Annotation of src/usr.bin/ssh/auth-rhosts.c, Revision 1.46
1.46 ! djm 1: /* $OpenBSD: auth-rhosts.c,v 1.45 2014/07/15 15:54:14 millert Exp $ */
1.1 deraadt 2: /*
1.10 deraadt 3: * Author: Tatu Ylonen <ylo@cs.hut.fi>
4: * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5: * All rights reserved
6: * Rhosts authentication. This file contains code to check whether to admit
7: * the login based on rhosts authentication. This file also processes
8: * /etc/hosts.equiv.
1.13 markus 9: *
1.15 deraadt 10: * As far as I am concerned, the code I have written for this software
11: * can be used freely for any purpose. Any derived versions of this
12: * software must be clearly marked as such, and if the derived work is
13: * incompatible with the protocol description in the RFC file, it must be
14: * called by a name other than "ssh" or "Secure Shell".
1.10 deraadt 15: */
1.1 deraadt 16:
1.35 stevesk 17: #include <sys/types.h>
18: #include <sys/stat.h>
1.34 stevesk 19:
1.42 djm 20: #include <fcntl.h>
1.34 stevesk 21: #include <netgroup.h>
1.38 stevesk 22: #include <pwd.h>
1.40 stevesk 23: #include <stdio.h>
1.39 stevesk 24: #include <string.h>
1.41 deraadt 25: #include <stdarg.h>
1.43 dtucker 26: #include <unistd.h>
1.1 deraadt 27:
28: #include "packet.h"
1.41 deraadt 29: #include "buffer.h"
1.1 deraadt 30: #include "uidswap.h"
1.19 markus 31: #include "pathnames.h"
32: #include "log.h"
1.45 millert 33: #include "misc.h"
1.6 markus 34: #include "servconf.h"
1.19 markus 35: #include "canohost.h"
1.41 deraadt 36: #include "key.h"
37: #include "hostfile.h"
1.21 itojun 38: #include "auth.h"
1.1 deraadt 39:
1.23 markus 40: /* import */
41: extern ServerOptions options;
1.28 markus 42: extern int use_privsep;
1.23 markus 43:
1.11 markus 44: /*
45: * This function processes an rhosts-style file (.rhosts, .shosts, or
46: * /etc/hosts.equiv). This returns true if authentication can be granted
47: * based on the file, and returns zero otherwise.
48: */
1.1 deraadt 49:
1.24 itojun 50: static int
1.9 markus 51: check_rhosts_file(const char *filename, const char *hostname,
52: const char *ipaddr, const char *client_user,
53: const char *server_user)
1.1 deraadt 54: {
1.9 markus 55: FILE *f;
1.46 ! djm 56: #define RBUFLN 1024
! 57: char buf[RBUFLN];/* Must not be larger than host, user, dummy below. */
1.42 djm 58: int fd;
59: struct stat st;
1.1 deraadt 60:
1.9 markus 61: /* Open the .rhosts file, deny if unreadable */
1.42 djm 62: if ((fd = open(filename, O_RDONLY|O_NONBLOCK)) == -1)
1.9 markus 63: return 0;
1.42 djm 64: if (fstat(fd, &st) == -1) {
65: close(fd);
66: return 0;
67: }
68: if (!S_ISREG(st.st_mode)) {
69: logit("User %s hosts file %s is not a regular file",
70: server_user, filename);
71: close(fd);
72: return 0;
73: }
74: unset_nonblock(fd);
75: if ((f = fdopen(fd, "r")) == NULL) {
76: close(fd);
77: return 0;
78: }
1.9 markus 79: while (fgets(buf, sizeof(buf), f)) {
1.46 ! djm 80: /* All three must have length >= buf to avoid overflows. */
! 81: char hostbuf[RBUFLN], userbuf[RBUFLN], dummy[RBUFLN];
! 82: char *host, *user, *cp;
1.9 markus 83: int negated;
84:
85: for (cp = buf; *cp == ' ' || *cp == '\t'; cp++)
86: ;
87: if (*cp == '#' || *cp == '\n' || !*cp)
88: continue;
89:
1.11 markus 90: /*
91: * NO_PLUS is supported at least on OSF/1. We skip it (we
92: * don't ever support the plus syntax).
93: */
1.9 markus 94: if (strncmp(cp, "NO_PLUS", 7) == 0)
95: continue;
96:
1.11 markus 97: /*
98: * This should be safe because each buffer is as big as the
99: * whole string, and thus cannot be overwritten.
100: */
1.30 itojun 101: switch (sscanf(buf, "%1023s %1023s %1023s", hostbuf, userbuf,
102: dummy)) {
1.9 markus 103: case 0:
1.28 markus 104: auth_debug_add("Found empty line in %.100s.", filename);
1.9 markus 105: continue;
106: case 1:
107: /* Host name only. */
108: strlcpy(userbuf, server_user, sizeof(userbuf));
109: break;
110: case 2:
111: /* Got both host and user name. */
112: break;
113: case 3:
1.28 markus 114: auth_debug_add("Found garbage in %.100s.", filename);
1.9 markus 115: continue;
116: default:
117: /* Weird... */
118: continue;
119: }
120:
121: host = hostbuf;
122: user = userbuf;
123: negated = 0;
124:
125: /* Process negated host names, or positive netgroups. */
126: if (host[0] == '-') {
127: negated = 1;
128: host++;
129: } else if (host[0] == '+')
130: host++;
131:
132: if (user[0] == '-') {
133: negated = 1;
134: user++;
135: } else if (user[0] == '+')
136: user++;
137:
138: /* Check for empty host/user names (particularly '+'). */
139: if (!host[0] || !user[0]) {
140: /* We come here if either was '+' or '-'. */
1.46 ! djm 141: auth_debug_add("Ignoring wild host/user names "
! 142: "in %.100s.", filename);
1.9 markus 143: continue;
144: }
145: /* Verify that host name matches. */
146: if (host[0] == '@') {
147: if (!innetgr(host + 1, hostname, NULL, NULL) &&
148: !innetgr(host + 1, ipaddr, NULL, NULL))
149: continue;
1.46 ! djm 150: } else if (strcasecmp(host, hostname) &&
! 151: strcmp(host, ipaddr) != 0)
1.9 markus 152: continue; /* Different hostname. */
153:
154: /* Verify that user name matches. */
155: if (user[0] == '@') {
156: if (!innetgr(user + 1, NULL, client_user, NULL))
157: continue;
158: } else if (strcmp(user, client_user) != 0)
159: continue; /* Different username. */
160:
161: /* Found the user and host. */
162: fclose(f);
163:
164: /* If the entry was negated, deny access. */
165: if (negated) {
1.28 markus 166: auth_debug_add("Matched negative entry in %.100s.",
1.33 djm 167: filename);
1.9 markus 168: return 0;
169: }
170: /* Accept authentication. */
171: return 1;
172: }
173:
174: /* Authentication using this file denied. */
175: fclose(f);
176: return 0;
1.1 deraadt 177: }
178:
1.11 markus 179: /*
180: * Tries to authenticate the user using the .shosts or .rhosts file. Returns
181: * true if authentication succeeds. If ignore_rhosts is true, only
182: * /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored).
183: */
1.1 deraadt 184:
1.13 markus 185: int
1.9 markus 186: auth_rhosts(struct passwd *pw, const char *client_user)
1.1 deraadt 187: {
1.23 markus 188: const char *hostname, *ipaddr;
189:
1.31 markus 190: hostname = get_canonical_hostname(options.use_dns);
1.23 markus 191: ipaddr = get_remote_ipaddr();
1.28 markus 192: return auth_rhosts2(pw, client_user, hostname, ipaddr);
1.23 markus 193: }
194:
1.28 markus 195: static int
196: auth_rhosts2_raw(struct passwd *pw, const char *client_user, const char *hostname,
1.23 markus 197: const char *ipaddr)
198: {
1.9 markus 199: char buf[1024];
200: struct stat st;
201: static const char *rhosts_files[] = {".shosts", ".rhosts", NULL};
1.17 markus 202: u_int rhosts_file_index;
1.9 markus 203:
1.23 markus 204: debug2("auth_rhosts2: clientuser %s hostname %s ipaddr %s",
205: client_user, hostname, ipaddr);
206:
1.9 markus 207: /* Switch to the user's uid. */
1.22 markus 208: temporarily_use_uid(pw);
1.11 markus 209: /*
1.46 ! djm 210: * Quick check: if the user has no .shosts or .rhosts files and
! 211: * no system hosts.equiv/shosts.equiv files exist then return
1.11 markus 212: * failure immediately without doing costly lookups from name
213: * servers.
214: */
1.9 markus 215: for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
1.25 deraadt 216: rhosts_file_index++) {
1.9 markus 217: /* Check users .rhosts or .shosts. */
218: snprintf(buf, sizeof buf, "%.500s/%.100s",
219: pw->pw_dir, rhosts_files[rhosts_file_index]);
220: if (stat(buf, &st) >= 0)
221: break;
222: }
223: /* Switch back to privileged uid. */
224: restore_uid();
225:
1.46 ! djm 226: /*
! 227: * Deny if The user has no .shosts or .rhosts file and there
! 228: * are no system-wide files.
! 229: */
1.9 markus 230: if (!rhosts_files[rhosts_file_index] &&
1.18 markus 231: stat(_PATH_RHOSTS_EQUIV, &st) < 0 &&
1.46 ! djm 232: stat(_PATH_SSH_HOSTS_EQUIV, &st) < 0) {
! 233: debug3("%s: no hosts access files exist", __func__);
1.9 markus 234: return 0;
1.46 ! djm 235: }
1.9 markus 236:
1.46 ! djm 237: /*
! 238: * If not logging in as superuser, try /etc/hosts.equiv and
! 239: * shosts.equiv.
! 240: */
! 241: if (pw->pw_uid == 0)
! 242: debug3("%s: root user, ignoring system hosts files", __func__);
! 243: else {
1.25 deraadt 244: if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr,
245: client_user, pw->pw_name)) {
1.46 ! djm 246: auth_debug_add("Accepted for %.100s [%.100s] by "
! 247: "/etc/hosts.equiv.", hostname, ipaddr);
1.9 markus 248: return 1;
249: }
1.25 deraadt 250: if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr,
251: client_user, pw->pw_name)) {
1.46 ! djm 252: auth_debug_add("Accepted for %.100s [%.100s] by "
! 253: "%.100s.", hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);
1.9 markus 254: return 1;
255: }
256: }
1.46 ! djm 257:
1.11 markus 258: /*
259: * Check that the home directory is owned by root or the user, and is
260: * not group or world writable.
261: */
1.9 markus 262: if (stat(pw->pw_dir, &st) < 0) {
1.29 itojun 263: logit("Rhosts authentication refused for %.100s: "
1.28 markus 264: "no home directory %.200s", pw->pw_name, pw->pw_dir);
265: auth_debug_add("Rhosts authentication refused for %.100s: "
266: "no home directory %.200s", pw->pw_name, pw->pw_dir);
1.9 markus 267: return 0;
268: }
269: if (options.strict_modes &&
270: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.25 deraadt 271: (st.st_mode & 022) != 0)) {
1.29 itojun 272: logit("Rhosts authentication refused for %.100s: "
1.28 markus 273: "bad ownership or modes for home directory.", pw->pw_name);
274: auth_debug_add("Rhosts authentication refused for %.100s: "
275: "bad ownership or modes for home directory.", pw->pw_name);
1.9 markus 276: return 0;
277: }
278: /* Temporarily use the user's uid. */
1.22 markus 279: temporarily_use_uid(pw);
1.9 markus 280:
281: /* Check all .rhosts files (currently .shosts and .rhosts). */
282: for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
1.25 deraadt 283: rhosts_file_index++) {
1.9 markus 284: /* Check users .rhosts or .shosts. */
285: snprintf(buf, sizeof buf, "%.500s/%.100s",
286: pw->pw_dir, rhosts_files[rhosts_file_index]);
287: if (stat(buf, &st) < 0)
288: continue;
289:
1.11 markus 290: /*
291: * Make sure that the file is either owned by the user or by
292: * root, and make sure it is not writable by anyone but the
293: * owner. This is to help avoid novices accidentally
294: * allowing access to their account by anyone.
295: */
1.9 markus 296: if (options.strict_modes &&
297: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.25 deraadt 298: (st.st_mode & 022) != 0)) {
1.29 itojun 299: logit("Rhosts authentication refused for %.100s: bad modes for %.200s",
1.9 markus 300: pw->pw_name, buf);
1.28 markus 301: auth_debug_add("Bad file modes for %.200s", buf);
1.9 markus 302: continue;
303: }
1.46 ! djm 304: /*
! 305: * Check if we have been configured to ignore .rhosts
! 306: * and .shosts files.
! 307: */
1.9 markus 308: if (options.ignore_rhosts) {
1.46 ! djm 309: auth_debug_add("Server has been configured to "
! 310: "ignore %.100s.", rhosts_files[rhosts_file_index]);
1.9 markus 311: continue;
312: }
313: /* Check if authentication is permitted by the file. */
1.46 ! djm 314: if (check_rhosts_file(buf, hostname, ipaddr,
! 315: client_user, pw->pw_name)) {
1.28 markus 316: auth_debug_add("Accepted by %.100s.",
317: rhosts_files[rhosts_file_index]);
1.9 markus 318: /* Restore the privileged uid. */
319: restore_uid();
1.46 ! djm 320: auth_debug_add("Accepted host %s ip %s client_user "
! 321: "%s server_user %s", hostname, ipaddr,
! 322: client_user, pw->pw_name);
1.9 markus 323: return 1;
324: }
325: }
326:
327: /* Restore the privileged uid. */
328: restore_uid();
329: return 0;
1.28 markus 330: }
331:
332: int
333: auth_rhosts2(struct passwd *pw, const char *client_user, const char *hostname,
334: const char *ipaddr)
335: {
1.44 dtucker 336: return auth_rhosts2_raw(pw, client_user, hostname, ipaddr);
1.1 deraadt 337: }
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