source/lib/afs.c

   1 /*
   2  *  Unix SMB/CIFS implementation.
   3  *  Generate AFS tickets
   4  *  Copyright (C) Volker Lendecke 2003
   5  *
   6  *  This program is free software; you can redistribute it and/or modify
   7  *  it under the terms of the GNU General Public License as published by
   8  *  the Free Software Foundation; either version 3 of the License, or
   9  *  (at your option) any later version.
  10  *
  11  *  This program is distributed in the hope that it will be useful,
  12  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  *  GNU General Public License for more details.
  15  *
  16  *  You should have received a copy of the GNU General Public License
  17  *  along with this program; if not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include "includes.h"
  21
  22 #ifdef WITH_FAKE_KASERVER
  23
  24 #define NO_ASN1_TYPEDEFS 1
  25
  26 #include <afs/stds.h>
  27 #include <afs/afs.h>
  28 #include <afs/auth.h>
  29 #include <afs/venus.h>
  30 #include <asm/unistd.h>
  31 #include <openssl/des.h>
  32
  33 struct ClearToken {
  34         uint32 AuthHandle;
  35         char HandShakeKey[8];
  36         uint32 ViceId;
  37         uint32 BeginTimestamp;
  38         uint32 EndTimestamp;
  39 };
  40
  41 static char *afs_encode_token(const char *cell, const DATA_BLOB ticket,
  42                               const struct ClearToken *ct)
  43 {
  44         char *base64_ticket;
  45         char *result = NULL;
  46
  47         DATA_BLOB key = data_blob(ct->HandShakeKey, 8);
  48         char *base64_key;
  49         TALLOC_CTX *mem_ctx;
  50
  51         mem_ctx = talloc_stackframe();
  52         if (mem_ctx == NULL)
  53                 goto done;
  54
  55         base64_ticket = base64_encode_data_blob(mem_ctx, ticket);
  56         if (base64_ticket == NULL)
  57                 goto done;
  58
  59         base64_key = base64_encode_data_blob(mem_ctx, key);
  60         if (base64_key == NULL)
  61                 goto done;
  62
  63         asprintf(&result, "%s\n%u\n%s\n%u\n%u\n%u\n%s\n", cell,
  64                  ct->AuthHandle, base64_key, ct->ViceId, ct->BeginTimestamp,
  65                  ct->EndTimestamp, base64_ticket);
  66
  67         DEBUG(10, ("Got ticket string:\n%s\n", result));
  68
  69 done:
  70         TALLOC_FREE(mem_ctx);
  71
  72         return result;
  73 }
  74
  75 /* Create a ClearToken and an encrypted ticket. ClearToken has not yet the
  76  * ViceId set, this should be set by the caller. */
  77
  78 static bool afs_createtoken(const char *username, const char *cell,
  79                             DATA_BLOB *ticket, struct ClearToken *ct)
  80 {
  81         fstring clear_ticket;
  82         char *p = clear_ticket;
  83         uint32 len;
  84         uint32 now;
  85
  86         struct afs_key key;
  87         des_key_schedule key_schedule;
  88
  89         if (!secrets_init())
  90                 return False;
  91
  92         if (!secrets_fetch_afs_key(cell, &key)) {
  93                 DEBUG(1, ("Could not fetch AFS service key\n"));
  94                 return False;
  95         }
  96
  97         ct->AuthHandle = key.kvno;
  98
  99         /* Build the ticket. This is going to be encrypted, so in our
 100            way we fill in ct while we still have the unencrypted
 101            form. */
 102
 103         p = clear_ticket;
 104
 105         /* The byte-order */
 106         *p = 1;
 107         p += 1;
 108
 109         /* "Alice", the client username */
 110         strncpy(p, username, sizeof(clear_ticket)-PTR_DIFF(p,clear_ticket)-1);
 111         p += strlen(p)+1;
 112         strncpy(p, "", sizeof(clear_ticket)-PTR_DIFF(p,clear_ticket)-1);
 113         p += strlen(p)+1;
 114         strncpy(p, cell, sizeof(clear_ticket)-PTR_DIFF(p,clear_ticket)-1);
 115         p += strlen(p)+1;
 116
 117         /* Alice's network layer address. At least Openafs-1.2.10
 118            ignores this, so we fill in a dummy value here. */
 119         SIVAL(p, 0, 0);
 120         p += 4;
 121
 122         /* We need to create a session key */
 123         generate_random_buffer(p, 8);
 124
 125         /* Our client code needs the the key in the clear, it does not
 126            know the server-key ... */
 127         memcpy(ct->HandShakeKey, p, 8);
 128
 129         p += 8;
 130
 131         /* This is a kerberos 4 life time. The life time is expressed
 132          * in units of 5 minute intervals up to 38400 seconds, after
 133          * that a table is used up to lifetime 0xBF. Values between
 134          * 0xC0 and 0xFF is undefined. 0xFF is defined to be the
 135          * infinite time that never expire.
 136          *
 137          * So here we cheat and use the infinite time */
 138         *p = 255;
 139         p += 1;
 140
 141         /* Ticket creation time */
 142         now = time(NULL);
 143         SIVAL(p, 0, now);
 144         ct->BeginTimestamp = now;
 145
 146         if(lp_afs_token_lifetime() == 0)
 147                 ct->EndTimestamp = NEVERDATE;
 148         else
 149                 ct->EndTimestamp = now + lp_afs_token_lifetime();
 150
 151         if (((ct->EndTimestamp - ct->BeginTimestamp) & 1) == 1) {
 152                 ct->BeginTimestamp += 1; /* Lifetime must be even */
 153         }
 154         p += 4;
 155
 156         /* And here comes Bob's name and instance, in this case the
 157            AFS server. */
 158         strncpy(p, "afs", sizeof(clear_ticket)-PTR_DIFF(p,clear_ticket)-1);
 159         p += strlen(p)+1;
 160         strncpy(p, "", sizeof(clear_ticket)-PTR_DIFF(p,clear_ticket)-1);
 161         p += strlen(p)+1;
 162
 163         /* And zero-pad to a multiple of 8 bytes */
 164         len = PTR_DIFF(p, clear_ticket);
 165         if (len & 7) {
 166                 uint32 extra_space = 8-(len & 7);
 167                 memset(p, 0, extra_space);
 168                 p+=extra_space;
 169         }
 170         len = PTR_DIFF(p, clear_ticket);
 171
 172         des_key_sched((const_des_cblock *)key.key, key_schedule);
 173         des_pcbc_encrypt(clear_ticket, clear_ticket,
 174                          len, key_schedule, (C_Block *)key.key, 1);
 175
 176         ZERO_STRUCT(key);
 177
 178         *ticket = data_blob(clear_ticket, len);
 179
 180         return True;
 181 }
 182
 183 char *afs_createtoken_str(const char *username, const char *cell)
 184 {
 185         DATA_BLOB ticket;
 186         struct ClearToken ct;
 187         char *result;
 188
 189         if (!afs_createtoken(username, cell, &ticket, &ct))
 190                 return NULL;
 191
 192         result = afs_encode_token(cell, ticket, &ct);
 193
 194         data_blob_free(&ticket);
 195
 196         return result;
 197 }
 198
 199 /*
 200   This routine takes a radical approach completely bypassing the
 201   Kerberos idea of security and using AFS simply as an intelligent
 202   file backend. Samba has persuaded itself somehow that the user is
 203   actually correctly identified and then we create a ticket that the
 204   AFS server hopefully accepts using its KeyFile that the admin has
 205   kindly stored to our secrets.tdb.
 206
 207   Thanks to the book "Network Security -- PRIVATE Communication in a
 208   PUBLIC World" by Charlie Kaufman, Radia Perlman and Mike Speciner
 209   Kerberos 4 tickets are not really hard to construct.
 210
 211   For the comments "Alice" is the User to be auth'ed, and "Bob" is the
 212   AFS server.  */
 213
 214 bool afs_login(connection_struct *conn)
 215 {
 216         extern userdom_struct current_user_info;
 217         extern struct current_user current_user;
 218         DATA_BLOB ticket;
 219         char *afs_username = NULL;
 220         char *cell = NULL;
 221         bool result;
 222         char *ticket_str = NULL;
 223         const DOM_SID *user_sid;
 224         TALLOC_CTX *ctx = talloc_tos();
 225
 226         struct ClearToken ct;
 227
 228         afs_username = talloc_strdup(ctx,
 229                                 lp_afs_username_map());
 230         if (!afs_username) {
 231                 return false;
 232         }
 233
 234         afs_username = talloc_sub_advanced(ctx,
 235                                 SNUM(conn), conn->user,
 236                                 conn->connectpath, conn->gid,
 237                                 get_current_username(),
 238                                 current_user_info.domain,
 239                                 afs_username);
 240         if (!afs_username) {
 241                 return false;
 242         }
 243
 244         user_sid = &current_user.nt_user_token->user_sids[0];
 245         afs_username = talloc_string_sub(talloc_tos(),
 246                                         afs_username,
 247                                         "%s",
 248                                         sid_string_tos(user_sid));
 249         if (!afs_username) {
 250                 return false;
 251         }
 252
 253         /* The pts command always generates completely lower-case user
 254          * names. */
 255         strlower_m(afs_username);
 256
 257         cell = strchr(afs_username, '@');
 258
 259         if (cell == NULL) {
 260                 DEBUG(1, ("AFS username doesn't contain a @, "
 261                           "could not find cell\n"));
 262                 return false;
 263         }
 264
 265         *cell = '\0';
 266         cell += 1;
 267
 268         DEBUG(10, ("Trying to log into AFS for user %s@%s\n",
 269                    afs_username, cell));
 270
 271         if (!afs_createtoken(afs_username, cell, &ticket, &ct))
 272                 return False;
 273
 274         /* For which Unix-UID do we want to set the token? */
 275         ct.ViceId = getuid();
 276
 277         ticket_str = afs_encode_token(cell, ticket, &ct);
 278
 279         result = afs_settoken_str(ticket_str);
 280
 281         SAFE_FREE(ticket_str);
 282
 283         data_blob_free(&ticket);
 284
 285         return result;
 286 }
 287
 288 #else
 289
 290 bool afs_login(connection_struct *conn)
 291 {
 292         return True;
 293 }
 294
 295 char *afs_createtoken_str(const char *username, const char *cell)
 296 {
 297         return NULL;
 298 }
 299
 300 #endif /* WITH_FAKE_KASERVER */