authenticate.c

   1 /* -*- c-file-style: "linux"; -*-
   2
   3    Copyright (C) 1998-2000 by Andrew Tridgell
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 2 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program; if not, write to the Free Software
  17    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  18 */
  19
  20 /* support rsync authentication */
  21 #include "rsync.h"
  22
  23 extern char *password_file;
  24 extern int am_root;
  25
  26 /***************************************************************************
  27 encode a buffer using base64 - simple and slow algorithm. null terminates
  28 the result.
  29   ***************************************************************************/
  30 void base64_encode(char *buf, int len, char *out)
  31 {
  32         char *b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  33         int bit_offset, byte_offset, idx, i;
  34         unsigned char *d = (unsigned char *)buf;
  35         int bytes = (len*8 + 5)/6;
  36
  37         memset(out, 0, bytes+1);
  38
  39         for (i = 0; i < bytes; i++) {
  40                 byte_offset = (i*6)/8;
  41                 bit_offset = (i*6)%8;
  42                 if (bit_offset < 3) {
  43                         idx = (d[byte_offset] >> (2-bit_offset)) & 0x3F;
  44                 } else {
  45                         idx = (d[byte_offset] << (bit_offset-2)) & 0x3F;
  46                         if (byte_offset+1 < len) {
  47                                 idx |= (d[byte_offset+1] >> (8-(bit_offset-2)));
  48                         }
  49                 }
  50                 out[i] = b64[idx];
  51         }
  52 }
  53
  54 /* create a 16 byte challenge buffer */
  55 static void gen_challenge(char *addr, char *challenge)
  56 {
  57         char input[32];
  58         struct timeval tv;
  59
  60         memset(input, 0, sizeof input);
  61
  62         strlcpy((char *)input, addr, 17);
  63         sys_gettimeofday(&tv);
  64         SIVAL(input, 16, tv.tv_sec);
  65         SIVAL(input, 20, tv.tv_usec);
  66         SIVAL(input, 24, getpid());
  67
  68         sum_init(0);
  69         sum_update(input, sizeof input);
  70         sum_end(challenge);
  71 }
  72
  73
  74 /* Return the secret for a user from the secret file, null terminated.
  75  * Maximum length is len (not counting the null). */
  76 static int get_secret(int module, char *user, char *secret, int len)
  77 {
  78         char *fname = lp_secrets_file(module);
  79         STRUCT_STAT st;
  80         int fd, ok = 1;
  81         char ch, *p;
  82
  83         if (!fname || !*fname)
  84                 return 0;
  85
  86         if ((fd = open(fname, O_RDONLY)) < 0)
  87                 return 0;
  88
  89         if (do_stat(fname, &st) == -1) {
  90                 rsyserr(FLOG, errno, "stat(%s)", safe_fname(fname));
  91                 ok = 0;
  92         } else if (lp_strict_modes(module)) {
  93                 if ((st.st_mode & 06) != 0) {
  94                         rprintf(FLOG, "secrets file must not be other-accessible (see strict modes option)\n");
  95                         ok = 0;
  96                 } else if (am_root && (st.st_uid != 0)) {
  97                         rprintf(FLOG, "secrets file must be owned by root when running as root (see strict modes)\n");
  98                         ok = 0;
  99                 }
 100         }
 101         if (!ok) {
 102                 rprintf(FLOG, "continuing without secrets file\n");
 103                 close(fd);
 104                 return 0;
 105         }
 106
 107         if (*user == '#') {
 108                 /* Reject attempt to match a comment. */
 109                 close(fd);
 110                 return 0;
 111         }
 112
 113         /* Try to find a line that starts with the user name and a ':'. */
 114         p = user;
 115         while (1) {
 116                 if (read(fd, &ch, 1) != 1) {
 117                         close(fd);
 118                         return 0;
 119                 }
 120                 if (ch == '\n')
 121                         p = user;
 122                 else if (p) {
 123                         if (*p == ch)
 124                                 p++;
 125                         else if (!*p && ch == ':')
 126                                 break;
 127                         else
 128                                 p = NULL;
 129                 }
 130         }
 131
 132         /* Slurp the secret into the "secret" buffer. */
 133         p = secret;
 134         while (len > 0) {
 135                 if (read(fd, p, 1) != 1 || *p == '\n')
 136                         break;
 137                 if (*p == '\r')
 138                         continue;
 139                 p++;
 140                 len--;
 141         }
 142         *p = '\0';
 143         close(fd);
 144
 145         return 1;
 146 }
 147
 148 static char *getpassf(char *filename)
 149 {
 150         STRUCT_STAT st;
 151         char buffer[512], *p;
 152         int fd, n, ok = 1;
 153         char *envpw = getenv("RSYNC_PASSWORD");
 154
 155         if (!filename)
 156                 return NULL;
 157
 158         if ((fd = open(filename,O_RDONLY)) < 0) {
 159                 rsyserr(FERROR, errno, "could not open password file \"%s\"",
 160                         safe_fname(filename));
 161                 if (envpw)
 162                         rprintf(FERROR, "falling back to RSYNC_PASSWORD environment variable.\n");
 163                 return NULL;
 164         }
 165
 166         if (do_stat(filename, &st) == -1) {
 167                 rsyserr(FERROR, errno, "stat(%s)", safe_fname(filename));
 168                 ok = 0;
 169         } else if ((st.st_mode & 06) != 0) {
 170                 rprintf(FERROR,"password file must not be other-accessible\n");
 171                 ok = 0;
 172         } else if (am_root && st.st_uid != 0) {
 173                 rprintf(FERROR,"password file must be owned by root when running as root\n");
 174                 ok = 0;
 175         }
 176         if (!ok) {
 177                 rprintf(FERROR,"continuing without password file\n");
 178                 if (envpw)
 179                         rprintf(FERROR, "using RSYNC_PASSWORD environment variable.\n");
 180                 close(fd);
 181                 return NULL;
 182         }
 183
 184         if (envpw)
 185                 rprintf(FERROR, "RSYNC_PASSWORD environment variable ignored\n");
 186
 187         n = read(fd, buffer, sizeof buffer - 1);
 188         close(fd);
 189         if (n > 0) {
 190                 buffer[n] = '\0';
 191                 if ((p = strtok(buffer, "\n\r")) != NULL)
 192                         return strdup(p);
 193         }
 194
 195         return NULL;
 196 }
 197
 198 /* generate a 16 byte hash from a password and challenge */
 199 static void generate_hash(char *in, char *challenge, char *out)
 200 {
 201         char buf[16];
 202
 203         sum_init(0);
 204         sum_update(in, strlen(in));
 205         sum_update(challenge, strlen(challenge));
 206         sum_end(buf);
 207
 208         base64_encode(buf, 16, out);
 209 }
 210
 211 /* Possibly negotiate authentication with the client.  Use "leader" to
 212  * start off the auth if necessary.
 213  *
 214  * Return NULL if authentication failed.  Return "" if anonymous access.
 215  * Otherwise return username.
 216  */
 217 char *auth_server(int f_in, int f_out, int module, char *addr, char *leader)
 218 {
 219         char *users = lp_auth_users(module);
 220         char challenge[16];
 221         char b64_challenge[30];
 222         char line[MAXPATHLEN];
 223         static char user[100];
 224         char secret[100];
 225         char pass[30];
 226         char pass2[30];
 227         char *tok;
 228
 229         /* if no auth list then allow anyone in! */
 230         if (!users || !*users)
 231                 return "";
 232
 233         gen_challenge(addr, challenge);
 234
 235         base64_encode(challenge, 16, b64_challenge);
 236
 237         io_printf(f_out, "%s%s\n", leader, b64_challenge);
 238
 239         if (!read_line(f_in, line, sizeof line - 1))
 240                 return NULL;
 241
 242         memset(user, 0, sizeof user);
 243         memset(pass, 0, sizeof pass);
 244
 245         if (sscanf(line,"%99s %29s", user, pass) != 2)
 246                 return NULL;
 247
 248         users = strdup(users);
 249         if (!users)
 250                 return NULL;
 251
 252         for (tok=strtok(users," ,\t"); tok; tok = strtok(NULL," ,\t")) {
 253                 if (wildmatch(tok, user))
 254                         break;
 255         }
 256         free(users);
 257
 258         if (!tok)
 259                 return NULL;
 260
 261         memset(secret, 0, sizeof secret);
 262         if (!get_secret(module, user, secret, sizeof secret - 1)) {
 263                 memset(secret, 0, sizeof secret);
 264                 return NULL;
 265         }
 266
 267         generate_hash(secret, b64_challenge, pass2);
 268         memset(secret, 0, sizeof secret);
 269
 270         if (strcmp(pass, pass2) == 0)
 271                 return user;
 272
 273         return NULL;
 274 }
 275
 276
 277 void auth_client(int fd, char *user, char *challenge)
 278 {
 279         char *pass;
 280         char pass2[30];
 281
 282         if (!user || !*user)
 283                 user = "nobody";
 284
 285         if (!(pass = getpassf(password_file))
 286          && !(pass = getenv("RSYNC_PASSWORD"))) {
 287                 /* XXX: cyeoh says that getpass is deprecated, because
 288                  * it may return a truncated password on some systems,
 289                  * and it is not in the LSB.
 290                  *
 291                  * Andrew Klein says that getpassphrase() is present
 292                  * on Solaris and reads up to 256 characters.
 293                  *
 294                  * OpenBSD has a readpassphrase() that might be more suitable.
 295                  */
 296                 pass = getpass("Password: ");
 297         }
 298
 299         if (!pass)
 300                 pass = "";
 301
 302         generate_hash(pass, challenge, pass2);
 303         io_printf(fd, "%s %s\n", user, pass2);
 304 }
 305
 306