1 /***************************************************************************
2  *                                  _   _ ____  _
3  *  Project                     ___| | | |  _ \| |
4  *                             / __| | | | |_) | |
5  *                            | (__| |_| |  _ <| |___
6  *                             \___|\___/|_| \_\_____|
7  *
8  * Copyright (C) 2014 - 2019, Steve Holme, <steve_holme@hotmail.com>.
9  * Copyright (C) 2015, 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.haxx.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  * RFC4752 The Kerberos V5 ("GSSAPI") SASL Mechanism
23  *
24  ***************************************************************************/
25 
26 #include "curl_setup.h"
27 
28 #if defined(HAVE_GSSAPI) && defined(USE_KERBEROS5)
29 
30 #include <curl/curl.h>
31 
32 #include "vauth/vauth.h"
33 #include "curl_sasl.h"
34 #include "urldata.h"
35 #include "curl_base64.h"
36 #include "curl_gssapi.h"
37 #include "sendf.h"
38 #include "curl_printf.h"
39 
40 /* The last #include files should be: */
41 #include "curl_memory.h"
42 #include "memdebug.h"
43 
44 /*
45  * Curl_auth_is_gssapi_supported()
46  *
47  * This is used to evaluate if GSSAPI (Kerberos V5) is supported.
48  *
49  * Parameters: None
50  *
51  * Returns TRUE if Kerberos V5 is supported by the GSS-API library.
52  */
Curl_auth_is_gssapi_supported(void)53 bool Curl_auth_is_gssapi_supported(void)
54 {
55   return TRUE;
56 }
57 
58 /*
59  * Curl_auth_create_gssapi_user_message()
60  *
61  * This is used to generate an already encoded GSSAPI (Kerberos V5) user token
62  * message ready for sending to the recipient.
63  *
64  * Parameters:
65  *
66  * data        [in]     - The session handle.
67  * userp       [in]     - The user name.
68  * passwdp     [in]     - The user's password.
69  * service     [in]     - The service type such as http, smtp, pop or imap.
70  * host        [in[     - The host name.
71  * mutual_auth [in]     - Flag specifying whether or not mutual authentication
72  *                        is enabled.
73  * chlg64      [in]     - Pointer to the optional base64 encoded challenge
74  *                        message.
75  * krb5        [in/out] - The Kerberos 5 data struct being used and modified.
76  * outptr      [in/out] - The address where a pointer to newly allocated memory
77  *                        holding the result will be stored upon completion.
78  * outlen      [out]    - The length of the output message.
79  *
80  * Returns CURLE_OK on success.
81  */
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 char * chlg64,struct kerberos5data * krb5,char ** outptr,size_t * outlen)82 CURLcode Curl_auth_create_gssapi_user_message(struct Curl_easy *data,
83                                               const char *userp,
84                                               const char *passwdp,
85                                               const char *service,
86                                               const char *host,
87                                               const bool mutual_auth,
88                                               const char *chlg64,
89                                               struct kerberos5data *krb5,
90                                               char **outptr, size_t *outlen)
91 {
92   CURLcode result = CURLE_OK;
93   size_t chlglen = 0;
94   unsigned char *chlg = NULL;
95   OM_uint32 major_status;
96   OM_uint32 minor_status;
97   OM_uint32 unused_status;
98   gss_buffer_desc spn_token = GSS_C_EMPTY_BUFFER;
99   gss_buffer_desc input_token = GSS_C_EMPTY_BUFFER;
100   gss_buffer_desc output_token = GSS_C_EMPTY_BUFFER;
101 
102   (void) userp;
103   (void) passwdp;
104 
105   if(!krb5->spn) {
106     /* Generate our SPN */
107     char *spn = Curl_auth_build_spn(service, NULL, host);
108     if(!spn)
109       return CURLE_OUT_OF_MEMORY;
110 
111     /* Populate the SPN structure */
112     spn_token.value = spn;
113     spn_token.length = strlen(spn);
114 
115     /* Import the SPN */
116     major_status = gss_import_name(&minor_status, &spn_token,
117                                    GSS_C_NT_HOSTBASED_SERVICE, &krb5->spn);
118     if(GSS_ERROR(major_status)) {
119       Curl_gss_log_error(data, "gss_import_name() failed: ",
120                          major_status, minor_status);
121 
122       free(spn);
123 
124       return CURLE_AUTH_ERROR;
125     }
126 
127     free(spn);
128   }
129 
130   if(chlg64 && *chlg64) {
131     /* Decode the base-64 encoded challenge message */
132     if(*chlg64 != '=') {
133       result = Curl_base64_decode(chlg64, &chlg, &chlglen);
134       if(result)
135         return result;
136     }
137 
138     /* Ensure we have a valid challenge message */
139     if(!chlg) {
140       infof(data, "GSSAPI handshake failure (empty challenge message)\n");
141 
142       return CURLE_BAD_CONTENT_ENCODING;
143     }
144 
145     /* Setup the challenge "input" security buffer */
146     input_token.value = chlg;
147     input_token.length = chlglen;
148   }
149 
150   major_status = Curl_gss_init_sec_context(data,
151                                            &minor_status,
152                                            &krb5->context,
153                                            krb5->spn,
154                                            &Curl_krb5_mech_oid,
155                                            GSS_C_NO_CHANNEL_BINDINGS,
156                                            &input_token,
157                                            &output_token,
158                                            mutual_auth,
159                                            NULL);
160 
161   /* Free the decoded challenge as it is not required anymore */
162   free(input_token.value);
163 
164   if(GSS_ERROR(major_status)) {
165     if(output_token.value)
166       gss_release_buffer(&unused_status, &output_token);
167 
168     Curl_gss_log_error(data, "gss_init_sec_context() failed: ",
169                        major_status, minor_status);
170 
171     return CURLE_AUTH_ERROR;
172   }
173 
174   if(output_token.value && output_token.length) {
175     /* Base64 encode the response */
176     result = Curl_base64_encode(data, (char *) output_token.value,
177                                 output_token.length, outptr, outlen);
178 
179     gss_release_buffer(&unused_status, &output_token);
180   }
181   else if(mutual_auth) {
182     *outptr = strdup("");
183     if(!*outptr)
184       result = CURLE_OUT_OF_MEMORY;
185   }
186 
187   return result;
188 }
189 
190 /*
191  * Curl_auth_create_gssapi_security_message()
192  *
193  * This is used to generate an already encoded GSSAPI (Kerberos V5) security
194  * token message ready for sending to the recipient.
195  *
196  * Parameters:
197  *
198  * data    [in]     - The session handle.
199  * chlg64  [in]     - Pointer to the optional base64 encoded challenge message.
200  * krb5    [in/out] - The Kerberos 5 data struct being used and modified.
201  * outptr  [in/out] - The address where a pointer to newly allocated memory
202  *                    holding the result will be stored upon completion.
203  * outlen  [out]    - The length of the output message.
204  *
205  * Returns CURLE_OK on success.
206  */
Curl_auth_create_gssapi_security_message(struct Curl_easy * data,const char * chlg64,struct kerberos5data * krb5,char ** outptr,size_t * outlen)207 CURLcode Curl_auth_create_gssapi_security_message(struct Curl_easy *data,
208                                                   const char *chlg64,
209                                                   struct kerberos5data *krb5,
210                                                   char **outptr,
211                                                   size_t *outlen)
212 {
213   CURLcode result = CURLE_OK;
214   size_t chlglen = 0;
215   size_t messagelen = 0;
216   unsigned char *chlg = NULL;
217   unsigned char *message = NULL;
218   OM_uint32 major_status;
219   OM_uint32 minor_status;
220   OM_uint32 unused_status;
221   gss_buffer_desc input_token = GSS_C_EMPTY_BUFFER;
222   gss_buffer_desc output_token = GSS_C_EMPTY_BUFFER;
223   unsigned int indata = 0;
224   unsigned int outdata = 0;
225   gss_qop_t qop = GSS_C_QOP_DEFAULT;
226   unsigned int sec_layer = 0;
227   unsigned int max_size = 0;
228   gss_name_t username = GSS_C_NO_NAME;
229   gss_buffer_desc username_token;
230 
231   /* Decode the base-64 encoded input message */
232   if(strlen(chlg64) && *chlg64 != '=') {
233     result = Curl_base64_decode(chlg64, &chlg, &chlglen);
234     if(result)
235       return result;
236   }
237 
238   /* Ensure we have a valid challenge message */
239   if(!chlg) {
240     infof(data, "GSSAPI handshake failure (empty security message)\n");
241 
242     return CURLE_BAD_CONTENT_ENCODING;
243   }
244 
245   /* Get the fully qualified username back from the context */
246   major_status = gss_inquire_context(&minor_status, krb5->context,
247                                      &username, NULL, NULL, NULL, NULL,
248                                      NULL, NULL);
249   if(GSS_ERROR(major_status)) {
250     Curl_gss_log_error(data, "gss_inquire_context() failed: ",
251                        major_status, minor_status);
252 
253     free(chlg);
254 
255     return CURLE_AUTH_ERROR;
256   }
257 
258   /* Convert the username from internal format to a displayable token */
259   major_status = gss_display_name(&minor_status, username,
260                                   &username_token, NULL);
261   if(GSS_ERROR(major_status)) {
262     Curl_gss_log_error(data, "gss_display_name() failed: ",
263                        major_status, minor_status);
264 
265     free(chlg);
266 
267     return CURLE_AUTH_ERROR;
268   }
269 
270   /* Setup the challenge "input" security buffer */
271   input_token.value = chlg;
272   input_token.length = chlglen;
273 
274   /* Decrypt the inbound challenge and obtain the qop */
275   major_status = gss_unwrap(&minor_status, krb5->context, &input_token,
276                             &output_token, NULL, &qop);
277   if(GSS_ERROR(major_status)) {
278     Curl_gss_log_error(data, "gss_unwrap() failed: ",
279                        major_status, minor_status);
280 
281     gss_release_buffer(&unused_status, &username_token);
282     free(chlg);
283 
284     return CURLE_BAD_CONTENT_ENCODING;
285   }
286 
287   /* Not 4 octets long so fail as per RFC4752 Section 3.1 */
288   if(output_token.length != 4) {
289     infof(data, "GSSAPI handshake failure (invalid security data)\n");
290 
291     gss_release_buffer(&unused_status, &username_token);
292     free(chlg);
293 
294     return CURLE_BAD_CONTENT_ENCODING;
295   }
296 
297   /* Copy the data out and free the challenge as it is not required anymore */
298   memcpy(&indata, output_token.value, 4);
299   gss_release_buffer(&unused_status, &output_token);
300   free(chlg);
301 
302   /* Extract the security layer */
303   sec_layer = indata & 0x000000FF;
304   if(!(sec_layer & GSSAUTH_P_NONE)) {
305     infof(data, "GSSAPI handshake failure (invalid security layer)\n");
306 
307     gss_release_buffer(&unused_status, &username_token);
308 
309     return CURLE_BAD_CONTENT_ENCODING;
310   }
311 
312   /* Extract the maximum message size the server can receive */
313   max_size = ntohl(indata & 0xFFFFFF00);
314   if(max_size > 0) {
315     /* The server has told us it supports a maximum receive buffer, however, as
316        we don't require one unless we are encrypting data, we tell the server
317        our receive buffer is zero. */
318     max_size = 0;
319   }
320 
321   /* Allocate our message */
322   messagelen = sizeof(outdata) + username_token.length + 1;
323   message = malloc(messagelen);
324   if(!message) {
325     gss_release_buffer(&unused_status, &username_token);
326 
327     return CURLE_OUT_OF_MEMORY;
328   }
329 
330   /* Populate the message with the security layer, client supported receive
331      message size and authorization identity including the 0x00 based
332      terminator. Note: Despite RFC4752 Section 3.1 stating "The authorization
333      identity is not terminated with the zero-valued (%x00) octet." it seems
334      necessary to include it. */
335   outdata = htonl(max_size) | sec_layer;
336   memcpy(message, &outdata, sizeof(outdata));
337   memcpy(message + sizeof(outdata), username_token.value,
338          username_token.length);
339   message[messagelen - 1] = '\0';
340 
341   /* Free the username token as it is not required anymore */
342   gss_release_buffer(&unused_status, &username_token);
343 
344   /* Setup the "authentication data" security buffer */
345   input_token.value = message;
346   input_token.length = messagelen;
347 
348   /* Encrypt the data */
349   major_status = gss_wrap(&minor_status, krb5->context, 0,
350                           GSS_C_QOP_DEFAULT, &input_token, NULL,
351                           &output_token);
352   if(GSS_ERROR(major_status)) {
353     Curl_gss_log_error(data, "gss_wrap() failed: ",
354                        major_status, minor_status);
355 
356     free(message);
357 
358     return CURLE_AUTH_ERROR;
359   }
360 
361   /* Base64 encode the response */
362   result = Curl_base64_encode(data, (char *) output_token.value,
363                               output_token.length, outptr, outlen);
364 
365   /* Free the output buffer */
366   gss_release_buffer(&unused_status, &output_token);
367 
368   /* Free the message buffer */
369   free(message);
370 
371   return result;
372 }
373 
374 /*
375  * Curl_auth_cleanup_gssapi()
376  *
377  * This is used to clean up the GSSAPI (Kerberos V5) specific data.
378  *
379  * Parameters:
380  *
381  * krb5     [in/out] - The Kerberos 5 data struct being cleaned up.
382  *
383  */
Curl_auth_cleanup_gssapi(struct kerberos5data * krb5)384 void Curl_auth_cleanup_gssapi(struct kerberos5data *krb5)
385 {
386   OM_uint32 minor_status;
387 
388   /* Free our security context */
389   if(krb5->context != GSS_C_NO_CONTEXT) {
390     gss_delete_sec_context(&minor_status, &krb5->context, GSS_C_NO_BUFFER);
391     krb5->context = GSS_C_NO_CONTEXT;
392   }
393 
394   /* Free the SPN */
395   if(krb5->spn != GSS_C_NO_NAME) {
396     gss_release_name(&minor_status, &krb5->spn);
397     krb5->spn = GSS_C_NO_NAME;
398   }
399 }
400 
401 #endif /* HAVE_GSSAPI && USE_KERBEROS5 */
402