Commit 348f5669 authored by David Howells's avatar David Howells
Browse files

crypto/krb5: Implement the Kerberos5 rfc3961 get_mic and verify_mic 



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: default avatarDavid 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
parent 00244da4

crypto/krb5/internal.h

+10 −0
Original line number Diff line number Diff line
@@ -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);

crypto/krb5/rfc3961_simplified.c

+130 −0
Original line number Diff line number Diff line
@@ -653,6 +653,134 @@ int krb5_aead_decrypt(const struct krb5_enctype *krb5, 
	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,

};