authenticate.c

   1 /*
   2  * Support rsync daemon authentication.
   3  *
   4  * Copyright (C) 1998-2000 Andrew Tridgell
   5  * Copyright (C) 2002-2008 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
  25 /***************************************************************************
  26 encode a buffer using base64 - simple and slow algorithm. null terminates
  27 the result.
  28   ***************************************************************************/
  29 void base64_encode(const char *buf, int len, char *out, int pad)
  30 {
  31         char *b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  32         int bit_offset, byte_offset, idx, i;
  33         const uchar *d = (const uchar *)buf;
  34         int bytes = (len*8 + 5)/6;
  35
  36         for (i = 0; i < bytes; i++) {
  37                 byte_offset = (i*6)/8;
  38                 bit_offset = (i*6)%8;
  39                 if (bit_offset < 3) {
  40                         idx = (d[byte_offset] >> (2-bit_offset)) & 0x3F;
  41                 } else {
  42                         idx = (d[byte_offset] << (bit_offset-2)) & 0x3F;
  43                         if (byte_offset+1 < len) {
  44                                 idx |= (d[byte_offset+1] >> (8-(bit_offset-2)));
  45                         }
  46                 }
  47                 out[i] = b64[idx];
  48         }
  49
  50         while (pad && (i % 4))
  51                 out[i++] = '=';
  52
  53         out[i] = '\0';
  54 }
  55
  56 /* Generate a challenge buffer and return it base64-encoded. */
  57 static void gen_challenge(const char *addr, char *challenge)
  58 {
  59         char input[32];
  60         char digest[MAX_DIGEST_LEN];
  61         struct timeval tv;
  62         int len;
  63
  64         memset(input, 0, sizeof input);
  65
  66         strlcpy(input, addr, 17);
  67         sys_gettimeofday(&tv);
  68         SIVAL(input, 16, tv.tv_sec);
  69         SIVAL(input, 20, tv.tv_usec);
  70         SIVAL(input, 24, getpid());
  71
  72         sum_init(0);
  73         sum_update(input, sizeof input);
  74         len = sum_end(digest);
  75
  76         base64_encode(digest, len, challenge, 0);
  77 }
  78
  79
  80 /* Return the secret for a user from the secret file, null terminated.
  81  * Maximum length is len (not counting the null). */
  82 static int get_secret(int module, const char *user, char *secret, int len)
  83 {
  84         const char *fname = lp_secrets_file(module);
  85         STRUCT_STAT st;
  86         int fd, ok = 1;
  87         const char *p;
  88         char ch, *s;
  89
  90         if (!fname || !*fname)
  91                 return 0;
  92
  93         if ((fd = open(fname, O_RDONLY)) < 0)
  94                 return 0;
  95
  96         if (do_stat(fname, &st) == -1) {
  97                 rsyserr(FLOG, errno, "stat(%s)", fname);
  98                 ok = 0;
  99         } else if (lp_strict_modes(module)) {
 100                 if ((st.st_mode & 06) != 0) {
 101                         rprintf(FLOG, "secrets file must not be other-accessible (see strict modes option)\n");
 102                         ok = 0;
 103                 } else if (MY_UID() == 0 && st.st_uid != 0) {
 104                         rprintf(FLOG, "secrets file must be owned by root when running as root (see strict modes)\n");
 105                         ok = 0;
 106                 }
 107         }
 108         if (!ok) {
 109                 rprintf(FLOG, "continuing without secrets file\n");
 110                 close(fd);
 111                 return 0;
 112         }
 113
 114         if (*user == '#') {
 115                 /* Reject attempt to match a comment. */
 116                 close(fd);
 117                 return 0;
 118         }
 119
 120         /* Try to find a line that starts with the user name and a ':'. */
 121         p = user;
 122         while (1) {
 123                 if (read(fd, &ch, 1) != 1) {
 124                         close(fd);
 125                         return 0;
 126                 }
 127                 if (ch == '\n')
 128                         p = user;
 129                 else if (p) {
 130                         if (*p == ch)
 131                                 p++;
 132                         else if (!*p && ch == ':')
 133                                 break;
 134                         else
 135                                 p = NULL;
 136                 }
 137         }
 138
 139         /* Slurp the secret into the "secret" buffer. */
 140         s = secret;
 141         while (len > 0) {
 142                 if (read(fd, s, 1) != 1 || *s == '\n')
 143                         break;
 144                 if (*s == '\r')
 145                         continue;
 146                 s++;
 147                 len--;
 148         }
 149         *s = '\0';
 150         close(fd);
 151
 152         return 1;
 153 }
 154
 155 static const char *getpassf(const char *filename)
 156 {
 157         STRUCT_STAT st;
 158         char buffer[512], *p;
 159         int fd, n, ok = 1;
 160         const char *envpw = getenv("RSYNC_PASSWORD");
 161
 162         if (!filename)
 163                 return NULL;
 164
 165         if ((fd = open(filename,O_RDONLY)) < 0) {
 166                 rsyserr(FWARNING, errno, "could not open password file \"%s\"",
 167                         filename);
 168                 if (envpw)
 169                         rprintf(FINFO, "falling back to RSYNC_PASSWORD environment variable.\n");
 170                 return NULL;
 171         }
 172
 173         if (do_stat(filename, &st) == -1) {
 174                 rsyserr(FWARNING, errno, "stat(%s)", filename);
 175                 ok = 0;
 176         } else if ((st.st_mode & 06) != 0) {
 177                 rprintf(FWARNING, "password file must not be other-accessible\n");
 178                 ok = 0;
 179         } else if (MY_UID() == 0 && st.st_uid != 0) {
 180                 rprintf(FWARNING, "password file must be owned by root when running as root\n");
 181                 ok = 0;
 182         }
 183         if (!ok) {
 184                 close(fd);
 185                 rprintf(FWARNING, "continuing without password file\n");
 186                 if (envpw)
 187                         rprintf(FINFO, "falling back to RSYNC_PASSWORD environment variable.\n");
 188                 return NULL;
 189         }
 190
 191         n = read(fd, buffer, sizeof buffer - 1);
 192         close(fd);
 193         if (n > 0) {
 194                 buffer[n] = '\0';
 195                 if ((p = strtok(buffer, "\n\r")) != NULL)
 196                         return strdup(p);
 197         }
 198
 199         return NULL;
 200 }
 201
 202 /* Generate an MD4 hash created from the combination of the password
 203  * and the challenge string and return it base64-encoded. */
 204 static void generate_hash(const char *in, const char *challenge, char *out)
 205 {
 206         char buf[MAX_DIGEST_LEN];
 207         int len;
 208
 209         sum_init(0);
 210         sum_update(in, strlen(in));
 211         sum_update(challenge, strlen(challenge));
 212         len = sum_end(buf);
 213
 214         base64_encode(buf, len, out, 0);
 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 secret[512];
 230         char pass2[MAX_DIGEST_LEN*2];
 231         char *tok, *pass;
 232
 233         /* if no auth list then allow anyone in! */
 234         if (!users || !*users)
 235                 return "";
 236
 237         gen_challenge(addr, challenge);
 238
 239         io_printf(f_out, "%s%s\n", leader, challenge);
 240
 241         if (!read_line_old(f_in, line, sizeof line)
 242          || (pass = strchr(line, ' ')) == NULL) {
 243                 rprintf(FLOG, "auth failed on module %s from %s (%s): "
 244                         "invalid challenge response\n",
 245                         lp_name(module), host, addr);
 246                 return NULL;
 247         }
 248         *pass++ = '\0';
 249
 250         if (!(users = strdup(users)))
 251                 out_of_memory("auth_server");
 252
 253         for (tok = strtok(users, " ,\t"); tok; tok = strtok(NULL, " ,\t")) {
 254                 if (wildmatch(tok, line))
 255                         break;
 256         }
 257         free(users);
 258
 259         if (!tok) {
 260                 rprintf(FLOG, "auth failed on module %s from %s (%s): "
 261                         "unauthorized user\n",
 262                         lp_name(module), host, addr);
 263                 return NULL;
 264         }
 265
 266         memset(secret, 0, sizeof secret);
 267         if (!get_secret(module, line, secret, sizeof secret - 1)) {
 268                 memset(secret, 0, sizeof secret);
 269                 rprintf(FLOG, "auth failed on module %s from %s (%s): "
 270                         "missing secret for user \"%s\"\n",
 271                         lp_name(module), host, addr, line);
 272                 return NULL;
 273         }
 274
 275         generate_hash(secret, challenge, pass2);
 276         memset(secret, 0, sizeof secret);
 277
 278         if (strcmp(pass, pass2) != 0) {
 279                 rprintf(FLOG, "auth failed on module %s from %s (%s): "
 280                         "password mismatch\n",
 281                         lp_name(module), host, addr);
 282                 return NULL;
 283         }
 284
 285         return strdup(line);
 286 }
 287
 288 void auth_client(int fd, const char *user, const char *challenge)
 289 {
 290         const char *pass;
 291         char pass2[MAX_DIGEST_LEN*2];
 292
 293         if (!user || !*user)
 294                 user = "nobody";
 295
 296         if (!(pass = getpassf(password_file))
 297          && !(pass = getenv("RSYNC_PASSWORD"))) {
 298                 /* XXX: cyeoh says that getpass is deprecated, because
 299                  * it may return a truncated password on some systems,
 300                  * and it is not in the LSB.
 301                  *
 302                  * Andrew Klein says that getpassphrase() is present
 303                  * on Solaris and reads up to 256 characters.
 304                  *
 305                  * OpenBSD has a readpassphrase() that might be more suitable.
 306                  */
 307                 pass = getpass("Password: ");
 308         }
 309
 310         if (!pass)
 311                 pass = "";
 312
 313         generate_hash(pass, challenge, pass2);
 314         io_printf(fd, "%s %s\n", user, pass2);
 315 }