Annotation of src/usr.bin/ssh/auth-rhosts.c, Revision 1.57
1.57 ! dtucker 1: /* $OpenBSD: auth-rhosts.c,v 1.56 2022/02/23 21:21:49 djm 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:
1.57 ! dtucker 20: #include <errno.h>
1.42 djm 21: #include <fcntl.h>
1.34 stevesk 22: #include <netgroup.h>
1.38 stevesk 23: #include <pwd.h>
1.40 stevesk 24: #include <stdio.h>
1.39 stevesk 25: #include <string.h>
1.41 deraadt 26: #include <stdarg.h>
1.56 djm 27: #include <stdlib.h>
1.43 dtucker 28: #include <unistd.h>
1.1 deraadt 29:
30: #include "packet.h"
31: #include "uidswap.h"
1.19 markus 32: #include "pathnames.h"
33: #include "log.h"
1.45 millert 34: #include "misc.h"
1.55 djm 35: #include "xmalloc.h"
1.49 markus 36: #include "sshbuf.h"
37: #include "sshkey.h"
1.6 markus 38: #include "servconf.h"
1.19 markus 39: #include "canohost.h"
1.41 deraadt 40: #include "hostfile.h"
1.21 itojun 41: #include "auth.h"
1.1 deraadt 42:
1.23 markus 43: /* import */
44: extern ServerOptions options;
1.28 markus 45: extern int use_privsep;
1.23 markus 46:
1.11 markus 47: /*
48: * This function processes an rhosts-style file (.rhosts, .shosts, or
49: * /etc/hosts.equiv). This returns true if authentication can be granted
50: * based on the file, and returns zero otherwise.
51: */
1.1 deraadt 52:
1.24 itojun 53: static int
1.9 markus 54: check_rhosts_file(const char *filename, const char *hostname,
55: const char *ipaddr, const char *client_user,
56: const char *server_user)
1.1 deraadt 57: {
1.9 markus 58: FILE *f;
1.46 djm 59: #define RBUFLN 1024
60: char buf[RBUFLN];/* Must not be larger than host, user, dummy below. */
1.42 djm 61: int fd;
62: struct stat st;
1.1 deraadt 63:
1.9 markus 64: /* Open the .rhosts file, deny if unreadable */
1.42 djm 65: if ((fd = open(filename, O_RDONLY|O_NONBLOCK)) == -1)
1.9 markus 66: return 0;
1.42 djm 67: if (fstat(fd, &st) == -1) {
68: close(fd);
69: return 0;
70: }
71: if (!S_ISREG(st.st_mode)) {
72: logit("User %s hosts file %s is not a regular file",
73: server_user, filename);
74: close(fd);
75: return 0;
76: }
77: unset_nonblock(fd);
78: if ((f = fdopen(fd, "r")) == NULL) {
79: close(fd);
80: return 0;
81: }
1.9 markus 82: while (fgets(buf, sizeof(buf), f)) {
1.46 djm 83: /* All three must have length >= buf to avoid overflows. */
84: char hostbuf[RBUFLN], userbuf[RBUFLN], dummy[RBUFLN];
85: char *host, *user, *cp;
1.9 markus 86: int negated;
87:
88: for (cp = buf; *cp == ' ' || *cp == '\t'; cp++)
89: ;
90: if (*cp == '#' || *cp == '\n' || !*cp)
91: continue;
92:
1.11 markus 93: /*
94: * NO_PLUS is supported at least on OSF/1. We skip it (we
95: * don't ever support the plus syntax).
96: */
1.9 markus 97: if (strncmp(cp, "NO_PLUS", 7) == 0)
98: continue;
99:
1.11 markus 100: /*
101: * This should be safe because each buffer is as big as the
102: * whole string, and thus cannot be overwritten.
103: */
1.30 itojun 104: switch (sscanf(buf, "%1023s %1023s %1023s", hostbuf, userbuf,
105: dummy)) {
1.9 markus 106: case 0:
1.28 markus 107: auth_debug_add("Found empty line in %.100s.", filename);
1.9 markus 108: continue;
109: case 1:
110: /* Host name only. */
111: strlcpy(userbuf, server_user, sizeof(userbuf));
112: break;
113: case 2:
114: /* Got both host and user name. */
115: break;
116: case 3:
1.28 markus 117: auth_debug_add("Found garbage in %.100s.", filename);
1.9 markus 118: continue;
119: default:
120: /* Weird... */
121: continue;
122: }
123:
124: host = hostbuf;
125: user = userbuf;
126: negated = 0;
127:
128: /* Process negated host names, or positive netgroups. */
129: if (host[0] == '-') {
130: negated = 1;
131: host++;
132: } else if (host[0] == '+')
133: host++;
134:
135: if (user[0] == '-') {
136: negated = 1;
137: user++;
138: } else if (user[0] == '+')
139: user++;
140:
141: /* Check for empty host/user names (particularly '+'). */
142: if (!host[0] || !user[0]) {
143: /* We come here if either was '+' or '-'. */
1.46 djm 144: auth_debug_add("Ignoring wild host/user names "
145: "in %.100s.", filename);
1.9 markus 146: continue;
147: }
148: /* Verify that host name matches. */
149: if (host[0] == '@') {
150: if (!innetgr(host + 1, hostname, NULL, NULL) &&
151: !innetgr(host + 1, ipaddr, NULL, NULL))
152: continue;
1.46 djm 153: } else if (strcasecmp(host, hostname) &&
154: strcmp(host, ipaddr) != 0)
1.9 markus 155: continue; /* Different hostname. */
156:
157: /* Verify that user name matches. */
158: if (user[0] == '@') {
159: if (!innetgr(user + 1, NULL, client_user, NULL))
160: continue;
161: } else if (strcmp(user, client_user) != 0)
162: continue; /* Different username. */
163:
164: /* Found the user and host. */
165: fclose(f);
166:
167: /* If the entry was negated, deny access. */
168: if (negated) {
1.28 markus 169: auth_debug_add("Matched negative entry in %.100s.",
1.33 djm 170: filename);
1.9 markus 171: return 0;
172: }
173: /* Accept authentication. */
174: return 1;
175: }
176:
177: /* Authentication using this file denied. */
178: fclose(f);
179: return 0;
1.1 deraadt 180: }
181:
1.11 markus 182: /*
183: * Tries to authenticate the user using the .shosts or .rhosts file. Returns
184: * true if authentication succeeds. If ignore_rhosts is true, only
185: * /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored).
186: */
1.13 markus 187: int
1.48 markus 188: auth_rhosts2(struct passwd *pw, const char *client_user, const char *hostname,
1.23 markus 189: const char *ipaddr)
190: {
1.55 djm 191: char *path = NULL;
1.9 markus 192: struct stat st;
1.54 djm 193: static const char * const rhosts_files[] = {".shosts", ".rhosts", NULL};
1.17 markus 194: u_int rhosts_file_index;
1.55 djm 195: int r;
1.9 markus 196:
1.55 djm 197: debug2_f("clientuser %s hostname %s ipaddr %s",
1.23 markus 198: client_user, hostname, ipaddr);
199:
1.9 markus 200: /* Switch to the user's uid. */
1.22 markus 201: temporarily_use_uid(pw);
1.11 markus 202: /*
1.46 djm 203: * Quick check: if the user has no .shosts or .rhosts files and
204: * no system hosts.equiv/shosts.equiv files exist then return
1.11 markus 205: * failure immediately without doing costly lookups from name
206: * servers.
207: */
1.9 markus 208: for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
1.25 deraadt 209: rhosts_file_index++) {
1.9 markus 210: /* Check users .rhosts or .shosts. */
1.55 djm 211: xasprintf(&path, "%s/%s",
212: pw->pw_dir, rhosts_files[rhosts_file_index]);
213: r = stat(path, &st);
214: free(path);
215: if (r >= 0)
1.9 markus 216: break;
217: }
218: /* Switch back to privileged uid. */
219: restore_uid();
220:
1.46 djm 221: /*
222: * Deny if The user has no .shosts or .rhosts file and there
223: * are no system-wide files.
224: */
1.9 markus 225: if (!rhosts_files[rhosts_file_index] &&
1.50 deraadt 226: stat(_PATH_RHOSTS_EQUIV, &st) == -1 &&
227: stat(_PATH_SSH_HOSTS_EQUIV, &st) == -1) {
1.53 djm 228: debug3_f("no hosts access files exist");
1.9 markus 229: return 0;
1.46 djm 230: }
1.9 markus 231:
1.46 djm 232: /*
233: * If not logging in as superuser, try /etc/hosts.equiv and
234: * shosts.equiv.
235: */
236: if (pw->pw_uid == 0)
1.53 djm 237: debug3_f("root user, ignoring system hosts files");
1.46 djm 238: else {
1.25 deraadt 239: if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr,
240: client_user, pw->pw_name)) {
1.46 djm 241: auth_debug_add("Accepted for %.100s [%.100s] by "
242: "/etc/hosts.equiv.", hostname, ipaddr);
1.9 markus 243: return 1;
244: }
1.25 deraadt 245: if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr,
246: client_user, pw->pw_name)) {
1.46 djm 247: auth_debug_add("Accepted for %.100s [%.100s] by "
248: "%.100s.", hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV);
1.9 markus 249: return 1;
250: }
251: }
1.46 djm 252:
1.11 markus 253: /*
254: * Check that the home directory is owned by root or the user, and is
255: * not group or world writable.
256: */
1.50 deraadt 257: if (stat(pw->pw_dir, &st) == -1) {
1.29 itojun 258: logit("Rhosts authentication refused for %.100s: "
1.28 markus 259: "no home directory %.200s", pw->pw_name, pw->pw_dir);
260: auth_debug_add("Rhosts authentication refused for %.100s: "
261: "no home directory %.200s", pw->pw_name, pw->pw_dir);
1.9 markus 262: return 0;
263: }
264: if (options.strict_modes &&
265: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.25 deraadt 266: (st.st_mode & 022) != 0)) {
1.29 itojun 267: logit("Rhosts authentication refused for %.100s: "
1.28 markus 268: "bad ownership or modes for home directory.", pw->pw_name);
269: auth_debug_add("Rhosts authentication refused for %.100s: "
270: "bad ownership or modes for home directory.", pw->pw_name);
1.9 markus 271: return 0;
272: }
273: /* Temporarily use the user's uid. */
1.22 markus 274: temporarily_use_uid(pw);
1.9 markus 275:
276: /* Check all .rhosts files (currently .shosts and .rhosts). */
277: for (rhosts_file_index = 0; rhosts_files[rhosts_file_index];
1.25 deraadt 278: rhosts_file_index++) {
1.9 markus 279: /* Check users .rhosts or .shosts. */
1.55 djm 280: xasprintf(&path, "%s/%s",
281: pw->pw_dir, rhosts_files[rhosts_file_index]);
282: if (stat(path, &st) == -1) {
1.57 ! dtucker 283: debug3_f("stat %s: %s", path, strerror(errno));
1.55 djm 284: free(path);
1.9 markus 285: continue;
1.55 djm 286: }
1.9 markus 287:
1.11 markus 288: /*
289: * Make sure that the file is either owned by the user or by
290: * root, and make sure it is not writable by anyone but the
291: * owner. This is to help avoid novices accidentally
292: * allowing access to their account by anyone.
293: */
1.9 markus 294: if (options.strict_modes &&
295: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
1.25 deraadt 296: (st.st_mode & 022) != 0)) {
1.55 djm 297: logit("Rhosts authentication refused for %.100s: "
298: "bad modes for %.200s", pw->pw_name, path);
299: auth_debug_add("Bad file modes for %.200s", path);
300: free(path);
1.9 markus 301: continue;
302: }
1.46 djm 303: /*
304: * Check if we have been configured to ignore .rhosts
305: * and .shosts files.
306: */
1.52 djm 307: if (options.ignore_rhosts == IGNORE_RHOSTS_YES ||
308: (options.ignore_rhosts == IGNORE_RHOSTS_SHOSTS &&
309: strcmp(rhosts_files[rhosts_file_index], ".shosts") != 0)) {
1.46 djm 310: auth_debug_add("Server has been configured to "
311: "ignore %.100s.", rhosts_files[rhosts_file_index]);
1.55 djm 312: free(path);
1.9 markus 313: continue;
314: }
315: /* Check if authentication is permitted by the file. */
1.55 djm 316: if (check_rhosts_file(path, hostname, ipaddr,
1.46 djm 317: client_user, pw->pw_name)) {
1.28 markus 318: auth_debug_add("Accepted by %.100s.",
319: rhosts_files[rhosts_file_index]);
1.9 markus 320: /* Restore the privileged uid. */
321: restore_uid();
1.46 djm 322: auth_debug_add("Accepted host %s ip %s client_user "
323: "%s server_user %s", hostname, ipaddr,
324: client_user, pw->pw_name);
1.55 djm 325: free(path);
1.9 markus 326: return 1;
327: }
1.55 djm 328: free(path);
1.9 markus 329: }
330:
331: /* Restore the privileged uid. */
332: restore_uid();
333: return 0;
1.1 deraadt 334: }
![[BACK]](/icons/back.gif){kind=icon}
Return to auth-rhosts.c CVS log ![[TXT]](/icons/text.gif){kind=icon}
![[DIR]](/icons/dir.gif){kind=icon}
Up to [local] / src / usr.bin / ssh