authenticate.c

   1 /*
   2  * Support rsync daemon authentication.
   3  *
   4  * Copyright (C) 1998-2000 Andrew Tridgell
   5  * Copyright (C) 2002-2009 Wayne Davison
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 3 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License along
  18  * with this program; if not, visit the http://fsf.org website.
  19  */
  20
  21 #include "rsync.h"
  22 #include "itypes.h"
  23
  24 extern int read_only;
  25 extern char *password_file;
  26
  27 /***************************************************************************
  28 encode a buffer using base64 - simple and slow algorithm. null terminates
  29 the result.
  30   ***************************************************************************/
  31 void base64_encode(const char *buf, int len, char *out, int pad)
  32 {
  33         char *b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  34         int bit_offset, byte_offset, idx, i;
  35         const uchar *d = (const uchar *)buf;
  36         int bytes = (len*8 + 5)/6;
  37
  38         for (i = 0; i < bytes; i++) {
  39                 byte_offset = (i*6)/8;
  40                 bit_offset = (i*6)%8;
  41                 if (bit_offset < 3) {
  42                         idx = (d[byte_offset] >> (2-bit_offset)) & 0x3F;
  43                 } else {
  44                         idx = (d[byte_offset] << (bit_offset-2)) & 0x3F;
  45                         if (byte_offset+1 < len) {
  46                                 idx |= (d[byte_offset+1] >> (8-(bit_offset-2)));
  47                         }
  48                 }
  49                 out[i] = b64[idx];
  50         }
  51
  52         while (pad && (i % 4))
  53                 out[i++] = '=';
  54
  55         out[i] = '\0';
  56 }
  57
  58 /* Generate a challenge buffer and return it base64-encoded. */
  59 static void gen_challenge(const char *addr, char *challenge)
  60 {
  61         char input[32];
  62         char digest[MAX_DIGEST_LEN];
  63         struct timeval tv;
  64         int len;
  65
  66         memset(input, 0, sizeof input);
  67
  68         strlcpy(input, addr, 17);
  69         sys_gettimeofday(&tv);
  70         SIVAL(input, 16, tv.tv_sec);
  71         SIVAL(input, 20, tv.tv_usec);
  72         SIVAL(input, 24, getpid());
  73
  74         sum_init(0);
  75         sum_update(input, sizeof input);
  76         len = sum_end(digest);
  77
  78         base64_encode(digest, len, challenge, 0);
  79 }
  80
  81 /* Generate an MD4 hash created from the combination of the password
  82  * and the challenge string and return it base64-encoded. */
  83 static void generate_hash(const char *in, const char *challenge, char *out)
  84 {
  85         char buf[MAX_DIGEST_LEN];
  86         int len;
  87
  88         sum_init(0);
  89         sum_update(in, strlen(in));
  90         sum_update(challenge, strlen(challenge));
  91         len = sum_end(buf);
  92
  93         base64_encode(buf, len, out, 0);
  94 }
  95
  96 /* Return the secret for a user from the secret file, null terminated.
  97  * Maximum length is len (not counting the null). */
  98 static const char *check_secret(int module, const char *user, const char *group,
  99                                 const char *challenge, const char *pass)
 100 {
 101         char line[1024];
 102         char pass2[MAX_DIGEST_LEN*2];
 103         const char *fname = lp_secrets_file(module);
 104         STRUCT_STAT st;
 105         int fd, ok = 1;
 106         int user_len = strlen(user);
 107         int group_len = group ? strlen(group) : 0;
 108         char *err;
 109
 110         if (!fname || !*fname || (fd = open(fname, O_RDONLY)) < 0)
 111                 return "no secrets file";
 112
 113         if (do_fstat(fd, &st) == -1) {
 114                 rsyserr(FLOG, errno, "fstat(%s)", fname);
 115                 ok = 0;
 116         } else if (lp_strict_modes(module)) {
 117                 if ((st.st_mode & 06) != 0) {
 118                         rprintf(FLOG, "secrets file must not be other-accessible (see strict modes option)\n");
 119                         ok = 0;
 120                 } else if (MY_UID() == 0 && st.st_uid != 0) {
 121                         rprintf(FLOG, "secrets file must be owned by root when running as root (see strict modes)\n");
 122                         ok = 0;
 123                 }
 124         }
 125         if (!ok) {
 126                 close(fd);
 127                 return "ignoring secrets file";
 128         }
 129
 130         if (*user == '#') {
 131                 /* Reject attempt to match a comment. */
 132                 close(fd);
 133                 return "invalid username";
 134         }
 135
 136         /* Try to find a line that starts with the user (or @group) name and a ':'. */
 137         err = "secret not found";
 138         while ((user || group) && read_line_old(fd, line, sizeof line, 1)) {
 139                 const char **ptr, *s;
 140                 int len;
 141                 if (*line == '@') {
 142                         ptr = &group;
 143                         len = group_len;
 144                         s = line+1;
 145                 } else {
 146                         ptr = &user;
 147                         len = user_len;
 148                         s = line;
 149                 }
 150                 if (!*ptr || strncmp(s, *ptr, len) != 0 || s[len] != ':')
 151                         continue;
 152                 generate_hash(s+len+1, challenge, pass2);
 153                 if (strcmp(pass, pass2) == 0) {
 154                         err = NULL;
 155                         break;
 156                 }
 157                 err = "password mismatch";
 158                 *ptr = NULL; /* Don't look for name again. */
 159         }
 160
 161         close(fd);
 162
 163         memset(line, 0, sizeof line);
 164         memset(pass2, 0, sizeof pass2);
 165
 166         return err;
 167 }
 168
 169 static const char *getpassf(const char *filename)
 170 {
 171         STRUCT_STAT st;
 172         char buffer[512], *p;
 173         int fd, n, ok = 1;
 174         const char *envpw = getenv("RSYNC_PASSWORD");
 175
 176         if (!filename)
 177                 return NULL;
 178
 179         if ((fd = open(filename,O_RDONLY)) < 0) {
 180                 rsyserr(FWARNING, errno, "could not open password file \"%s\"",
 181                         filename);
 182                 if (envpw)
 183                         rprintf(FINFO, "falling back to RSYNC_PASSWORD environment variable.\n");
 184                 return NULL;
 185         }
 186
 187         if (do_stat(filename, &st) == -1) {
 188                 rsyserr(FWARNING, errno, "stat(%s)", filename);
 189                 ok = 0;
 190         } else if ((st.st_mode & 06) != 0) {
 191                 rprintf(FWARNING, "password file must not be other-accessible\n");
 192                 ok = 0;
 193         } else if (MY_UID() == 0 && st.st_uid != 0) {
 194                 rprintf(FWARNING, "password file must be owned by root when running as root\n");
 195                 ok = 0;
 196         }
 197         if (!ok) {
 198                 close(fd);
 199                 rprintf(FWARNING, "continuing without password file\n");
 200                 if (envpw)
 201                         rprintf(FINFO, "falling back to RSYNC_PASSWORD environment variable.\n");
 202                 return NULL;
 203         }
 204
 205         n = read(fd, buffer, sizeof buffer - 1);
 206         close(fd);
 207         if (n > 0) {
 208                 buffer[n] = '\0';
 209                 if ((p = strtok(buffer, "\n\r")) != NULL)
 210                         return strdup(p);
 211         }
 212
 213         return NULL;
 214 }
 215
 216 /* Possibly negotiate authentication with the client.  Use "leader" to
 217  * start off the auth if necessary.
 218  *
 219  * Return NULL if authentication failed.  Return "" if anonymous access.
 220  * Otherwise return username.
 221  */
 222 char *auth_server(int f_in, int f_out, int module, const char *host,
 223                   const char *addr, const char *leader)
 224 {
 225         char *users = lp_auth_users(module);
 226         char challenge[MAX_DIGEST_LEN*2];
 227         char line[BIGPATHBUFLEN];
 228         char **auth_uid_groups = NULL;
 229         int auth_uid_groups_cnt = -1;
 230         const char *err = NULL;
 231         int group_match = -1;
 232         char *tok, *pass;
 233         char opt_ch = '\0';
 234
 235         /* if no auth list then allow anyone in! */
 236         if (!users || !*users)
 237                 return "";
 238
 239         gen_challenge(addr, challenge);
 240
 241         io_printf(f_out, "%s%s\n", leader, challenge);
 242
 243         if (!read_line_old(f_in, line, sizeof line, 0)
 244          || (pass = strchr(line, ' ')) == NULL) {
 245                 rprintf(FLOG, "auth failed on module %s from %s (%s): "
 246                         "invalid challenge response\n",
 247                         lp_name(module), host, addr);
 248                 return NULL;
 249         }
 250         *pass++ = '\0';
 251
 252         if (!(users = strdup(users)))
 253                 out_of_memory("auth_server");
 254
 255         for (tok = strtok(users, " ,\t"); tok; tok = strtok(NULL, " ,\t")) {
 256                 char *opts;
 257                 /* See if the user appended :deny, :ro, or :rw. */
 258                 if ((opts = strchr(tok, ':')) != NULL) {
 259                         *opts++ = '\0';
 260                         opt_ch = isUpper(opts) ? toLower(opts) : *opts;
 261                         if (opt_ch == 'r') { /* handle ro and rw */
 262                                 opt_ch = isUpper(opts+1) ? toLower(opts+1) : opts[1];
 263                                 if (opt_ch == 'o')
 264                                         opt_ch = 'r';
 265                                 else if (opt_ch != 'w')
 266                                         opt_ch = '\0';
 267                         } else if (opt_ch != 'd') /* if it's not deny, ignore it */
 268                                 opt_ch = '\0';
 269                 } else
 270                         opt_ch = '\0';
 271                 if (*tok != '@') {
 272                         /* Match the username */
 273                         if (wildmatch(tok, line))
 274                                 break;
 275                 } else {
 276 #ifdef HAVE_GETGROUPLIST
 277                         int j;
 278                         /* See if authorizing user is a real user, and if so, see
 279                          * if it is in a group that matches tok+1 wildmat. */
 280                         if (auth_uid_groups_cnt < 0) {
 281                                 gid_t gid_list[64];
 282                                 uid_t auth_uid;
 283                                 auth_uid_groups_cnt = sizeof gid_list / sizeof (gid_t);
 284                                 if (!user_to_uid(line, &auth_uid, False)
 285                                  || getallgroups(auth_uid, gid_list, &auth_uid_groups_cnt) != NULL)
 286                                         auth_uid_groups_cnt = 0;
 287                                 else {
 288                                         if ((auth_uid_groups = new_array(char *, auth_uid_groups_cnt)) == NULL)
 289                                                 out_of_memory("auth_server");
 290                                         for (j = 0; j < auth_uid_groups_cnt; j++)
 291                                                 auth_uid_groups[j] = gid_to_group(gid_list[j]);
 292                                 }
 293                         }
 294                         for (j = 0; j < auth_uid_groups_cnt; j++) {
 295                                 if (auth_uid_groups[j] && wildmatch(tok+1, auth_uid_groups[j])) {
 296                                         group_match = j;
 297                                         break;
 298                                 }
 299                         }
 300                         if (group_match >= 0)
 301                                 break;
 302 #else
 303                         rprintf(FLOG, "your computer doesn't support getgrouplist(), so no @group authorization is possible.\n");
 304 #endif
 305                 }
 306         }
 307
 308         free(users);
 309
 310         if (!tok)
 311                 err = "no matching rule";
 312         else if (opt_ch == 'd')
 313                 err = "denied by rule";
 314         else {
 315                 char *group = group_match >= 0 ? auth_uid_groups[group_match] : NULL;
 316                 err = check_secret(module, line, group, challenge, pass);
 317         }
 318
 319         memset(challenge, 0, sizeof challenge);
 320         memset(pass, 0, strlen(pass));
 321
 322         if (auth_uid_groups) {
 323                 int j;
 324                 for (j = 0; j < auth_uid_groups_cnt; j++) {
 325                         if (auth_uid_groups[j])
 326                                 free(auth_uid_groups[j]);
 327                 }
 328                 free(auth_uid_groups);
 329         }
 330
 331         if (err) {
 332                 rprintf(FLOG, "auth failed on module %s from %s (%s) for %s: %s\n",
 333                         lp_name(module), host, addr, line, err);
 334                 return NULL;
 335         }
 336
 337         if (opt_ch == 'r')
 338                 read_only = 1;
 339         else if (opt_ch == 'w')
 340                 read_only = 0;
 341
 342         return strdup(line);
 343 }
 344
 345 void auth_client(int fd, const char *user, const char *challenge)
 346 {
 347         const char *pass;
 348         char pass2[MAX_DIGEST_LEN*2];
 349
 350         if (!user || !*user)
 351                 user = "nobody";
 352
 353         if (!(pass = getpassf(password_file))
 354          && !(pass = getenv("RSYNC_PASSWORD"))) {
 355                 /* XXX: cyeoh says that getpass is deprecated, because
 356                  * it may return a truncated password on some systems,
 357                  * and it is not in the LSB.
 358                  *
 359                  * Andrew Klein says that getpassphrase() is present
 360                  * on Solaris and reads up to 256 characters.
 361                  *
 362                  * OpenBSD has a readpassphrase() that might be more suitable.
 363                  */
 364                 pass = getpass("Password: ");
 365         }
 366
 367         if (!pass)
 368                 pass = "";
 369
 370         generate_hash(pass, challenge, pass2);
 371         io_printf(fd, "%s %s\n", user, pass2);
 372 }