1 /* GSSAPI/krb5 support for FTP - loosely based on old krb4.c
2  *
3  * Copyright (c) 1995, 1996, 1997, 1998, 1999 Kungliga Tekniska H�gskolan
4  * (Royal Institute of Technology, Stockholm, Sweden).
5  * Copyright (c) 2004 - 2015 Daniel Stenberg
6  * All rights reserved.
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  *
12  * 1. Redistributions of source code must retain the above copyright
13  *    notice, this list of conditions and the following disclaimer.
14  *
15  * 2. Redistributions in binary form must reproduce the above copyright
16  *    notice, this list of conditions and the following disclaimer in the
17  *    documentation and/or other materials provided with the distribution.
18  *
19  * 3. Neither the name of the Institute nor the names of its contributors
20  *    may be used to endorse or promote products derived from this software
21  *    without specific prior written permission.
22  *
23  * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33  * SUCH DAMAGE.  */
34 
35 #include "curl_setup.h"
36 
37 #if defined(HAVE_GSSAPI) && !defined(CURL_DISABLE_FTP)
38 
39 #ifdef HAVE_NETDB_H
40 #include <netdb.h>
41 #endif
42 
43 #include "urldata.h"
44 #include "curl_base64.h"
45 #include "ftp.h"
46 #include "curl_gssapi.h"
47 #include "sendf.h"
48 #include "curl_sec.h"
49 #include "warnless.h"
50 #include "curl_printf.h"
51 
52 /* The last #include files should be: */
53 #include "curl_memory.h"
54 #include "memdebug.h"
55 
56 #define LOCAL_ADDR (&conn->local_addr)
57 #define REMOTE_ADDR conn->ip_addr->ai_addr
58 
59 static int
krb5_init(void * app_data)60 krb5_init(void *app_data)
61 {
62   gss_ctx_id_t *context = app_data;
63   /* Make sure our context is initialized for krb5_end. */
64   *context = GSS_C_NO_CONTEXT;
65   return 0;
66 }
67 
68 static int
krb5_check_prot(void * app_data,int level)69 krb5_check_prot(void *app_data, int level)
70 {
71   (void)app_data; /* unused */
72   if(level == PROT_CONFIDENTIAL)
73     return -1;
74   return 0;
75 }
76 
77 static int
krb5_decode(void * app_data,void * buf,int len,int level UNUSED_PARAM,struct connectdata * conn UNUSED_PARAM)78 krb5_decode(void *app_data, void *buf, int len,
79             int level UNUSED_PARAM,
80             struct connectdata *conn UNUSED_PARAM)
81 {
82   gss_ctx_id_t *context = app_data;
83   OM_uint32 maj, min;
84   gss_buffer_desc enc, dec;
85 
86   (void)level;
87   (void)conn;
88 
89   enc.value = buf;
90   enc.length = len;
91   maj = gss_unseal(&min, *context, &enc, &dec, NULL, NULL);
92   if(maj != GSS_S_COMPLETE) {
93     if(len >= 4)
94       strcpy(buf, "599 ");
95     return -1;
96   }
97 
98   memcpy(buf, dec.value, dec.length);
99   len = curlx_uztosi(dec.length);
100   gss_release_buffer(&min, &dec);
101 
102   return len;
103 }
104 
105 static int
krb5_overhead(void * app_data,int level,int len)106 krb5_overhead(void *app_data, int level, int len)
107 {
108   /* no arguments are used */
109   (void)app_data;
110   (void)level;
111   (void)len;
112   return 0;
113 }
114 
115 static int
krb5_encode(void * app_data,const void * from,int length,int level,void ** to)116 krb5_encode(void *app_data, const void *from, int length, int level, void **to)
117 {
118   gss_ctx_id_t *context = app_data;
119   gss_buffer_desc dec, enc;
120   OM_uint32 maj, min;
121   int state;
122   int len;
123 
124   /* NOTE that the cast is safe, neither of the krb5, gnu gss and heimdal
125    * libraries modify the input buffer in gss_seal()
126    */
127   dec.value = (void*)from;
128   dec.length = length;
129   maj = gss_seal(&min, *context,
130                  level == PROT_PRIVATE,
131                  GSS_C_QOP_DEFAULT,
132                  &dec, &state, &enc);
133 
134   if(maj != GSS_S_COMPLETE)
135     return -1;
136 
137   /* malloc a new buffer, in case gss_release_buffer doesn't work as
138      expected */
139   *to = malloc(enc.length);
140   if(!*to)
141     return -1;
142   memcpy(*to, enc.value, enc.length);
143   len = curlx_uztosi(enc.length);
144   gss_release_buffer(&min, &enc);
145   return len;
146 }
147 
148 static int
krb5_auth(void * app_data,struct connectdata * conn)149 krb5_auth(void *app_data, struct connectdata *conn)
150 {
151   int ret = AUTH_OK;
152   char *p;
153   const char *host = conn->host.name;
154   ssize_t nread;
155   curl_socklen_t l = sizeof(conn->local_addr);
156   struct SessionHandle *data = conn->data;
157   CURLcode result;
158   const char *service = "ftp", *srv_host = "host";
159   gss_buffer_desc input_buffer, output_buffer, _gssresp, *gssresp;
160   OM_uint32 maj, min;
161   gss_name_t gssname;
162   gss_ctx_id_t *context = app_data;
163   struct gss_channel_bindings_struct chan;
164   size_t base64_sz = 0;
165 
166   if(getsockname(conn->sock[FIRSTSOCKET],
167                  (struct sockaddr *)LOCAL_ADDR, &l) < 0)
168     perror("getsockname()");
169 
170   chan.initiator_addrtype = GSS_C_AF_INET;
171   chan.initiator_address.length = l - 4;
172   chan.initiator_address.value =
173     &((struct sockaddr_in *)LOCAL_ADDR)->sin_addr.s_addr;
174   chan.acceptor_addrtype = GSS_C_AF_INET;
175   chan.acceptor_address.length = l - 4;
176   chan.acceptor_address.value =
177     &((struct sockaddr_in *)REMOTE_ADDR)->sin_addr.s_addr;
178   chan.application_data.length = 0;
179   chan.application_data.value = NULL;
180 
181   /* this loop will execute twice (once for service, once for host) */
182   for(;;) {
183     /* this really shouldn't be repeated here, but can't help it */
184     if(service == srv_host) {
185       result = Curl_ftpsendf(conn, "AUTH GSSAPI");
186 
187       if(result)
188         return -2;
189       if(Curl_GetFTPResponse(&nread, conn, NULL))
190         return -1;
191 
192       if(data->state.buffer[0] != '3')
193         return -1;
194     }
195 
196     input_buffer.value = data->state.buffer;
197     input_buffer.length = snprintf(input_buffer.value, BUFSIZE, "%s@%s",
198                                    service, host);
199     maj = gss_import_name(&min, &input_buffer, GSS_C_NT_HOSTBASED_SERVICE,
200                           &gssname);
201     if(maj != GSS_S_COMPLETE) {
202       gss_release_name(&min, &gssname);
203       if(service == srv_host) {
204         Curl_failf(data, "Error importing service name %s",
205                    input_buffer.value);
206         return AUTH_ERROR;
207       }
208       service = srv_host;
209       continue;
210     }
211     /* We pass NULL as |output_name_type| to avoid a leak. */
212     gss_display_name(&min, gssname, &output_buffer, NULL);
213     Curl_infof(data, "Trying against %s\n", output_buffer.value);
214     gssresp = GSS_C_NO_BUFFER;
215     *context = GSS_C_NO_CONTEXT;
216 
217     do {
218       /* Release the buffer at each iteration to avoid leaking: the first time
219          we are releasing the memory from gss_display_name. The last item is
220          taken care by a final gss_release_buffer. */
221       gss_release_buffer(&min, &output_buffer);
222       ret = AUTH_OK;
223       maj = Curl_gss_init_sec_context(data,
224                                       &min,
225                                       context,
226                                       gssname,
227                                       &Curl_krb5_mech_oid,
228                                       &chan,
229                                       gssresp,
230                                       &output_buffer,
231                                       TRUE,
232                                       NULL);
233 
234       if(gssresp) {
235         free(_gssresp.value);
236         gssresp = NULL;
237       }
238 
239       if(GSS_ERROR(maj)) {
240         Curl_infof(data, "Error creating security context\n");
241         ret = AUTH_ERROR;
242         break;
243       }
244 
245       if(output_buffer.length != 0) {
246         result = Curl_base64_encode(data, (char *)output_buffer.value,
247                                     output_buffer.length, &p, &base64_sz);
248         if(result) {
249           Curl_infof(data, "base64-encoding: %s\n",
250                      curl_easy_strerror(result));
251           ret = AUTH_CONTINUE;
252           break;
253         }
254 
255         result = Curl_ftpsendf(conn, "ADAT %s", p);
256 
257         free(p);
258 
259         if(result) {
260           ret = -2;
261           break;
262         }
263 
264         if(Curl_GetFTPResponse(&nread, conn, NULL)) {
265           ret = -1;
266           break;
267         }
268 
269         if(data->state.buffer[0] != '2' && data->state.buffer[0] != '3') {
270           Curl_infof(data, "Server didn't accept auth data\n");
271           ret = AUTH_ERROR;
272           break;
273         }
274 
275         p = data->state.buffer + 4;
276         p = strstr(p, "ADAT=");
277         if(p) {
278           result = Curl_base64_decode(p + 5,
279                                       (unsigned char **)&_gssresp.value,
280                                       &_gssresp.length);
281           if(result) {
282             Curl_failf(data, "base64-decoding: %s",
283                        curl_easy_strerror(result));
284             ret = AUTH_CONTINUE;
285             break;
286           }
287         }
288 
289         gssresp = &_gssresp;
290       }
291     } while(maj == GSS_S_CONTINUE_NEEDED);
292 
293     gss_release_name(&min, &gssname);
294     gss_release_buffer(&min, &output_buffer);
295 
296     if(gssresp)
297       free(_gssresp.value);
298 
299     if(ret == AUTH_OK || service == srv_host)
300       return ret;
301 
302     service = srv_host;
303   }
304   return ret;
305 }
306 
krb5_end(void * app_data)307 static void krb5_end(void *app_data)
308 {
309     OM_uint32 min;
310     gss_ctx_id_t *context = app_data;
311     if(*context != GSS_C_NO_CONTEXT) {
312 #ifdef DEBUGBUILD
313       OM_uint32 maj =
314 #endif
315       gss_delete_sec_context(&min, context, GSS_C_NO_BUFFER);
316       DEBUGASSERT(maj == GSS_S_COMPLETE);
317     }
318 }
319 
320 struct Curl_sec_client_mech Curl_krb5_client_mech = {
321     "GSSAPI",
322     sizeof(gss_ctx_id_t),
323     krb5_init,
324     krb5_auth,
325     krb5_end,
326     krb5_check_prot,
327     krb5_overhead,
328     krb5_encode,
329     krb5_decode
330 };
331 
332 #endif /* HAVE_GSSAPI && !CURL_DISABLE_FTP */
333