The SP800-108 compliant Key Derivation Function provides three KDF types which are all implemented, including the counter-based KDF, the double-pipeline KDF and the feedback KDF. The code comments provide details about how to invoke the different KDF types. Signed-off-by: Stephan Mueller <smueller@xxxxxxxxxx> --- crypto/Kconfig | 7 + crypto/Makefile | 1 + crypto/kdf_sp800108.c | 491 ++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 499 insertions(+) create mode 100644 crypto/kdf_sp800108.c diff --git a/crypto/Kconfig b/crypto/Kconfig index 86960aa53e0f..7c0336c9ba9c 100644 --- a/crypto/Kconfig +++ b/crypto/Kconfig @@ -561,6 +561,13 @@ config CRYPTO_HMAC HMAC: Keyed-Hashing for Message Authentication (RFC2104). This is required for IPSec. +config CRYPTO_KDF_SP800108 + tristate "Key Derivation Function (SP800-108)" + select CRYPTO_RNG + help + Support for KDF compliant to SP800-108. All three types of + KDF specified in SP800-108 are implemented. + config CRYPTO_XCBC tristate "XCBC support" select CRYPTO_HASH diff --git a/crypto/Makefile b/crypto/Makefile index 799ed5e94606..eead7ec9fd8e 100644 --- a/crypto/Makefile +++ b/crypto/Makefile @@ -58,6 +58,7 @@ crypto_user-y := crypto_user_base.o crypto_user-$(CONFIG_CRYPTO_STATS) += crypto_user_stat.o obj-$(CONFIG_CRYPTO_CMAC) += cmac.o obj-$(CONFIG_CRYPTO_HMAC) += hmac.o +obj-$(CONFIG_CRYPTO_KDF_SP800108) += kdf_sp800108.o obj-$(CONFIG_CRYPTO_VMAC) += vmac.o obj-$(CONFIG_CRYPTO_XCBC) += xcbc.o obj-$(CONFIG_CRYPTO_NULL2) += crypto_null.o diff --git a/crypto/kdf_sp800108.c b/crypto/kdf_sp800108.c new file mode 100644 index 000000000000..33b26659afa7 --- /dev/null +++ b/crypto/kdf_sp800108.c @@ -0,0 +1,491 @@ +// SPDX-License-Identifier: GPL-2.0 + +/* + * SP800-108 Key-derivation function + * + * Copyright (C) 2019, Stephan Mueller <smueller@xxxxxxxxxx> + */ + +/* + * For performing a KDF operation, the following input is required + * from the caller: + * + * * Keying material to be used to derive the new keys from + * (denoted as Ko in SP800-108) + * * Label -- a free form binary string + * * Context -- a free form binary string + * + * The KDF is implemented as a random number generator. + * + * The Ko keying material is to be provided with the initialization of the KDF + * "random number generator", i.e. with the crypto_rng_reset function. + * + * The Label and Context concatenated string is provided when obtaining random + * numbers, i.e. with the crypto_rng_generate function. The caller must format + * the free-form Label || Context input as deemed necessary for the given + * purpose. Note, SP800-108 mandates that the Label and Context are separated + * by a 0x00 byte, i.e. the caller shall provide the input as + * Label || 0x00 || Context when trying to be compliant to SP800-108. For + * the feedback KDF, an IV is required as documented below. + * + * Example without proper error handling: + * char *keying_material = "\x00\x11\x22\x33\x44\x55\x66\x77"; + * char *label_context = "\xde\xad\xbe\xef\x00\xde\xad\xbe\xef"; + * kdf = crypto_alloc_rng(name, 0, 0); + * crypto_rng_reset(kdf, keying_material, 8); + * crypto_rng_generate(kdf, label_context, 9, outbuf, outbuflen); + */ + +#include <linux/module.h> +#include <crypto/rng.h> +#include <crypto/internal/rng.h> +#include <crypto/hash.h> +#include <crypto/internal/hash.h> + +struct crypto_kdf_ctx { + struct crypto_shash *kmd; +}; + +#define CRYPTO_KDF_MAX_DIGESTSIZE 64 +#define CRYPTO_KDF_MAX_ALIGNMASK 0x3f + +static inline void crypto_kdf_init_desc(struct shash_desc *desc, + struct crypto_shash *kmd) +{ + desc->tfm = kmd; + desc->flags = 0; +} + +/* + * Implementation of the KDF in double pipeline iteration mode according with + * counter to SP800-108 section 5.3. + * + * The caller must provide Label || 0x00 || Context in src. This src pointer + * may also be NULL if the caller wishes not to provide anything. + */ +static int crypto_kdf_dpi_generate(struct crypto_rng *rng, + const u8 *src, unsigned int slen, + u8 *dst, unsigned int dlen) +{ + const struct crypto_kdf_ctx *ctx = crypto_tfm_ctx(crypto_rng_tfm(rng)); + struct crypto_shash *kmd = ctx->kmd; + SHASH_DESC_ON_STACK(desc, kmd); + __be32 counter = cpu_to_be32(1); + const unsigned int h = crypto_shash_digestsize(kmd); + const unsigned int alignmask = crypto_shash_alignmask(kmd); + int err = 0; + u8 *dst_orig = dst; + u8 Aiblock[CRYPTO_KDF_MAX_DIGESTSIZE + CRYPTO_KDF_MAX_ALIGNMASK]; + u8 *Ai = PTR_ALIGN((u8 *)Aiblock, alignmask + 1); + + crypto_kdf_init_desc(desc, kmd); + + memset(Ai, 0, h); + + while (dlen) { + /* Calculate A(i) */ + if (dst == dst_orig && src && slen) + /* 5.3 step 4 and 5.a */ + err = crypto_shash_digest(desc, src, slen, Ai); + else + /* 5.3 step 5.a */ + err = crypto_shash_digest(desc, Ai, h, Ai); + if (err) + goto out; + + /* Calculate K(i) -- step 5.b */ + err = crypto_shash_init(desc); + if (err) + goto out; + + err = crypto_shash_update(desc, Ai, h); + if (err) + goto out; + + err = crypto_shash_update(desc, (u8 *)&counter, sizeof(__be32)); + if (err) + goto out; + if (src && slen) { + err = crypto_shash_update(desc, src, slen); + if (err) + goto out; + } + + if (dlen < h) { + u8 tmpbuffer[CRYPTO_KDF_MAX_DIGESTSIZE]; + + err = crypto_shash_final(desc, tmpbuffer); + if (err) + goto out; + memcpy(dst, tmpbuffer, dlen); + memzero_explicit(tmpbuffer, h); + goto out; + } + + err = crypto_shash_final(desc, dst); + if (err) + goto out; + dlen -= h; + dst += h; + counter = cpu_to_be32(be32_to_cpu(counter) + 1); + } + +out: + if (err) + memzero_explicit(dst_orig, dlen); + shash_desc_zero(desc); + memzero_explicit(Ai, h); + return err; +} + +/* + * Implementation of the KDF in feedback mode with a non-NULL IV and with + * counter according to SP800-108 section 5.2. The IV is supplied with src + * and must be equal to the digestsize of the used keyed message digest. + * + * In addition, the caller must provide Label || 0x00 || Context in src. This + * src pointer must not be NULL as the IV is required. The ultimate format of + * the src pointer is IV || Label || 0x00 || Context where the length of the + * IV is equal to the output size of the PRF. + */ +static int crypto_kdf_fb_generate(struct crypto_rng *rng, + const u8 *src, unsigned int slen, + u8 *dst, unsigned int dlen) +{ + const struct crypto_kdf_ctx *ctx = crypto_tfm_ctx(crypto_rng_tfm(rng)); + struct crypto_shash *kmd = ctx->kmd; + SHASH_DESC_ON_STACK(desc, kmd); + __be32 counter = cpu_to_be32(1); + const unsigned int h = crypto_shash_digestsize(kmd); + unsigned int labellen = 0; + int err = 0; + u8 *dst_orig = dst; + const u8 *label; + + /* require the presence of an IV */ + if (!src || slen < h) + return -EINVAL; + + crypto_kdf_init_desc(desc, kmd); + + /* calculate the offset of the label / context data */ + label = src + h; + labellen = slen - h; + + while (dlen) { + err = crypto_shash_init(desc); + if (err) + goto out; + + /* + * Feedback mode applies to all rounds except first which uses + * the IV. + */ + if (dst_orig == dst) + err = crypto_shash_update(desc, src, h); + else + err = crypto_shash_update(desc, dst - h, h); + if (err) + goto out; + + err = crypto_shash_update(desc, (u8 *)&counter, sizeof(__be32)); + if (err) + goto out; + if (labellen) { + err = crypto_shash_update(desc, label, labellen); + if (err) + goto out; + } + + if (dlen < h) { + u8 tmpbuffer[CRYPTO_KDF_MAX_DIGESTSIZE]; + + err = crypto_shash_final(desc, tmpbuffer); + if (err) + goto out; + memcpy(dst, tmpbuffer, dlen); + memzero_explicit(tmpbuffer, h); + goto out; + } + + err = crypto_shash_final(desc, dst); + if (err) + goto out; + dlen -= h; + dst += h; + counter = cpu_to_be32(be32_to_cpu(counter) + 1); + } + +out: + if (err) + memzero_explicit(dst_orig, dlen); + return err; +} + +/* + * Implementation of the KDF in counter mode according to SP800-108 section 5.1 + * as well as SP800-56A section 5.8.1 (Single-step KDF). + * + * SP800-108: + * The caller must provide Label || 0x00 || Context in src. This src pointer + * may also be NULL if the caller wishes not to provide anything. + * + * SP800-56A: + * The key provided for the HMAC during the crypto_rng_reset shall NOT be the + * shared secret from the DH operation, but an independently generated key. + * The src pointer is defined as Z || other info where Z is the shared secret + * from DH and other info is an arbitrary string (see SP800-56A section + * 5.8.1.2). + */ +static int crypto_kdf_ctr_generate(struct crypto_rng *rng, + const u8 *src, unsigned int slen, + u8 *dst, unsigned int dlen) +{ + const struct crypto_kdf_ctx *ctx = crypto_tfm_ctx(crypto_rng_tfm(rng)); + struct crypto_shash *kmd = ctx->kmd; + SHASH_DESC_ON_STACK(desc, kmd); + __be32 counter = cpu_to_be32(1); + const unsigned int h = crypto_shash_digestsize(kmd); + int err = 0; + u8 *dst_orig = dst; + + crypto_kdf_init_desc(desc, kmd); + + while (dlen) { + err = crypto_shash_init(desc); + if (err) + goto out; + + err = crypto_shash_update(desc, (u8 *)&counter, sizeof(__be32)); + if (err) + goto out; + + if (src && slen) { + err = crypto_shash_update(desc, src, slen); + if (err) + goto out; + } + + if (dlen < h) { + u8 tmpbuffer[CRYPTO_KDF_MAX_DIGESTSIZE]; + + err = crypto_shash_final(desc, tmpbuffer); + if (err) + goto out; + memcpy(dst, tmpbuffer, dlen); + memzero_explicit(tmpbuffer, h); + return 0; + } + + err = crypto_shash_final(desc, dst); + if (err) + goto out; + + dlen -= h; + dst += h; + counter = cpu_to_be32(be32_to_cpu(counter) + 1); + } + +out: + if (err) + memzero_explicit(dst_orig, dlen); + shash_desc_zero(desc); + return err; +} + +/* + * The seeding of the KDF allows to set a key which must be at least + * digestsize long. + */ +static int crypto_kdf_seed(struct crypto_rng *rng, + const u8 *seed, unsigned int slen) +{ + const struct crypto_kdf_ctx *ctx = crypto_tfm_ctx(crypto_rng_tfm(rng)); + unsigned int ds = crypto_shash_digestsize(ctx->kmd); + + /* Check according to SP800-108 section 7.2 */ + if (ds > slen) + return -EINVAL; + + /* + * We require that we operate on a MAC -- if we do not operate on a + * MAC, this function returns an error. + */ + return crypto_shash_setkey(ctx->kmd, seed, slen); +} + +static int crypto_kdf_init_tfm(struct crypto_tfm *tfm) +{ + struct crypto_instance *inst = crypto_tfm_alg_instance(tfm); + struct crypto_shash_spawn *spawn = crypto_instance_ctx(inst); + struct crypto_kdf_ctx *ctx = crypto_tfm_ctx(tfm); + struct crypto_shash *kmd; + + kmd = crypto_spawn_shash(spawn); + if (IS_ERR(kmd)) + return PTR_ERR(kmd); + + ctx->kmd = kmd; + + return 0; +} + +static void crypto_kdf_exit_tfm(struct crypto_tfm *tfm) +{ + struct crypto_kdf_ctx *ctx = crypto_tfm_ctx(tfm); + + crypto_free_shash(ctx->kmd); +} + +static void crypto_kdf_free(struct rng_instance *inst) +{ + crypto_drop_spawn(rng_instance_ctx(inst)); + kfree(inst); +} + +static int crypto_kdf_alloc_common(struct crypto_template *tmpl, + struct rtattr **tb, + const u8 *name, + int (*generate)(struct crypto_rng *tfm, + const u8 *src, + unsigned int slen, + u8 *dst, unsigned int dlen)) +{ + struct rng_instance *inst; + struct crypto_alg *alg; + struct shash_alg *salg; + int err; + unsigned int ds; + + err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_RNG); + if (err) + return err; + + salg = shash_attr_alg(tb[1], 0, 0); + if (IS_ERR(salg)) + return PTR_ERR(salg); + + /* Require a keyed message digest */ + if (!salg->setkey) + return -EOPNOTSUPP; + + ds = salg->digestsize; + /* Hashes with no digest size are not allowed for KDFs. */ + if (!ds || WARN_ON(ds > CRYPTO_KDF_MAX_DIGESTSIZE)) + return -EOPNOTSUPP; + + alg = &salg->base; + if (WARN_ON(CRYPTO_KDF_MAX_ALIGNMASK < alg->cra_alignmask)) + return -EOPNOTSUPP; + + inst = rng_alloc_instance(name, alg); + err = PTR_ERR(inst); + if (IS_ERR(inst)) + goto out_put_alg; + + err = crypto_init_shash_spawn(rng_instance_ctx(inst), salg, + rng_crypto_instance(inst)); + if (err) + goto free_inst; + + inst->alg.base.cra_priority = alg->cra_priority; + inst->alg.base.cra_blocksize = alg->cra_blocksize; + inst->alg.base.cra_alignmask = alg->cra_alignmask; + + inst->alg.generate = generate; + inst->alg.seed = crypto_kdf_seed; + inst->alg.seedsize = ds; + + inst->alg.base.cra_init = crypto_kdf_init_tfm; + inst->alg.base.cra_exit = crypto_kdf_exit_tfm; + inst->alg.base.cra_ctxsize = sizeof(struct crypto_kdf_ctx); + + inst->free = crypto_kdf_free; + + err = rng_register_instance(tmpl, inst); + + if (err) { + crypto_drop_spawn(rng_instance_ctx(inst)); +free_inst: + kfree(inst); + } + +out_put_alg: + crypto_mod_put(alg); + return err; +} + +static int crypto_kdf_ctr_create(struct crypto_template *tmpl, + struct rtattr **tb) +{ + return crypto_kdf_alloc_common(tmpl, tb, "kdf_ctr", + crypto_kdf_ctr_generate); +} + +static struct crypto_template crypto_kdf_ctr_tmpl = { + .name = "kdf_ctr", + .create = crypto_kdf_ctr_create, + .module = THIS_MODULE, +}; + +static int crypto_kdf_fb_create(struct crypto_template *tmpl, + struct rtattr **tb) { + return crypto_kdf_alloc_common(tmpl, tb, "kdf_fb", + crypto_kdf_fb_generate); +} + +static struct crypto_template crypto_kdf_fb_tmpl = { + .name = "kdf_fb", + .create = crypto_kdf_fb_create, + .module = THIS_MODULE, +}; + +static int crypto_kdf_dpi_create(struct crypto_template *tmpl, + struct rtattr **tb) { + return crypto_kdf_alloc_common(tmpl, tb, "kdf_dpi", + crypto_kdf_dpi_generate); +} + +static struct crypto_template crypto_kdf_dpi_tmpl = { + .name = "kdf_dpi", + .create = crypto_kdf_dpi_create, + .module = THIS_MODULE, +}; + +static int __init crypto_kdf_init(void) +{ + int err = crypto_register_template(&crypto_kdf_ctr_tmpl); + + if (err) + return err; + + err = crypto_register_template(&crypto_kdf_fb_tmpl); + if (err) { + crypto_unregister_template(&crypto_kdf_ctr_tmpl); + return err; + } + + err = crypto_register_template(&crypto_kdf_dpi_tmpl); + if (err) { + crypto_unregister_template(&crypto_kdf_ctr_tmpl); + crypto_unregister_template(&crypto_kdf_fb_tmpl); + } + return err; +} + +static void __exit crypto_kdf_exit(void) +{ + crypto_unregister_template(&crypto_kdf_ctr_tmpl); + crypto_unregister_template(&crypto_kdf_fb_tmpl); + crypto_unregister_template(&crypto_kdf_dpi_tmpl); +} + +module_init(crypto_kdf_init); +module_exit(crypto_kdf_exit); + +MODULE_LICENSE("GPL v2"); +MODULE_AUTHOR("Stephan Mueller <smueller@xxxxxxxxxx>"); +MODULE_DESCRIPTION("Key Derivation Function conformant to SP800-108"); +MODULE_ALIAS_CRYPTO("kdf_ctr"); +MODULE_ALIAS_CRYPTO("kdf_fb"); +MODULE_ALIAS_CRYPTO("kdf_dpi"); -- 2.20.1