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gss_krb5: add ability to have a keyed checksum (hmac)
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Encryption types besides DES may use a keyed checksum (hmac).
Modify the make_checksum() function to allow for a key
and take care of enctype-specific processing such as truncating
the resulting hash.

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>
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Kevin Coffman authored and Trond Myklebust committed May 14, 2010
1 parent 81d4a43 commit e1f6c07
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Showing 6 changed files with 88 additions and 34 deletions.
11 changes: 8 additions & 3 deletions include/linux/sunrpc/gss_krb5.h
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Original file line number Diff line number Diff line change
Expand Up @@ -41,6 +41,9 @@
#include <linux/sunrpc/gss_err.h>
#include <linux/sunrpc/gss_asn1.h>

/* Maximum key length (in bytes) for the supported crypto algorithms*/
#define GSS_KRB5_MAX_KEYLEN (32)

/* Maximum checksum function output for the supported crypto algorithms */
#define GSS_KRB5_MAX_CKSUM_LEN (20)

Expand Down Expand Up @@ -74,6 +77,7 @@ struct krb5_ctx {
const struct gss_krb5_enctype *gk5e; /* enctype-specific info */
struct crypto_blkcipher *enc;
struct crypto_blkcipher *seq;
u8 cksum[GSS_KRB5_MAX_KEYLEN];
s32 endtime;
u32 seq_send;
struct xdr_netobj mech_used;
Expand Down Expand Up @@ -159,9 +163,10 @@ enum seal_alg {
+ GSS_KRB5_TOK_HDR_LEN \
+ GSS_KRB5_MAX_CKSUM_LEN)

s32
make_checksum(char *, char *header, int hdrlen, struct xdr_buf *body,
int body_offset, struct xdr_netobj *cksum);
u32
make_checksum(struct krb5_ctx *kctx, char *header, int hdrlen,
struct xdr_buf *body, int body_offset, u8 *cksumkey,
struct xdr_netobj *cksumout);

u32 gss_get_mic_kerberos(struct gss_ctx *, struct xdr_buf *,
struct xdr_netobj *);
Expand Down
54 changes: 46 additions & 8 deletions net/sunrpc/auth_gss/gss_krb5_crypto.c
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Original file line number Diff line number Diff line change
Expand Up @@ -123,21 +123,42 @@ checksummer(struct scatterlist *sg, void *data)
return crypto_hash_update(desc, sg, sg->length);
}

/* checksum the plaintext data and hdrlen bytes of the token header */
s32
make_checksum(char *cksumname, char *header, int hdrlen, struct xdr_buf *body,
int body_offset, struct xdr_netobj *cksum)
/*
* checksum the plaintext data and hdrlen bytes of the token header
* The checksum is performed over the first 8 bytes of the
* gss token header and then over the data body
*/
u32
make_checksum(struct krb5_ctx *kctx, char *header, int hdrlen,
struct xdr_buf *body, int body_offset, u8 *cksumkey,
struct xdr_netobj *cksumout)
{
struct hash_desc desc; /* XXX add to ctx? */
struct hash_desc desc;
struct scatterlist sg[1];
int err;
u8 checksumdata[GSS_KRB5_MAX_CKSUM_LEN];
unsigned int checksumlen;

if (cksumout->len < kctx->gk5e->cksumlength) {
dprintk("%s: checksum buffer length, %u, too small for %s\n",
__func__, cksumout->len, kctx->gk5e->name);
return GSS_S_FAILURE;
}

desc.tfm = crypto_alloc_hash(cksumname, 0, CRYPTO_ALG_ASYNC);
desc.tfm = crypto_alloc_hash(kctx->gk5e->cksum_name, 0, CRYPTO_ALG_ASYNC);
if (IS_ERR(desc.tfm))
return GSS_S_FAILURE;
cksum->len = crypto_hash_digestsize(desc.tfm);
desc.flags = CRYPTO_TFM_REQ_MAY_SLEEP;

checksumlen = crypto_hash_digestsize(desc.tfm);

if (cksumkey != NULL) {
err = crypto_hash_setkey(desc.tfm, cksumkey,
kctx->gk5e->keylength);
if (err)
goto out;
}

err = crypto_hash_init(&desc);
if (err)
goto out;
Expand All @@ -149,8 +170,25 @@ make_checksum(char *cksumname, char *header, int hdrlen, struct xdr_buf *body,
checksummer, &desc);
if (err)
goto out;
err = crypto_hash_final(&desc, cksum->data);
err = crypto_hash_final(&desc, checksumdata);
if (err)
goto out;

switch (kctx->gk5e->ctype) {
case CKSUMTYPE_RSA_MD5:
err = kctx->gk5e->encrypt(kctx->seq, NULL, checksumdata,
checksumdata, checksumlen);
if (err)
goto out;
memcpy(cksumout->data,
checksumdata + checksumlen - kctx->gk5e->cksumlength,
kctx->gk5e->cksumlength);
break;
default:
BUG();
break;
}
cksumout->len = kctx->gk5e->cksumlength;
out:
crypto_free_hash(desc.tfm);
return err ? GSS_S_FAILURE : 0;
Expand Down
1 change: 1 addition & 0 deletions net/sunrpc/auth_gss/gss_krb5_mech.c
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Original file line number Diff line number Diff line change
Expand Up @@ -66,6 +66,7 @@ static const struct gss_krb5_enctype supported_gss_krb5_enctypes[] = {
.keylength = 8,
.blocksize = 8,
.cksumlength = 8,
.keyed_cksum = 0,
},
};

Expand Down
13 changes: 7 additions & 6 deletions net/sunrpc/auth_gss/gss_krb5_seal.c
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Original file line number Diff line number Diff line change
Expand Up @@ -101,6 +101,7 @@ gss_get_mic_v1(struct krb5_ctx *ctx, struct xdr_buf *text,
void *ptr;
s32 now;
u32 seq_send;
u8 *cksumkey;

dprintk("RPC: %s\n", __func__);
BUG_ON(ctx == NULL);
Expand All @@ -109,15 +110,15 @@ gss_get_mic_v1(struct krb5_ctx *ctx, struct xdr_buf *text,

ptr = setup_token(ctx, token);

if (make_checksum((char *)ctx->gk5e->cksum_name, ptr, 8,
text, 0, &md5cksum))
return GSS_S_FAILURE;
if (ctx->gk5e->keyed_cksum)
cksumkey = ctx->cksum;
else
cksumkey = NULL;

if (krb5_encrypt(ctx->seq, NULL, md5cksum.data,
md5cksum.data, md5cksum.len))
if (make_checksum(ctx, ptr, 8, text, 0, cksumkey, &md5cksum))
return GSS_S_FAILURE;

memcpy(ptr + GSS_KRB5_TOK_HDR_LEN, md5cksum.data + md5cksum.len - 8, 8);
memcpy(ptr + GSS_KRB5_TOK_HDR_LEN, md5cksum.data, md5cksum.len);

spin_lock(&krb5_seq_lock);
seq_send = ctx->seq_send++;
Expand Down
13 changes: 8 additions & 5 deletions net/sunrpc/auth_gss/gss_krb5_unseal.c
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Original file line number Diff line number Diff line change
Expand Up @@ -84,6 +84,7 @@ gss_verify_mic_v1(struct krb5_ctx *ctx,
u32 seqnum;
unsigned char *ptr = (unsigned char *)read_token->data;
int bodysize;
u8 *cksumkey;

dprintk("RPC: krb5_read_token\n");

Expand All @@ -108,14 +109,16 @@ gss_verify_mic_v1(struct krb5_ctx *ctx,
if ((ptr[6] != 0xff) || (ptr[7] != 0xff))
return GSS_S_DEFECTIVE_TOKEN;

if (make_checksum((char *)ctx->gk5e->cksum_name, ptr, 8,
message_buffer, 0, &md5cksum))
return GSS_S_FAILURE;
if (ctx->gk5e->keyed_cksum)
cksumkey = ctx->cksum;
else
cksumkey = NULL;

if (krb5_encrypt(ctx->seq, NULL, md5cksum.data, md5cksum.data, 16))
if (make_checksum(ctx, ptr, 8, message_buffer, 0,
cksumkey, &md5cksum))
return GSS_S_FAILURE;

if (memcmp(md5cksum.data + 8, ptr + GSS_KRB5_TOK_HDR_LEN,
if (memcmp(md5cksum.data, ptr + GSS_KRB5_TOK_HDR_LEN,
ctx->gk5e->cksumlength))
return GSS_S_BAD_SIG;

Expand Down
30 changes: 18 additions & 12 deletions net/sunrpc/auth_gss/gss_krb5_wrap.c
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Original file line number Diff line number Diff line change
Expand Up @@ -167,6 +167,7 @@ gss_wrap_kerberos_v1(struct krb5_ctx *kctx, int offset,
int headlen;
struct page **tmp_pages;
u32 seq_send;
u8 *cksumkey;

dprintk("RPC: %s\n", __func__);

Expand Down Expand Up @@ -205,18 +206,20 @@ gss_wrap_kerberos_v1(struct krb5_ctx *kctx, int offset,

make_confounder(msg_start, blocksize);

if (kctx->gk5e->keyed_cksum)
cksumkey = kctx->cksum;
else
cksumkey = NULL;

/* XXXJBF: UGH!: */
tmp_pages = buf->pages;
buf->pages = pages;
if (make_checksum((char *)kctx->gk5e->cksum_name, ptr, 8, buf,
offset + headlen - blocksize, &md5cksum))
if (make_checksum(kctx, ptr, 8, buf, offset + headlen - blocksize,
cksumkey, &md5cksum))
return GSS_S_FAILURE;
buf->pages = tmp_pages;

if (krb5_encrypt(kctx->seq, NULL, md5cksum.data,
md5cksum.data, md5cksum.len))
return GSS_S_FAILURE;
memcpy(ptr + GSS_KRB5_TOK_HDR_LEN, md5cksum.data + md5cksum.len - 8, 8);
memcpy(ptr + GSS_KRB5_TOK_HDR_LEN, md5cksum.data, md5cksum.len);

spin_lock(&krb5_seq_lock);
seq_send = kctx->seq_send++;
Expand Down Expand Up @@ -252,6 +255,7 @@ gss_unwrap_kerberos_v1(struct krb5_ctx *kctx, int offset, struct xdr_buf *buf)
int data_len;
int blocksize;
int crypt_offset;
u8 *cksumkey;

dprintk("RPC: gss_unwrap_kerberos\n");

Expand Down Expand Up @@ -288,15 +292,17 @@ gss_unwrap_kerberos_v1(struct krb5_ctx *kctx, int offset, struct xdr_buf *buf)
if (gss_decrypt_xdr_buf(kctx->enc, buf, crypt_offset))
return GSS_S_DEFECTIVE_TOKEN;

if (make_checksum((char *)kctx->gk5e->cksum_name, ptr, 8, buf,
crypt_offset, &md5cksum))
return GSS_S_FAILURE;
if (kctx->gk5e->keyed_cksum)
cksumkey = kctx->cksum;
else
cksumkey = NULL;

if (krb5_encrypt(kctx->seq, NULL, md5cksum.data,
md5cksum.data, md5cksum.len))
if (make_checksum(kctx, ptr, 8, buf, crypt_offset,
cksumkey, &md5cksum))
return GSS_S_FAILURE;

if (memcmp(md5cksum.data + 8, ptr + GSS_KRB5_TOK_HDR_LEN, 8))
if (memcmp(md5cksum.data, ptr + GSS_KRB5_TOK_HDR_LEN,
kctx->gk5e->cksumlength))
return GSS_S_BAD_SIG;

/* it got through unscathed. Make sure the context is unexpired */
Expand Down

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