2 * Copyright (c) 2012, JANET(UK)
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 * notice, this list of conditions and the following disclaimer in the
14 * documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of JANET(UK) nor the names of its contributors
17 * may be used to endorse or promote products derived from this software
18 * without specific prior written permission.
20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
21 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
23 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
24 * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
25 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
26 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
27 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
29 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
30 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
31 * OF THE POSSIBILITY OF SUCH DAMAGE.
33 * This code was adapted from the MIT Kerberos Consortium's
34 * GSS example code, which was distributed under the following
37 * Copyright 2004-2006 Massachusetts Institute of Technology.
38 * All Rights Reserved.
40 * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
41 * distribute this software and its documentation for any purpose and
42 * without fee is hereby granted, provided that the above copyright
43 * notice appear in all copies and that both that copyright notice and
44 * this permission notice appear in supporting documentation, and that
45 * the name of M.I.T. not be used in advertising or publicity pertaining
46 * to distribution of the software without specific, written prior
47 * permission. Furthermore if you modify this software you must label
48 * your software as modified software and not distribute it in such a
49 * fashion that it might be confused with the original M.I.T. software.
50 * M.I.T. makes no representations about the suitability of
51 * this software for any purpose. It is provided "as is" without express
52 * or implied warranty.
61 /* ---------------------------------------------------------------------------
64 int gsscon_connect (const char *inHost, unsigned int inPort, const char *inServiceName, int *outFD, gss_ctx_id_t *outGSSContext)
68 OM_uint32 majorStatus;
69 OM_uint32 minorStatus = 0, minorStatusToo = 0;
70 struct addrinfo *ai=NULL;
71 struct addrinfo *ai_head=NULL;
72 struct addrinfo hints={.ai_family=AF_UNSPEC, .ai_socktype=SOCK_STREAM, .ai_protocol=IPPROTO_TCP};
73 struct sockaddr_in saddr;
75 gss_name_t serviceName = NULL;
76 gss_cred_id_t clientCredentials = GSS_C_NO_CREDENTIAL;
77 gss_ctx_id_t gssContext = GSS_C_NO_CONTEXT;
78 OM_uint32 actualFlags = 0;
79 char *inputTokenBuffer = NULL;
80 size_t inputTokenBufferLength = 0;
81 gss_buffer_desc inputToken; /* buffer received from the server */
82 gss_buffer_desc nameBuffer;
83 gss_buffer_t inputTokenPtr = GSS_C_NO_BUFFER;
87 if (!inServiceName) { err = EINVAL; }
88 if (!outGSSContext) { err = EINVAL; }
91 /* get a string for getaddrinfo */
92 if (asprintf(&port, "%d", inPort)>0) {
93 err=getaddrinfo(inHost, port, &hints, &ai_head);
100 /* try all options returned until one works */
101 for (ai=ai_head,fd=-1; (ai!=NULL) && (fd==-1); ai=ai->ai_next) {
102 fd=socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
108 fprintf(stderr, "gss_connect: Connecting to host '%s' on port %d\n", inHost, inPort);
109 err=connect(fd, ai->ai_addr, ai->ai_addrlen);
123 fd = -1; /* takes ownership */
125 gsscon_print_error (err, "OpenConnection failed");
128 if (fd >= 0) { close (fd); }
131 majorStatus = gss_acquire_cred (&minorStatus, GSS_C_NO_NAME, GSS_C_INDEFINITE, GSS_C_NO_OID_SET,
132 GSS_C_INITIATE, &clientCredentials, NULL, NULL);
133 if (majorStatus != GSS_S_COMPLETE) {
134 gsscon_print_gss_errors ("gss_acquire_cred", majorStatus, minorStatus);
135 err = minorStatus ? minorStatus : majorStatus;
140 * Here is where the client picks the service principal it will
141 * try to use to connect to the server. In the case of the
142 * gssClientSample, the service principal is passed in on the
143 * command line, however, in a real world example, this would be
144 * unacceptable from a user interface standpoint since the user
145 * shouldn't need to know the server's service principal.
147 * In traditional Kerberos setups, the service principal would be
148 * constructed from the type of the service (eg: "imap"), the DNS
149 * hostname of the server (eg: "mailserver.domain.com") and the
150 * client's local realm (eg: "DOMAIN.COM") to form a full
151 * principal string (eg: "imap/mailserver.domain.com@DOMAIN.COM").
153 * Now that many sites do not have DNS, this setup is becoming
154 * less common. However you decide to generate the service
155 * principal, you need to adhere to the following constraint: The
156 * service principal must be constructed by the client, typed in
157 * by the user or administrator, or transmitted to the client in a
158 * secure manner from a trusted third party -- such as through an
159 * encrypted connection to a directory server. You should not
160 * have the server send the client the service principal name as
161 * part of the authentication negotiation.
163 * The reason you can't let the server tell the client which
164 * principal to use is that many machines at a site will have
165 * their own service principal and keytab which identifies the
166 * machine -- in a Windows Active Directory environment all
167 * machines have a service principal and keytab. Some of these
168 * machines (such as a financial services server) will be more
169 * trustworthy than others (such as a random machine on a
170 * coworker's desk). If the owner of one of these untrustworthy
171 * machines can trick the client into using the untrustworthy
172 * machine's principal instead of the financial services server's
173 * principal, then he can trick the client into authenticating and
174 * connecting to the untrustworthy machine. The untrustworthy
175 * machine can then harvest any confidential information the
176 * client sends to it, such as credit card information or social
179 * If your protocol already involves sending the service principal
180 * as part of your authentication negotiation, your client should
181 * cache the name it gets after the first successful
182 * authentication so that the problem above can only happen on the
183 * first connection attempt -- similar to what ssh does with host
188 len = asprintf(&name, "%s@%s", inServiceName, inHost);
190 /* asprintf failed, pick an error to return... */
191 err = GSS_S_BAD_NAME;
193 nameBuffer.length = (size_t) len;
194 nameBuffer.value = name;
196 majorStatus = gss_import_name (&minorStatus, &nameBuffer, (gss_OID) GSS_C_NT_HOSTBASED_SERVICE, &serviceName);
197 if (majorStatus != GSS_S_COMPLETE) {
198 gsscon_print_gss_errors ("gss_import_name(inServiceName)", majorStatus, minorStatus);
199 err = minorStatus ? minorStatus : majorStatus;
202 /* free the input name and null pointers to avoid reuse */
205 nameBuffer.value = NULL;
210 * The main authentication loop:
212 * GSS is a multimechanism API. Because the number of packet
213 * exchanges required to authenticate can vary between mechanisms,
214 * we need to loop calling gss_init_sec_context, passing the
215 * "input tokens" received from the server and send the resulting
216 * "output tokens" back until we get GSS_S_COMPLETE or an error.
219 majorStatus = GSS_S_CONTINUE_NEEDED;
221 gss_OID_desc EAP_OID = { 9, "\x2B\x06\x01\x05\x05\x0F\x01\x01\x11" };
223 while (!err && (majorStatus != GSS_S_COMPLETE)) {
224 gss_buffer_desc outputToken = { 0, NULL }; /* buffer to send to the server */
225 OM_uint32 requestedFlags = (GSS_C_MUTUAL_FLAG | GSS_C_REPLAY_FLAG | GSS_C_SEQUENCE_FLAG |
226 GSS_C_CONF_FLAG | GSS_C_INTEG_FLAG);
228 majorStatus = gss_init_sec_context (&minorStatus,
232 &EAP_OID /* mech_type */,
235 GSS_C_NO_CHANNEL_BINDINGS,
237 NULL /* actual_mech_type */,
240 NULL /* time_rec */);
242 /* Send the output token to the server (even on error) */
243 if ((outputToken.length > 0) && (outputToken.value != NULL)) {
244 err = gsscon_write_token (*outFD, outputToken.value, outputToken.length);
246 /* free the output token */
247 gss_release_buffer (&minorStatusToo, &outputToken);
251 if (majorStatus == GSS_S_CONTINUE_NEEDED) {
252 /* Protocol requires another packet exchange */
254 /* Clean up old input buffer */
255 if (inputTokenBuffer) {
256 free (inputTokenBuffer);
257 inputTokenBuffer = NULL; /* don't double-free */
260 /* Read another input token from the server */
261 err = gsscon_read_token (*outFD, &inputTokenBuffer, &inputTokenBufferLength);
264 /* Set up input buffers for the next run through the loop */
265 inputToken.value = inputTokenBuffer;
266 inputToken.length = inputTokenBufferLength;
267 inputTokenPtr = &inputToken;
269 } else if (majorStatus != GSS_S_COMPLETE) {
270 gsscon_print_gss_errors ("gss_init_sec_context", majorStatus, minorStatus);
271 err = minorStatus ? minorStatus : majorStatus;
277 *outGSSContext = gssContext;
280 gsscon_print_error (err, "AuthenticateToServer failed");
283 if (inputTokenBuffer) { free (inputTokenBuffer); }
284 if (serviceName ) { gss_release_name (&minorStatus, &serviceName); }
285 if (ai_head ) { freeaddrinfo(ai_head); }
287 if (clientCredentials != GSS_C_NO_CREDENTIAL) {
288 gss_release_cred (&minorStatus, &clientCredentials); }
289 if (gssContext != GSS_C_NO_CONTEXT) {
290 gss_delete_sec_context (&minorStatus, &gssContext, GSS_C_NO_BUFFER); }