authenticate.c

   1 /*
   2  * Support rsync daemon authentication.
   3  *
   4  * Copyright (C) 1998-2000 Andrew Tridgell
   5  * Copyright (C) 2002-2022 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 #include "ifuncs.h"
  24
  25 extern int read_only;
  26 extern char *password_file;
  27 extern struct name_num_obj valid_auth_checksums;
  28
  29 /***************************************************************************
  30 encode a buffer using base64 - simple and slow algorithm. null terminates
  31 the result.
  32   ***************************************************************************/
  33 void base64_encode(const char *buf, int len, char *out, int pad)
  34 {
  35         char *b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  36         int bit_offset, byte_offset, idx, i;
  37         const uchar *d = (const uchar *)buf;
  38         int bytes = (len*8 + 5)/6;
  39
  40         for (i = 0; i < bytes; i++) {
  41                 byte_offset = (i*6)/8;
  42                 bit_offset = (i*6)%8;
  43                 if (bit_offset < 3) {
  44                         idx = (d[byte_offset] >> (2-bit_offset)) & 0x3F;
  45                 } else {
  46                         idx = (d[byte_offset] << (bit_offset-2)) & 0x3F;
  47                         if (byte_offset+1 < len) {
  48                                 idx |= (d[byte_offset+1] >> (8-(bit_offset-2)));
  49                         }
  50                 }
  51                 out[i] = b64[idx];
  52         }
  53
  54         while (pad && (i % 4))
  55                 out[i++] = '=';
  56
  57         out[i] = '\0';
  58 }
  59
  60 /* Generate a challenge buffer and return it base64-encoded. */
  61 static void gen_challenge(const char *addr, char *challenge)
  62 {
  63         char input[32];
  64         char digest[MAX_DIGEST_LEN];
  65         struct timeval tv;
  66         int len;
  67
  68         memset(input, 0, sizeof input);
  69
  70         strlcpy(input, addr, 17);
  71         sys_gettimeofday(&tv);
  72         SIVAL(input, 16, tv.tv_sec);
  73         SIVAL(input, 20, tv.tv_usec);
  74         SIVAL(input, 24, getpid());
  75
  76         len = sum_init(valid_auth_checksums.negotiated_nni, 0);
  77         sum_update(input, sizeof input);
  78         sum_end(digest);
  79
  80         base64_encode(digest, len, challenge, 0);
  81 }
  82
  83 /* Generate an MD4 hash created from the combination of the password
  84  * and the challenge string and return it base64-encoded. */
  85 static void generate_hash(const char *in, const char *challenge, char *out)
  86 {
  87         char buf[MAX_DIGEST_LEN];
  88         int len;
  89
  90         len = sum_init(valid_auth_checksums.negotiated_nni, 0);
  91         sum_update(in, strlen(in));
  92         sum_update(challenge, strlen(challenge));
  93         sum_end(buf);
  94
  95         base64_encode(buf, len, out, 0);
  96 }
  97
  98 /* Return the secret for a user from the secret file, null terminated.
  99  * Maximum length is len (not counting the null). */
 100 static const char *check_secret(int module, const char *user, const char *group,
 101                                 const char *challenge, const char *pass)
 102 {
 103         char line[1024];
 104         char pass2[MAX_DIGEST_LEN*2];
 105         const char *fname = lp_secrets_file(module);
 106         STRUCT_STAT st;
 107         int ok = 1;
 108         int user_len = strlen(user);
 109         int group_len = group ? strlen(group) : 0;
 110         char *err;
 111         FILE *fh;
 112
 113         if (!fname || !*fname || (fh = fopen(fname, "r")) == NULL)
 114                 return "no secrets file";
 115
 116         if (do_fstat(fileno(fh), &st) == -1) {
 117                 rsyserr(FLOG, errno, "fstat(%s)", fname);
 118                 ok = 0;
 119         } else if (lp_strict_modes(module)) {
 120                 if ((st.st_mode & 06) != 0) {
 121                         rprintf(FLOG, "secrets file must not be other-accessible (see strict modes option)\n");
 122                         ok = 0;
 123                 } else if (MY_UID() == ROOT_UID && st.st_uid != ROOT_UID) {
 124                         rprintf(FLOG, "secrets file must be owned by root when running as root (see strict modes)\n");
 125                         ok = 0;
 126                 }
 127         }
 128         if (!ok) {
 129                 fclose(fh);
 130                 return "ignoring secrets file";
 131         }
 132
 133         if (*user == '#') {
 134                 /* Reject attempt to match a comment. */
 135                 fclose(fh);
 136                 return "invalid username";
 137         }
 138
 139         /* Try to find a line that starts with the user (or @group) name and a ':'. */
 140         err = "secret not found";
 141         while ((user || group) && fgets(line, sizeof line, fh) != NULL) {
 142                 const char **ptr, *s = strtok(line, "\n\r");
 143                 int len;
 144                 if (!s)
 145                         continue;
 146                 if (*s == '@') {
 147                         ptr = &group;
 148                         len = group_len;
 149                         s++;
 150                 } else {
 151                         ptr = &user;
 152                         len = user_len;
 153                 }
 154                 if (!*ptr || strncmp(s, *ptr, len) != 0 || s[len] != ':')
 155                         continue;
 156                 generate_hash(s+len+1, challenge, pass2);
 157                 if (strcmp(pass, pass2) == 0) {
 158                         err = NULL;
 159                         break;
 160                 }
 161                 err = "password mismatch";
 162                 *ptr = NULL; /* Don't look for name again. */
 163         }
 164
 165         fclose(fh);
 166
 167         force_memzero(line, sizeof line);
 168         force_memzero(pass2, sizeof pass2);
 169
 170         return err;
 171 }
 172
 173 static const char *getpassf(const char *filename)
 174 {
 175         STRUCT_STAT st;
 176         char buffer[512], *p;
 177         int n;
 178
 179         if (!filename)
 180                 return NULL;
 181
 182         if (strcmp(filename, "-") == 0) {
 183                 n = fgets(buffer, sizeof buffer, stdin) == NULL ? -1 : (int)strlen(buffer);
 184         } else {
 185                 int fd;
 186
 187                 if ((fd = open(filename,O_RDONLY)) < 0) {
 188                         rsyserr(FERROR, errno, "could not open password file %s", filename);
 189                         exit_cleanup(RERR_SYNTAX);
 190                 }
 191
 192                 if (do_stat(filename, &st) == -1) {
 193                         rsyserr(FERROR, errno, "stat(%s)", filename);
 194                         exit_cleanup(RERR_SYNTAX);
 195                 }
 196                 if ((st.st_mode & 06) != 0) {
 197                         rprintf(FERROR, "ERROR: password file must not be other-accessible\n");
 198                         exit_cleanup(RERR_SYNTAX);
 199                 }
 200                 if (MY_UID() == ROOT_UID && st.st_uid != ROOT_UID) {
 201                         rprintf(FERROR, "ERROR: password file must be owned by root when running as root\n");
 202                         exit_cleanup(RERR_SYNTAX);
 203                 }
 204
 205                 n = read(fd, buffer, sizeof buffer - 1);
 206                 close(fd);
 207         }
 208
 209         if (n > 0) {
 210                 buffer[n] = '\0';
 211                 if ((p = strtok(buffer, "\n\r")) != NULL)
 212                         return strdup(p);
 213         }
 214
 215         rprintf(FERROR, "ERROR: failed to read a password from %s\n", filename);
 216         exit_cleanup(RERR_SYNTAX);
 217 }
 218
 219 /* Possibly negotiate authentication with the client.  Use "leader" to
 220  * start off the auth if necessary.
 221  *
 222  * Return NULL if authentication failed.  Return "" if anonymous access.
 223  * Otherwise return username.
 224  */
 225 char *auth_server(int f_in, int f_out, int module, const char *host,
 226                   const char *addr, const char *leader)
 227 {
 228         char *users = lp_auth_users(module);
 229         char challenge[MAX_DIGEST_LEN*2];
 230         char line[BIGPATHBUFLEN];
 231         const char **auth_uid_groups = NULL;
 232         int auth_uid_groups_cnt = -1;
 233         const char *err = NULL;
 234         int group_match = -1;
 235         char *tok, *pass;
 236         char opt_ch = '\0';
 237
 238         /* if no auth list then allow anyone in! */
 239         if (!users || !*users)
 240                 return "";
 241
 242         negotiate_daemon_auth(f_out, 0);
 243         gen_challenge(addr, challenge);
 244
 245         io_printf(f_out, "%s%s\n", leader, challenge);
 246
 247         if (!read_line_old(f_in, line, sizeof line, 0)
 248          || (pass = strchr(line, ' ')) == NULL) {
 249                 rprintf(FLOG, "auth failed on module %s from %s (%s): "
 250                         "invalid challenge response\n",
 251                         lp_name(module), host, addr);
 252                 return NULL;
 253         }
 254         *pass++ = '\0';
 255
 256         users = strdup(users);
 257
 258         for (tok = strtok(users, " ,\t"); tok; tok = strtok(NULL, " ,\t")) {
 259                 char *opts;
 260                 /* See if the user appended :deny, :ro, or :rw. */
 261                 if ((opts = strchr(tok, ':')) != NULL) {
 262                         *opts++ = '\0';
 263                         opt_ch = isUpper(opts) ? toLower(opts) : *opts;
 264                         if (opt_ch == 'r') { /* handle ro and rw */
 265                                 opt_ch = isUpper(opts+1) ? toLower(opts+1) : opts[1];
 266                                 if (opt_ch == 'o')
 267                                         opt_ch = 'r';
 268                                 else if (opt_ch != 'w')
 269                                         opt_ch = '\0';
 270                         } else if (opt_ch != 'd') /* if it's not deny, ignore it */
 271                                 opt_ch = '\0';
 272                 } else
 273                         opt_ch = '\0';
 274                 if (*tok != '@') {
 275                         /* Match the username */
 276                         if (wildmatch(tok, line))
 277                                 break;
 278                 } else {
 279 #ifdef HAVE_GETGROUPLIST
 280                         int j;
 281                         /* See if authorizing user is a real user, and if so, see
 282                          * if it is in a group that matches tok+1 wildmat. */
 283                         if (auth_uid_groups_cnt < 0) {
 284                                 item_list gid_list = EMPTY_ITEM_LIST;
 285                                 uid_t auth_uid;
 286                                 if (!user_to_uid(line, &auth_uid, False)
 287                                  || getallgroups(auth_uid, &gid_list) != NULL)
 288                                         auth_uid_groups_cnt = 0;
 289                                 else {
 290                                         gid_t *gid_array = gid_list.items;
 291                                         auth_uid_groups_cnt = gid_list.count;
 292                                         auth_uid_groups = new_array(const char *, auth_uid_groups_cnt);
 293                                         for (j = 0; j < auth_uid_groups_cnt; j++)
 294                                                 auth_uid_groups[j] = gid_to_group(gid_array[j]);
 295                                 }
 296                         }
 297                         for (j = 0; j < auth_uid_groups_cnt; j++) {
 298                                 if (auth_uid_groups[j] && wildmatch(tok+1, auth_uid_groups[j])) {
 299                                         group_match = j;
 300                                         break;
 301                                 }
 302                         }
 303                         if (group_match >= 0)
 304                                 break;
 305 #else
 306                         rprintf(FLOG, "your computer doesn't support getgrouplist(), so no @group authorization is possible.\n");
 307 #endif
 308                 }
 309         }
 310
 311         free(users);
 312
 313         if (!tok)
 314                 err = "no matching rule";
 315         else if (opt_ch == 'd')
 316                 err = "denied by rule";
 317         else {
 318                 const char *group = group_match >= 0 ? auth_uid_groups[group_match] : NULL;
 319                 err = check_secret(module, line, group, challenge, pass);
 320         }
 321
 322         force_memzero(challenge, sizeof challenge);
 323         force_memzero(pass, strlen(pass));
 324
 325         if (auth_uid_groups) {
 326                 int j;
 327                 for (j = 0; j < auth_uid_groups_cnt; j++) {
 328                         if (auth_uid_groups[j])
 329                                 free((char*)auth_uid_groups[j]);
 330                 }
 331                 free(auth_uid_groups);
 332         }
 333
 334         if (err) {
 335                 rprintf(FLOG, "auth failed on module %s from %s (%s) for %s: %s\n",
 336                         lp_name(module), host, addr, line, err);
 337                 return NULL;
 338         }
 339
 340         if (opt_ch == 'r')
 341                 read_only = 1;
 342         else if (opt_ch == 'w')
 343                 read_only = 0;
 344
 345         return strdup(line);
 346 }
 347
 348 void auth_client(int fd, const char *user, const char *challenge)
 349 {
 350         const char *pass;
 351         char pass2[MAX_DIGEST_LEN*2];
 352
 353         if (!user || !*user)
 354                 user = "nobody";
 355         negotiate_daemon_auth(-1, 1);
 356
 357         if (!(pass = getpassf(password_file))
 358          && !(pass = getenv("RSYNC_PASSWORD"))) {
 359                 /* XXX: cyeoh says that getpass is deprecated, because
 360                  * it may return a truncated password on some systems,
 361                  * and it is not in the LSB.
 362                  *
 363                  * Andrew Klein says that getpassphrase() is present
 364                  * on Solaris and reads up to 256 characters.
 365                  *
 366                  * OpenBSD has a readpassphrase() that might be more suitable.
 367                  */
 368                 pass = getpass("Password: ");
 369         }
 370
 371         if (!pass)
 372                 pass = "";
 373
 374         generate_hash(pass, challenge, pass2);
 375         io_printf(fd, "%s %s\n", user, pass2);
 376 }