authenticate.c

   1 /*
   2  * Support rsync daemon authentication.
   3  *
   4  * Copyright (C) 1998-2000 Andrew Tridgell
   5  * Copyright (C) 2002-2020 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(-1, 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(-1, 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 ok = 1;
 106         int user_len = strlen(user);
 107         int group_len = group ? strlen(group) : 0;
 108         char *err;
 109         FILE *fh;
 110
 111         if (!fname || !*fname || (fh = fopen(fname, "r")) == NULL)
 112                 return "no secrets file";
 113
 114         if (do_fstat(fileno(fh), &st) == -1) {
 115                 rsyserr(FLOG, errno, "fstat(%s)", fname);
 116                 ok = 0;
 117         } else if (lp_strict_modes(module)) {
 118                 if ((st.st_mode & 06) != 0) {
 119                         rprintf(FLOG, "secrets file must not be other-accessible (see strict modes option)\n");
 120                         ok = 0;
 121                 } else if (MY_UID() == 0 && st.st_uid != 0) {
 122                         rprintf(FLOG, "secrets file must be owned by root when running as root (see strict modes)\n");
 123                         ok = 0;
 124                 }
 125         }
 126         if (!ok) {
 127                 fclose(fh);
 128                 return "ignoring secrets file";
 129         }
 130
 131         if (*user == '#') {
 132                 /* Reject attempt to match a comment. */
 133                 fclose(fh);
 134                 return "invalid username";
 135         }
 136
 137         /* Try to find a line that starts with the user (or @group) name and a ':'. */
 138         err = "secret not found";
 139         while ((user || group) && fgets(line, sizeof line, fh) != NULL) {
 140                 const char **ptr, *s = strtok(line, "\n\r");
 141                 int len;
 142                 if (!s)
 143                         continue;
 144                 if (*s == '@') {
 145                         ptr = &group;
 146                         len = group_len;
 147                         s++;
 148                 } else {
 149                         ptr = &user;
 150                         len = user_len;
 151                 }
 152                 if (!*ptr || strncmp(s, *ptr, len) != 0 || s[len] != ':')
 153                         continue;
 154                 generate_hash(s+len+1, challenge, pass2);
 155                 if (strcmp(pass, pass2) == 0) {
 156                         err = NULL;
 157                         break;
 158                 }
 159                 err = "password mismatch";
 160                 *ptr = NULL; /* Don't look for name again. */
 161         }
 162
 163         fclose(fh);
 164
 165         force_memzero(line, sizeof line);
 166         force_memzero(pass2, sizeof pass2);
 167
 168         return err;
 169 }
 170
 171 static const char *getpassf(const char *filename)
 172 {
 173         STRUCT_STAT st;
 174         char buffer[512], *p;
 175         int n;
 176
 177         if (!filename)
 178                 return NULL;
 179
 180         if (strcmp(filename, "-") == 0) {
 181                 n = fgets(buffer, sizeof buffer, stdin) == NULL ? -1 : (int)strlen(buffer);
 182         } else {
 183                 int fd;
 184
 185                 if ((fd = open(filename,O_RDONLY)) < 0) {
 186                         rsyserr(FERROR, errno, "could not open password file %s", filename);
 187                         exit_cleanup(RERR_SYNTAX);
 188                 }
 189
 190                 if (do_stat(filename, &st) == -1) {
 191                         rsyserr(FERROR, errno, "stat(%s)", filename);
 192                         exit_cleanup(RERR_SYNTAX);
 193                 }
 194                 if ((st.st_mode & 06) != 0) {
 195                         rprintf(FERROR, "ERROR: password file must not be other-accessible\n");
 196                         exit_cleanup(RERR_SYNTAX);
 197                 }
 198                 if (MY_UID() == 0 && st.st_uid != 0) {
 199                         rprintf(FERROR, "ERROR: password file must be owned by root when running as root\n");
 200                         exit_cleanup(RERR_SYNTAX);
 201                 }
 202
 203                 n = read(fd, buffer, sizeof buffer - 1);
 204                 close(fd);
 205         }
 206
 207         if (n > 0) {
 208                 buffer[n] = '\0';
 209                 if ((p = strtok(buffer, "\n\r")) != NULL)
 210                         return strdup(p);
 211         }
 212
 213         rprintf(FERROR, "ERROR: failed to read a password from %s\n", filename);
 214         exit_cleanup(RERR_SYNTAX);
 215 }
 216
 217 /* Possibly negotiate authentication with the client.  Use "leader" to
 218  * start off the auth if necessary.
 219  *
 220  * Return NULL if authentication failed.  Return "" if anonymous access.
 221  * Otherwise return username.
 222  */
 223 char *auth_server(int f_in, int f_out, int module, const char *host,
 224                   const char *addr, const char *leader)
 225 {
 226         char *users = lp_auth_users(module);
 227         char challenge[MAX_DIGEST_LEN*2];
 228         char line[BIGPATHBUFLEN];
 229         char **auth_uid_groups = NULL;
 230         int auth_uid_groups_cnt = -1;
 231         const char *err = NULL;
 232         int group_match = -1;
 233         char *tok, *pass;
 234         char opt_ch = '\0';
 235
 236         /* if no auth list then allow anyone in! */
 237         if (!users || !*users)
 238                 return "";
 239
 240         gen_challenge(addr, challenge);
 241
 242         io_printf(f_out, "%s%s\n", leader, challenge);
 243
 244         if (!read_line_old(f_in, line, sizeof line, 0)
 245          || (pass = strchr(line, ' ')) == NULL) {
 246                 rprintf(FLOG, "auth failed on module %s from %s (%s): "
 247                         "invalid challenge response\n",
 248                         lp_name(module), host, addr);
 249                 return NULL;
 250         }
 251         *pass++ = '\0';
 252
 253         if (!(users = strdup(users)))
 254                 out_of_memory("auth_server");
 255
 256         for (tok = strtok(users, " ,\t"); tok; tok = strtok(NULL, " ,\t")) {
 257                 char *opts;
 258                 /* See if the user appended :deny, :ro, or :rw. */
 259                 if ((opts = strchr(tok, ':')) != NULL) {
 260                         *opts++ = '\0';
 261                         opt_ch = isUpper(opts) ? toLower(opts) : *opts;
 262                         if (opt_ch == 'r') { /* handle ro and rw */
 263                                 opt_ch = isUpper(opts+1) ? toLower(opts+1) : opts[1];
 264                                 if (opt_ch == 'o')
 265                                         opt_ch = 'r';
 266                                 else if (opt_ch != 'w')
 267                                         opt_ch = '\0';
 268                         } else if (opt_ch != 'd') /* if it's not deny, ignore it */
 269                                 opt_ch = '\0';
 270                 } else
 271                         opt_ch = '\0';
 272                 if (*tok != '@') {
 273                         /* Match the username */
 274                         if (wildmatch(tok, line))
 275                                 break;
 276                 } else {
 277 #ifdef HAVE_GETGROUPLIST
 278                         int j;
 279                         /* See if authorizing user is a real user, and if so, see
 280                          * if it is in a group that matches tok+1 wildmat. */
 281                         if (auth_uid_groups_cnt < 0) {
 282                                 item_list gid_list = EMPTY_ITEM_LIST;
 283                                 uid_t auth_uid;
 284                                 if (!user_to_uid(line, &auth_uid, False)
 285                                  || getallgroups(auth_uid, &gid_list) != NULL)
 286                                         auth_uid_groups_cnt = 0;
 287                                 else {
 288                                         gid_t *gid_array = gid_list.items;
 289                                         auth_uid_groups_cnt = gid_list.count;
 290                                         if ((auth_uid_groups = new_array(char *, auth_uid_groups_cnt)) == NULL)
 291                                                 out_of_memory("auth_server");
 292                                         for (j = 0; j < auth_uid_groups_cnt; j++)
 293                                                 auth_uid_groups[j] = gid_to_group(gid_array[j]);
 294                                 }
 295                         }
 296                         for (j = 0; j < auth_uid_groups_cnt; j++) {
 297                                 if (auth_uid_groups[j] && wildmatch(tok+1, auth_uid_groups[j])) {
 298                                         group_match = j;
 299                                         break;
 300                                 }
 301                         }
 302                         if (group_match >= 0)
 303                                 break;
 304 #else
 305                         rprintf(FLOG, "your computer doesn't support getgrouplist(), so no @group authorization is possible.\n");
 306 #endif
 307                 }
 308         }
 309
 310         free(users);
 311
 312         if (!tok)
 313                 err = "no matching rule";
 314         else if (opt_ch == 'd')
 315                 err = "denied by rule";
 316         else {
 317                 char *group = group_match >= 0 ? auth_uid_groups[group_match] : NULL;
 318                 err = check_secret(module, line, group, challenge, pass);
 319         }
 320
 321         force_memzero(challenge, sizeof challenge);
 322         force_memzero(pass, strlen(pass));
 323
 324         if (auth_uid_groups) {
 325                 int j;
 326                 for (j = 0; j < auth_uid_groups_cnt; j++) {
 327                         if (auth_uid_groups[j])
 328                                 free(auth_uid_groups[j]);
 329                 }
 330                 free(auth_uid_groups);
 331         }
 332
 333         if (err) {
 334                 rprintf(FLOG, "auth failed on module %s from %s (%s) for %s: %s\n",
 335                         lp_name(module), host, addr, line, err);
 336                 return NULL;
 337         }
 338
 339         if (opt_ch == 'r')
 340                 read_only = 1;
 341         else if (opt_ch == 'w')
 342                 read_only = 0;
 343
 344         return strdup(line);
 345 }
 346
 347 void auth_client(int fd, const char *user, const char *challenge)
 348 {
 349         const char *pass;
 350         char pass2[MAX_DIGEST_LEN*2];
 351
 352         if (!user || !*user)
 353                 user = "nobody";
 354
 355         if (!(pass = getpassf(password_file))
 356          && !(pass = getenv("RSYNC_PASSWORD"))) {
 357                 /* XXX: cyeoh says that getpass is deprecated, because
 358                  * it may return a truncated password on some systems,
 359                  * and it is not in the LSB.
 360                  *
 361                  * Andrew Klein says that getpassphrase() is present
 362                  * on Solaris and reads up to 256 characters.
 363                  *
 364                  * OpenBSD has a readpassphrase() that might be more suitable.
 365                  */
 366                 pass = getpass("Password: ");
 367         }
 368
 369         if (!pass)
 370                 pass = "";
 371
 372         generate_hash(pass, challenge, pass2);
 373         io_printf(fd, "%s %s\n", user, pass2);
 374 }