authenticate.c

   1 /*
   2  * Support rsync daemon authentication.
   3  *
   4  * Copyright (C) 1998-2000 Andrew Tridgell
   5  * Copyright (C) 2002-2007 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
  23 extern char *password_file;
  24 extern int log_got_error;
  25
  26 /***************************************************************************
  27 encode a buffer using base64 - simple and slow algorithm. null terminates
  28 the result.
  29   ***************************************************************************/
  30 void base64_encode(const char *buf, int len, char *out, int pad)
  31 {
  32         char *b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  33         int bit_offset, byte_offset, idx, i;
  34         const uchar *d = (const uchar *)buf;
  35         int bytes = (len*8 + 5)/6;
  36
  37         for (i = 0; i < bytes; i++) {
  38                 byte_offset = (i*6)/8;
  39                 bit_offset = (i*6)%8;
  40                 if (bit_offset < 3) {
  41                         idx = (d[byte_offset] >> (2-bit_offset)) & 0x3F;
  42                 } else {
  43                         idx = (d[byte_offset] << (bit_offset-2)) & 0x3F;
  44                         if (byte_offset+1 < len) {
  45                                 idx |= (d[byte_offset+1] >> (8-(bit_offset-2)));
  46                         }
  47                 }
  48                 out[i] = b64[idx];
  49         }
  50
  51         while (pad && (i % 4))
  52                 out[i++] = '=';
  53
  54         out[i] = '\0';
  55 }
  56
  57 /* Generate a challenge buffer and return it base64-encoded. */
  58 static void gen_challenge(const char *addr, char *challenge)
  59 {
  60         char input[32];
  61         char digest[MAX_DIGEST_LEN];
  62         struct timeval tv;
  63         int len;
  64
  65         memset(input, 0, sizeof input);
  66
  67         strlcpy(input, addr, 17);
  68         sys_gettimeofday(&tv);
  69         SIVAL(input, 16, tv.tv_sec);
  70         SIVAL(input, 20, tv.tv_usec);
  71         SIVAL(input, 24, getpid());
  72
  73         sum_init(0);
  74         sum_update(input, sizeof input);
  75         len = sum_end(digest);
  76
  77         base64_encode(digest, len, challenge, 0);
  78 }
  79
  80
  81 /* Return the secret for a user from the secret file, null terminated.
  82  * Maximum length is len (not counting the null). */
  83 static int get_secret(int module, const char *user, char *secret, int len)
  84 {
  85         const char *fname = lp_secrets_file(module);
  86         STRUCT_STAT st;
  87         int fd, ok = 1;
  88         const char *p;
  89         char ch, *s;
  90
  91         if (!fname || !*fname)
  92                 return 0;
  93
  94         if ((fd = open(fname, O_RDONLY)) < 0)
  95                 return 0;
  96
  97         if (do_stat(fname, &st) == -1) {
  98                 rsyserr(FLOG, errno, "stat(%s)", fname);
  99                 ok = 0;
 100         } else if (lp_strict_modes(module)) {
 101                 if ((st.st_mode & 06) != 0) {
 102                         rprintf(FLOG, "secrets file must not be other-accessible (see strict modes option)\n");
 103                         ok = 0;
 104                 } else if (MY_UID() == 0 && st.st_uid != 0) {
 105                         rprintf(FLOG, "secrets file must be owned by root when running as root (see strict modes)\n");
 106                         ok = 0;
 107                 }
 108         }
 109         if (!ok) {
 110                 rprintf(FLOG, "continuing without secrets file\n");
 111                 close(fd);
 112                 return 0;
 113         }
 114
 115         if (*user == '#') {
 116                 /* Reject attempt to match a comment. */
 117                 close(fd);
 118                 return 0;
 119         }
 120
 121         /* Try to find a line that starts with the user name and a ':'. */
 122         p = user;
 123         while (1) {
 124                 if (read(fd, &ch, 1) != 1) {
 125                         close(fd);
 126                         return 0;
 127                 }
 128                 if (ch == '\n')
 129                         p = user;
 130                 else if (p) {
 131                         if (*p == ch)
 132                                 p++;
 133                         else if (!*p && ch == ':')
 134                                 break;
 135                         else
 136                                 p = NULL;
 137                 }
 138         }
 139
 140         /* Slurp the secret into the "secret" buffer. */
 141         s = secret;
 142         while (len > 0) {
 143                 if (read(fd, s, 1) != 1 || *s == '\n')
 144                         break;
 145                 if (*s == '\r')
 146                         continue;
 147                 s++;
 148                 len--;
 149         }
 150         *s = '\0';
 151         close(fd);
 152
 153         return 1;
 154 }
 155
 156 static const char *getpassf(const char *filename)
 157 {
 158         STRUCT_STAT st;
 159         char buffer[512], *p;
 160         int fd, n, ok = 1;
 161         const char *envpw = getenv("RSYNC_PASSWORD");
 162
 163         if (!filename)
 164                 return NULL;
 165
 166         if ((fd = open(filename,O_RDONLY)) < 0) {
 167                 rsyserr(FERROR, errno, "could not open password file \"%s\"",
 168                         filename);
 169                 if (envpw)
 170                         rprintf(FINFO, "falling back to RSYNC_PASSWORD environment variable.\n");
 171                 return NULL;
 172         }
 173
 174         if (do_stat(filename, &st) == -1) {
 175                 rsyserr(FERROR, errno, "stat(%s)", filename);
 176                 ok = 0;
 177         } else if ((st.st_mode & 06) != 0) {
 178                 rprintf(FERROR, "password file must not be other-accessible\n");
 179                 ok = 0;
 180         } else if (MY_UID() == 0 && st.st_uid != 0) {
 181                 rprintf(FERROR, "password file must be owned by root when running as root\n");
 182                 ok = 0;
 183         }
 184         if (!ok) {
 185                 close(fd);
 186                 rprintf(FERROR, "continuing without password file\n");
 187                 if (envpw)
 188                         rprintf(FINFO, "falling back to RSYNC_PASSWORD environment variable.\n");
 189                 return NULL;
 190         }
 191
 192         n = read(fd, buffer, sizeof buffer - 1);
 193         close(fd);
 194         if (n > 0) {
 195                 buffer[n] = '\0';
 196                 if ((p = strtok(buffer, "\n\r")) != NULL)
 197                         return strdup(p);
 198         }
 199
 200         return NULL;
 201 }
 202
 203 /* Generate an MD4 hash created from the combination of the password
 204  * and the challenge string and return it base64-encoded. */
 205 static void generate_hash(const char *in, const char *challenge, char *out)
 206 {
 207         char buf[MAX_DIGEST_LEN];
 208         int len;
 209
 210         sum_init(0);
 211         sum_update(in, strlen(in));
 212         sum_update(challenge, strlen(challenge));
 213         len = sum_end(buf);
 214
 215         base64_encode(buf, len, out, 0);
 216 }
 217
 218 /* Possibly negotiate authentication with the client.  Use "leader" to
 219  * start off the auth if necessary.
 220  *
 221  * Return NULL if authentication failed.  Return "" if anonymous access.
 222  * Otherwise return username.
 223  */
 224 char *auth_server(int f_in, int f_out, int module, const char *host,
 225                   const char *addr, const char *leader)
 226 {
 227         char *users = lp_auth_users(module);
 228         char challenge[MAX_DIGEST_LEN*2];
 229         char line[BIGPATHBUFLEN];
 230         char secret[512];
 231         char pass2[MAX_DIGEST_LEN*2];
 232         char *tok, *pass;
 233
 234         /* if no auth list then allow anyone in! */
 235         if (!users || !*users)
 236                 return "";
 237
 238         gen_challenge(addr, challenge);
 239
 240         io_printf(f_out, "%s%s\n", leader, challenge);
 241
 242         if (!read_line_old(f_in, line, sizeof line)
 243          || (pass = strchr(line, ' ')) == NULL) {
 244                 rprintf(FLOG, "auth failed on module %s from %s (%s): "
 245                         "invalid challenge response\n",
 246                         lp_name(module), host, addr);
 247                 return NULL;
 248         }
 249         *pass++ = '\0';
 250
 251         if (!(users = strdup(users)))
 252                 out_of_memory("auth_server");
 253
 254         for (tok = strtok(users, " ,\t"); tok; tok = strtok(NULL, " ,\t")) {
 255                 if (wildmatch(tok, line))
 256                         break;
 257         }
 258         free(users);
 259
 260         if (!tok) {
 261                 rprintf(FLOG, "auth failed on module %s from %s (%s): "
 262                         "unauthorized user\n",
 263                         lp_name(module), host, addr);
 264                 return NULL;
 265         }
 266
 267         memset(secret, 0, sizeof secret);
 268         if (!get_secret(module, line, secret, sizeof secret - 1)) {
 269                 memset(secret, 0, sizeof secret);
 270                 rprintf(FLOG, "auth failed on module %s from %s (%s): "
 271                         "missing secret for user \"%s\"\n",
 272                         lp_name(module), host, addr, line);
 273                 return NULL;
 274         }
 275
 276         generate_hash(secret, challenge, pass2);
 277         memset(secret, 0, sizeof secret);
 278
 279         if (strcmp(pass, pass2) != 0) {
 280                 rprintf(FLOG, "auth failed on module %s from %s (%s): "
 281                         "password mismatch\n",
 282                         lp_name(module), host, addr);
 283                 return NULL;
 284         }
 285
 286         return strdup(line);
 287 }
 288
 289 void auth_client(int fd, const char *user, const char *challenge)
 290 {
 291         const char *pass;
 292         char pass2[MAX_DIGEST_LEN*2];
 293
 294         if (!user || !*user)
 295                 user = "nobody";
 296
 297         if (!(pass = getpassf(password_file))
 298          && !(pass = getenv("RSYNC_PASSWORD"))) {
 299                 /* XXX: cyeoh says that getpass is deprecated, because
 300                  * it may return a truncated password on some systems,
 301                  * and it is not in the LSB.
 302                  *
 303                  * Andrew Klein says that getpassphrase() is present
 304                  * on Solaris and reads up to 256 characters.
 305                  *
 306                  * OpenBSD has a readpassphrase() that might be more suitable.
 307                  */
 308                 pass = getpass("Password: ");
 309         }
 310
 311         /* Any errors output during password handling aren't transfer errors. */
 312         log_got_error = 0;
 313
 314         if (!pass)
 315                 pass = "";
 316
 317         generate_hash(pass, challenge, pass2);
 318         io_printf(fd, "%s %s\n", user, pass2);
 319 }