xref: /openssh-portable/auth-krb5.c (revision c7d39ac8)
1 /* $OpenBSD: auth-krb5.c,v 1.23 2018/07/09 21:35:50 markus 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, &authctxt->krb5_fwd_ccache);
167 	if (problem)
168 		goto out;
169 
170 	problem = krb5_cc_initialize(authctxt->krb5_ctx, authctxt->krb5_fwd_ccache,
171 				     authctxt->krb5_user);
172 	if (problem)
173 		goto out;
174 
175 	problem= krb5_cc_store_cred(authctxt->krb5_ctx, authctxt->krb5_fwd_ccache,
176 				 &creds);
177 	if (problem)
178 		goto out;
179 #endif
180 
181 	authctxt->krb5_ticket_file = (char *)krb5_cc_get_name(authctxt->krb5_ctx, authctxt->krb5_fwd_ccache);
182 
183 	len = strlen(authctxt->krb5_ticket_file) + 6;
184 	authctxt->krb5_ccname = xmalloc(len);
185 	snprintf(authctxt->krb5_ccname, len, "FILE:%s",
186 	    authctxt->krb5_ticket_file);
187 
188 #ifdef USE_PAM
189 	if (options.use_pam)
190 		do_pam_putenv("KRB5CCNAME", authctxt->krb5_ccname);
191 #endif
192 
193  out:
194 	restore_uid();
195 
196 	free(platform_client);
197 
198 	if (problem) {
199 		if (ccache)
200 			krb5_cc_destroy(authctxt->krb5_ctx, ccache);
201 
202 		if (authctxt->krb5_ctx != NULL && problem!=-1) {
203 			errmsg = krb5_get_error_message(authctxt->krb5_ctx,
204 			    problem);
205  			debug("Kerberos password authentication failed: %s",
206 			    errmsg);
207 			krb5_free_error_message(authctxt->krb5_ctx, errmsg);
208 		} else
209 			debug("Kerberos password authentication failed: %d",
210 			    problem);
211 
212 		krb5_cleanup_proc(authctxt);
213 
214 		if (options.kerberos_or_local_passwd)
215 			return (-1);
216 		else
217 			return (0);
218 	}
219 	return (authctxt->valid ? 1 : 0);
220 }
221 
222 void
krb5_cleanup_proc(Authctxt * authctxt)223 krb5_cleanup_proc(Authctxt *authctxt)
224 {
225 	debug("krb5_cleanup_proc called");
226 	if (authctxt->krb5_fwd_ccache) {
227 		krb5_cc_destroy(authctxt->krb5_ctx, authctxt->krb5_fwd_ccache);
228 		authctxt->krb5_fwd_ccache = NULL;
229 	}
230 	if (authctxt->krb5_user) {
231 		krb5_free_principal(authctxt->krb5_ctx, authctxt->krb5_user);
232 		authctxt->krb5_user = NULL;
233 	}
234 	if (authctxt->krb5_ctx) {
235 		krb5_free_context(authctxt->krb5_ctx);
236 		authctxt->krb5_ctx = NULL;
237 	}
238 }
239 
240 #ifndef HEIMDAL
241 krb5_error_code
ssh_krb5_cc_gen(krb5_context ctx,krb5_ccache * ccache)242 ssh_krb5_cc_gen(krb5_context ctx, krb5_ccache *ccache) {
243 	int tmpfd, ret, oerrno;
244 	char ccname[40];
245 	mode_t old_umask;
246 
247 	ret = snprintf(ccname, sizeof(ccname),
248 	    "FILE:/tmp/krb5cc_%d_XXXXXXXXXX", geteuid());
249 	if (ret < 0 || (size_t)ret >= sizeof(ccname))
250 		return ENOMEM;
251 
252 	old_umask = umask(0177);
253 	tmpfd = mkstemp(ccname + strlen("FILE:"));
254 	oerrno = errno;
255 	umask(old_umask);
256 	if (tmpfd == -1) {
257 		logit("mkstemp(): %.100s", strerror(oerrno));
258 		return oerrno;
259 	}
260 
261 	if (fchmod(tmpfd,S_IRUSR | S_IWUSR) == -1) {
262 		oerrno = errno;
263 		logit("fchmod(): %.100s", strerror(oerrno));
264 		close(tmpfd);
265 		return oerrno;
266 	}
267 	close(tmpfd);
268 
269 	return (krb5_cc_resolve(ctx, ccname, ccache));
270 }
271 #endif /* !HEIMDAL */
272 #endif /* KRB5 */
273