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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 - 2017 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   char *stringp;
    168 
    169   if(getsockname(conn->sock[FIRSTSOCKET],
    170                  (struct sockaddr *)&conn->local_addr, &l) < 0)
    171     perror("getsockname()");
    172 
    173   chan.initiator_addrtype = GSS_C_AF_INET;
    174   chan.initiator_address.length = l - 4;
    175   chan.initiator_address.value = &conn->local_addr.sin_addr.s_addr;
    176   chan.acceptor_addrtype = GSS_C_AF_INET;
    177   chan.acceptor_address.length = l - 4;
    178   chan.acceptor_address.value = &(*remote_addr)->sin_addr.s_addr;
    179   chan.application_data.length = 0;
    180   chan.application_data.value = NULL;
    181 
    182   /* this loop will execute twice (once for service, once for host) */
    183   for(;;) {
    184     /* this really shouldn't be repeated here, but can't help it */
    185     if(service == srv_host) {
    186       result = Curl_ftpsend(conn, "AUTH GSSAPI");
    187       if(result)
    188         return -2;
    189 
    190       if(Curl_GetFTPResponse(&nread, conn, NULL))
    191         return -1;
    192 
    193       if(data->state.buffer[0] != '3')
    194         return -1;
    195     }
    196 
    197     stringp = aprintf("%s@%s", service, host);
    198     if(!stringp)
    199       return -2;
    200 
    201     input_buffer.value = stringp;
    202     input_buffer.length = strlen(stringp);
    203     maj = gss_import_name(&min, &input_buffer, GSS_C_NT_HOSTBASED_SERVICE,
    204                           &gssname);
    205     free(stringp);
    206     if(maj != GSS_S_COMPLETE) {
    207       gss_release_name(&min, &gssname);
    208       if(service == srv_host) {
    209         Curl_failf(data, "Error importing service name %s@%s", service, host);
    210         return AUTH_ERROR;
    211       }
    212       service = srv_host;
    213       continue;
    214     }
    215     /* We pass NULL as |output_name_type| to avoid a leak. */
    216     gss_display_name(&min, gssname, &output_buffer, NULL);
    217     Curl_infof(data, "Trying against %s\n", output_buffer.value);
    218     gssresp = GSS_C_NO_BUFFER;
    219     *context = GSS_C_NO_CONTEXT;
    220 
    221     do {
    222       /* Release the buffer at each iteration to avoid leaking: the first time
    223          we are releasing the memory from gss_display_name. The last item is
    224          taken care by a final gss_release_buffer. */
    225       gss_release_buffer(&min, &output_buffer);
    226       ret = AUTH_OK;
    227       maj = Curl_gss_init_sec_context(data,
    228                                       &min,
    229                                       context,
    230                                       gssname,
    231                                       &Curl_krb5_mech_oid,
    232                                       &chan,
    233                                       gssresp,
    234                                       &output_buffer,
    235                                       TRUE,
    236                                       NULL);
    237 
    238       if(gssresp) {
    239         free(_gssresp.value);
    240         gssresp = NULL;
    241       }
    242 
    243       if(GSS_ERROR(maj)) {
    244         Curl_infof(data, "Error creating security context\n");
    245         ret = AUTH_ERROR;
    246         break;
    247       }
    248 
    249       if(output_buffer.length != 0) {
    250         char *cmd;
    251 
    252         result = Curl_base64_encode(data, (char *)output_buffer.value,
    253                                     output_buffer.length, &p, &base64_sz);
    254         if(result) {
    255           Curl_infof(data, "base64-encoding: %s\n",
    256                      curl_easy_strerror(result));
    257           ret = AUTH_ERROR;
    258           break;
    259         }
    260 
    261         cmd = aprintf("ADAT %s", p);
    262         if(cmd)
    263           result = Curl_ftpsend(conn, cmd);
    264         else
    265           result = CURLE_OUT_OF_MEMORY;
    266 
    267         free(p);
    268 
    269         if(result) {
    270           ret = -2;
    271           break;
    272         }
    273 
    274         if(Curl_GetFTPResponse(&nread, conn, NULL)) {
    275           ret = -1;
    276           break;
    277         }
    278 
    279         if(data->state.buffer[0] != '2' && data->state.buffer[0] != '3') {
    280           Curl_infof(data, "Server didn't accept auth data\n");
    281           ret = AUTH_ERROR;
    282           break;
    283         }
    284 
    285         _gssresp.value = NULL; /* make sure it is initialized */
    286         p = data->state.buffer + 4;
    287         p = strstr(p, "ADAT=");
    288         if(p) {
    289           result = Curl_base64_decode(p + 5,
    290                                       (unsigned char **)&_gssresp.value,
    291                                       &_gssresp.length);
    292           if(result) {
    293             Curl_failf(data, "base64-decoding: %s",
    294                        curl_easy_strerror(result));
    295             ret = AUTH_CONTINUE;
    296             break;
    297           }
    298         }
    299 
    300         gssresp = &_gssresp;
    301       }
    302     } while(maj == GSS_S_CONTINUE_NEEDED);
    303 
    304     gss_release_name(&min, &gssname);
    305     gss_release_buffer(&min, &output_buffer);
    306 
    307     if(gssresp)
    308       free(_gssresp.value);
    309 
    310     if(ret == AUTH_OK || service == srv_host)
    311       return ret;
    312 
    313     service = srv_host;
    314   }
    315   return ret;
    316 }
    317 
    318 static void krb5_end(void *app_data)
    319 {
    320     OM_uint32 min;
    321     gss_ctx_id_t *context = app_data;
    322     if(*context != GSS_C_NO_CONTEXT) {
    323 #ifdef DEBUGBUILD
    324       OM_uint32 maj =
    325 #endif
    326       gss_delete_sec_context(&min, context, GSS_C_NO_BUFFER);
    327       DEBUGASSERT(maj == GSS_S_COMPLETE);
    328     }
    329 }
    330 
    331 struct Curl_sec_client_mech Curl_krb5_client_mech = {
    332     "GSSAPI",
    333     sizeof(gss_ctx_id_t),
    334     krb5_init,
    335     krb5_auth,
    336     krb5_end,
    337     krb5_check_prot,
    338     krb5_overhead,
    339     krb5_encode,
    340     krb5_decode
    341 };
    342 
    343 #endif /* HAVE_GSSAPI && !CURL_DISABLE_FTP */
    344