net/sunrpc/auth_gss/gss_krb5_keys.c

   1 /*
   2  * COPYRIGHT (c) 2008
   3  * The Regents of the University of Michigan
   4  * ALL RIGHTS RESERVED
   5  *
   6  * Permission is granted to use, copy, create derivative works
   7  * and redistribute this software and such derivative works
   8  * for any purpose, so long as the name of The University of
   9  * Michigan is not used in any advertising or publicity
  10  * pertaining to the use of distribution of this software
  11  * without specific, written prior authorization.  If the
  12  * above copyright notice or any other identification of the
  13  * University of Michigan is included in any copy of any
  14  * portion of this software, then the disclaimer below must
  15  * also be included.
  16  *
  17  * THIS SOFTWARE IS PROVIDED AS IS, WITHOUT REPRESENTATION
  18  * FROM THE UNIVERSITY OF MICHIGAN AS TO ITS FITNESS FOR ANY
  19  * PURPOSE, AND WITHOUT WARRANTY BY THE UNIVERSITY OF
  20  * MICHIGAN OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING
  21  * WITHOUT LIMITATION THE IMPLIED WARRANTIES OF
  22  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE
  23  * REGENTS OF THE UNIVERSITY OF MICHIGAN SHALL NOT BE LIABLE
  24  * FOR ANY DAMAGES, INCLUDING SPECIAL, INDIRECT, INCIDENTAL, OR
  25  * CONSEQUENTIAL DAMAGES, WITH RESPECT TO ANY CLAIM ARISING
  26  * OUT OF OR IN CONNECTION WITH THE USE OF THE SOFTWARE, EVEN
  27  * IF IT HAS BEEN OR IS HEREAFTER ADVISED OF THE POSSIBILITY OF
  28  * SUCH DAMAGES.
  29  */
  30
  31 /*
  32  * Copyright (C) 1998 by the FundsXpress, INC.
  33  *
  34  * All rights reserved.
  35  *
  36  * Export of this software from the United States of America may require
  37  * a specific license from the United States Government.  It is the
  38  * responsibility of any person or organization contemplating export to
  39  * obtain such a license before exporting.
  40  *
  41  * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
  42  * distribute this software and its documentation for any purpose and
  43  * without fee is hereby granted, provided that the above copyright
  44  * notice appear in all copies and that both that copyright notice and
  45  * this permission notice appear in supporting documentation, and that
  46  * the name of FundsXpress. not be used in advertising or publicity pertaining
  47  * to distribution of the software without specific, written prior
  48  * permission.  FundsXpress makes no representations about the suitability of
  49  * this software for any purpose.  It is provided "as is" without express
  50  * or implied warranty.
  51  *
  52  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
  53  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
  54  * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  55  */
  56
  57 #include <linux/err.h>
  58 #include <linux/types.h>
  59 #include <linux/crypto.h>
  60 #include <linux/sunrpc/gss_krb5.h>
  61 #include <linux/sunrpc/xdr.h>
  62
  63 #ifdef RPC_DEBUG
  64 # define RPCDBG_FACILITY        RPCDBG_AUTH
  65 #endif
  66
  67 /*
  68  * This is the n-fold function as described in rfc3961, sec 5.1
  69  * Taken from MIT Kerberos and modified.
  70  */
  71
  72 static void krb5_nfold(u32 inbits, const u8 *in,
  73                        u32 outbits, u8 *out)
  74 {
  75         int a, b, c, lcm;
  76         int byte, i, msbit;
  77
  78         /* the code below is more readable if I make these bytes
  79            instead of bits */
  80
  81         inbits >>= 3;
  82         outbits >>= 3;
  83
  84         /* first compute lcm(n,k) */
  85
  86         a = outbits;
  87         b = inbits;
  88
  89         while (b != 0) {
  90                 c = b;
  91                 b = a%b;
  92                 a = c;
  93         }
  94
  95         lcm = outbits*inbits/a;
  96
  97         /* now do the real work */
  98
  99         memset(out, 0, outbits);
 100         byte = 0;
 101
 102         /* this will end up cycling through k lcm(k,n)/k times, which
 103            is correct */
 104         for (i = lcm-1; i >= 0; i--) {
 105                 /* compute the msbit in k which gets added into this byte */
 106                 msbit = (
 107                         /* first, start with the msbit in the first,
 108                          * unrotated byte */
 109                          ((inbits << 3) - 1)
 110                          /* then, for each byte, shift to the right
 111                           * for each repetition */
 112                          + (((inbits << 3) + 13) * (i/inbits))
 113                          /* last, pick out the correct byte within
 114                           * that shifted repetition */
 115                          + ((inbits - (i % inbits)) << 3)
 116                          ) % (inbits << 3);
 117
 118                 /* pull out the byte value itself */
 119                 byte += (((in[((inbits - 1) - (msbit >> 3)) % inbits] << 8)|
 120                                   (in[((inbits) - (msbit >> 3)) % inbits]))
 121                                  >> ((msbit & 7) + 1)) & 0xff;
 122
 123                 /* do the addition */
 124                 byte += out[i % outbits];
 125                 out[i % outbits] = byte & 0xff;
 126
 127                 /* keep around the carry bit, if any */
 128                 byte >>= 8;
 129
 130         }
 131
 132         /* if there's a carry bit left over, add it back in */
 133         if (byte) {
 134                 for (i = outbits - 1; i >= 0; i--) {
 135                         /* do the addition */
 136                         byte += out[i];
 137                         out[i] = byte & 0xff;
 138
 139                         /* keep around the carry bit, if any */
 140                         byte >>= 8;
 141                 }
 142         }
 143 }
 144
 145 /*
 146  * This is the DK (derive_key) function as described in rfc3961, sec 5.1
 147  * Taken from MIT Kerberos and modified.
 148  */
 149
 150 u32 krb5_derive_key(const struct gss_krb5_enctype *gk5e,
 151                     const struct xdr_netobj *inkey,
 152                     struct xdr_netobj *outkey,
 153                     const struct xdr_netobj *in_constant,
 154                     gfp_t gfp_mask)
 155 {
 156         size_t blocksize, keybytes, keylength, n;
 157         unsigned char *inblockdata, *outblockdata, *rawkey;
 158         struct xdr_netobj inblock, outblock;
 159         struct crypto_blkcipher *cipher;
 160         u32 ret = EINVAL;
 161
 162         blocksize = gk5e->blocksize;
 163         keybytes = gk5e->keybytes;
 164         keylength = gk5e->keylength;
 165
 166         if ((inkey->len != keylength) || (outkey->len != keylength))
 167                 goto err_return;
 168
 169         cipher = crypto_alloc_blkcipher(gk5e->encrypt_name, 0,
 170                                         CRYPTO_ALG_ASYNC);
 171         if (IS_ERR(cipher))
 172                 goto err_return;
 173         if (crypto_blkcipher_setkey(cipher, inkey->data, inkey->len))
 174                 goto err_return;
 175
 176         /* allocate and set up buffers */
 177
 178         ret = ENOMEM;
 179         inblockdata = kmalloc(blocksize, gfp_mask);
 180         if (inblockdata == NULL)
 181                 goto err_free_cipher;
 182
 183         outblockdata = kmalloc(blocksize, gfp_mask);
 184         if (outblockdata == NULL)
 185                 goto err_free_in;
 186
 187         rawkey = kmalloc(keybytes, gfp_mask);
 188         if (rawkey == NULL)
 189                 goto err_free_out;
 190
 191         inblock.data = (char *) inblockdata;
 192         inblock.len = blocksize;
 193
 194         outblock.data = (char *) outblockdata;
 195         outblock.len = blocksize;
 196
 197         /* initialize the input block */
 198
 199         if (in_constant->len == inblock.len) {
 200                 memcpy(inblock.data, in_constant->data, inblock.len);
 201         } else {
 202                 krb5_nfold(in_constant->len * 8, in_constant->data,
 203                            inblock.len * 8, inblock.data);
 204         }
 205
 206         /* loop encrypting the blocks until enough key bytes are generated */
 207
 208         n = 0;
 209         while (n < keybytes) {
 210                 (*(gk5e->encrypt))(cipher, NULL, inblock.data,
 211                                    outblock.data, inblock.len);
 212
 213                 if ((keybytes - n) <= outblock.len) {
 214                         memcpy(rawkey + n, outblock.data, (keybytes - n));
 215                         break;
 216                 }
 217
 218                 memcpy(rawkey + n, outblock.data, outblock.len);
 219                 memcpy(inblock.data, outblock.data, outblock.len);
 220                 n += outblock.len;
 221         }
 222
 223         /* postprocess the key */
 224
 225         inblock.data = (char *) rawkey;
 226         inblock.len = keybytes;
 227
 228         BUG_ON(gk5e->mk_key == NULL);
 229         ret = (*(gk5e->mk_key))(gk5e, &inblock, outkey);
 230         if (ret) {
 231                 dprintk("%s: got %d from mk_key function for '%s'\n",
 232                         __func__, ret, gk5e->encrypt_name);
 233                 goto err_free_raw;
 234         }
 235
 236         /* clean memory, free resources and exit */
 237
 238         ret = 0;
 239
 240 err_free_raw:
 241         memset(rawkey, 0, keybytes);
 242         kfree(rawkey);
 243 err_free_out:
 244         memset(outblockdata, 0, blocksize);
 245         kfree(outblockdata);
 246 err_free_in:
 247         memset(inblockdata, 0, blocksize);
 248         kfree(inblockdata);
 249 err_free_cipher:
 250         crypto_free_blkcipher(cipher);
 251 err_return:
 252         return ret;
 253 }
 254
 255 #define smask(step) ((1<<step)-1)
 256 #define pstep(x, step) (((x)&smask(step))^(((x)>>step)&smask(step)))
 257 #define parity_char(x) pstep(pstep(pstep((x), 4), 2), 1)
 258
 259 static void mit_des_fixup_key_parity(u8 key[8])
 260 {
 261         int i;
 262         for (i = 0; i < 8; i++) {
 263                 key[i] &= 0xfe;
 264                 key[i] |= 1^parity_char(key[i]);
 265         }
 266 }
 267
 268 /*
 269  * This is the des3 key derivation postprocess function
 270  */
 271 u32 gss_krb5_des3_make_key(const struct gss_krb5_enctype *gk5e,
 272                            struct xdr_netobj *randombits,
 273                            struct xdr_netobj *key)
 274 {
 275         int i;
 276         u32 ret = EINVAL;
 277
 278         if (key->len != 24) {
 279                 dprintk("%s: key->len is %d\n", __func__, key->len);
 280                 goto err_out;
 281         }
 282         if (randombits->len != 21) {
 283                 dprintk("%s: randombits->len is %d\n",
 284                         __func__, randombits->len);
 285                 goto err_out;
 286         }
 287
 288         /* take the seven bytes, move them around into the top 7 bits of the
 289            8 key bytes, then compute the parity bits.  Do this three times. */
 290
 291         for (i = 0; i < 3; i++) {
 292                 memcpy(key->data + i*8, randombits->data + i*7, 7);
 293                 key->data[i*8+7] = (((key->data[i*8]&1)<<1) |
 294                                     ((key->data[i*8+1]&1)<<2) |
 295                                     ((key->data[i*8+2]&1)<<3) |
 296                                     ((key->data[i*8+3]&1)<<4) |
 297                                     ((key->data[i*8+4]&1)<<5) |
 298                                     ((key->data[i*8+5]&1)<<6) |
 299                                     ((key->data[i*8+6]&1)<<7));
 300
 301                 mit_des_fixup_key_parity(key->data + i*8);
 302         }
 303         ret = 0;
 304 err_out:
 305         return ret;
 306 }
 307
 308 /*
 309  * This is the aes key derivation postprocess function
 310  */
 311 u32 gss_krb5_aes_make_key(const struct gss_krb5_enctype *gk5e,
 312                           struct xdr_netobj *randombits,
 313                           struct xdr_netobj *key)
 314 {
 315         u32 ret = EINVAL;
 316
 317         if (key->len != 16 && key->len != 32) {
 318                 dprintk("%s: key->len is %d\n", __func__, key->len);
 319                 goto err_out;
 320         }
 321         if (randombits->len != 16 && randombits->len != 32) {
 322                 dprintk("%s: randombits->len is %d\n",
 323                         __func__, randombits->len);
 324                 goto err_out;
 325         }
 326         if (randombits->len != key->len) {
 327                 dprintk("%s: randombits->len is %d, key->len is %d\n",
 328                         __func__, randombits->len, key->len);
 329                 goto err_out;
 330         }
 331         memcpy(key->data, randombits->data, key->len);
 332         ret = 0;
 333 err_out:
 334         return ret;
 335 }
 336