authenticate.c

   1 /* -*- c-file-style: "linux"; -*-
   2
   3    Copyright (C) 1998-2000 by Andrew Tridgell
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 2 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program; if not, write to the Free Software
  17    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  18 */
  19
  20 /* support rsync authentication */
  21 #include "rsync.h"
  22
  23 extern char *password_file;
  24 extern int am_root;
  25
  26 /***************************************************************************
  27 encode a buffer using base64 - simple and slow algorithm. null terminates
  28 the result.
  29   ***************************************************************************/
  30 void base64_encode(char *buf, int len, char *out)
  31 {
  32         char *b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  33         int bit_offset, byte_offset, idx, i;
  34         unsigned char *d = (unsigned char *)buf;
  35         int bytes = (len*8 + 5)/6;
  36
  37         memset(out, 0, bytes+1);
  38
  39         for (i = 0; i < bytes; i++) {
  40                 byte_offset = (i*6)/8;
  41                 bit_offset = (i*6)%8;
  42                 if (bit_offset < 3) {
  43                         idx = (d[byte_offset] >> (2-bit_offset)) & 0x3F;
  44                 } else {
  45                         idx = (d[byte_offset] << (bit_offset-2)) & 0x3F;
  46                         if (byte_offset+1 < len) {
  47                                 idx |= (d[byte_offset+1] >> (8-(bit_offset-2)));
  48                         }
  49                 }
  50                 out[i] = b64[idx];
  51         }
  52 }
  53
  54 /* Generate a challenge buffer and return it base64-encoded. */
  55 static void gen_challenge(char *addr, char *challenge)
  56 {
  57         char input[32];
  58         char md4_out[MD4_SUM_LENGTH];
  59         struct timeval tv;
  60
  61         memset(input, 0, sizeof input);
  62
  63         strlcpy((char *)input, addr, 17);
  64         sys_gettimeofday(&tv);
  65         SIVAL(input, 16, tv.tv_sec);
  66         SIVAL(input, 20, tv.tv_usec);
  67         SIVAL(input, 24, getpid());
  68
  69         sum_init(0);
  70         sum_update(input, sizeof input);
  71         sum_end(md4_out);
  72
  73         base64_encode(md4_out, MD4_SUM_LENGTH, challenge);
  74 }
  75
  76
  77 /* Return the secret for a user from the secret file, null terminated.
  78  * Maximum length is len (not counting the null). */
  79 static int get_secret(int module, char *user, char *secret, int len)
  80 {
  81         char *fname = lp_secrets_file(module);
  82         STRUCT_STAT st;
  83         int fd, ok = 1;
  84         char ch, *p;
  85
  86         if (!fname || !*fname)
  87                 return 0;
  88
  89         if ((fd = open(fname, O_RDONLY)) < 0)
  90                 return 0;
  91
  92         if (do_stat(fname, &st) == -1) {
  93                 rsyserr(FLOG, errno, "stat(%s)", safe_fname(fname));
  94                 ok = 0;
  95         } else if (lp_strict_modes(module)) {
  96                 if ((st.st_mode & 06) != 0) {
  97                         rprintf(FLOG, "secrets file must not be other-accessible (see strict modes option)\n");
  98                         ok = 0;
  99                 } else if (am_root && (st.st_uid != 0)) {
 100                         rprintf(FLOG, "secrets file must be owned by root when running as root (see strict modes)\n");
 101                         ok = 0;
 102                 }
 103         }
 104         if (!ok) {
 105                 rprintf(FLOG, "continuing without secrets file\n");
 106                 close(fd);
 107                 return 0;
 108         }
 109
 110         if (*user == '#') {
 111                 /* Reject attempt to match a comment. */
 112                 close(fd);
 113                 return 0;
 114         }
 115
 116         /* Try to find a line that starts with the user name and a ':'. */
 117         p = user;
 118         while (1) {
 119                 if (read(fd, &ch, 1) != 1) {
 120                         close(fd);
 121                         return 0;
 122                 }
 123                 if (ch == '\n')
 124                         p = user;
 125                 else if (p) {
 126                         if (*p == ch)
 127                                 p++;
 128                         else if (!*p && ch == ':')
 129                                 break;
 130                         else
 131                                 p = NULL;
 132                 }
 133         }
 134
 135         /* Slurp the secret into the "secret" buffer. */
 136         p = secret;
 137         while (len > 0) {
 138                 if (read(fd, p, 1) != 1 || *p == '\n')
 139                         break;
 140                 if (*p == '\r')
 141                         continue;
 142                 p++;
 143                 len--;
 144         }
 145         *p = '\0';
 146         close(fd);
 147
 148         return 1;
 149 }
 150
 151 static char *getpassf(char *filename)
 152 {
 153         STRUCT_STAT st;
 154         char buffer[512], *p;
 155         int fd, n, ok = 1;
 156         char *envpw = getenv("RSYNC_PASSWORD");
 157
 158         if (!filename)
 159                 return NULL;
 160
 161         if ((fd = open(filename,O_RDONLY)) < 0) {
 162                 rsyserr(FERROR, errno, "could not open password file \"%s\"",
 163                         safe_fname(filename));
 164                 if (envpw)
 165                         rprintf(FERROR, "falling back to RSYNC_PASSWORD environment variable.\n");
 166                 return NULL;
 167         }
 168
 169         if (do_stat(filename, &st) == -1) {
 170                 rsyserr(FERROR, errno, "stat(%s)", safe_fname(filename));
 171                 ok = 0;
 172         } else if ((st.st_mode & 06) != 0) {
 173                 rprintf(FERROR,"password file must not be other-accessible\n");
 174                 ok = 0;
 175         } else if (am_root && st.st_uid != 0) {
 176                 rprintf(FERROR,"password file must be owned by root when running as root\n");
 177                 ok = 0;
 178         }
 179         if (!ok) {
 180                 rprintf(FERROR,"continuing without password file\n");
 181                 if (envpw)
 182                         rprintf(FERROR, "using RSYNC_PASSWORD environment variable.\n");
 183                 close(fd);
 184                 return NULL;
 185         }
 186
 187         if (envpw)
 188                 rprintf(FERROR, "RSYNC_PASSWORD environment variable ignored\n");
 189
 190         n = read(fd, buffer, sizeof buffer - 1);
 191         close(fd);
 192         if (n > 0) {
 193                 buffer[n] = '\0';
 194                 if ((p = strtok(buffer, "\n\r")) != NULL)
 195                         return strdup(p);
 196         }
 197
 198         return NULL;
 199 }
 200
 201 /* Generate an MD4 hash created from the combination of the password
 202  * and the challenge string and return it base64-encoded. */
 203 static void generate_hash(char *in, char *challenge, char *out)
 204 {
 205         char buf[MD4_SUM_LENGTH];
 206
 207         sum_init(0);
 208         sum_update(in, strlen(in));
 209         sum_update(challenge, strlen(challenge));
 210         sum_end(buf);
 211
 212         base64_encode(buf, MD4_SUM_LENGTH, out);
 213 }
 214
 215 /* Possibly negotiate authentication with the client.  Use "leader" to
 216  * start off the auth if necessary.
 217  *
 218  * Return NULL if authentication failed.  Return "" if anonymous access.
 219  * Otherwise return username.
 220  */
 221 char *auth_server(int f_in, int f_out, int module, char *host, char *addr,
 222                   char *leader)
 223 {
 224         char *users = lp_auth_users(module);
 225         char challenge[MD4_SUM_LENGTH*2];
 226         char line[MAXPATHLEN];
 227         char secret[512];
 228         char pass2[MD4_SUM_LENGTH*2];
 229         char *tok, *pass;
 230
 231         /* if no auth list then allow anyone in! */
 232         if (!users || !*users)
 233                 return "";
 234
 235         gen_challenge(addr, challenge);
 236
 237         io_printf(f_out, "%s%s\n", leader, challenge);
 238
 239         if (!read_line(f_in, line, sizeof line - 1)
 240          || (pass = strchr(line, ' ')) == NULL) {
 241                 rprintf(FLOG, "auth failed on module %s from %s (%s): "
 242                         "invalid challenge response\n",
 243                         lp_name(module), host, addr);
 244                 return NULL;
 245         }
 246         *pass++ = '\0';
 247
 248         if (!(users = strdup(users)))
 249                 out_of_memory("auth_server");
 250
 251         for (tok = strtok(users, " ,\t"); tok; tok = strtok(NULL, " ,\t")) {
 252                 if (wildmatch(tok, line))
 253                         break;
 254         }
 255         free(users);
 256
 257         if (!tok) {
 258                 rprintf(FLOG, "auth failed on module %s from %s (%s): "
 259                         "unauthorized user\n",
 260                         lp_name(module), host, addr);
 261                 return NULL;
 262         }
 263
 264         memset(secret, 0, sizeof secret);
 265         if (!get_secret(module, line, secret, sizeof secret - 1)) {
 266                 memset(secret, 0, sizeof secret);
 267                 rprintf(FLOG, "auth failed on module %s from %s (%s): "
 268                         "missing secret for user \"%s\"\n",
 269                         lp_name(module), host, addr, line);
 270                 return NULL;
 271         }
 272
 273         generate_hash(secret, challenge, pass2);
 274         memset(secret, 0, sizeof secret);
 275
 276         if (strcmp(pass, pass2) != 0) {
 277                 rprintf(FLOG, "auth failed on module %s from %s (%s): "
 278                         "password mismatch\n",
 279                         lp_name(module), host, addr);
 280                 return NULL;
 281         }
 282
 283         return strdup(line);
 284 }
 285
 286
 287 void auth_client(int fd, char *user, char *challenge)
 288 {
 289         char *pass;
 290         char pass2[MD4_SUM_LENGTH*2];
 291
 292         if (!user || !*user)
 293                 user = "nobody";
 294
 295         if (!(pass = getpassf(password_file))
 296          && !(pass = getenv("RSYNC_PASSWORD"))) {
 297                 /* XXX: cyeoh says that getpass is deprecated, because
 298                  * it may return a truncated password on some systems,
 299                  * and it is not in the LSB.
 300                  *
 301                  * Andrew Klein says that getpassphrase() is present
 302                  * on Solaris and reads up to 256 characters.
 303                  *
 304                  * OpenBSD has a readpassphrase() that might be more suitable.
 305                  */
 306                 pass = getpass("Password: ");
 307         }
 308
 309         if (!pass)
 310                 pass = "";
 311
 312         generate_hash(pass, challenge, pass2);
 313         io_printf(fd, "%s %s\n", user, pass2);
 314 }