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crypto/krb5: Implement the Kerberos5 rfc3961 get_mic and verify_mic

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Add functions that sign and verify a message according to rfc3961 sec 5.4,
using Kc to generate a checksum and insert it into the MIC field in the
skbuff in the sign phase then checksum the data and compare it to the MIC
in the verify phase.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Herbert Xu <herbert@gondor.apana.org.au>
cc: "David S. Miller" <davem@davemloft.net>
cc: Chuck Lever <chuck.lever@oracle.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: Eric Dumazet <edumazet@google.com>
cc: Jakub Kicinski <kuba@kernel.org>
cc: Paolo Abeni <pabeni@redhat.com>
cc: Simon Horman <horms@kernel.org>
cc: linux-afs@lists.infradead.org
cc: linux-nfs@vger.kernel.org
cc: linux-crypto@vger.kernel.org
cc: netdev@vger.kernel.org
This commit is contained in:
David Howells 2020-09-24 10:23:48 +01:00
parent 00244da40f
commit 348f5669d1
2 changed files with 140 additions and 0 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

10
crypto/krb5/internal.h
View file

@ -169,3 +169,13 @@ int krb5_aead_decrypt(const struct krb5_enctype *krb5,
struct crypto_aead *aead,
struct scatterlist *sg, unsigned int nr_sg,
size_t *_offset, size_t *_len);
ssize_t rfc3961_get_mic(const struct krb5_enctype *krb5,
struct crypto_shash *shash,
const struct krb5_buffer *metadata,
struct scatterlist *sg, unsigned int nr_sg, size_t sg_len,
size_t data_offset, size_t data_len);
int rfc3961_verify_mic(const struct krb5_enctype *krb5,
struct crypto_shash *shash,
const struct krb5_buffer *metadata,
struct scatterlist *sg, unsigned int nr_sg,
size_t *_offset, size_t *_len);

130
crypto/krb5/rfc3961_simplified.c
View file

@ -653,6 +653,134 @@ error:
return ret;
}
/*
* Generate a checksum over some metadata and part of an skbuff and insert the
* MIC into the skbuff immediately prior to the data.
*/
ssize_t rfc3961_get_mic(const struct krb5_enctype *krb5,
struct crypto_shash *shash,
const struct krb5_buffer *metadata,
struct scatterlist *sg, unsigned int nr_sg, size_t sg_len,
size_t data_offset, size_t data_len)
{
struct shash_desc *desc;
ssize_t ret, done;
size_t bsize;
void *buffer, *digest;
if (WARN_ON(data_offset != krb5->cksum_len))
return -EMSGSIZE;
bsize = krb5_shash_size(shash) +
krb5_digest_size(shash);
buffer = kzalloc(bsize, GFP_NOFS);
if (!buffer)
return -ENOMEM;
/* Calculate the MIC with key Kc and store it into the skb */
desc = buffer;
desc->tfm = shash;
ret = crypto_shash_init(desc);
if (ret < 0)
goto error;
if (metadata) {
ret = crypto_shash_update(desc, metadata->data, metadata->len);
if (ret < 0)
goto error;
}
ret = crypto_shash_update_sg(desc, sg, data_offset, data_len);
if (ret < 0)
goto error;
digest = buffer + krb5_shash_size(shash);
ret = crypto_shash_final(desc, digest);
if (ret < 0)
goto error;
ret = -EFAULT;
done = sg_pcopy_from_buffer(sg, nr_sg, digest, krb5->cksum_len,
data_offset - krb5->cksum_len);
if (done != krb5->cksum_len)
goto error;
ret = krb5->cksum_len + data_len;
error:
kfree_sensitive(buffer);
return ret;
}
/*
* Check the MIC on a region of an skbuff. The offset and length are updated
* to reflect the actual content of the secure region.
*/
int rfc3961_verify_mic(const struct krb5_enctype *krb5,
struct crypto_shash *shash,
const struct krb5_buffer *metadata,
struct scatterlist *sg, unsigned int nr_sg,
size_t *_offset, size_t *_len)
{
struct shash_desc *desc;
ssize_t done;
size_t bsize, data_offset, data_len, offset = *_offset, len = *_len;
void *buffer = NULL;
int ret;
u8 *cksum, *cksum2;
if (len < krb5->cksum_len)
return -EPROTO;
data_offset = offset + krb5->cksum_len;
data_len = len - krb5->cksum_len;
bsize = krb5_shash_size(shash) +
krb5_digest_size(shash) * 2;
buffer = kzalloc(bsize, GFP_NOFS);
if (!buffer)
return -ENOMEM;
cksum = buffer +
krb5_shash_size(shash);
cksum2 = buffer +
krb5_shash_size(shash) +
krb5_digest_size(shash);
/* Calculate the MIC */
desc = buffer;
desc->tfm = shash;
ret = crypto_shash_init(desc);
if (ret < 0)
goto error;
if (metadata) {
ret = crypto_shash_update(desc, metadata->data, metadata->len);
if (ret < 0)
goto error;
}
crypto_shash_update_sg(desc, sg, data_offset, data_len);
crypto_shash_final(desc, cksum);
ret = -EFAULT;
done = sg_pcopy_to_buffer(sg, nr_sg, cksum2, krb5->cksum_len, offset);
if (done != krb5->cksum_len)
goto error;
if (memcmp(cksum, cksum2, krb5->cksum_len) != 0) {
ret = -EBADMSG;
goto error;
}
*_offset += krb5->cksum_len;
*_len -= krb5->cksum_len;
ret = 0;
error:
kfree_sensitive(buffer);
return ret;
}
const struct krb5_crypto_profile rfc3961_simplified_profile = {
.calc_PRF = rfc3961_calc_PRF,
.calc_Kc = rfc3961_calc_DK,
@ -664,4 +792,6 @@ const struct krb5_crypto_profile rfc3961_simplified_profile = {
.load_checksum_key = rfc3961_load_checksum_key,
.encrypt = krb5_aead_encrypt,
.decrypt = krb5_aead_decrypt,
.get_mic = rfc3961_get_mic,
.verify_mic = rfc3961_verify_mic,
};