xref: /curl/lib/vauth/krb5_gssapi.c (revision fbf5d507)
1 /***************************************************************************
2  *                                  _   _ ____  _
3  *  Project                     ___| | | |  _ \| |
4  *                             / __| | | | |_) | |
5  *                            | (__| |_| |  _ <| |___
6  *                             \___|\___/|_| \_\_____|
7  *
8  * Copyright (C) Steve Holme, <steve_holme@hotmail.com>.
9  * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
10  *
11  * This software is licensed as described in the file COPYING, which
12  * you should have received as part of this distribution. The terms
13  * are also available at https://curl.se/docs/copyright.html.
14  *
15  * You may opt to use, copy, modify, merge, publish, distribute and/or sell
16  * copies of the Software, and permit persons to whom the Software is
17  * furnished to do so, under the terms of the COPYING file.
18  *
19  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
20  * KIND, either express or implied.
21  *
22  * SPDX-License-Identifier: curl
23  *
24  * RFC4752 The Kerberos V5 ("GSSAPI") SASL Mechanism
25  *
26  ***************************************************************************/
27 
28 #include "curl_setup.h"
29 
30 #if defined(HAVE_GSSAPI) && defined(USE_KERBEROS5)
31 
32 #include <curl/curl.h>
33 
34 #include "vauth/vauth.h"
35 #include "curl_sasl.h"
36 #include "urldata.h"
37 #include "curl_gssapi.h"
38 #include "sendf.h"
39 #include "curl_printf.h"
40 
41 /* The last #include files should be: */
42 #include "curl_memory.h"
43 #include "memdebug.h"
44 
45 /*
46  * Curl_auth_is_gssapi_supported()
47  *
48  * This is used to evaluate if GSSAPI (Kerberos V5) is supported.
49  *
50  * Parameters: None
51  *
52  * Returns TRUE if Kerberos V5 is supported by the GSS-API library.
53  */
Curl_auth_is_gssapi_supported(void)54 bool Curl_auth_is_gssapi_supported(void)
55 {
56   return TRUE;
57 }
58 
59 /*
60  * Curl_auth_create_gssapi_user_message()
61  *
62  * This is used to generate an already encoded GSSAPI (Kerberos V5) user token
63  * message ready for sending to the recipient.
64  *
65  * Parameters:
66  *
67  * data        [in]     - The session handle.
68  * userp       [in]     - The username.
69  * passwdp     [in]     - The user's password.
70  * service     [in]     - The service type such as http, smtp, pop or imap.
71  * host        [in[     - The hostname.
72  * mutual_auth [in]     - Flag specifying whether or not mutual authentication
73  *                        is enabled.
74  * chlg        [in]     - Optional challenge message.
75  * krb5        [in/out] - The Kerberos 5 data struct being used and modified.
76  * out         [out]    - The result storage.
77  *
78  * Returns CURLE_OK on success.
79  */
Curl_auth_create_gssapi_user_message(struct Curl_easy * data,const char * userp,const char * passwdp,const char * service,const char * host,const bool mutual_auth,const struct bufref * chlg,struct kerberos5data * krb5,struct bufref * out)80 CURLcode Curl_auth_create_gssapi_user_message(struct Curl_easy *data,
81                                               const char *userp,
82                                               const char *passwdp,
83                                               const char *service,
84                                               const char *host,
85                                               const bool mutual_auth,
86                                               const struct bufref *chlg,
87                                               struct kerberos5data *krb5,
88                                               struct bufref *out)
89 {
90   CURLcode result = CURLE_OK;
91   OM_uint32 major_status;
92   OM_uint32 minor_status;
93   OM_uint32 unused_status;
94   gss_buffer_desc spn_token = GSS_C_EMPTY_BUFFER;
95   gss_buffer_desc input_token = GSS_C_EMPTY_BUFFER;
96   gss_buffer_desc output_token = GSS_C_EMPTY_BUFFER;
97 
98   (void) userp;
99   (void) passwdp;
100 
101   if(!krb5->spn) {
102     /* Generate our SPN */
103     char *spn = Curl_auth_build_spn(service, NULL, host);
104     if(!spn)
105       return CURLE_OUT_OF_MEMORY;
106 
107     /* Populate the SPN structure */
108     spn_token.value = spn;
109     spn_token.length = strlen(spn);
110 
111     /* Import the SPN */
112     major_status = gss_import_name(&minor_status, &spn_token,
113                                    GSS_C_NT_HOSTBASED_SERVICE, &krb5->spn);
114     if(GSS_ERROR(major_status)) {
115       Curl_gss_log_error(data, "gss_import_name() failed: ",
116                          major_status, minor_status);
117 
118       free(spn);
119 
120       return CURLE_AUTH_ERROR;
121     }
122 
123     free(spn);
124   }
125 
126   if(chlg) {
127     if(!Curl_bufref_len(chlg)) {
128       infof(data, "GSSAPI handshake failure (empty challenge message)");
129       return CURLE_BAD_CONTENT_ENCODING;
130     }
131     input_token.value = (void *) Curl_bufref_ptr(chlg);
132     input_token.length = Curl_bufref_len(chlg);
133   }
134 
135   major_status = Curl_gss_init_sec_context(data,
136                                            &minor_status,
137                                            &krb5->context,
138                                            krb5->spn,
139                                            &Curl_krb5_mech_oid,
140                                            GSS_C_NO_CHANNEL_BINDINGS,
141                                            &input_token,
142                                            &output_token,
143                                            mutual_auth,
144                                            NULL);
145 
146   if(GSS_ERROR(major_status)) {
147     if(output_token.value)
148       gss_release_buffer(&unused_status, &output_token);
149 
150     Curl_gss_log_error(data, "gss_init_sec_context() failed: ",
151                        major_status, minor_status);
152 
153     return CURLE_AUTH_ERROR;
154   }
155 
156   if(output_token.value && output_token.length) {
157     result = Curl_bufref_memdup(out, output_token.value, output_token.length);
158     gss_release_buffer(&unused_status, &output_token);
159   }
160   else
161     Curl_bufref_set(out, mutual_auth ? "": NULL, 0, NULL);
162 
163   return result;
164 }
165 
166 /*
167  * Curl_auth_create_gssapi_security_message()
168  *
169  * This is used to generate an already encoded GSSAPI (Kerberos V5) security
170  * token message ready for sending to the recipient.
171  *
172  * Parameters:
173  *
174  * data    [in]     - The session handle.
175  * authzid [in]     - The authorization identity if some.
176  * chlg    [in]     - Optional challenge message.
177  * krb5    [in/out] - The Kerberos 5 data struct being used and modified.
178  * out     [out]    - The result storage.
179  *
180  * Returns CURLE_OK on success.
181  */
Curl_auth_create_gssapi_security_message(struct Curl_easy * data,const char * authzid,const struct bufref * chlg,struct kerberos5data * krb5,struct bufref * out)182 CURLcode Curl_auth_create_gssapi_security_message(struct Curl_easy *data,
183                                                   const char *authzid,
184                                                   const struct bufref *chlg,
185                                                   struct kerberos5data *krb5,
186                                                   struct bufref *out)
187 {
188   CURLcode result = CURLE_OK;
189   size_t messagelen = 0;
190   unsigned char *message = NULL;
191   OM_uint32 major_status;
192   OM_uint32 minor_status;
193   OM_uint32 unused_status;
194   gss_buffer_desc input_token = GSS_C_EMPTY_BUFFER;
195   gss_buffer_desc output_token = GSS_C_EMPTY_BUFFER;
196   unsigned char *indata;
197   gss_qop_t qop = GSS_C_QOP_DEFAULT;
198   unsigned int sec_layer = 0;
199   unsigned int max_size = 0;
200 
201   /* Ensure we have a valid challenge message */
202   if(!Curl_bufref_len(chlg)) {
203     infof(data, "GSSAPI handshake failure (empty security message)");
204     return CURLE_BAD_CONTENT_ENCODING;
205   }
206 
207   /* Setup the challenge "input" security buffer */
208   input_token.value = (void *) Curl_bufref_ptr(chlg);
209   input_token.length = Curl_bufref_len(chlg);
210 
211   /* Decrypt the inbound challenge and obtain the qop */
212   major_status = gss_unwrap(&minor_status, krb5->context, &input_token,
213                             &output_token, NULL, &qop);
214   if(GSS_ERROR(major_status)) {
215     Curl_gss_log_error(data, "gss_unwrap() failed: ",
216                        major_status, minor_status);
217     return CURLE_BAD_CONTENT_ENCODING;
218   }
219 
220   /* Not 4 octets long so fail as per RFC4752 Section 3.1 */
221   if(output_token.length != 4) {
222     infof(data, "GSSAPI handshake failure (invalid security data)");
223     return CURLE_BAD_CONTENT_ENCODING;
224   }
225 
226   /* Extract the security layer and the maximum message size */
227   indata = output_token.value;
228   sec_layer = indata[0];
229   max_size = ((unsigned int)indata[1] << 16) |
230              ((unsigned int)indata[2] << 8) | indata[3];
231 
232   /* Free the challenge as it is not required anymore */
233   gss_release_buffer(&unused_status, &output_token);
234 
235   /* Process the security layer */
236   if(!(sec_layer & GSSAUTH_P_NONE)) {
237     infof(data, "GSSAPI handshake failure (invalid security layer)");
238 
239     return CURLE_BAD_CONTENT_ENCODING;
240   }
241   sec_layer &= GSSAUTH_P_NONE;  /* We do not support a security layer */
242 
243   /* Process the maximum message size the server can receive */
244   if(max_size > 0) {
245     /* The server has told us it supports a maximum receive buffer, however, as
246        we do not require one unless we are encrypting data, we tell the server
247        our receive buffer is zero. */
248     max_size = 0;
249   }
250 
251   /* Allocate our message */
252   messagelen = 4;
253   if(authzid)
254     messagelen += strlen(authzid);
255   message = malloc(messagelen);
256   if(!message)
257     return CURLE_OUT_OF_MEMORY;
258 
259   /* Populate the message with the security layer and client supported receive
260      message size. */
261   message[0] = sec_layer & 0xFF;
262   message[1] = (max_size >> 16) & 0xFF;
263   message[2] = (max_size >> 8) & 0xFF;
264   message[3] = max_size & 0xFF;
265 
266   /* If given, append the authorization identity. */
267 
268   if(authzid && *authzid)
269     memcpy(message + 4, authzid, messagelen - 4);
270 
271   /* Setup the "authentication data" security buffer */
272   input_token.value = message;
273   input_token.length = messagelen;
274 
275   /* Encrypt the data */
276   major_status = gss_wrap(&minor_status, krb5->context, 0,
277                           GSS_C_QOP_DEFAULT, &input_token, NULL,
278                           &output_token);
279   if(GSS_ERROR(major_status)) {
280     Curl_gss_log_error(data, "gss_wrap() failed: ",
281                        major_status, minor_status);
282     free(message);
283     return CURLE_AUTH_ERROR;
284   }
285 
286   /* Return the response. */
287   result = Curl_bufref_memdup(out, output_token.value, output_token.length);
288   /* Free the output buffer */
289   gss_release_buffer(&unused_status, &output_token);
290 
291   /* Free the message buffer */
292   free(message);
293 
294   return result;
295 }
296 
297 /*
298  * Curl_auth_cleanup_gssapi()
299  *
300  * This is used to clean up the GSSAPI (Kerberos V5) specific data.
301  *
302  * Parameters:
303  *
304  * krb5     [in/out] - The Kerberos 5 data struct being cleaned up.
305  *
306  */
Curl_auth_cleanup_gssapi(struct kerberos5data * krb5)307 void Curl_auth_cleanup_gssapi(struct kerberos5data *krb5)
308 {
309   OM_uint32 minor_status;
310 
311   /* Free our security context */
312   if(krb5->context != GSS_C_NO_CONTEXT) {
313     gss_delete_sec_context(&minor_status, &krb5->context, GSS_C_NO_BUFFER);
314     krb5->context = GSS_C_NO_CONTEXT;
315   }
316 
317   /* Free the SPN */
318   if(krb5->spn != GSS_C_NO_NAME) {
319     gss_release_name(&minor_status, &krb5->spn);
320     krb5->spn = GSS_C_NO_NAME;
321   }
322 }
323 
324 #endif /* HAVE_GSSAPI && USE_KERBEROS5 */
325