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.
57 /* --------------------------------------------------------------------------- */
59 int gsscon_connect (const char *inHost, int inPort, const char *inServiceName, int *outFD, gss_ctx_id_t *outGSSContext)
63 OM_uint32 majorStatus;
64 OM_uint32 minorStatus = 0;
65 struct hostent *hp = NULL;
66 struct sockaddr_in saddr;
67 gss_name_t serviceName = NULL;
68 gss_name_t clientName = NULL;
69 gss_cred_id_t clientCredentials = GSS_C_NO_CREDENTIAL;
70 gss_ctx_id_t gssContext = GSS_C_NO_CONTEXT;
71 OM_uint32 actualFlags = 0;
72 char *inputTokenBuffer = NULL;
73 size_t inputTokenBufferLength = 0;
74 gss_buffer_desc inputToken; /* buffer received from the server */
75 gss_buffer_desc nameBuffer;
76 gss_buffer_t inputTokenPtr = GSS_C_NO_BUFFER;
78 if (!inServiceName) { err = EINVAL; }
79 if (!outGSSContext) { err = EINVAL; }
82 hp = gethostbyname (inHost);
83 if (hp == NULL) { err = errno; }
87 saddr.sin_family = hp->h_addrtype;
88 memcpy ((char *) &saddr.sin_addr, hp->h_addr, sizeof (saddr.sin_addr));
89 saddr.sin_port = htons(inPort);
91 fd = socket (AF_INET, SOCK_STREAM, 0);
92 if (fd < 0) { err = errno; }
96 err = connect (fd, (struct sockaddr *) &saddr, sizeof (saddr));
97 if (err < 0) { err = errno; }
101 printf ("connecting to host '%s' on port %d\n", inHost, inPort);
103 fd = -1; /* takes ownership */
105 gsscon_print_error (err, "OpenConnection failed");
108 if (fd >= 0) { close (fd); }
111 majorStatus = gss_acquire_cred (&minorStatus, clientName, GSS_C_INDEFINITE, GSS_C_NO_OID_SET,
112 GSS_C_INITIATE, &clientCredentials, NULL, NULL);
113 if (majorStatus != GSS_S_COMPLETE) {
114 gsscon_print_gss_errors ("gss_acquire_cred", majorStatus, minorStatus);
115 err = minorStatus ? minorStatus : majorStatus;
120 * Here is where the client picks the service principal it will
121 * try to use to connect to the server. In the case of the
122 * gssClientSample, the service principal is passed in on the
123 * command line, however, in a real world example, this would be
124 * unacceptable from a user interface standpoint since the user
125 * shouldn't need to know the server's service principal.
127 * In traditional Kerberos setups, the service principal would be
128 * constructed from the type of the service (eg: "imap"), the DNS
129 * hostname of the server (eg: "mailserver.domain.com") and the
130 * client's local realm (eg: "DOMAIN.COM") to form a full
131 * principal string (eg: "imap/mailserver.domain.com@DOMAIN.COM").
133 * Now that many sites do not have DNS, this setup is becoming
134 * less common. However you decide to generate the service
135 * principal, you need to adhere to the following constraint: The
136 * service principal must be constructed by the client, typed in
137 * by the user or administrator, or transmitted to the client in a
138 * secure manner from a trusted third party -- such as through an
139 * encrypted connection to a directory server. You should not
140 * have the server send the client the service principal name as
141 * part of the authentication negotiation.
143 * The reason you can't let the server tell the client which
144 * principal to use is that many machines at a site will have
145 * their own service principal and keytab which identifies the
146 * machine -- in a Windows Active Directory environment all
147 * machines have a service principal and keytab. Some of these
148 * machines (such as a financial services server) will be more
149 * trustworthy than others (such as a random machine on a
150 * coworker's desk). If the owner of one of these untrustworthy
151 * machines can trick the client into using the untrustworthy
152 * machine's principal instead of the financial services server's
153 * principal, then he can trick the client into authenticating and
154 * connecting to the untrustworthy machine. The untrustworthy
155 * machine can then harvest any confidential information the
156 * client sends to it, such as credit card information or social
159 * If your protocol already involves sending the service principal
160 * as part of your authentication negotiation, your client should
161 * cache the name it gets after the first successful
162 * authentication so that the problem above can only happen on the
163 * first connection attempt -- similar to what ssh does with host
168 nameBuffer.length = asprintf(&name, "%s@%s", inServiceName, inHost);
169 nameBuffer.value = name;
171 majorStatus = gss_import_name (&minorStatus, &nameBuffer, (gss_OID) GSS_KRB5_NT_PRINCIPAL_NAME, &serviceName);
172 if (majorStatus != GSS_S_COMPLETE) {
173 gsscon_print_gss_errors ("gss_import_name(inServiceName)", majorStatus, minorStatus);
174 err = minorStatus ? minorStatus : majorStatus;
179 * The main authentication loop:
181 * GSS is a multimechanism API. Because the number of packet
182 * exchanges required to authenticate can vary between mechanisms,
183 * we need to loop calling gss_init_sec_context, passing the
184 * "input tokens" received from the server and send the resulting
185 * "output tokens" back until we get GSS_S_COMPLETE or an error.
188 majorStatus = GSS_S_CONTINUE_NEEDED;
190 gss_OID_desc EAP_OID = { 9, "\x2B\x06\x01\x05\x05\x0F\x01\x01\x11" };
192 while (!err && (majorStatus != GSS_S_COMPLETE)) {
193 gss_buffer_desc outputToken = { 0, NULL }; /* buffer to send to the server */
194 OM_uint32 requestedFlags = (GSS_C_MUTUAL_FLAG | GSS_C_REPLAY_FLAG | GSS_C_SEQUENCE_FLAG |
195 GSS_C_CONF_FLAG | GSS_C_INTEG_FLAG);
197 // printf ("Calling gss_init_sec_context...\n");
198 majorStatus = gss_init_sec_context (&minorStatus,
202 &EAP_OID /* mech_type */,
205 GSS_C_NO_CHANNEL_BINDINGS,
207 NULL /* actual_mech_type */,
210 NULL /* time_rec */);
212 /* Send the output token to the server (even on error) */
213 if ((outputToken.length > 0) && (outputToken.value != NULL)) {
214 err = gsscon_write_token (*outFD, outputToken.value, outputToken.length);
216 /* free the output token */
217 gss_release_buffer (&minorStatus, &outputToken);
221 if (majorStatus == GSS_S_CONTINUE_NEEDED) {
222 /* Protocol requires another packet exchange */
224 /* Clean up old input buffer */
225 if (inputTokenBuffer) {
226 free (inputTokenBuffer);
227 inputTokenBuffer = NULL; /* don't double-free */
230 /* Read another input token from the server */
231 err = gsscon_read_token (*outFD, &inputTokenBuffer, &inputTokenBufferLength);
234 /* Set up input buffers for the next run through the loop */
235 inputToken.value = inputTokenBuffer;
236 inputToken.length = inputTokenBufferLength;
237 inputTokenPtr = &inputToken;
239 } else if (majorStatus != GSS_S_COMPLETE) {
240 gsscon_print_gss_errors ("gss_init_sec_context", majorStatus, minorStatus);
241 err = minorStatus ? minorStatus : majorStatus;
247 *outGSSContext = gssContext;
250 gsscon_print_error (err, "AuthenticateToServer failed");
253 if (inputTokenBuffer) { free (inputTokenBuffer); }
254 if (serviceName ) { gss_release_name (&minorStatus, &serviceName); }
255 if (clientName ) { gss_release_name (&minorStatus, &clientName); }
257 if (clientCredentials != GSS_C_NO_CREDENTIAL) {
258 gss_release_cred (&minorStatus, &clientCredentials); }
259 if (gssContext != GSS_C_NO_CONTEXT) {
260 gss_delete_sec_context (&minorStatus, &gssContext, GSS_C_NO_BUFFER); }