diff options
Diffstat (limited to 'crypto/krb5enc.c')
| -rw-r--r-- | crypto/krb5enc.c | 504 |
1 files changed, 504 insertions, 0 deletions
diff --git a/crypto/krb5enc.c b/crypto/krb5enc.c new file mode 100644 index 000000000000..d07769bf149e --- /dev/null +++ b/crypto/krb5enc.c @@ -0,0 +1,504 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * AEAD wrapper for Kerberos 5 RFC3961 simplified profile. + * + * Copyright (C) 2025 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + * + * Derived from authenc: + * Copyright (c) 2007-2015 Herbert Xu <herbert@gondor.apana.org.au> + */ + +#include <crypto/internal/aead.h> +#include <crypto/internal/hash.h> +#include <crypto/internal/skcipher.h> +#include <crypto/authenc.h> +#include <crypto/scatterwalk.h> +#include <linux/err.h> +#include <linux/init.h> +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/rtnetlink.h> +#include <linux/slab.h> +#include <linux/spinlock.h> + +struct krb5enc_instance_ctx { + struct crypto_ahash_spawn auth; + struct crypto_skcipher_spawn enc; + unsigned int reqoff; +}; + +struct krb5enc_ctx { + struct crypto_ahash *auth; + struct crypto_skcipher *enc; +}; + +struct krb5enc_request_ctx { + struct scatterlist src[2]; + struct scatterlist dst[2]; + char tail[]; +}; + +static void krb5enc_request_complete(struct aead_request *req, int err) +{ + if (err != -EINPROGRESS) + aead_request_complete(req, err); +} + +/** + * crypto_krb5enc_extractkeys - Extract Ke and Ki keys from the key blob. + * @keys: Where to put the key sizes and pointers + * @key: Encoded key material + * @keylen: Amount of key material + * + * Decode the key blob we're given. It starts with an rtattr that indicates + * the format and the length. Format CRYPTO_AUTHENC_KEYA_PARAM is: + * + * rtattr || __be32 enckeylen || authkey || enckey + * + * Note that the rtattr is in cpu-endian form, unlike enckeylen. This must be + * handled correctly in static testmgr data. + */ +int crypto_krb5enc_extractkeys(struct crypto_authenc_keys *keys, const u8 *key, + unsigned int keylen) +{ + struct rtattr *rta = (struct rtattr *)key; + struct crypto_authenc_key_param *param; + + if (!RTA_OK(rta, keylen)) + return -EINVAL; + if (rta->rta_type != CRYPTO_AUTHENC_KEYA_PARAM) + return -EINVAL; + + /* + * RTA_OK() didn't align the rtattr's payload when validating that it + * fits in the buffer. Yet, the keys should start on the next 4-byte + * aligned boundary. To avoid confusion, require that the rtattr + * payload be exactly the param struct, which has a 4-byte aligned size. + */ + if (RTA_PAYLOAD(rta) != sizeof(*param)) + return -EINVAL; + BUILD_BUG_ON(sizeof(*param) % RTA_ALIGNTO); + + param = RTA_DATA(rta); + keys->enckeylen = be32_to_cpu(param->enckeylen); + + key += rta->rta_len; + keylen -= rta->rta_len; + + if (keylen < keys->enckeylen) + return -EINVAL; + + keys->authkeylen = keylen - keys->enckeylen; + keys->authkey = key; + keys->enckey = key + keys->authkeylen; + return 0; +} +EXPORT_SYMBOL(crypto_krb5enc_extractkeys); + +static int krb5enc_setkey(struct crypto_aead *krb5enc, const u8 *key, + unsigned int keylen) +{ + struct crypto_authenc_keys keys; + struct krb5enc_ctx *ctx = crypto_aead_ctx(krb5enc); + struct crypto_skcipher *enc = ctx->enc; + struct crypto_ahash *auth = ctx->auth; + unsigned int flags = crypto_aead_get_flags(krb5enc); + int err = -EINVAL; + + if (crypto_krb5enc_extractkeys(&keys, key, keylen) != 0) + goto out; + + crypto_ahash_clear_flags(auth, CRYPTO_TFM_REQ_MASK); + crypto_ahash_set_flags(auth, flags & CRYPTO_TFM_REQ_MASK); + err = crypto_ahash_setkey(auth, keys.authkey, keys.authkeylen); + if (err) + goto out; + + crypto_skcipher_clear_flags(enc, CRYPTO_TFM_REQ_MASK); + crypto_skcipher_set_flags(enc, flags & CRYPTO_TFM_REQ_MASK); + err = crypto_skcipher_setkey(enc, keys.enckey, keys.enckeylen); +out: + memzero_explicit(&keys, sizeof(keys)); + return err; +} + +static void krb5enc_encrypt_done(void *data, int err) +{ + struct aead_request *req = data; + + krb5enc_request_complete(req, err); +} + +/* + * Start the encryption of the plaintext. We skip over the associated data as + * that only gets included in the hash. + */ +static int krb5enc_dispatch_encrypt(struct aead_request *req, + unsigned int flags) +{ + struct crypto_aead *krb5enc = crypto_aead_reqtfm(req); + struct aead_instance *inst = aead_alg_instance(krb5enc); + struct krb5enc_ctx *ctx = crypto_aead_ctx(krb5enc); + struct krb5enc_instance_ctx *ictx = aead_instance_ctx(inst); + struct krb5enc_request_ctx *areq_ctx = aead_request_ctx(req); + struct crypto_skcipher *enc = ctx->enc; + struct skcipher_request *skreq = (void *)(areq_ctx->tail + + ictx->reqoff); + struct scatterlist *src, *dst; + + src = scatterwalk_ffwd(areq_ctx->src, req->src, req->assoclen); + if (req->src == req->dst) + dst = src; + else + dst = scatterwalk_ffwd(areq_ctx->dst, req->dst, req->assoclen); + + skcipher_request_set_tfm(skreq, enc); + skcipher_request_set_callback(skreq, aead_request_flags(req), + krb5enc_encrypt_done, req); + skcipher_request_set_crypt(skreq, src, dst, req->cryptlen, req->iv); + + return crypto_skcipher_encrypt(skreq); +} + +/* + * Insert the hash into the checksum field in the destination buffer directly + * after the encrypted region. + */ +static void krb5enc_insert_checksum(struct aead_request *req, u8 *hash) +{ + struct crypto_aead *krb5enc = crypto_aead_reqtfm(req); + + scatterwalk_map_and_copy(hash, req->dst, + req->assoclen + req->cryptlen, + crypto_aead_authsize(krb5enc), 1); +} + +/* + * Upon completion of an asynchronous digest, transfer the hash to the checksum + * field. + */ +static void krb5enc_encrypt_ahash_done(void *data, int err) +{ + struct aead_request *req = data; + struct crypto_aead *krb5enc = crypto_aead_reqtfm(req); + struct aead_instance *inst = aead_alg_instance(krb5enc); + struct krb5enc_instance_ctx *ictx = aead_instance_ctx(inst); + struct krb5enc_request_ctx *areq_ctx = aead_request_ctx(req); + struct ahash_request *ahreq = (void *)(areq_ctx->tail + ictx->reqoff); + + if (err) + return krb5enc_request_complete(req, err); + + krb5enc_insert_checksum(req, ahreq->result); + + err = krb5enc_dispatch_encrypt(req, 0); + if (err != -EINPROGRESS) + aead_request_complete(req, err); +} + +/* + * Start the digest of the plaintext for encryption. In theory, this could be + * run in parallel with the encryption, provided the src and dst buffers don't + * overlap. + */ +static int krb5enc_dispatch_encrypt_hash(struct aead_request *req) +{ + struct crypto_aead *krb5enc = crypto_aead_reqtfm(req); + struct aead_instance *inst = aead_alg_instance(krb5enc); + struct krb5enc_ctx *ctx = crypto_aead_ctx(krb5enc); + struct krb5enc_instance_ctx *ictx = aead_instance_ctx(inst); + struct crypto_ahash *auth = ctx->auth; + struct krb5enc_request_ctx *areq_ctx = aead_request_ctx(req); + struct ahash_request *ahreq = (void *)(areq_ctx->tail + ictx->reqoff); + u8 *hash = areq_ctx->tail; + int err; + + ahash_request_set_callback(ahreq, aead_request_flags(req), + krb5enc_encrypt_ahash_done, req); + ahash_request_set_tfm(ahreq, auth); + ahash_request_set_crypt(ahreq, req->src, hash, req->assoclen + req->cryptlen); + + err = crypto_ahash_digest(ahreq); + if (err) + return err; + + krb5enc_insert_checksum(req, hash); + return 0; +} + +/* + * Process an encryption operation. We can perform the cipher and the hash in + * parallel, provided the src and dst buffers are separate. + */ +static int krb5enc_encrypt(struct aead_request *req) +{ + int err; + + err = krb5enc_dispatch_encrypt_hash(req); + if (err < 0) + return err; + + return krb5enc_dispatch_encrypt(req, aead_request_flags(req)); +} + +static int krb5enc_verify_hash(struct aead_request *req) +{ + struct crypto_aead *krb5enc = crypto_aead_reqtfm(req); + struct aead_instance *inst = aead_alg_instance(krb5enc); + struct krb5enc_instance_ctx *ictx = aead_instance_ctx(inst); + struct krb5enc_request_ctx *areq_ctx = aead_request_ctx(req); + struct ahash_request *ahreq = (void *)(areq_ctx->tail + ictx->reqoff); + unsigned int authsize = crypto_aead_authsize(krb5enc); + u8 *calc_hash = areq_ctx->tail; + u8 *msg_hash = areq_ctx->tail + authsize; + + scatterwalk_map_and_copy(msg_hash, req->src, ahreq->nbytes, authsize, 0); + + if (crypto_memneq(msg_hash, calc_hash, authsize)) + return -EBADMSG; + return 0; +} + +static void krb5enc_decrypt_hash_done(void *data, int err) +{ + struct aead_request *req = data; + + if (err) + return krb5enc_request_complete(req, err); + + err = krb5enc_verify_hash(req); + krb5enc_request_complete(req, err); +} + +/* + * Dispatch the hashing of the plaintext after we've done the decryption. + */ +static int krb5enc_dispatch_decrypt_hash(struct aead_request *req) +{ + struct crypto_aead *krb5enc = crypto_aead_reqtfm(req); + struct aead_instance *inst = aead_alg_instance(krb5enc); + struct krb5enc_ctx *ctx = crypto_aead_ctx(krb5enc); + struct krb5enc_instance_ctx *ictx = aead_instance_ctx(inst); + struct krb5enc_request_ctx *areq_ctx = aead_request_ctx(req); + struct ahash_request *ahreq = (void *)(areq_ctx->tail + ictx->reqoff); + struct crypto_ahash *auth = ctx->auth; + unsigned int authsize = crypto_aead_authsize(krb5enc); + u8 *hash = areq_ctx->tail; + int err; + + ahash_request_set_tfm(ahreq, auth); + ahash_request_set_crypt(ahreq, req->dst, hash, + req->assoclen + req->cryptlen - authsize); + ahash_request_set_callback(ahreq, aead_request_flags(req), + krb5enc_decrypt_hash_done, req); + + err = crypto_ahash_digest(ahreq); + if (err < 0) + return err; + + return krb5enc_verify_hash(req); +} + +/* + * Dispatch the decryption of the ciphertext. + */ +static int krb5enc_dispatch_decrypt(struct aead_request *req) +{ + struct crypto_aead *krb5enc = crypto_aead_reqtfm(req); + struct aead_instance *inst = aead_alg_instance(krb5enc); + struct krb5enc_ctx *ctx = crypto_aead_ctx(krb5enc); + struct krb5enc_instance_ctx *ictx = aead_instance_ctx(inst); + struct krb5enc_request_ctx *areq_ctx = aead_request_ctx(req); + struct skcipher_request *skreq = (void *)(areq_ctx->tail + + ictx->reqoff); + unsigned int authsize = crypto_aead_authsize(krb5enc); + struct scatterlist *src, *dst; + + src = scatterwalk_ffwd(areq_ctx->src, req->src, req->assoclen); + dst = src; + + if (req->src != req->dst) + dst = scatterwalk_ffwd(areq_ctx->dst, req->dst, req->assoclen); + + skcipher_request_set_tfm(skreq, ctx->enc); + skcipher_request_set_callback(skreq, aead_request_flags(req), + req->base.complete, req->base.data); + skcipher_request_set_crypt(skreq, src, dst, + req->cryptlen - authsize, req->iv); + + return crypto_skcipher_decrypt(skreq); +} + +static int krb5enc_decrypt(struct aead_request *req) +{ + int err; + + err = krb5enc_dispatch_decrypt(req); + if (err < 0) + return err; + + return krb5enc_dispatch_decrypt_hash(req); +} + +static int krb5enc_init_tfm(struct crypto_aead *tfm) +{ + struct aead_instance *inst = aead_alg_instance(tfm); + struct krb5enc_instance_ctx *ictx = aead_instance_ctx(inst); + struct krb5enc_ctx *ctx = crypto_aead_ctx(tfm); + struct crypto_ahash *auth; + struct crypto_skcipher *enc; + int err; + + auth = crypto_spawn_ahash(&ictx->auth); + if (IS_ERR(auth)) + return PTR_ERR(auth); + + enc = crypto_spawn_skcipher(&ictx->enc); + err = PTR_ERR(enc); + if (IS_ERR(enc)) + goto err_free_ahash; + + ctx->auth = auth; + ctx->enc = enc; + + crypto_aead_set_reqsize( + tfm, + sizeof(struct krb5enc_request_ctx) + + ictx->reqoff + /* Space for two checksums */ + umax(sizeof(struct ahash_request) + crypto_ahash_reqsize(auth), + sizeof(struct skcipher_request) + crypto_skcipher_reqsize(enc))); + + return 0; + +err_free_ahash: + crypto_free_ahash(auth); + return err; +} + +static void krb5enc_exit_tfm(struct crypto_aead *tfm) +{ + struct krb5enc_ctx *ctx = crypto_aead_ctx(tfm); + + crypto_free_ahash(ctx->auth); + crypto_free_skcipher(ctx->enc); +} + +static void krb5enc_free(struct aead_instance *inst) +{ + struct krb5enc_instance_ctx *ctx = aead_instance_ctx(inst); + + crypto_drop_skcipher(&ctx->enc); + crypto_drop_ahash(&ctx->auth); + kfree(inst); +} + +/* + * Create an instance of a template for a specific hash and cipher pair. + */ +static int krb5enc_create(struct crypto_template *tmpl, struct rtattr **tb) +{ + struct krb5enc_instance_ctx *ictx; + struct skcipher_alg_common *enc; + struct hash_alg_common *auth; + struct aead_instance *inst; + struct crypto_alg *auth_base; + u32 mask; + int err; + + err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_AEAD, &mask); + if (err) { + pr_err("attr_type failed\n"); + return err; + } + + inst = kzalloc(sizeof(*inst) + sizeof(*ictx), GFP_KERNEL); + if (!inst) + return -ENOMEM; + ictx = aead_instance_ctx(inst); + + err = crypto_grab_ahash(&ictx->auth, aead_crypto_instance(inst), + crypto_attr_alg_name(tb[1]), 0, mask); + if (err) { + pr_err("grab ahash failed\n"); + goto err_free_inst; + } + auth = crypto_spawn_ahash_alg(&ictx->auth); + auth_base = &auth->base; + + err = crypto_grab_skcipher(&ictx->enc, aead_crypto_instance(inst), + crypto_attr_alg_name(tb[2]), 0, mask); + if (err) { + pr_err("grab skcipher failed\n"); + goto err_free_inst; + } + enc = crypto_spawn_skcipher_alg_common(&ictx->enc); + + ictx->reqoff = 2 * auth->digestsize; + + err = -ENAMETOOLONG; + if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME, + "krb5enc(%s,%s)", auth_base->cra_name, + enc->base.cra_name) >= + CRYPTO_MAX_ALG_NAME) + goto err_free_inst; + + if (snprintf(inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME, + "krb5enc(%s,%s)", auth_base->cra_driver_name, + enc->base.cra_driver_name) >= CRYPTO_MAX_ALG_NAME) + goto err_free_inst; + + inst->alg.base.cra_priority = enc->base.cra_priority * 10 + + auth_base->cra_priority; + inst->alg.base.cra_blocksize = enc->base.cra_blocksize; + inst->alg.base.cra_alignmask = enc->base.cra_alignmask; + inst->alg.base.cra_ctxsize = sizeof(struct krb5enc_ctx); + + inst->alg.ivsize = enc->ivsize; + inst->alg.chunksize = enc->chunksize; + inst->alg.maxauthsize = auth->digestsize; + + inst->alg.init = krb5enc_init_tfm; + inst->alg.exit = krb5enc_exit_tfm; + + inst->alg.setkey = krb5enc_setkey; + inst->alg.encrypt = krb5enc_encrypt; + inst->alg.decrypt = krb5enc_decrypt; + + inst->free = krb5enc_free; + + err = aead_register_instance(tmpl, inst); + if (err) { + pr_err("ref failed\n"); + goto err_free_inst; + } + + return 0; + +err_free_inst: + krb5enc_free(inst); + return err; +} + +static struct crypto_template crypto_krb5enc_tmpl = { + .name = "krb5enc", + .create = krb5enc_create, + .module = THIS_MODULE, +}; + +static int __init crypto_krb5enc_module_init(void) +{ + return crypto_register_template(&crypto_krb5enc_tmpl); +} + +static void __exit crypto_krb5enc_module_exit(void) +{ + crypto_unregister_template(&crypto_krb5enc_tmpl); +} + +subsys_initcall(crypto_krb5enc_module_init); +module_exit(crypto_krb5enc_module_exit); + +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("Simple AEAD wrapper for Kerberos 5 RFC3961"); +MODULE_ALIAS_CRYPTO("krb5enc"); |