gss_krb5: introduce encryption type framework
authorKevin Coffman <kwc@citi.umich.edu>
Wed, 17 Mar 2010 17:02:51 +0000 (13:02 -0400)
committerTrond Myklebust <Trond.Myklebust@netapp.com>
Fri, 14 May 2010 19:09:16 +0000 (15:09 -0400)
Add enctype framework and change functions to use the generic
values from it rather than the values hard-coded for des.

Signed-off-by: Kevin Coffman <kwc@citi.umich.edu>
Signed-off-by: Steve Dickson <steved@redhat.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
include/linux/sunrpc/gss_krb5.h
net/sunrpc/auth_gss/gss_krb5_crypto.c
net/sunrpc/auth_gss/gss_krb5_mech.c
net/sunrpc/auth_gss/gss_krb5_seal.c
net/sunrpc/auth_gss/gss_krb5_unseal.c
net/sunrpc/auth_gss/gss_krb5_wrap.c

index 5378e455482cf5db06a149ff929d524fbfb94c43..f94935599d1384b901f06d728ef9fbfd305df901 100644 (file)
@@ -4,7 +4,7 @@
  *  Adapted from MIT Kerberos 5-1.2.1 lib/include/krb5.h,
  *  lib/gssapi/krb5/gssapiP_krb5.h, and others
  *
- *  Copyright (c) 2000 The Regents of the University of Michigan.
+ *  Copyright (c) 2000-2008 The Regents of the University of Michigan.
  *  All rights reserved.
  *
  *  Andy Adamson   <andros@umich.edu>
@@ -36,6 +36,7 @@
  *
  */
 
+#include <linux/crypto.h>
 #include <linux/sunrpc/auth_gss.h>
 #include <linux/sunrpc/gss_err.h>
 #include <linux/sunrpc/gss_asn1.h>
 /* Maximum blocksize for the supported crypto algorithms */
 #define GSS_KRB5_MAX_BLOCKSIZE  (16)
 
+struct gss_krb5_enctype {
+       const u32               etype;          /* encryption (key) type */
+       const u32               ctype;          /* checksum type */
+       const char              *name;          /* "friendly" name */
+       const char              *encrypt_name;  /* crypto encrypt name */
+       const char              *cksum_name;    /* crypto checksum name */
+       const u16               signalg;        /* signing algorithm */
+       const u16               sealalg;        /* sealing algorithm */
+       const u32               blocksize;      /* encryption blocksize */
+       const u32               cksumlength;    /* checksum length */
+       const u32               keyed_cksum;    /* is it a keyed cksum? */
+       const u32               keybytes;       /* raw key len, in bytes */
+       const u32               keylength;      /* final key len, in bytes */
+       u32 (*encrypt) (struct crypto_blkcipher *tfm,
+                       void *iv, void *in, void *out,
+                       int length);            /* encryption function */
+       u32 (*decrypt) (struct crypto_blkcipher *tfm,
+                       void *iv, void *in, void *out,
+                       int length);            /* decryption function */
+};
+
 struct krb5_ctx {
        int                     initiate; /* 1 = initiating, 0 = accepting */
        u32                     enctype;
+       const struct gss_krb5_enctype *gk5e; /* enctype-specific info */
        struct crypto_blkcipher *enc;
        struct crypto_blkcipher *seq;
        s32                     endtime;
index 746b3e139aede6de4091cb931bc6980a6fbab6b1..ccd5236953f779229841e3d0f4f20892183ca7d4 100644 (file)
@@ -1,7 +1,7 @@
 /*
  *  linux/net/sunrpc/gss_krb5_crypto.c
  *
- *  Copyright (c) 2000 The Regents of the University of Michigan.
+ *  Copyright (c) 2000-2008 The Regents of the University of Michigan.
  *  All rights reserved.
  *
  *  Andy Adamson   <andros@umich.edu>
@@ -58,13 +58,13 @@ krb5_encrypt(
 {
        u32 ret = -EINVAL;
        struct scatterlist sg[1];
-       u8 local_iv[16] = {0};
+       u8 local_iv[GSS_KRB5_MAX_BLOCKSIZE] = {0};
        struct blkcipher_desc desc = { .tfm = tfm, .info = local_iv };
 
        if (length % crypto_blkcipher_blocksize(tfm) != 0)
                goto out;
 
-       if (crypto_blkcipher_ivsize(tfm) > 16) {
+       if (crypto_blkcipher_ivsize(tfm) > GSS_KRB5_MAX_BLOCKSIZE) {
                dprintk("RPC:       gss_k5encrypt: tfm iv size too large %d\n",
                        crypto_blkcipher_ivsize(tfm));
                goto out;
@@ -92,13 +92,13 @@ krb5_decrypt(
 {
        u32 ret = -EINVAL;
        struct scatterlist sg[1];
-       u8 local_iv[16] = {0};
+       u8 local_iv[GSS_KRB5_MAX_BLOCKSIZE] = {0};
        struct blkcipher_desc desc = { .tfm = tfm, .info = local_iv };
 
        if (length % crypto_blkcipher_blocksize(tfm) != 0)
                goto out;
 
-       if (crypto_blkcipher_ivsize(tfm) > 16) {
+       if (crypto_blkcipher_ivsize(tfm) > GSS_KRB5_MAX_BLOCKSIZE) {
                dprintk("RPC:       gss_k5decrypt: tfm iv size too large %d\n",
                        crypto_blkcipher_ivsize(tfm));
                goto out;
@@ -157,7 +157,7 @@ out:
 }
 
 struct encryptor_desc {
-       u8 iv[8]; /* XXX hard-coded blocksize */
+       u8 iv[GSS_KRB5_MAX_BLOCKSIZE];
        struct blkcipher_desc desc;
        int pos;
        struct xdr_buf *outbuf;
@@ -198,7 +198,7 @@ encryptor(struct scatterlist *sg, void *data)
        desc->fraglen += sg->length;
        desc->pos += sg->length;
 
-       fraglen = thislen & 7; /* XXX hardcoded blocksize */
+       fraglen = thislen & (crypto_blkcipher_blocksize(desc->desc.tfm) - 1);
        thislen -= fraglen;
 
        if (thislen == 0)
@@ -256,7 +256,7 @@ gss_encrypt_xdr_buf(struct crypto_blkcipher *tfm, struct xdr_buf *buf,
 }
 
 struct decryptor_desc {
-       u8 iv[8]; /* XXX hard-coded blocksize */
+       u8 iv[GSS_KRB5_MAX_BLOCKSIZE];
        struct blkcipher_desc desc;
        struct scatterlist frags[4];
        int fragno;
@@ -278,7 +278,7 @@ decryptor(struct scatterlist *sg, void *data)
        desc->fragno++;
        desc->fraglen += sg->length;
 
-       fraglen = thislen & 7; /* XXX hardcoded blocksize */
+       fraglen = thislen & (crypto_blkcipher_blocksize(desc->desc.tfm) - 1);
        thislen -= fraglen;
 
        if (thislen == 0)
index afe09108e1b040e29f87b46670f53e2d49a2b434..a66eb706aeb727dd482976c592f60e09d7ddc64e 100644 (file)
@@ -1,7 +1,7 @@
 /*
  *  linux/net/sunrpc/gss_krb5_mech.c
  *
- *  Copyright (c) 2001 The Regents of the University of Michigan.
+ *  Copyright (c) 2001-2008 The Regents of the University of Michigan.
  *  All rights reserved.
  *
  *  Andy Adamson <andros@umich.edu>
 # define RPCDBG_FACILITY       RPCDBG_AUTH
 #endif
 
+static const struct gss_krb5_enctype supported_gss_krb5_enctypes[] = {
+       /*
+        * DES (All DES enctypes are mapped to the same gss functionality)
+        */
+       {
+         .etype = ENCTYPE_DES_CBC_RAW,
+         .ctype = CKSUMTYPE_RSA_MD5,
+         .name = "des-cbc-crc",
+         .encrypt_name = "cbc(des)",
+         .cksum_name = "md5",
+         .encrypt = krb5_encrypt,
+         .decrypt = krb5_decrypt,
+         .signalg = SGN_ALG_DES_MAC_MD5,
+         .sealalg = SEAL_ALG_DES,
+         .keybytes = 7,
+         .keylength = 8,
+         .blocksize = 8,
+         .cksumlength = 8,
+       },
+};
+
+static const int num_supported_enctypes =
+       ARRAY_SIZE(supported_gss_krb5_enctypes);
+
+static int
+supported_gss_krb5_enctype(int etype)
+{
+       int i;
+       for (i = 0; i < num_supported_enctypes; i++)
+               if (supported_gss_krb5_enctypes[i].etype == etype)
+                       return 1;
+       return 0;
+}
+
+static const struct gss_krb5_enctype *
+get_gss_krb5_enctype(int etype)
+{
+       int i;
+       for (i = 0; i < num_supported_enctypes; i++)
+               if (supported_gss_krb5_enctypes[i].etype == etype)
+                       return &supported_gss_krb5_enctypes[i];
+       return NULL;
+}
+
 static const void *
 simple_get_bytes(const void *p, const void *end, void *res, int len)
 {
@@ -78,35 +122,45 @@ simple_get_netobj(const void *p, const void *end, struct xdr_netobj *res)
 }
 
 static inline const void *
-get_key(const void *p, const void *end, struct crypto_blkcipher **res)
+get_key(const void *p, const void *end,
+       struct krb5_ctx *ctx, struct crypto_blkcipher **res)
 {
        struct xdr_netobj       key;
        int                     alg;
-       char                    *alg_name;
 
        p = simple_get_bytes(p, end, &alg, sizeof(alg));
        if (IS_ERR(p))
                goto out_err;
+
+       switch (alg) {
+       case ENCTYPE_DES_CBC_CRC:
+       case ENCTYPE_DES_CBC_MD4:
+       case ENCTYPE_DES_CBC_MD5:
+               /* Map all these key types to ENCTYPE_DES_CBC_RAW */
+               alg = ENCTYPE_DES_CBC_RAW;
+               break;
+       }
+
+       if (!supported_gss_krb5_enctype(alg)) {
+               printk(KERN_WARNING "gss_kerberos_mech: unsupported "
+                       "encryption key algorithm %d\n", alg);
+               goto out_err;
+       }
        p = simple_get_netobj(p, end, &key);
        if (IS_ERR(p))
                goto out_err;
 
-       switch (alg) {
-               case ENCTYPE_DES_CBC_RAW:
-                       alg_name = "cbc(des)";
-                       break;
-               default:
-                       printk("gss_kerberos_mech: unsupported algorithm %d\n", alg);
-                       goto out_err_free_key;
-       }
-       *res = crypto_alloc_blkcipher(alg_name, 0, CRYPTO_ALG_ASYNC);
+       *res = crypto_alloc_blkcipher(ctx->gk5e->encrypt_name, 0,
+                                                       CRYPTO_ALG_ASYNC);
        if (IS_ERR(*res)) {
-               printk("gss_kerberos_mech: unable to initialize crypto algorithm %s\n", alg_name);
+               printk(KERN_WARNING "gss_kerberos_mech: unable to initialize "
+                       "crypto algorithm %s\n", ctx->gk5e->encrypt_name);
                *res = NULL;
                goto out_err_free_key;
        }
        if (crypto_blkcipher_setkey(*res, key.data, key.len)) {
-               printk("gss_kerberos_mech: error setting key for crypto algorithm %s\n", alg_name);
+               printk(KERN_WARNING "gss_kerberos_mech: error setting key for "
+                       "crypto algorithm %s\n", ctx->gk5e->encrypt_name);
                goto out_err_free_tfm;
        }
 
@@ -134,6 +188,10 @@ gss_import_v1_context(const void *p, const void *end, struct krb5_ctx *ctx)
        /* Old format supports only DES!  Any other enctype uses new format */
        ctx->enctype = ENCTYPE_DES_CBC_RAW;
 
+       ctx->gk5e = get_gss_krb5_enctype(ctx->enctype);
+       if (ctx->gk5e == NULL)
+               goto out_err;
+
        /* The downcall format was designed before we completely understood
         * the uses of the context fields; so it includes some stuff we
         * just give some minimal sanity-checking, and some we ignore
@@ -164,10 +222,10 @@ gss_import_v1_context(const void *p, const void *end, struct krb5_ctx *ctx)
        p = simple_get_netobj(p, end, &ctx->mech_used);
        if (IS_ERR(p))
                goto out_err;
-       p = get_key(p, end, &ctx->enc);
+       p = get_key(p, end, ctx, &ctx->enc);
        if (IS_ERR(p))
                goto out_err_free_mech;
-       p = get_key(p, end, &ctx->seq);
+       p = get_key(p, end, ctx, &ctx->seq);
        if (IS_ERR(p))
                goto out_err_free_key1;
        if (p != end) {
index 71c2014e7ebfe542f06f71102449f0b6f8803196..46c6f44e5c3f6eba3051ade8775c55f16766a93c 100644 (file)
@@ -3,7 +3,7 @@
  *
  *  Adapted from MIT Kerberos 5-1.2.1 lib/gssapi/krb5/k5seal.c
  *
- *  Copyright (c) 2000 The Regents of the University of Michigan.
+ *  Copyright (c) 2000-2008 The Regents of the University of Michigan.
  *  All rights reserved.
  *
  *  Andy Adamson       <andros@umich.edu>
 
 DEFINE_SPINLOCK(krb5_seq_lock);
 
+static char *
+setup_token(struct krb5_ctx *ctx, struct xdr_netobj *token)
+{
+       __be16 *ptr, *krb5_hdr;
+       int body_size = GSS_KRB5_TOK_HDR_LEN + ctx->gk5e->cksumlength;
+
+       token->len = g_token_size(&ctx->mech_used, body_size);
+
+       ptr = (__be16 *)token->data;
+       g_make_token_header(&ctx->mech_used, body_size, (unsigned char **)&ptr);
+
+       /* ptr now at start of header described in rfc 1964, section 1.2.1: */
+       krb5_hdr = ptr;
+       *ptr++ = KG_TOK_MIC_MSG;
+       *ptr++ = cpu_to_le16(ctx->gk5e->signalg);
+       *ptr++ = SEAL_ALG_NONE;
+       *ptr++ = 0xffff;
+
+       return (char *)krb5_hdr;
+}
+
 static u32
 gss_get_mic_v1(struct krb5_ctx *ctx, struct xdr_buf *text,
                struct xdr_netobj *token)
 {
-       char                    cksumdata[16];
-       struct xdr_netobj       md5cksum = {.len = 0, .data = cksumdata};
-       unsigned char           *ptr, *msg_start;
+       char                    cksumdata[GSS_KRB5_MAX_CKSUM_LEN];
+       struct xdr_netobj       md5cksum = {.len = sizeof(cksumdata),
+                                           .data = cksumdata};
+       void                    *ptr;
        s32                     now;
        u32                     seq_send;
 
-       dprintk("RPC:       gss_krb5_seal\n");
+       dprintk("RPC:       %s\n", __func__);
        BUG_ON(ctx == NULL);
 
        now = get_seconds();
 
-       token->len = g_token_size(&ctx->mech_used, GSS_KRB5_TOK_HDR_LEN + 8);
-
-       ptr = token->data;
-       g_make_token_header(&ctx->mech_used, GSS_KRB5_TOK_HDR_LEN + 8, &ptr);
-
-       /* ptr now at header described in rfc 1964, section 1.2.1: */
-       ptr[0] = (unsigned char) ((KG_TOK_MIC_MSG >> 8) & 0xff);
-       ptr[1] = (unsigned char) (KG_TOK_MIC_MSG & 0xff);
-
-       msg_start = ptr + GSS_KRB5_TOK_HDR_LEN + 8;
-
-       *(__be16 *)(ptr + 2) = htons(SGN_ALG_DES_MAC_MD5);
-       memset(ptr + 4, 0xff, 4);
+       ptr = setup_token(ctx, token);
 
-       if (make_checksum("md5", ptr, 8, text, 0, &md5cksum))
+       if (make_checksum((char *)ctx->gk5e->cksum_name, ptr, 8,
+                                               text, 0, &md5cksum))
                return GSS_S_FAILURE;
 
        if (krb5_encrypt(ctx->seq, NULL, md5cksum.data,
index 069d4b59807a0267052066f1f67b614fd74c3535..10ee641a39d0e0aaabbb8cc6d65c25df98211ae6 100644 (file)
@@ -3,7 +3,7 @@
  *
  *  Adapted from MIT Kerberos 5-1.2.1 lib/gssapi/krb5/k5unseal.c
  *
- *  Copyright (c) 2000 The Regents of the University of Michigan.
+ *  Copyright (c) 2000-2008 The Regents of the University of Michigan.
  *  All rights reserved.
  *
  *  Andy Adamson   <andros@umich.edu>
@@ -76,8 +76,9 @@ gss_verify_mic_v1(struct krb5_ctx *ctx,
 {
        int                     signalg;
        int                     sealalg;
-       char                    cksumdata[16];
-       struct xdr_netobj       md5cksum = {.len = 0, .data = cksumdata};
+       char                    cksumdata[GSS_KRB5_MAX_CKSUM_LEN];
+       struct xdr_netobj       md5cksum = {.len = sizeof(cksumdata),
+                                           .data = cksumdata};
        s32                     now;
        int                     direction;
        u32                     seqnum;
@@ -97,7 +98,7 @@ gss_verify_mic_v1(struct krb5_ctx *ctx,
        /* XXX sanity-check bodysize?? */
 
        signalg = ptr[2] + (ptr[3] << 8);
-       if (signalg != SGN_ALG_DES_MAC_MD5)
+       if (signalg != ctx->gk5e->signalg)
                return GSS_S_DEFECTIVE_TOKEN;
 
        sealalg = ptr[4] + (ptr[5] << 8);
@@ -107,13 +108,15 @@ gss_verify_mic_v1(struct krb5_ctx *ctx,
        if ((ptr[6] != 0xff) || (ptr[7] != 0xff))
                return GSS_S_DEFECTIVE_TOKEN;
 
-       if (make_checksum("md5", ptr, 8, message_buffer, 0, &md5cksum))
+       if (make_checksum((char *)ctx->gk5e->cksum_name, ptr, 8,
+                                       message_buffer, 0, &md5cksum))
                return GSS_S_FAILURE;
 
        if (krb5_encrypt(ctx->seq, NULL, md5cksum.data, md5cksum.data, 16))
                return GSS_S_FAILURE;
 
-       if (memcmp(md5cksum.data + 8, ptr + GSS_KRB5_TOK_HDR_LEN, 8))
+       if (memcmp(md5cksum.data + 8, ptr + GSS_KRB5_TOK_HDR_LEN,
+                                       ctx->gk5e->cksumlength))
                return GSS_S_BAD_SIG;
 
        /* it got through unscathed.  Make sure the context is unexpired */
index b45b59b17ae1b21e56c7cd72db4ef0f1a074fb18..7188891bcc33dea28a945f1147788f403c9157c4 100644 (file)
@@ -1,3 +1,33 @@
+/*
+ * COPYRIGHT (c) 2008
+ * The Regents of the University of Michigan
+ * ALL RIGHTS RESERVED
+ *
+ * Permission is granted to use, copy, create derivative works
+ * and redistribute this software and such derivative works
+ * for any purpose, so long as the name of The University of
+ * Michigan is not used in any advertising or publicity
+ * pertaining to the use of distribution of this software
+ * without specific, written prior authorization.  If the
+ * above copyright notice or any other identification of the
+ * University of Michigan is included in any copy of any
+ * portion of this software, then the disclaimer below must
+ * also be included.
+ *
+ * THIS SOFTWARE IS PROVIDED AS IS, WITHOUT REPRESENTATION
+ * FROM THE UNIVERSITY OF MICHIGAN AS TO ITS FITNESS FOR ANY
+ * PURPOSE, AND WITHOUT WARRANTY BY THE UNIVERSITY OF
+ * MICHIGAN OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING
+ * WITHOUT LIMITATION THE IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE
+ * REGENTS OF THE UNIVERSITY OF MICHIGAN SHALL NOT BE LIABLE
+ * FOR ANY DAMAGES, INCLUDING SPECIAL, INDIRECT, INCIDENTAL, OR
+ * CONSEQUENTIAL DAMAGES, WITH RESPECT TO ANY CLAIM ARISING
+ * OUT OF OR IN CONNECTION WITH THE USE OF THE SOFTWARE, EVEN
+ * IF IT HAS BEEN OR IS HEREAFTER ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGES.
+ */
+
 #include <linux/types.h>
 #include <linux/jiffies.h>
 #include <linux/sunrpc/gss_krb5.h>
@@ -128,8 +158,9 @@ static u32
 gss_wrap_kerberos_v1(struct krb5_ctx *kctx, int offset,
                struct xdr_buf *buf, struct page **pages)
 {
-       char                    cksumdata[16];
-       struct xdr_netobj       md5cksum = {.len = 0, .data = cksumdata};
+       char                    cksumdata[GSS_KRB5_MAX_CKSUM_LEN];
+       struct xdr_netobj       md5cksum = {.len = sizeof(cksumdata),
+                                           .data = cksumdata};
        int                     blocksize = 0, plainlen;
        unsigned char           *ptr, *msg_start;
        s32                     now;
@@ -137,7 +168,7 @@ gss_wrap_kerberos_v1(struct krb5_ctx *kctx, int offset,
        struct page             **tmp_pages;
        u32                     seq_send;
 
-       dprintk("RPC:       gss_wrap_kerberos\n");
+       dprintk("RPC:       %s\n", __func__);
 
        now = get_seconds();
 
@@ -146,8 +177,9 @@ gss_wrap_kerberos_v1(struct krb5_ctx *kctx, int offset,
        BUG_ON((buf->len - offset) % blocksize);
        plainlen = blocksize + buf->len - offset;
 
-       headlen = g_token_size(&kctx->mech_used, 24 + plainlen) -
-                                               (buf->len - offset);
+       headlen = g_token_size(&kctx->mech_used,
+               GSS_KRB5_TOK_HDR_LEN + kctx->gk5e->cksumlength + plainlen) -
+               (buf->len - offset);
 
        ptr = buf->head[0].iov_base + offset;
        /* shift data to make room for header. */
@@ -157,25 +189,26 @@ gss_wrap_kerberos_v1(struct krb5_ctx *kctx, int offset,
        BUG_ON((buf->len - offset - headlen) % blocksize);
 
        g_make_token_header(&kctx->mech_used,
-                               GSS_KRB5_TOK_HDR_LEN + 8 + plainlen, &ptr);
+                               GSS_KRB5_TOK_HDR_LEN +
+                               kctx->gk5e->cksumlength + plainlen, &ptr);
 
 
        /* ptr now at header described in rfc 1964, section 1.2.1: */
        ptr[0] = (unsigned char) ((KG_TOK_WRAP_MSG >> 8) & 0xff);
        ptr[1] = (unsigned char) (KG_TOK_WRAP_MSG & 0xff);
 
-       msg_start = ptr + 24;
+       msg_start = ptr + GSS_KRB5_TOK_HDR_LEN + kctx->gk5e->cksumlength;
 
-       *(__be16 *)(ptr + 2) = htons(SGN_ALG_DES_MAC_MD5);
+       *(__be16 *)(ptr + 2) = cpu_to_le16(kctx->gk5e->signalg);
        memset(ptr + 4, 0xff, 4);
-       *(__be16 *)(ptr + 4) = htons(SEAL_ALG_DES);
+       *(__be16 *)(ptr + 4) = cpu_to_le16(kctx->gk5e->sealalg);
 
        make_confounder(msg_start, blocksize);
 
        /* XXXJBF: UGH!: */
        tmp_pages = buf->pages;
        buf->pages = pages;
-       if (make_checksum("md5", ptr, 8, buf,
+       if (make_checksum((char *)kctx->gk5e->cksum_name, ptr, 8, buf,
                                offset + headlen - blocksize, &md5cksum))
                return GSS_S_FAILURE;
        buf->pages = tmp_pages;
@@ -207,8 +240,9 @@ gss_unwrap_kerberos_v1(struct krb5_ctx *kctx, int offset, struct xdr_buf *buf)
 {
        int                     signalg;
        int                     sealalg;
-       char                    cksumdata[16];
-       struct xdr_netobj       md5cksum = {.len = 0, .data = cksumdata};
+       char                    cksumdata[GSS_KRB5_MAX_CKSUM_LEN];
+       struct xdr_netobj       md5cksum = {.len = sizeof(cksumdata),
+                                           .data = cksumdata};
        s32                     now;
        int                     direction;
        s32                     seqnum;
@@ -217,6 +251,7 @@ gss_unwrap_kerberos_v1(struct krb5_ctx *kctx, int offset, struct xdr_buf *buf)
        void                    *data_start, *orig_start;
        int                     data_len;
        int                     blocksize;
+       int                     crypt_offset;
 
        dprintk("RPC:       gss_unwrap_kerberos\n");
 
@@ -234,22 +269,27 @@ gss_unwrap_kerberos_v1(struct krb5_ctx *kctx, int offset, struct xdr_buf *buf)
        /* get the sign and seal algorithms */
 
        signalg = ptr[2] + (ptr[3] << 8);
-       if (signalg != SGN_ALG_DES_MAC_MD5)
+       if (signalg != kctx->gk5e->signalg)
                return GSS_S_DEFECTIVE_TOKEN;
 
        sealalg = ptr[4] + (ptr[5] << 8);
-       if (sealalg != SEAL_ALG_DES)
+       if (sealalg != kctx->gk5e->sealalg)
                return GSS_S_DEFECTIVE_TOKEN;
 
        if ((ptr[6] != 0xff) || (ptr[7] != 0xff))
                return GSS_S_DEFECTIVE_TOKEN;
 
-       if (gss_decrypt_xdr_buf(kctx->enc, buf,
-                       ptr + GSS_KRB5_TOK_HDR_LEN + 8 - (unsigned char *)buf->head[0].iov_base))
+       /*
+        * Data starts after token header and checksum.  ptr points
+        * to the beginning of the token header
+        */
+       crypt_offset = ptr + (GSS_KRB5_TOK_HDR_LEN + kctx->gk5e->cksumlength) -
+                                       (unsigned char *)buf->head[0].iov_base;
+       if (gss_decrypt_xdr_buf(kctx->enc, buf, crypt_offset))
                return GSS_S_DEFECTIVE_TOKEN;
 
-       if (make_checksum("md5", ptr, 8, buf,
-                ptr + GSS_KRB5_TOK_HDR_LEN + 8 - (unsigned char *)buf->head[0].iov_base, &md5cksum))
+       if (make_checksum((char *)kctx->gk5e->cksum_name, ptr, 8, buf,
+                                               crypt_offset, &md5cksum))
                return GSS_S_FAILURE;
 
        if (krb5_encrypt(kctx->seq, NULL, md5cksum.data,
@@ -280,7 +320,8 @@ gss_unwrap_kerberos_v1(struct krb5_ctx *kctx, int offset, struct xdr_buf *buf)
         * better to copy and encrypt at the same time. */
 
        blocksize = crypto_blkcipher_blocksize(kctx->enc);
-       data_start = ptr + GSS_KRB5_TOK_HDR_LEN + 8 + blocksize;
+       data_start = ptr + (GSS_KRB5_TOK_HDR_LEN + kctx->gk5e->cksumlength) +
+                                       blocksize;
        orig_start = buf->head[0].iov_base + offset;
        data_len = (buf->head[0].iov_base + buf->head[0].iov_len) - data_start;
        memmove(orig_start, data_start, data_len);