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 /* read_token is a mic token, and message_buffer is the data that the mic was
  72  * supposedly taken over. */
  73
  74 u32
  75 gss_verify_mic_kerberos(struct gss_ctx *gss_ctx,
  76                 struct xdr_buf *message_buffer, struct xdr_netobj *read_token)
  77 {
  78         struct krb5_ctx         *ctx = gss_ctx->internal_ctx_id;
  79         int                     signalg;
  80         int                     sealalg;
  81         s32                     checksum_type;
  82         struct xdr_netobj       md5cksum = {.len = 0, .data = NULL};
  83         s32                     now;
  84         int                     direction;
  85         s32                     seqnum;
  86         unsigned char           *ptr = (unsigned char *)read_token->data;
  87         int                     bodysize;
  88         u32                     ret = GSS_S_DEFECTIVE_TOKEN;
  89
  90         dprintk("RPC:      krb5_read_token\n");
  91
  92         if (g_verify_token_header(&ctx->mech_used, &bodysize, &ptr,
  93                                         read_token->len))
  94                 goto out;
  95
  96         if ((*ptr++ != ((KG_TOK_MIC_MSG>>8)&0xff)) ||
  97             (*ptr++ != ( KG_TOK_MIC_MSG    &0xff))   )
  98                 goto out;
  99
 100         /* XXX sanity-check bodysize?? */
 101
 102         /* get the sign and seal algorithms */
 103
 104         signalg = ptr[0] + (ptr[1] << 8);
 105         sealalg = ptr[2] + (ptr[3] << 8);
 106
 107         /* Sanity checks */
 108
 109         if ((ptr[4] != 0xff) || (ptr[5] != 0xff))
 110                 goto out;
 111
 112         if (sealalg != 0xffff)
 113                 goto out;
 114
 115         /* there are several mappings of seal algorithms to sign algorithms,
 116            but few enough that we can try them all. */
 117
 118         if ((ctx->sealalg == SEAL_ALG_NONE && signalg > 1) ||
 119             (ctx->sealalg == SEAL_ALG_1 && signalg != SGN_ALG_3) ||
 120             (ctx->sealalg == SEAL_ALG_DES3KD &&
 121              signalg != SGN_ALG_HMAC_SHA1_DES3_KD))
 122                 goto out;
 123
 124         /* compute the checksum of the message */
 125
 126         /* initialize the the cksum */
 127         switch (signalg) {
 128         case SGN_ALG_DES_MAC_MD5:
 129                 checksum_type = CKSUMTYPE_RSA_MD5;
 130                 break;
 131         default:
 132                 ret = GSS_S_DEFECTIVE_TOKEN;
 133                 goto out;
 134         }
 135
 136         switch (signalg) {
 137         case SGN_ALG_DES_MAC_MD5:
 138                 ret = make_checksum(checksum_type, ptr - 2, 8,
 139                                          message_buffer, 0, &md5cksum);
 140                 if (ret)
 141                         goto out;
 142
 143                 ret = krb5_encrypt(ctx->seq, NULL, md5cksum.data,
 144                                    md5cksum.data, 16);
 145                 if (ret)
 146                         goto out;
 147
 148                 if (memcmp(md5cksum.data + 8, ptr + 14, 8)) {
 149                         ret = GSS_S_BAD_SIG;
 150                         goto out;
 151                 }
 152                 break;
 153         default:
 154                 ret = GSS_S_DEFECTIVE_TOKEN;
 155                 goto out;
 156         }
 157
 158         /* it got through unscathed.  Make sure the context is unexpired */
 159
 160         now = get_seconds();
 161
 162         ret = GSS_S_CONTEXT_EXPIRED;
 163         if (now > ctx->endtime)
 164                 goto out;
 165
 166         /* do sequencing checks */
 167
 168         ret = GSS_S_BAD_SIG;
 169         if ((ret = krb5_get_seq_num(ctx->seq, ptr + 14, ptr + 6, &direction,
 170                                     &seqnum)))
 171                 goto out;
 172
 173         if ((ctx->initiate && direction != 0xff) ||
 174             (!ctx->initiate && direction != 0))
 175                 goto out;
 176
 177         ret = GSS_S_COMPLETE;
 178 out:
 179         kfree(md5cksum.data);
 180         return ret;
 181 }