net/sunrpc/auth_gss/gss_krb5_unseal.c

   1 /*
   2  *  linux/net/sunrpc/gss_krb5_unseal.c
   3  *
   4  *  Adapted from MIT Kerberos 5-1.2.1 lib/gssapi/krb5/k5unseal.c
   5  *
   6  *  Copyright (c) 2000 The Regents of the University of Michigan.
   7  *  All rights reserved.
   8  *
   9  *  Andy Adamson   <andros@umich.edu>
  10  */
  11
  12 /*
  13  * Copyright 1993 by OpenVision Technologies, Inc.
  14  *
  15  * Permission to use, copy, modify, distribute, and sell this software
  16  * and its documentation for any purpose is hereby granted without fee,
  17  * provided that the above copyright notice appears in all copies and
  18  * that both that copyright notice and this permission notice appear in
  19  * supporting documentation, and that the name of OpenVision not be used
  20  * in advertising or publicity pertaining to distribution of the software
  21  * without specific, written prior permission. OpenVision makes no
  22  * representations about the suitability of this software for any
  23  * purpose.  It is provided "as is" without express or implied warranty.
  24  *
  25  * OPENVISION DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
  26  * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
  27  * EVENT SHALL OPENVISION BE LIABLE FOR ANY SPECIAL, INDIRECT OR
  28  * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
  29  * USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
  30  * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
  31  * PERFORMANCE OF THIS SOFTWARE.
  32  */
  33
  34 /*
  35  * Copyright (C) 1998 by the FundsXpress, INC.
  36  *
  37  * All rights reserved.
  38  *
  39  * Export of this software from the United States of America may require
  40  * a specific license from the United States Government.  It is the
  41  * responsibility of any person or organization contemplating export to
  42  * obtain such a license before exporting.
  43  *
  44  * WITHIN THAT CONSTRAINT, permission to use, copy, modify, and
  45  * distribute this software and its documentation for any purpose and
  46  * without fee is hereby granted, provided that the above copyright
  47  * notice appear in all copies and that both that copyright notice and
  48  * this permission notice appear in supporting documentation, and that
  49  * the name of FundsXpress. not be used in advertising or publicity pertaining
  50  * to distribution of the software without specific, written prior
  51  * permission.  FundsXpress makes no representations about the suitability of
  52  * this software for any purpose.  It is provided "as is" without express
  53  * or implied warranty.
  54  *
  55  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
  56  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
  57  * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
  58  */
  59
  60 #include <linux/types.h>
  61 #include <linux/slab.h>
  62 #include <linux/jiffies.h>
  63 #include <linux/sunrpc/gss_krb5.h>
  64 #include <linux/crypto.h>
  65
  66 #ifdef RPC_DEBUG
  67 # define RPCDBG_FACILITY        RPCDBG_AUTH
  68 #endif
  69
  70
  71 /* message_buffer is an input if toktype is MIC and an output if it is WRAP:
  72  * If toktype is MIC: read_token is a mic token, and message_buffer is the
  73  *   data that the mic was supposedly taken over.
  74  * If toktype is WRAP: read_token is a wrap token, and message_buffer is used
  75  *   to return the decrypted data.
  76  */
  77
  78 /* XXX will need to change prototype and/or just split into a separate function
  79  * when we add privacy (because read_token will be in pages too). */
  80 u32
  81 krb5_read_token(struct krb5_ctx *ctx,
  82                 struct xdr_netobj *read_token,
  83                 struct xdr_buf *message_buffer,
  84                 int *qop_state, int toktype)
  85 {
  86         int                     signalg;
  87         int                     sealalg;
  88         s32                     checksum_type;
  89         struct xdr_netobj       md5cksum = {.len = 0, .data = NULL};
  90         s32                     now;
  91         int                     direction;
  92         s32                     seqnum;
  93         unsigned char           *ptr = (unsigned char *)read_token->data;
  94         int                     bodysize;
  95         u32                     ret = GSS_S_DEFECTIVE_TOKEN;
  96
  97         dprintk("RPC:      krb5_read_token\n");
  98
  99         if (g_verify_token_header(&ctx->mech_used, &bodysize, &ptr,
 100                                         read_token->len))
 101                 goto out;
 102
 103         if ((*ptr++ != ((toktype>>8)&0xff)) || (*ptr++ != (toktype&0xff)))
 104                 goto out;
 105
 106         /* XXX sanity-check bodysize?? */
 107
 108         if (toktype == KG_TOK_WRAP_MSG) {
 109                 /* XXX gone */
 110                 goto out;
 111         }
 112
 113         /* get the sign and seal algorithms */
 114
 115         signalg = ptr[0] + (ptr[1] << 8);
 116         sealalg = ptr[2] + (ptr[3] << 8);
 117
 118         /* Sanity checks */
 119
 120         if ((ptr[4] != 0xff) || (ptr[5] != 0xff))
 121                 goto out;
 122
 123         if (((toktype != KG_TOK_WRAP_MSG) && (sealalg != 0xffff)) ||
 124             ((toktype == KG_TOK_WRAP_MSG) && (sealalg == 0xffff)))
 125                 goto out;
 126
 127         /* in the current spec, there is only one valid seal algorithm per
 128            key type, so a simple comparison is ok */
 129
 130         if ((toktype == KG_TOK_WRAP_MSG) && !(sealalg == ctx->sealalg))
 131                 goto out;
 132
 133         /* there are several mappings of seal algorithms to sign algorithms,
 134            but few enough that we can try them all. */
 135
 136         if ((ctx->sealalg == SEAL_ALG_NONE && signalg > 1) ||
 137             (ctx->sealalg == SEAL_ALG_1 && signalg != SGN_ALG_3) ||
 138             (ctx->sealalg == SEAL_ALG_DES3KD &&
 139              signalg != SGN_ALG_HMAC_SHA1_DES3_KD))
 140                 goto out;
 141
 142         /* compute the checksum of the message */
 143
 144         /* initialize the the cksum */
 145         switch (signalg) {
 146         case SGN_ALG_DES_MAC_MD5:
 147                 checksum_type = CKSUMTYPE_RSA_MD5;
 148                 break;
 149         default:
 150                 ret = GSS_S_DEFECTIVE_TOKEN;
 151                 goto out;
 152         }
 153
 154         switch (signalg) {
 155         case SGN_ALG_DES_MAC_MD5:
 156                 ret = make_checksum(checksum_type, ptr - 2, 8,
 157                                          message_buffer, &md5cksum);
 158                 if (ret)
 159                         goto out;
 160
 161                 ret = krb5_encrypt(ctx->seq, NULL, md5cksum.data,
 162                                    md5cksum.data, 16);
 163                 if (ret)
 164                         goto out;
 165
 166                 if (memcmp(md5cksum.data + 8, ptr + 14, 8)) {
 167                         ret = GSS_S_BAD_SIG;
 168                         goto out;
 169                 }
 170                 break;
 171         default:
 172                 ret = GSS_S_DEFECTIVE_TOKEN;
 173                 goto out;
 174         }
 175
 176         /* it got through unscathed.  Make sure the context is unexpired */
 177
 178         if (qop_state)
 179                 *qop_state = GSS_C_QOP_DEFAULT;
 180
 181         now = get_seconds();
 182
 183         ret = GSS_S_CONTEXT_EXPIRED;
 184         if (now > ctx->endtime)
 185                 goto out;
 186
 187         /* do sequencing checks */
 188
 189         ret = GSS_S_BAD_SIG;
 190         if ((ret = krb5_get_seq_num(ctx->seq, ptr + 14, ptr + 6, &direction,
 191                                     &seqnum)))
 192                 goto out;
 193
 194         if ((ctx->initiate && direction != 0xff) ||
 195             (!ctx->initiate && direction != 0))
 196                 goto out;
 197
 198         ret = GSS_S_COMPLETE;
 199 out:
 200         if (md5cksum.data) kfree(md5cksum.data);
 201         return ret;
 202 }