2 * Copyright (c) 2011, 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.
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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
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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
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46 * to distribution of the software without specific, written prior
47 * permission. Furthermore if you modify this software you must label
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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
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52 * or implied warranty.
57 const char *gServiceName = NULL;
59 int gsscon_passive_authenticate (int inSocket,
60 gss_ctx_id_t *outGSSContext)
63 OM_uint32 majorStatus;
64 OM_uint32 minorStatus = 0;
65 gss_ctx_id_t gssContext = GSS_C_NO_CONTEXT;
67 char *inputTokenBuffer = NULL;
68 size_t inputTokenBufferLength = 0;
69 gss_buffer_desc inputToken; /* buffer received from the server */
71 if (inSocket < 0 ) { err = EINVAL; }
72 if (!outGSSContext) { err = EINVAL; }
75 * The main authentication loop:
77 * GSS is a multimechanism API. The number of packet exchanges required to
78 * authenticatevaries between mechanisms. As a result, we need to loop reading
79 * input tokens from the client, calling gss_accept_sec_context on the input
80 * tokens and send the resulting output tokens back to the client until we
81 * get GSS_S_COMPLETE or an error.
83 * When we are done, save the client principal so we can make authorization
87 majorStatus = GSS_S_CONTINUE_NEEDED;
88 while (!err && (majorStatus != GSS_S_COMPLETE)) {
89 /* Clean up old input buffer */
90 if (inputTokenBuffer != NULL) {
91 free (inputTokenBuffer);
92 inputTokenBuffer = NULL; /* don't double-free */
95 err = gsscon_read_token (inSocket, &inputTokenBuffer, &inputTokenBufferLength);
98 /* Set up input buffers for the next run through the loop */
99 inputToken.value = inputTokenBuffer;
100 inputToken.length = inputTokenBufferLength;
104 /* buffer to send to the server */
105 gss_buffer_desc outputToken = { 0, NULL };
108 * accept_sec_context does the actual work of taking the client's
109 * request and generating an appropriate reply. Note that we pass
110 * GSS_C_NO_CREDENTIAL for the service principal. This causes the
111 * server to accept any service principal in the server's keytab,
112 * which enables you to support multihomed hosts by having one key
113 * in the keytab for each host identity the server responds on.
115 * However, since we may have more keys in the keytab than we want
116 * the server to actually use, we will need to check which service
117 * principal the client used after authentication succeeds. See
118 * ServicePrincipalIsValidForService() for where you would put these
119 * checks. We don't check here since if we stopped responding in the
120 * middle of the authentication negotiation, the client would get an
121 * EOF, and the user wouldn't know what went wrong.
124 printf ("Calling gss_accept_sec_context...\n");
125 majorStatus = gss_accept_sec_context (&minorStatus,
129 GSS_C_NO_CHANNEL_BINDINGS,
130 NULL /* client_name */,
131 NULL /* actual_mech_type */,
133 NULL /* req_flags */,
135 NULL /* delegated_cred_handle */);
137 if ((outputToken.length > 0) && (outputToken.value != NULL)) {
138 /* Send the output token to the client (even on error) */
139 err = gsscon_write_token (inSocket, outputToken.value, outputToken.length);
141 /* free the output token */
142 gss_release_buffer (&minorStatus, &outputToken);
146 if ((majorStatus != GSS_S_COMPLETE) && (majorStatus != GSS_S_CONTINUE_NEEDED)) {
147 gsscon_print_gss_errors ("gss_accept_sec_context", majorStatus, minorStatus);
148 err = minorStatus ? minorStatus : majorStatus;
153 *outGSSContext = gssContext;
156 gsscon_print_error (err, "Authenticate failed");
159 if (inputTokenBuffer) { free (inputTokenBuffer); }
160 if (gssContext != GSS_C_NO_CONTEXT) {
161 gss_delete_sec_context (&minorStatus, &gssContext, GSS_C_NO_BUFFER); }
166 /* --------------------------------------------------------------------------- */
168 static int ServicePrincipalIsValidForService (const char *inServicePrincipal)
171 krb5_context context = NULL;
172 krb5_principal principal = NULL;
174 if (!inServicePrincipal) { err = EINVAL; }
177 err = krb5_init_context (&context);
181 err = krb5_parse_name (context, inServicePrincipal, &principal);
186 * Here is where we check to see if the service principal the client
187 * used is valid. Typically we would just check that the first component
188 * is the name of the service provided by the server. This check exists
189 * to make sure the server is using the correct key in its keytab since
190 * we passed GSS_C_NO_CREDENTIAL into gss_accept_sec_context().
192 if (gServiceName && strcmp (gServiceName,
193 krb5_princ_name (context, principal)->data) != 0) {
194 err = KRB5KRB_AP_WRONG_PRINC;
198 if (principal) { krb5_free_principal (context, principal); }
199 if (context ) { krb5_free_context (context); }
205 /* --------------------------------------------------------------------------- */
207 static int ClientPrincipalIsAuthorizedForService (const char *inClientPrincipal)
210 krb5_context context = NULL;
211 krb5_principal principal = NULL;
213 if (!inClientPrincipal) { err = EINVAL; }
216 err = krb5_init_context (&context);
220 err = krb5_parse_name (context, inClientPrincipal, &principal);
225 * Here is where the server checks to see if the client principal should
226 * be allowed to use your service. Typically it should check both the name
227 * and the realm, since with cross-realm shared keys, a user at another
228 * realm may be trying to contact your service.
233 if (principal) { krb5_free_principal (context, principal); }
234 if (context ) { krb5_free_context (context); }
239 /* --------------------------------------------------------------------------- */
241 int gsscon_authorize (gss_ctx_id_t inContext,
243 int *outAuthorizationError)
246 OM_uint32 majorStatus;
247 OM_uint32 minorStatus = 0;
248 gss_name_t clientName = NULL;
249 gss_name_t serviceName = NULL;
250 char *clientPrincipal = NULL;
251 char *servicePrincipal = NULL;
253 if (!inContext ) { err = EINVAL; }
254 if (!outAuthorized ) { err = EINVAL; }
255 if (!outAuthorizationError) { err = EINVAL; }
258 /* Get the client and service principals used to authenticate */
259 majorStatus = gss_inquire_context (&minorStatus,
263 NULL, NULL, NULL, NULL, NULL);
264 if (majorStatus != GSS_S_COMPLETE) {
265 err = minorStatus ? minorStatus : majorStatus;
270 /* Pull the client principal string out of the gss name */
271 gss_buffer_desc nameToken;
273 majorStatus = gss_display_name (&minorStatus,
277 if (majorStatus != GSS_S_COMPLETE) {
278 err = minorStatus ? minorStatus : majorStatus;
282 clientPrincipal = malloc (nameToken.length + 1);
283 if (clientPrincipal == NULL) { err = ENOMEM; }
287 memcpy (clientPrincipal, nameToken.value, nameToken.length);
288 clientPrincipal[nameToken.length] = '\0';
291 if (nameToken.value) { gss_release_buffer (&minorStatus, &nameToken); }
295 /* Pull the service principal string out of the gss name */
296 gss_buffer_desc nameToken;
298 majorStatus = gss_display_name (&minorStatus,
302 if (majorStatus != GSS_S_COMPLETE) {
303 err = minorStatus ? minorStatus : majorStatus;
307 servicePrincipal = malloc (nameToken.length + 1);
308 if (servicePrincipal == NULL) { err = ENOMEM; }
312 memcpy (servicePrincipal, nameToken.value, nameToken.length);
313 servicePrincipal[nameToken.length] = '\0';
316 if (nameToken.value) { gss_release_buffer (&minorStatus, &nameToken); }
320 int authorizationErr = ServicePrincipalIsValidForService (servicePrincipal);
322 if (!authorizationErr) {
323 authorizationErr = ClientPrincipalIsAuthorizedForService (clientPrincipal);
326 printf ("'%s' is%s authorized for service '%s'\n",
327 clientPrincipal, authorizationErr ? " NOT" : "", servicePrincipal);
329 *outAuthorized = !authorizationErr;
330 *outAuthorizationError = authorizationErr;
333 if (serviceName ) { gss_release_name (&minorStatus, &serviceName); }
334 if (clientName ) { gss_release_name (&minorStatus, &clientName); }
335 if (clientPrincipal ) { free (clientPrincipal); }
336 if (servicePrincipal) { free (servicePrincipal); }