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 <crypto/skcipher.h>
  58 #include <linux/err.h>
  59 #include <linux/types.h>
  60 #include <linux/sunrpc/gss_krb5.h>
  61 #include <linux/sunrpc/xdr.h>
  62 #include <linux/lcm.h>
  63
  64 #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
  65 # define RPCDBG_FACILITY        RPCDBG_AUTH
  66 #endif
  67
  68 /*
  69  * This is the n-fold function as described in rfc3961, sec 5.1
  70  * Taken from MIT Kerberos and modified.
  71  */
  72
  73 static void krb5_nfold(u32 inbits, const u8 *in,
  74                        u32 outbits, u8 *out)
  75 {
  76         unsigned long ulcm;
  77         int byte, i, msbit;
  78
  79         /* the code below is more readable if I make these bytes
  80            instead of bits */
  81
  82         inbits >>= 3;
  83         outbits >>= 3;
  84
  85         /* first compute lcm(n,k) */
  86         ulcm = lcm(inbits, outbits);
  87
  88         /* now do the real work */
  89
  90         memset(out, 0, outbits);
  91         byte = 0;
  92
  93         /* this will end up cycling through k lcm(k,n)/k times, which
  94            is correct */
  95         for (i = ulcm-1; i >= 0; i--) {
  96                 /* compute the msbit in k which gets added into this byte */
  97                 msbit = (
  98                         /* first, start with the msbit in the first,
  99                          * unrotated byte */
 100                          ((inbits << 3) - 1)
 101                          /* then, for each byte, shift to the right
 102                           * for each repetition */
 103                          + (((inbits << 3) + 13) * (i/inbits))
 104                          /* last, pick out the correct byte within
 105                           * that shifted repetition */
 106                          + ((inbits - (i % inbits)) << 3)
 107                          ) % (inbits << 3);
 108
 109                 /* pull out the byte value itself */
 110                 byte += (((in[((inbits - 1) - (msbit >> 3)) % inbits] << 8)|
 111                                   (in[((inbits) - (msbit >> 3)) % inbits]))
 112                                  >> ((msbit & 7) + 1)) & 0xff;
 113
 114                 /* do the addition */
 115                 byte += out[i % outbits];
 116                 out[i % outbits] = byte & 0xff;
 117
 118                 /* keep around the carry bit, if any */
 119                 byte >>= 8;
 120
 121         }
 122
 123         /* if there's a carry bit left over, add it back in */
 124         if (byte) {
 125                 for (i = outbits - 1; i >= 0; i--) {
 126                         /* do the addition */
 127                         byte += out[i];
 128                         out[i] = byte & 0xff;
 129
 130                         /* keep around the carry bit, if any */
 131                         byte >>= 8;
 132                 }
 133         }
 134 }
 135
 136 /*
 137  * This is the DK (derive_key) function as described in rfc3961, sec 5.1
 138  * Taken from MIT Kerberos and modified.
 139  */
 140
 141 u32 krb5_derive_key(const struct gss_krb5_enctype *gk5e,
 142                     const struct xdr_netobj *inkey,
 143                     struct xdr_netobj *outkey,
 144                     const struct xdr_netobj *in_constant,
 145                     gfp_t gfp_mask)
 146 {
 147         size_t blocksize, keybytes, keylength, n;
 148         unsigned char *inblockdata, *outblockdata, *rawkey;
 149         struct xdr_netobj inblock, outblock;
 150         struct crypto_skcipher *cipher;
 151         u32 ret = EINVAL;
 152
 153         blocksize = gk5e->blocksize;
 154         keybytes = gk5e->keybytes;
 155         keylength = gk5e->keylength;
 156
 157         if ((inkey->len != keylength) || (outkey->len != keylength))
 158                 goto err_return;
 159
 160         cipher = crypto_alloc_skcipher(gk5e->encrypt_name, 0,
 161                                        CRYPTO_ALG_ASYNC);
 162         if (IS_ERR(cipher))
 163                 goto err_return;
 164         if (crypto_skcipher_setkey(cipher, inkey->data, inkey->len))
 165                 goto err_return;
 166
 167         /* allocate and set up buffers */
 168
 169         ret = ENOMEM;
 170         inblockdata = kmalloc(blocksize, gfp_mask);
 171         if (inblockdata == NULL)
 172                 goto err_free_cipher;
 173
 174         outblockdata = kmalloc(blocksize, gfp_mask);
 175         if (outblockdata == NULL)
 176                 goto err_free_in;
 177
 178         rawkey = kmalloc(keybytes, gfp_mask);
 179         if (rawkey == NULL)
 180                 goto err_free_out;
 181
 182         inblock.data = (char *) inblockdata;
 183         inblock.len = blocksize;
 184
 185         outblock.data = (char *) outblockdata;
 186         outblock.len = blocksize;
 187
 188         /* initialize the input block */
 189
 190         if (in_constant->len == inblock.len) {
 191                 memcpy(inblock.data, in_constant->data, inblock.len);
 192         } else {
 193                 krb5_nfold(in_constant->len * 8, in_constant->data,
 194                            inblock.len * 8, inblock.data);
 195         }
 196
 197         /* loop encrypting the blocks until enough key bytes are generated */
 198
 199         n = 0;
 200         while (n < keybytes) {
 201                 (*(gk5e->encrypt))(cipher, NULL, inblock.data,
 202                                    outblock.data, inblock.len);
 203
 204                 if ((keybytes - n) <= outblock.len) {
 205                         memcpy(rawkey + n, outblock.data, (keybytes - n));
 206                         break;
 207                 }
 208
 209                 memcpy(rawkey + n, outblock.data, outblock.len);
 210                 memcpy(inblock.data, outblock.data, outblock.len);
 211                 n += outblock.len;
 212         }
 213
 214         /* postprocess the key */
 215
 216         inblock.data = (char *) rawkey;
 217         inblock.len = keybytes;
 218
 219         BUG_ON(gk5e->mk_key == NULL);
 220         ret = (*(gk5e->mk_key))(gk5e, &inblock, outkey);
 221         if (ret) {
 222                 dprintk("%s: got %d from mk_key function for '%s'\n",
 223                         __func__, ret, gk5e->encrypt_name);
 224                 goto err_free_raw;
 225         }
 226
 227         /* clean memory, free resources and exit */
 228
 229         ret = 0;
 230
 231 err_free_raw:
 232         memset(rawkey, 0, keybytes);
 233         kfree(rawkey);
 234 err_free_out:
 235         memset(outblockdata, 0, blocksize);
 236         kfree(outblockdata);
 237 err_free_in:
 238         memset(inblockdata, 0, blocksize);
 239         kfree(inblockdata);
 240 err_free_cipher:
 241         crypto_free_skcipher(cipher);
 242 err_return:
 243         return ret;
 244 }
 245
 246 #define smask(step) ((1<<step)-1)
 247 #define pstep(x, step) (((x)&smask(step))^(((x)>>step)&smask(step)))
 248 #define parity_char(x) pstep(pstep(pstep((x), 4), 2), 1)
 249
 250 static void mit_des_fixup_key_parity(u8 key[8])
 251 {
 252         int i;
 253         for (i = 0; i < 8; i++) {
 254                 key[i] &= 0xfe;
 255                 key[i] |= 1^parity_char(key[i]);
 256         }
 257 }
 258
 259 /*
 260  * This is the des3 key derivation postprocess function
 261  */
 262 u32 gss_krb5_des3_make_key(const struct gss_krb5_enctype *gk5e,
 263                            struct xdr_netobj *randombits,
 264                            struct xdr_netobj *key)
 265 {
 266         int i;
 267         u32 ret = EINVAL;
 268
 269         if (key->len != 24) {
 270                 dprintk("%s: key->len is %d\n", __func__, key->len);
 271                 goto err_out;
 272         }
 273         if (randombits->len != 21) {
 274                 dprintk("%s: randombits->len is %d\n",
 275                         __func__, randombits->len);
 276                 goto err_out;
 277         }
 278
 279         /* take the seven bytes, move them around into the top 7 bits of the
 280            8 key bytes, then compute the parity bits.  Do this three times. */
 281
 282         for (i = 0; i < 3; i++) {
 283                 memcpy(key->data + i*8, randombits->data + i*7, 7);
 284                 key->data[i*8+7] = (((key->data[i*8]&1)<<1) |
 285                                     ((key->data[i*8+1]&1)<<2) |
 286                                     ((key->data[i*8+2]&1)<<3) |
 287                                     ((key->data[i*8+3]&1)<<4) |
 288                                     ((key->data[i*8+4]&1)<<5) |
 289                                     ((key->data[i*8+5]&1)<<6) |
 290                                     ((key->data[i*8+6]&1)<<7));
 291
 292                 mit_des_fixup_key_parity(key->data + i*8);
 293         }
 294         ret = 0;
 295 err_out:
 296         return ret;
 297 }
 298
 299 /*
 300  * This is the aes key derivation postprocess function
 301  */
 302 u32 gss_krb5_aes_make_key(const struct gss_krb5_enctype *gk5e,
 303                           struct xdr_netobj *randombits,
 304                           struct xdr_netobj *key)
 305 {
 306         u32 ret = EINVAL;
 307
 308         if (key->len != 16 && key->len != 32) {
 309                 dprintk("%s: key->len is %d\n", __func__, key->len);
 310                 goto err_out;
 311         }
 312         if (randombits->len != 16 && randombits->len != 32) {
 313                 dprintk("%s: randombits->len is %d\n",
 314                         __func__, randombits->len);
 315                 goto err_out;
 316         }
 317         if (randombits->len != key->len) {
 318                 dprintk("%s: randombits->len is %d, key->len is %d\n",
 319                         __func__, randombits->len, key->len);
 320                 goto err_out;
 321         }
 322         memcpy(key->data, randombits->data, key->len);
 323         ret = 0;
 324 err_out:
 325         return ret;
 326 }
 327