Annotation of src/usr.bin/ssh/auth.c, Revision 1.24
1.1 markus 1: /*
1.19 deraadt 2: * Copyright (c) 2000 Markus Friedl. All rights reserved.
1.9 deraadt 3: *
4: * Redistribution and use in source and binary forms, with or without
5: * modification, are permitted provided that the following conditions
6: * are met:
7: * 1. Redistributions of source code must retain the above copyright
8: * notice, this list of conditions and the following disclaimer.
9: * 2. Redistributions in binary form must reproduce the above copyright
10: * notice, this list of conditions and the following disclaimer in the
11: * documentation and/or other materials provided with the distribution.
12: *
13: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
14: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
15: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
16: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
17: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
18: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
19: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
20: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
22: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
1.1 markus 23: */
24:
25: #include "includes.h"
1.24 ! markus 26: RCSID("$OpenBSD: auth.c,v 1.23 2001/05/24 11:12:42 markus Exp $");
1.22 markus 27:
28: #include <libgen.h>
1.1 markus 29:
30: #include "xmalloc.h"
1.13 markus 31: #include "match.h"
1.14 markus 32: #include "groupaccess.h"
33: #include "log.h"
1.1 markus 34: #include "servconf.h"
1.2 markus 35: #include "auth.h"
1.13 markus 36: #include "auth-options.h"
1.14 markus 37: #include "canohost.h"
1.22 markus 38: #include "buffer.h"
39: #include "bufaux.h"
1.24 ! markus 40: #include "uidswap.h"
! 41: #include "tildexpand.h"
1.2 markus 42:
1.1 markus 43: /* import */
44: extern ServerOptions options;
45:
46: /*
1.12 markus 47: * Check if the user is allowed to log in via ssh. If user is listed
48: * in DenyUsers or one of user's groups is listed in DenyGroups, false
49: * will be returned. If AllowUsers isn't empty and user isn't listed
50: * there, or if AllowGroups isn't empty and one of user's groups isn't
51: * listed there, false will be returned.
1.1 markus 52: * If the user's shell is not executable, false will be returned.
1.4 markus 53: * Otherwise true is returned.
1.1 markus 54: */
1.5 markus 55: int
1.1 markus 56: allowed_user(struct passwd * pw)
57: {
58: struct stat st;
1.21 markus 59: char *shell;
1.1 markus 60: int i;
61:
62: /* Shouldn't be called if pw is NULL, but better safe than sorry... */
1.12 markus 63: if (!pw || !pw->pw_name)
1.1 markus 64: return 0;
65:
1.7 deraadt 66: /*
67: * Get the shell from the password data. An empty shell field is
68: * legal, and means /bin/sh.
69: */
70: shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell;
71:
1.1 markus 72: /* deny if shell does not exists or is not executable */
1.7 deraadt 73: if (stat(shell, &st) != 0)
1.1 markus 74: return 0;
75: if (!((st.st_mode & S_IFREG) && (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP))))
76: return 0;
77:
78: /* Return false if user is listed in DenyUsers */
79: if (options.num_deny_users > 0) {
80: for (i = 0; i < options.num_deny_users; i++)
81: if (match_pattern(pw->pw_name, options.deny_users[i]))
82: return 0;
83: }
84: /* Return false if AllowUsers isn't empty and user isn't listed there */
85: if (options.num_allow_users > 0) {
86: for (i = 0; i < options.num_allow_users; i++)
87: if (match_pattern(pw->pw_name, options.allow_users[i]))
88: break;
89: /* i < options.num_allow_users iff we break for loop */
90: if (i >= options.num_allow_users)
91: return 0;
92: }
93: if (options.num_deny_groups > 0 || options.num_allow_groups > 0) {
1.12 markus 94: /* Get the user's group access list (primary and supplementary) */
95: if (ga_init(pw->pw_name, pw->pw_gid) == 0)
1.1 markus 96: return 0;
97:
1.12 markus 98: /* Return false if one of user's groups is listed in DenyGroups */
99: if (options.num_deny_groups > 0)
100: if (ga_match(options.deny_groups,
101: options.num_deny_groups)) {
102: ga_free();
1.1 markus 103: return 0;
1.12 markus 104: }
1.1 markus 105: /*
1.12 markus 106: * Return false if AllowGroups isn't empty and one of user's groups
1.1 markus 107: * isn't listed there
108: */
1.12 markus 109: if (options.num_allow_groups > 0)
110: if (!ga_match(options.allow_groups,
111: options.num_allow_groups)) {
112: ga_free();
1.1 markus 113: return 0;
1.12 markus 114: }
115: ga_free();
1.1 markus 116: }
117: /* We found no reason not to let this user try to log on... */
118: return 1;
1.13 markus 119: }
120:
121: Authctxt *
122: authctxt_new(void)
123: {
1.16 stevesk 124: Authctxt *authctxt = xmalloc(sizeof(*authctxt));
125: memset(authctxt, 0, sizeof(*authctxt));
126: return authctxt;
1.13 markus 127: }
128:
129: void
130: auth_log(Authctxt *authctxt, int authenticated, char *method, char *info)
131: {
132: void (*authlog) (const char *fmt,...) = verbose;
133: char *authmsg;
134:
135: /* Raise logging level */
136: if (authenticated == 1 ||
137: !authctxt->valid ||
138: authctxt->failures >= AUTH_FAIL_LOG ||
139: strcmp(method, "password") == 0)
140: authlog = log;
141:
142: if (authctxt->postponed)
143: authmsg = "Postponed";
144: else
145: authmsg = authenticated ? "Accepted" : "Failed";
146:
147: authlog("%s %s for %s%.100s from %.200s port %d%s",
148: authmsg,
149: method,
150: authctxt->valid ? "" : "illegal user ",
151: authctxt->valid && authctxt->pw->pw_uid == 0 ? "ROOT" : authctxt->user,
152: get_remote_ipaddr(),
153: get_remote_port(),
154: info);
155: }
156:
157: /*
1.17 markus 158: * Check whether root logins are disallowed.
1.13 markus 159: */
160: int
1.17 markus 161: auth_root_allowed(char *method)
1.13 markus 162: {
1.17 markus 163: switch (options.permit_root_login) {
164: case PERMIT_YES:
1.13 markus 165: return 1;
1.17 markus 166: break;
167: case PERMIT_NO_PASSWD:
168: if (strcmp(method, "password") != 0)
169: return 1;
170: break;
171: case PERMIT_FORCED_ONLY:
172: if (forced_command) {
173: log("Root login accepted for forced command.");
174: return 1;
175: }
176: break;
1.13 markus 177: }
1.17 markus 178: log("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr());
1.22 markus 179: return 0;
180: }
181:
182:
183: /*
184: * Given a template and a passwd structure, build a filename
185: * by substituting % tokenised options. Currently, %% becomes '%',
186: * %h becomes the home directory and %u the username.
187: *
188: * This returns a buffer allocated by xmalloc.
189: */
190: char *
191: expand_filename(const char *filename, struct passwd *pw)
192: {
193: Buffer buffer;
194: char *file;
195: const char *cp;
196:
197: /*
198: * Build the filename string in the buffer by making the appropriate
199: * substitutions to the given file name.
200: */
201: buffer_init(&buffer);
202: for (cp = filename; *cp; cp++) {
203: if (cp[0] == '%' && cp[1] == '%') {
204: buffer_append(&buffer, "%", 1);
205: cp++;
206: continue;
207: }
208: if (cp[0] == '%' && cp[1] == 'h') {
209: buffer_append(&buffer, pw->pw_dir, strlen(pw->pw_dir));
210: cp++;
211: continue;
212: }
213: if (cp[0] == '%' && cp[1] == 'u') {
214: buffer_append(&buffer, pw->pw_name,
215: strlen(pw->pw_name));
216: cp++;
217: continue;
218: }
219: buffer_append(&buffer, cp, 1);
220: }
221: buffer_append(&buffer, "\0", 1);
222:
223: /*
224: * Ensure that filename starts anchored. If not, be backward
225: * compatible and prepend the '%h/'
226: */
227: file = xmalloc(MAXPATHLEN);
228: cp = buffer_ptr(&buffer);
229: if (*cp != '/')
230: snprintf(file, MAXPATHLEN, "%s/%s", pw->pw_dir, cp);
231: else
232: strlcpy(file, cp, MAXPATHLEN);
233:
234: buffer_free(&buffer);
235: return file;
236: }
237:
238: char *
239: authorized_keys_file(struct passwd *pw)
240: {
241: return expand_filename(options.authorized_keys_file, pw);
242: }
243:
244: char *
245: authorized_keys_file2(struct passwd *pw)
246: {
247: return expand_filename(options.authorized_keys_file2, pw);
248: }
1.24 ! markus 249:
! 250: /* return ok if key exists in sysfile or userfile */
! 251: HostStatus
! 252: check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host,
! 253: const char *sysfile, const char *userfile)
! 254: {
! 255: Key *found;
! 256: char *user_hostfile;
! 257: struct stat st;
! 258: int host_status;
! 259:
! 260: /* Check if we know the host and its host key. */
! 261: found = key_new(key->type);
! 262: host_status = check_host_in_hostfile(sysfile, host, key, found, NULL);
! 263:
! 264: if (host_status != HOST_OK && userfile != NULL) {
! 265: user_hostfile = tilde_expand_filename(userfile, pw->pw_uid);
! 266: if (options.strict_modes &&
! 267: (stat(user_hostfile, &st) == 0) &&
! 268: ((st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
! 269: (st.st_mode & 022) != 0)) {
! 270: log("Authentication refused for %.100s: "
! 271: "bad owner or modes for %.200s",
! 272: pw->pw_name, user_hostfile);
! 273: } else {
! 274: temporarily_use_uid(pw);
! 275: host_status = check_host_in_hostfile(user_hostfile,
! 276: host, key, found, NULL);
! 277: restore_uid();
! 278: }
! 279: xfree(user_hostfile);
! 280: }
! 281: key_free(found);
! 282:
! 283: debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ?
! 284: "ok" : "not found", host);
! 285: return host_status;
! 286: }
! 287:
1.22 markus 288:
289: /*
290: * Check a given file for security. This is defined as all components
291: * of the path to the file must either be owned by either the owner of
1.23 markus 292: * of the file or root and no directories must be group or world writable.
1.22 markus 293: *
294: * XXX Should any specific check be done for sym links ?
295: *
296: * Takes an open file descriptor, the file name, a uid and and
297: * error buffer plus max size as arguments.
298: *
299: * Returns 0 on success and -1 on failure
300: */
301: int
302: secure_filename(FILE *f, const char *file, uid_t uid, char *err, size_t errlen)
303: {
304: char buf[MAXPATHLEN];
305: char *cp;
306: struct stat st;
307:
308: if (realpath(file, buf) == NULL) {
309: snprintf(err, errlen, "realpath %s failed: %s", file,
310: strerror(errno));
311: return -1;
312: }
313:
314: /* check the open file to avoid races */
315: if (fstat(fileno(f), &st) < 0 ||
316: (st.st_uid != 0 && st.st_uid != uid) ||
317: (st.st_mode & 022) != 0) {
318: snprintf(err, errlen, "bad ownership or modes for file %s",
319: buf);
320: return -1;
321: }
322:
323: /* for each component of the canonical path, walking upwards */
324: for (;;) {
325: if ((cp = dirname(buf)) == NULL) {
326: snprintf(err, errlen, "dirname() failed");
327: return -1;
328: }
329: strlcpy(buf, cp, sizeof(buf));
330:
331: debug3("secure_filename: checking '%s'", buf);
332: if (stat(buf, &st) < 0 ||
333: (st.st_uid != 0 && st.st_uid != uid) ||
334: (st.st_mode & 022) != 0) {
335: snprintf(err, errlen,
336: "bad ownership or modes for directory %s", buf);
337: return -1;
338: }
339:
340: /*
341: * dirname should always complete with a "/" path,
342: * but we can be paranoid and check for "." too
343: */
344: if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0))
345: break;
346: }
1.17 markus 347: return 0;
1.1 markus 348: }
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