1 /* $OpenBSD: auth-krb5.c,v 1.24 2021/04/03 06:18:40 djm Exp $ */
2 /*
3 * Kerberos v5 authentication and ticket-passing routines.
4 *
5 * From: FreeBSD: src/crypto/openssh/auth-krb5.c,v 1.6 2001/02/13 16:58:04 assar
6 */
7 /*
8 * Copyright (c) 2002 Daniel Kouril. All rights reserved.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
20 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
21 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
22 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
23 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
24 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
28 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 */
30
31 #include "includes.h"
32
33 #include <sys/types.h>
34 #include <pwd.h>
35 #include <stdarg.h>
36
37 #include "xmalloc.h"
38 #include "ssh.h"
39 #include "packet.h"
40 #include "log.h"
41 #include "sshbuf.h"
42 #include "sshkey.h"
43 #include "misc.h"
44 #include "servconf.h"
45 #include "uidswap.h"
46 #include "hostfile.h"
47 #include "auth.h"
48
49 #ifdef KRB5
50 #include <errno.h>
51 #include <unistd.h>
52 #include <string.h>
53 #include <krb5.h>
54
55 extern ServerOptions options;
56
57 static int
krb5_init(void * context)58 krb5_init(void *context)
59 {
60 Authctxt *authctxt = (Authctxt *)context;
61 krb5_error_code problem;
62
63 if (authctxt->krb5_ctx == NULL) {
64 problem = krb5_init_context(&authctxt->krb5_ctx);
65 if (problem)
66 return (problem);
67 }
68 return (0);
69 }
70
71 int
auth_krb5_password(Authctxt * authctxt,const char * password)72 auth_krb5_password(Authctxt *authctxt, const char *password)
73 {
74 #ifndef HEIMDAL
75 krb5_creds creds;
76 krb5_principal server;
77 #endif
78 krb5_error_code problem;
79 krb5_ccache ccache = NULL;
80 int len;
81 char *client, *platform_client;
82 const char *errmsg;
83
84 /* get platform-specific kerberos client principal name (if it exists) */
85 platform_client = platform_krb5_get_principal_name(authctxt->pw->pw_name);
86 client = platform_client ? platform_client : authctxt->pw->pw_name;
87
88 temporarily_use_uid(authctxt->pw);
89
90 problem = krb5_init(authctxt);
91 if (problem)
92 goto out;
93
94 problem = krb5_parse_name(authctxt->krb5_ctx, client,
95 &authctxt->krb5_user);
96 if (problem)
97 goto out;
98
99 #ifdef HEIMDAL
100 # ifdef HAVE_KRB5_CC_NEW_UNIQUE
101 problem = krb5_cc_new_unique(authctxt->krb5_ctx,
102 krb5_mcc_ops.prefix, NULL, &ccache);
103 # else
104 problem = krb5_cc_gen_new(authctxt->krb5_ctx, &krb5_mcc_ops, &ccache);
105 # endif
106 if (problem)
107 goto out;
108
109 problem = krb5_cc_initialize(authctxt->krb5_ctx, ccache,
110 authctxt->krb5_user);
111 if (problem)
112 goto out;
113
114 restore_uid();
115
116 problem = krb5_verify_user(authctxt->krb5_ctx, authctxt->krb5_user,
117 ccache, password, 1, NULL);
118
119 temporarily_use_uid(authctxt->pw);
120
121 if (problem)
122 goto out;
123
124 # ifdef HAVE_KRB5_CC_NEW_UNIQUE
125 problem = krb5_cc_new_unique(authctxt->krb5_ctx,
126 krb5_fcc_ops.prefix, NULL, &authctxt->krb5_fwd_ccache);
127 # else
128 problem = krb5_cc_gen_new(authctxt->krb5_ctx, &krb5_fcc_ops,
129 &authctxt->krb5_fwd_ccache);
130 # endif
131 if (problem)
132 goto out;
133
134 problem = krb5_cc_copy_cache(authctxt->krb5_ctx, ccache,
135 authctxt->krb5_fwd_ccache);
136 krb5_cc_destroy(authctxt->krb5_ctx, ccache);
137 ccache = NULL;
138 if (problem)
139 goto out;
140
141 #else
142 problem = krb5_get_init_creds_password(authctxt->krb5_ctx, &creds,
143 authctxt->krb5_user, (char *)password, NULL, NULL, 0, NULL, NULL);
144 if (problem)
145 goto out;
146
147 problem = krb5_sname_to_principal(authctxt->krb5_ctx, NULL, NULL,
148 KRB5_NT_SRV_HST, &server);
149 if (problem)
150 goto out;
151
152 restore_uid();
153 problem = krb5_verify_init_creds(authctxt->krb5_ctx, &creds, server,
154 NULL, NULL, NULL);
155 krb5_free_principal(authctxt->krb5_ctx, server);
156 temporarily_use_uid(authctxt->pw);
157 if (problem)
158 goto out;
159
160 if (!krb5_kuserok(authctxt->krb5_ctx, authctxt->krb5_user,
161 authctxt->pw->pw_name)) {
162 problem = -1;
163 goto out;
164 }
165
166 problem = ssh_krb5_cc_gen(authctxt->krb5_ctx,
167 &authctxt->krb5_fwd_ccache);
168 if (problem)
169 goto out;
170
171 problem = krb5_cc_initialize(authctxt->krb5_ctx,
172 authctxt->krb5_fwd_ccache, authctxt->krb5_user);
173 if (problem)
174 goto out;
175
176 problem = krb5_cc_store_cred(authctxt->krb5_ctx,
177 authctxt->krb5_fwd_ccache, &creds);
178 if (problem)
179 goto out;
180 #endif
181
182 authctxt->krb5_ticket_file = (char *)krb5_cc_get_name(authctxt->krb5_ctx, authctxt->krb5_fwd_ccache);
183
184 len = strlen(authctxt->krb5_ticket_file) + 6;
185 authctxt->krb5_ccname = xmalloc(len);
186 snprintf(authctxt->krb5_ccname, len, "FILE:%s",
187 authctxt->krb5_ticket_file);
188
189 #ifdef USE_PAM
190 if (options.use_pam)
191 do_pam_putenv("KRB5CCNAME", authctxt->krb5_ccname);
192 #endif
193
194 out:
195 restore_uid();
196
197 free(platform_client);
198
199 if (problem) {
200 if (ccache)
201 krb5_cc_destroy(authctxt->krb5_ctx, ccache);
202
203 if (authctxt->krb5_ctx != NULL && problem!=-1) {
204 errmsg = krb5_get_error_message(authctxt->krb5_ctx,
205 problem);
206 debug("Kerberos password authentication failed: %s",
207 errmsg);
208 krb5_free_error_message(authctxt->krb5_ctx, errmsg);
209 } else
210 debug("Kerberos password authentication failed: %d",
211 problem);
212
213 krb5_cleanup_proc(authctxt);
214
215 if (options.kerberos_or_local_passwd)
216 return (-1);
217 else
218 return (0);
219 }
220 return (authctxt->valid ? 1 : 0);
221 }
222
223 void
krb5_cleanup_proc(Authctxt * authctxt)224 krb5_cleanup_proc(Authctxt *authctxt)
225 {
226 debug("krb5_cleanup_proc called");
227 if (authctxt->krb5_fwd_ccache) {
228 krb5_cc_destroy(authctxt->krb5_ctx, authctxt->krb5_fwd_ccache);
229 authctxt->krb5_fwd_ccache = NULL;
230 }
231 if (authctxt->krb5_user) {
232 krb5_free_principal(authctxt->krb5_ctx, authctxt->krb5_user);
233 authctxt->krb5_user = NULL;
234 }
235 if (authctxt->krb5_ctx) {
236 krb5_free_context(authctxt->krb5_ctx);
237 authctxt->krb5_ctx = NULL;
238 }
239 }
240
241 #ifndef HEIMDAL
242 krb5_error_code
ssh_krb5_cc_gen(krb5_context ctx,krb5_ccache * ccache)243 ssh_krb5_cc_gen(krb5_context ctx, krb5_ccache *ccache) {
244 int tmpfd, ret, oerrno;
245 char ccname[40];
246 mode_t old_umask;
247
248 ret = snprintf(ccname, sizeof(ccname),
249 "FILE:/tmp/krb5cc_%d_XXXXXXXXXX", geteuid());
250 if (ret < 0 || (size_t)ret >= sizeof(ccname))
251 return ENOMEM;
252
253 old_umask = umask(0177);
254 tmpfd = mkstemp(ccname + strlen("FILE:"));
255 oerrno = errno;
256 umask(old_umask);
257 if (tmpfd == -1) {
258 logit("mkstemp(): %.100s", strerror(oerrno));
259 return oerrno;
260 }
261
262 if (fchmod(tmpfd,S_IRUSR | S_IWUSR) == -1) {
263 oerrno = errno;
264 logit("fchmod(): %.100s", strerror(oerrno));
265 close(tmpfd);
266 return oerrno;
267 }
268 close(tmpfd);
269
270 return (krb5_cc_resolve(ctx, ccname, ccache));
271 }
272 #endif /* !HEIMDAL */
273 #endif /* KRB5 */
274