13, 6, 4, 9, 8,15, 3, 0,11, 1, 2,12, 5,10,14, 7,
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1,10,13, 0, 6, 9, 8, 7, 4,15,14, 3,11, 5, 2,12,
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},
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{ 7,13,14, 3, 0, 6, 9,10, 1, 2, 8, 5,11,12, 4,15,
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13, 8,11, 5, 6,15, 0, 3, 4, 7, 2,12, 1,10,14, 9,
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10, 6, 9, 0,12,11, 7,13,15, 1, 3,14, 5, 2, 8, 4,
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3,15, 0, 6,10, 1,13, 8, 9, 4, 5,11,12, 7, 2,14,
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},
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{ 2,12, 4, 1, 7,10,11, 6, 8, 5, 3,15,13, 0,14, 9,
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14,11, 2,12, 4, 7,13, 1, 5, 0,15,10, 3, 9, 8, 6,
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4, 2, 1,11,10,13, 7, 8,15, 9,12, 5, 6, 3, 0,14,
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11, 8,12, 7, 1,14, 2,13, 6,15, 0, 9,10, 4, 5, 3,
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},
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{ 12, 1,10,15, 9, 2, 6, 8, 0,13, 3, 4,14, 7, 5,11,
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10,15, 4, 2, 7,12, 9, 5, 6, 1,13,14, 0,11, 3, 8,
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9,14,15, 5, 2, 8,12, 3, 7, 0, 4,10, 1,13,11, 6,
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4, 3, 2,12, 9, 5,15,10,11,14, 1, 7, 6, 0, 8,13,
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},
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{ 4,11, 2,14,15, 0, 8,13, 3,12, 9, 7, 5,10, 6, 1,
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13, 0,11, 7, 4, 9, 1,10,14, 3, 5,12, 2,15, 8, 6,
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1, 4,11,13,12, 3, 7,14,10,15, 6, 8, 0, 5, 9, 2,
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6,11,13, 8, 1, 4,10, 7, 9, 5, 0,15,14, 2, 3,12,
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},
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{ 13, 2, 8, 4, 6,15,11, 1,10, 9, 3,14, 5, 0,12, 7,
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1,15,13, 8,10, 3, 7, 4,12, 5, 6,11, 0,14, 9, 2,
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7,11, 4, 1, 9,12,14, 2, 0, 6,10,13,15, 3, 5, 8,
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2, 1,14, 7, 4,10, 8,13,15,12, 9, 0, 3, 5, 6,11,
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},
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};
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static int rots[] = {
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1,1,2,2,2,2,2,2,1,2,2,2,2,2,2,1,
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};
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static void transpose(struct block *data, struct ordering *t, int n)
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{
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struct block x;
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x = *data;
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while (n-- > 0) {
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data->b_data[n] = x.b_data[t->o_data[n] - 1];
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}
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}
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static void rotate(struct block *key)
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{
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unsigned char *p = key->b_data;
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unsigned char *ep = &(key->b_data[55]);
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int data0 = key->b_data[0], data28 = key->b_data[28];
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while (p++ < ep) *(p-1) = *p;
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key->b_data[27] = data0;
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key->b_data[55] = data28;
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}
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static struct ordering *EP = &etr;
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static void f(int i, struct block *key, struct block *a, struct block *x)
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{
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struct block e, ikey, y;
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int k;
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unsigned char *p, *q, *r;
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e = *a;
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transpose(&e, EP, 48);
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for (k = rots[i]; k; k--) rotate(key);
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ikey = *key;
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transpose(&ikey, &KeyTr2, 48);
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p = &(y.b_data[48]);
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q = &(e.b_data[48]);
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r = &(ikey.b_data[48]);
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while (p > y.b_data) {
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*--p = *--q ^ *--r;
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}
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q = x->b_data;
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for (k = 0; k < 8; k++) {
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int xb, r;
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r = *p++ << 5;
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r += *p++ << 3;
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r += *p++ << 2;
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r += *p++ << 1;
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r += *p++;
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r += *p++ << 4;
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xb = s_boxes[k][r];
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*q++ = (xb >> 3) & 1;
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*q++ = (xb>>2) & 1;
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*q++ = (xb>>1) & 1;
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*q++ = (xb & 1);
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}
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transpose(x, &ptr, 32);
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}
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static void setkey(char *k)
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{
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key = *((struct block *) k);
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transpose(&key, &KeyTr1, 56);
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}
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static void encrypt(char *blck, int edflag)
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{
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struct block *p = (struct block *) blck;
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int i;
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transpose(p, &InitialTr, 64);
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for (i = 15; i>= 0; i--) {
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int j = edflag ? i : 15 - i;
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int k;
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struct block b, x;
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b = *p;
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for (k = 31; k >= 0; k--) {
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p->b_data[k] = b.b_data[k + 32];
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}
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f(j, &key, p, &x);
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for (k = 31; k >= 0; k--) {
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p->b_data[k+32] = b.b_data[k] ^ x.b_data[k];
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}
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}
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transpose(p, &swap, 64);
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transpose(p, &FinalTr, 64);
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}
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char *crypt(const char *pw, const char *salt)
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{
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char pwb[66];
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char *cp;
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static char result[16];
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char *p = pwb;
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struct ordering new_etr;
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int i;
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while (*pw && p < &pwb[64]) {
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int j = 7;
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while (j--) {
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*p++ = (*pw >> j) & 01;
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}
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pw++;
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*p++ = 0;
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}
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while (p < &pwb[64]) *p++ = 0;
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setkey(p = pwb);
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while (p < &pwb[66]) *p++ = 0;
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new_etr = etr;
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EP = &new_etr;
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if (salt[0] == 0 || salt[1] == 0) salt = "**";
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for (i = 0; i < 2; i++) {
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char c = *salt++;
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int j;
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result[i] = c;
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if ( c > 'Z') c -= 6 + 7 + '.'; /* c was a lower case letter */
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else if ( c > '9') c -= 7 + '.';/* c was upper case letter */
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else c -= '.'; /* c was digit, '.' or '/'. */
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/* now, 0 <= c <= 63 */
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for (j = 0; j < 6; j++) {
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if ((c >> j) & 01) {
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int t = 6*i + j;
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int temp = new_etr.o_data[t];
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new_etr.o_data[t] = new_etr.o_data[t+24];
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new_etr.o_data[t+24] = temp;
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}
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}
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}
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if (result[1] == 0) result[1] = result[0];
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for (i = 0; i < 25; i++) encrypt(pwb,0);
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EP = &etr;
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p = pwb;
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cp = result+2;
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while (p < &pwb[66]) {
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int c = 0;
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int j = 6;
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while (j--) {
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c <<= 1;
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c |= *p++;
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}
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c += '.'; /* becomes >= '.' */
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if (c > '9') c += 7; /* not in [./0-9], becomes upper */
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if (c > 'Z') c += 6; /* not in [A-Z], becomes lower */
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*cp++ = c;
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}
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*cp = 0;
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return result;
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}
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