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      1 /* GSSAPI/krb5 support for FTP - loosely based on old krb4.c
      2  *
      3  * Copyright (c) 1995, 1996, 1997, 1998, 1999 Kungliga Tekniska Hgskolan
      4  * (Royal Institute of Technology, Stockholm, Sweden).
      5  * Copyright (c) 2004 - 2016 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 
     51 /* The last 3 #include files should be in this order */
     52 #include "curl_printf.h"
     53 #include "curl_memory.h"
     54 #include "memdebug.h"
     55 
     56 static int
     57 krb5_init(void *app_data)
     58 {
     59   gss_ctx_id_t *context = app_data;
     60   /* Make sure our context is initialized for krb5_end. */
     61   *context = GSS_C_NO_CONTEXT;
     62   return 0;
     63 }
     64 
     65 static int
     66 krb5_check_prot(void *app_data, int level)
     67 {
     68   (void)app_data; /* unused */
     69   if(level == PROT_CONFIDENTIAL)
     70     return -1;
     71   return 0;
     72 }
     73 
     74 static int
     75 krb5_decode(void *app_data, void *buf, int len,
     76             int level UNUSED_PARAM,
     77             struct connectdata *conn UNUSED_PARAM)
     78 {
     79   gss_ctx_id_t *context = app_data;
     80   OM_uint32 maj, min;
     81   gss_buffer_desc enc, dec;
     82 
     83   (void)level;
     84   (void)conn;
     85 
     86   enc.value = buf;
     87   enc.length = len;
     88   maj = gss_unseal(&min, *context, &enc, &dec, NULL, NULL);
     89   if(maj != GSS_S_COMPLETE) {
     90     if(len >= 4)
     91       strcpy(buf, "599 ");
     92     return -1;
     93   }
     94 
     95   memcpy(buf, dec.value, dec.length);
     96   len = curlx_uztosi(dec.length);
     97   gss_release_buffer(&min, &dec);
     98 
     99   return len;
    100 }
    101 
    102 static int
    103 krb5_overhead(void *app_data, int level, int len)
    104 {
    105   /* no arguments are used */
    106   (void)app_data;
    107   (void)level;
    108   (void)len;
    109   return 0;
    110 }
    111 
    112 static int
    113 krb5_encode(void *app_data, const void *from, int length, int level, void **to)
    114 {
    115   gss_ctx_id_t *context = app_data;
    116   gss_buffer_desc dec, enc;
    117   OM_uint32 maj, min;
    118   int state;
    119   int len;
    120 
    121   /* NOTE that the cast is safe, neither of the krb5, gnu gss and heimdal
    122    * libraries modify the input buffer in gss_seal()
    123    */
    124   dec.value = (void*)from;
    125   dec.length = length;
    126   maj = gss_seal(&min, *context,
    127                  level == PROT_PRIVATE,
    128                  GSS_C_QOP_DEFAULT,
    129                  &dec, &state, &enc);
    130 
    131   if(maj != GSS_S_COMPLETE)
    132     return -1;
    133 
    134   /* malloc a new buffer, in case gss_release_buffer doesn't work as
    135      expected */
    136   *to = malloc(enc.length);
    137   if(!*to)
    138     return -1;
    139   memcpy(*to, enc.value, enc.length);
    140   len = curlx_uztosi(enc.length);
    141   gss_release_buffer(&min, &enc);
    142   return len;
    143 }
    144 
    145 static int
    146 krb5_auth(void *app_data, struct connectdata *conn)
    147 {
    148   int ret = AUTH_OK;
    149   char *p;
    150   const char *host = conn->host.name;
    151   ssize_t nread;
    152   curl_socklen_t l = sizeof(conn->local_addr);
    153   struct Curl_easy *data = conn->data;
    154   CURLcode result;
    155   const char *service = data->set.str[STRING_SERVICE_NAME] ?
    156                         data->set.str[STRING_SERVICE_NAME] :
    157                         "ftp";
    158   const char *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   struct sockaddr_in **remote_addr =
    166     (struct sockaddr_in **)&conn->ip_addr->ai_addr;
    167 
    168   if(getsockname(conn->sock[FIRSTSOCKET],
    169                  (struct sockaddr *)&conn->local_addr, &l) < 0)
    170     perror("getsockname()");
    171 
    172   chan.initiator_addrtype = GSS_C_AF_INET;
    173   chan.initiator_address.length = l - 4;
    174   chan.initiator_address.value = &conn->local_addr.sin_addr.s_addr;
    175   chan.acceptor_addrtype = GSS_C_AF_INET;
    176   chan.acceptor_address.length = l - 4;
    177   chan.acceptor_address.value = &(*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       if(result)
    187         return -2;
    188 
    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 
    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