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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 10/18] crypto/krb5: Implement the AES encrypt/decrypt from rfc8009 From: David Howells To: herbert@gondor.apana.org.au, bfields@fieldses.org Cc: dhowells@redhat.com, trond.myklebust@hammerspace.com, linux-crypto@vger.kernel.org, linux-afs@lists.infradead.org, linux-cifs@vger.kernel.org, linux-nfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Date: Thu, 12 Nov 2020 12:59:06 +0000 Message-ID: <160518594688.2277919.5319312384536950170.stgit@warthog.procyon.org.uk> In-Reply-To: <160518586534.2277919.14475638653680231924.stgit@warthog.procyon.org.uk> References: <160518586534.2277919.14475638653680231924.stgit@warthog.procyon.org.uk> User-Agent: StGit/0.23 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Implement encryption and decryption functions for AES + HMAC-SHA2 as described in rfc8009 sec 5. Signed-off-by: David Howells --- crypto/krb5/rfc8009_aes2.c | 205 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 203 insertions(+), 2 deletions(-) diff --git a/crypto/krb5/rfc8009_aes2.c b/crypto/krb5/rfc8009_aes2.c index 9f0f0f410d91..df517435be73 100644 --- a/crypto/krb5/rfc8009_aes2.c +++ b/crypto/krb5/rfc8009_aes2.c @@ -10,6 +10,7 @@ #include #include #include +#include #include "internal.h" static const struct krb5_buffer rfc8009_no_context = { .len = 0, .data = "" }; @@ -183,13 +184,213 @@ static int rfc8009_random_to_key(const struct krb5_enctype *krb5, return 0; } +/* + * Apply encryption and checksumming functions to part of an skbuff. + */ +static ssize_t rfc8009_encrypt(const struct krb5_enctype *krb5, + struct krb5_enc_keys *keys, + struct scatterlist *sg, unsigned nr_sg, size_t sg_len, + size_t data_offset, size_t data_len, + bool preconfounded) +{ + struct skcipher_request *req; + struct shash_desc *desc; + ssize_t ret, done; + size_t bsize, base_len, secure_offset, secure_len, pad_len, cksum_offset; + void *buffer; + u8 *cksum, *iv; + + if (WARN_ON(data_offset != krb5->conf_len)) + return -EINVAL; /* Can't set offset on skcipher */ + + base_len = krb5->conf_len + data_len; + secure_len = base_len; + pad_len = secure_len - base_len; + secure_offset = 0; + cksum_offset = secure_offset + secure_len; + + bsize = krb5_shash_size(keys->Ki) + + krb5_digest_size(keys->Ki) + + krb5_sync_skcipher_size(keys->Ke) + + krb5_sync_skcipher_ivsize(keys->Ke); + bsize = max_t(size_t, bsize, krb5->conf_len); + bsize = max_t(size_t, bsize, krb5->block_len); + buffer = kzalloc(bsize, GFP_NOFS); + if (!buffer) + return -ENOMEM; + + /* Insert the confounder into the skb */ + ret = -EFAULT; + if (!preconfounded) { + get_random_bytes(buffer, krb5->conf_len); + done = sg_pcopy_to_buffer(sg, nr_sg, buffer, krb5->conf_len, + secure_offset); + if (done != krb5->conf_len) + goto error; + } + + /* We need to pad out to the crypto blocksize. */ + if (pad_len) { + done = sg_zero_buffer(sg, nr_sg, pad_len, data_offset + data_len); + if (done != pad_len) + goto error; + } + + /* Encrypt the secure region with key Ke. */ + req = buffer + + krb5_shash_size(keys->Ki) + + krb5_digest_size(keys->Ki); + iv = buffer + + krb5_shash_size(keys->Ki) + + krb5_digest_size(keys->Ki) + + krb5_sync_skcipher_size(keys->Ke); + + skcipher_request_set_sync_tfm(req, keys->Ke); + skcipher_request_set_callback(req, 0, NULL, NULL); + skcipher_request_set_crypt(req, sg, sg, secure_len, iv); + ret = crypto_skcipher_encrypt(req); + if (ret < 0) + goto error; + + /* Calculate the checksum using key Ki */ + cksum = buffer + krb5_shash_size(keys->Ki); + + desc = buffer; + desc->tfm = keys->Ki; + ret = crypto_shash_init(desc); + if (ret < 0) + goto error; + + memset(iv, 0, crypto_sync_skcipher_ivsize(keys->Ke)); + ret = crypto_shash_update(desc, iv, crypto_sync_skcipher_ivsize(keys->Ke)); + if (ret < 0) + goto error; + + ret = crypto_shash_update_sg(desc, sg, secure_offset, secure_len); + if (ret < 0) + goto error; + + ret = crypto_shash_final(desc, cksum); + if (ret < 0) + goto error; + + /* Append the checksum into the buffer. */ + ret = -EFAULT; + sg_zero_buffer(sg, nr_sg, 3, cksum_offset); + done = sg_pcopy_from_buffer(sg, nr_sg, cksum, krb5->cksum_len, cksum_offset); + if (done != krb5->cksum_len) + goto error; + + ret = secure_len + krb5->cksum_len; + +error: + kfree_sensitive(buffer); + return ret; +} + +/* + * Apply decryption and checksumming functions to part of an skbuff. The + * offset and length are updated to reflect the actual content of the encrypted + * region. + */ +static int rfc8009_decrypt(const struct krb5_enctype *krb5, + struct krb5_enc_keys *keys, + struct scatterlist *sg, unsigned nr_sg, + size_t *_offset, size_t *_len, + int *_error_code) +{ + struct skcipher_request *req; + struct shash_desc *desc; + ssize_t done; + size_t bsize, secure_len, offset = *_offset, len = *_len; + void *buffer = NULL; + int ret; + u8 *cksum, *cksum2, *iv; + + if (WARN_ON(*_offset != 0)) + return -EINVAL; /* Can't set offset on skcipher */ + + if (len < krb5->conf_len + krb5->cksum_len) { + *_error_code = 1; //RXGK_SEALED_INCON; + return -EPROTO; + } + secure_len = len - krb5->cksum_len; + + bsize = krb5_shash_size(keys->Ki) + + krb5_digest_size(keys->Ki) * 2 + + krb5_sync_skcipher_size(keys->Ke) + + krb5_sync_skcipher_ivsize(keys->Ke); + buffer = kzalloc(bsize, GFP_NOFS); + if (!buffer) + return -ENOMEM; + + cksum = buffer + + krb5_shash_size(keys->Ki); + cksum2 = buffer + + krb5_shash_size(keys->Ki) + + krb5_digest_size(keys->Ki); + req = buffer + + krb5_shash_size(keys->Ki) + + krb5_digest_size(keys->Ki) * 2; + iv = buffer + + krb5_shash_size(keys->Ki) + + krb5_digest_size(keys->Ki) * 2 + + krb5_sync_skcipher_size(keys->Ke); + + /* Calculate the checksum using key Ki */ + desc = buffer; + desc->tfm = keys->Ki; + ret = crypto_shash_init(desc); + if (ret < 0) + goto error; + + ret = crypto_shash_update(desc, iv, crypto_sync_skcipher_ivsize(keys->Ke)); + if (ret < 0) + goto error; + + ret = crypto_shash_update_sg(desc, sg, 0, secure_len); + if (ret < 0) + goto error; + + ret = crypto_shash_final(desc, cksum); + if (ret < 0) + goto error; + + /* Get the checksum from the buffer. */ + ret = -EFAULT; + done = sg_pcopy_to_buffer(sg, nr_sg, cksum2, krb5->cksum_len, + offset + len - krb5->cksum_len); + if (done != krb5->cksum_len) + goto error; + + if (memcmp(cksum, cksum2, krb5->cksum_len) != 0) { + *_error_code = 1; //RXGK_SEALED_INCON; + ret = -EPROTO; + goto error; + } + + /* Decrypt the secure region with key Ke. */ + skcipher_request_set_sync_tfm(req, keys->Ke); + skcipher_request_set_callback(req, 0, NULL, NULL); + skcipher_request_set_crypt(req, sg, sg, secure_len, iv); + ret = crypto_skcipher_decrypt(req); + + *_offset += krb5->conf_len; + *_len -= krb5->conf_len + krb5->cksum_len; + ret = 0; + +error: + kfree_sensitive(buffer); + return ret; +} + static const struct krb5_crypto_profile rfc8009_crypto_profile = { .calc_PRF = rfc8009_calc_PRF, .calc_Kc = rfc8009_calc_Ki, .calc_Ke = rfc8009_calc_Ke, .calc_Ki = rfc8009_calc_Ki, - .encrypt = NULL, //rfc8009_encrypt, - .decrypt = NULL, //rfc8009_decrypt, + .encrypt = rfc8009_encrypt, + .decrypt = rfc8009_decrypt, .get_mic = rfc3961_get_mic, .verify_mic = rfc3961_verify_mic, };