krdc/vnc/vncauth.c

   1 /*
   2  *  Copyright (C) 1999 AT&T Laboratories Cambridge.  All Rights Reserved.
   3  *
   4  *  This is free software; you can redistribute it and/or modify
   5  *  it under the terms of the GNU General Public License as published by
   6  *  the Free Software Foundation; either version 2 of the License, or
   7  *  (at your option) any later version.
   8  *
   9  *  This software is distributed in the hope that it will be useful,
  10  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  *  GNU General Public License for more details.
  13  *
  14  *  You should have received a copy of the GNU General Public License
  15  *  along with this program; if not, write to the Free Software
  16  *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301,
  17  *  USA.
  18  */
  19
  20 /*
  21  * vncauth.c - Functions for VNC password management and authentication.
  22  */
  23
  24 #include <stdio.h>
  25 #include <stdlib.h>
  26 #include <string.h>
  27 #include <sys/types.h>
  28 #include <sys/stat.h>
  29 #include <vncauth.h>
  30 #include <d3des.h>
  31
  32 #ifdef __GNUC__
  33 #warning If we keep this, it needs to be cleaned up
  34 #endif
  35 #include <time.h>
  36 #include <sys/time.h>
  37
  38 /*
  39  * We use a fixed key to store passwords, since we assume that our local
  40  * file system is secure but nonetheless don't want to store passwords
  41  * as plaintext.
  42  */
  43
  44 unsigned char fixedkey[8] = {23,82,107,6,35,78,88,7};
  45
  46
  47 /*
  48  * Encrypt a password and store it in a file.  Returns 0 if successful,
  49  * 1 if the file could not be written.
  50  */
  51
  52 int
  53 vncEncryptAndStorePasswd(char *passwd, char *fname)
  54 {
  55     FILE *fp;
  56     int i;
  57     unsigned char encryptedPasswd[8];
  58
  59     if ((fp = fopen(fname,"w")) == NULL) return 1;
  60
  61     chmod(fname, S_IRUSR|S_IWUSR);
  62
  63     /* pad password with nulls */
  64
  65     for (i = 0; i < 8; i++) {
  66         if (i < strlen(passwd)) {
  67             encryptedPasswd[i] = passwd[i];
  68         } else {
  69             encryptedPasswd[i] = 0;
  70         }
  71     }
  72
  73     /* Do encryption in-place - this way we overwrite our copy of the plaintext
  74        password */
  75
  76     deskey(fixedkey, EN0);
  77     des(encryptedPasswd, encryptedPasswd);
  78
  79     for (i = 0; i < 8; i++) {
  80         putc(encryptedPasswd[i], fp);
  81     }
  82
  83     fclose(fp);
  84     return 0;
  85 }
  86
  87
  88 /*
  89  * Decrypt a password from a file.  Returns a pointer to a newly allocated
  90  * string containing the password or a null pointer if the password could
  91  * not be retrieved for some reason.
  92  */
  93
  94 char *
  95 vncDecryptPasswdFromFile(char *fname)
  96 {
  97     FILE *fp;
  98     int i, ch;
  99     unsigned char *passwd;
 100
 101     if ((fp = fopen(fname,"r")) == NULL) return NULL;
 102
 103     passwd = (unsigned char *)malloc(9);
 104
 105     for (i = 0; i < 8; i++) {
 106         ch = getc(fp);
 107         if (ch == EOF) {
 108             fclose(fp);
 109             return NULL;
 110         }
 111         passwd[i] = ch;
 112     }
 113
 114     fclose(fp);
 115
 116     deskey(fixedkey, DE1);
 117     des(passwd, passwd);
 118
 119     passwd[8] = 0;
 120
 121     return (char *)passwd;
 122 }
 123
 124
 125 /*
 126  * Generate CHALLENGESIZE random bytes for use in challenge-response
 127  * authentication.
 128  */
 129
 130 void
 131 vncRandomBytes(unsigned char *bytes)
 132 {
 133     int i;
 134     unsigned int seed = (unsigned int) time(0);
 135
 136     srandom(seed);
 137     for (i = 0; i < CHALLENGESIZE; i++) {
 138         bytes[i] = (unsigned char)(random() & 255);
 139     }
 140 }
 141
 142
 143 /*
 144  * Encrypt CHALLENGESIZE bytes in memory using a password.
 145  */
 146
 147 void
 148 vncEncryptBytes(unsigned char *bytes, char *passwd)
 149 {
 150     unsigned char key[8];
 151     int i;
 152
 153     /* key is simply password padded with nulls */
 154
 155     for (i = 0; i < 8; i++) {
 156         if (i < strlen(passwd)) {
 157             key[i] = passwd[i];
 158         } else {
 159             key[i] = 0;
 160         }
 161     }
 162
 163     deskey(key, EN0);
 164
 165     for (i = 0; i < CHALLENGESIZE; i += 8) {
 166         des(bytes+i, bytes+i);
 167     }
 168 }