hmac_s390.c

// SPDX-License-Identifier: GPL-2.0+
/*
 * Copyright IBM Corp. 2024
 *
 * s390 specific HMAC support.
 */

#define pr_fmt(fmt) "hmac_s390: " fmt

#include <asm/cpacf.h>
#include <crypto/internal/hash.h>
#include <crypto/hmac.h>
#include <crypto/sha2.h>
#include <linux/cpufeature.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/string.h>

/*
 * KMAC param block layout for sha2 function codes:
 * The layout of the param block for the KMAC instruction depends on the
 * blocksize of the used hashing sha2-algorithm function codes. The param block
 * contains the hash chaining value (cv), the input message bit-length (imbl)
 * and the hmac-secret (key). To prevent code duplication, the sizes of all
 * these are calculated based on the blocksize.
 *
 * param-block:
 * +-------+
 * | cv    |
 * +-------+
 * | imbl  |
 * +-------+
 * | key   |
 * +-------+
 *
 * sizes:
 * part | sh2-alg | calculation | size | type
 * -----+---------+-------------+------+--------
 * cv	| 224/256 | blocksize/2 |   32 |  u64[8]
 *	| 384/512 |		|   64 | u128[8]
 * imbl | 224/256 | blocksize/8 |    8 |     u64
 *	| 384/512 |		|   16 |    u128
 * key	| 224/256 | blocksize	|   64 |  u8[64]
 *	| 384/512 |		|  128 | u8[128]
 */

#define MAX_DIGEST_SIZE		SHA512_DIGEST_SIZE
#define MAX_IMBL_SIZE		sizeof(u128)
#define MAX_BLOCK_SIZE		SHA512_BLOCK_SIZE

#define SHA2_CV_SIZE(bs)	((bs) >> 1)
#define SHA2_IMBL_SIZE(bs)	((bs) >> 3)

#define SHA2_IMBL_OFFSET(bs)	(SHA2_CV_SIZE(bs))
#define SHA2_KEY_OFFSET(bs)	(SHA2_CV_SIZE(bs) + SHA2_IMBL_SIZE(bs))

struct s390_hmac_ctx {
	u8 key[MAX_BLOCK_SIZE];
};

union s390_kmac_gr0 {
	unsigned long reg;
	struct {
		unsigned long		: 48;
		unsigned long ikp	:  1;
		unsigned long iimp	:  1;
		unsigned long ccup	:  1;
		unsigned long		:  6;
		unsigned long fc	:  7;
	};
};

struct s390_kmac_sha2_ctx {
	u8 param[MAX_DIGEST_SIZE + MAX_IMBL_SIZE + MAX_BLOCK_SIZE];
	union s390_kmac_gr0 gr0;
	u64 buflen[2];
};

/*
 * kmac_sha2_set_imbl - sets the input message bit-length based on the blocksize
 */
static inline void kmac_sha2_set_imbl(u8 *param, u64 buflen_lo,
				      u64 buflen_hi, unsigned int blocksize)
{
	u8 *imbl = param + SHA2_IMBL_OFFSET(blocksize);

	switch (blocksize) {
	case SHA256_BLOCK_SIZE:
		*(u64 *)imbl = buflen_lo * BITS_PER_BYTE;
		break;
	case SHA512_BLOCK_SIZE:
		*(u128 *)imbl = (((u128)buflen_hi << 64) + buflen_lo) << 3;
		break;
	default:
		break;
	}
}

static int hash_data(const u8 *in, unsigned int inlen,
		     u8 *digest, unsigned int digestsize, bool final)
{
	unsigned long func;
	union {
		struct sha256_paramblock {
			u32 h[8];
			u64 mbl;
		} sha256;
		struct sha512_paramblock {
			u64 h[8];
			u128 mbl;
		} sha512;
	} __packed param;

#define PARAM_INIT(x, y, z)		   \
	param.sha##x.h[0] = SHA##y ## _H0; \
	param.sha##x.h[1] = SHA##y ## _H1; \
	param.sha##x.h[2] = SHA##y ## _H2; \
	param.sha##x.h[3] = SHA##y ## _H3; \
	param.sha##x.h[4] = SHA##y ## _H4; \
	param.sha##x.h[5] = SHA##y ## _H5; \
	param.sha##x.h[6] = SHA##y ## _H6; \
	param.sha##x.h[7] = SHA##y ## _H7; \
	param.sha##x.mbl = (z)

	switch (digestsize) {
	case SHA224_DIGEST_SIZE:
		func = final ? CPACF_KLMD_SHA_256 : CPACF_KIMD_SHA_256;
		PARAM_INIT(256, 224, inlen * 8);
		if (!final)
			digestsize = SHA256_DIGEST_SIZE;
		break;
	case SHA256_DIGEST_SIZE:
		func = final ? CPACF_KLMD_SHA_256 : CPACF_KIMD_SHA_256;
		PARAM_INIT(256, 256, inlen * 8);
		break;
	case SHA384_DIGEST_SIZE:
		func = final ? CPACF_KLMD_SHA_512 : CPACF_KIMD_SHA_512;
		PARAM_INIT(512, 384, inlen * 8);
		if (!final)
			digestsize = SHA512_DIGEST_SIZE;
		break;
	case SHA512_DIGEST_SIZE:
		func = final ? CPACF_KLMD_SHA_512 : CPACF_KIMD_SHA_512;
		PARAM_INIT(512, 512, inlen * 8);
		break;
	default:
		return -EINVAL;
	}

#undef PARAM_INIT

	cpacf_klmd(func, &param, in, inlen);

	memcpy(digest, &param, digestsize);

	return 0;
}

static int hash_key(const u8 *in, unsigned int inlen,
		    u8 *digest, unsigned int digestsize)
{
	return hash_data(in, inlen, digest, digestsize, true);
}

static int s390_hmac_sha2_setkey(struct crypto_shash *tfm,
				 const u8 *key, unsigned int keylen)
{
	struct s390_hmac_ctx *tfm_ctx = crypto_shash_ctx(tfm);
	unsigned int ds = crypto_shash_digestsize(tfm);
	unsigned int bs = crypto_shash_blocksize(tfm);

	memset(tfm_ctx, 0, sizeof(*tfm_ctx));

	if (keylen > bs)
		return hash_key(key, keylen, tfm_ctx->key, ds);

	memcpy(tfm_ctx->key, key, keylen);
	return 0;
}

static int s390_hmac_sha2_init(struct shash_desc *desc)
{
	struct s390_hmac_ctx *tfm_ctx = crypto_shash_ctx(desc->tfm);
	struct s390_kmac_sha2_ctx *ctx = shash_desc_ctx(desc);
	unsigned int bs = crypto_shash_blocksize(desc->tfm);

	memcpy(ctx->param + SHA2_KEY_OFFSET(bs),
	       tfm_ctx->key, bs);

	ctx->buflen[0] = 0;
	ctx->buflen[1] = 0;
	ctx->gr0.reg = 0;
	switch (crypto_shash_digestsize(desc->tfm)) {
	case SHA224_DIGEST_SIZE:
		ctx->gr0.fc = CPACF_KMAC_HMAC_SHA_224;
		break;
	case SHA256_DIGEST_SIZE:
		ctx->gr0.fc = CPACF_KMAC_HMAC_SHA_256;
		break;
	case SHA384_DIGEST_SIZE:
		ctx->gr0.fc = CPACF_KMAC_HMAC_SHA_384;
		break;
	case SHA512_DIGEST_SIZE:
		ctx->gr0.fc = CPACF_KMAC_HMAC_SHA_512;
		break;
	default:
		return -EINVAL;
	}

	return 0;
}

static int s390_hmac_sha2_update(struct shash_desc *desc,
				 const u8 *data, unsigned int len)
{
	struct s390_kmac_sha2_ctx *ctx = shash_desc_ctx(desc);
	unsigned int bs = crypto_shash_blocksize(desc->tfm);
	unsigned int n = round_down(len, bs);

	ctx->buflen[0] += n;
	if (ctx->buflen[0] < n)
		ctx->buflen[1]++;

	/* process as many blocks as possible */
	ctx->gr0.iimp = 1;
	_cpacf_kmac(&ctx->gr0.reg, ctx->param, data, n);
	return len - n;
}

static int s390_hmac_sha2_finup(struct shash_desc *desc, const u8 *src,
				unsigned int len, u8 *out)
{
	struct s390_kmac_sha2_ctx *ctx = shash_desc_ctx(desc);
	unsigned int bs = crypto_shash_blocksize(desc->tfm);

	ctx->buflen[0] += len;
	if (ctx->buflen[0] < len)
		ctx->buflen[1]++;

	ctx->gr0.iimp = 0;
	kmac_sha2_set_imbl(ctx->param, ctx->buflen[0], ctx->buflen[1], bs);
	_cpacf_kmac(&ctx->gr0.reg, ctx->param, src, len);
	memcpy(out, ctx->param, crypto_shash_digestsize(desc->tfm));

	return 0;
}

static int s390_hmac_sha2_digest(struct shash_desc *desc,
				 const u8 *data, unsigned int len, u8 *out)
{
	struct s390_kmac_sha2_ctx *ctx = shash_desc_ctx(desc);
	unsigned int ds = crypto_shash_digestsize(desc->tfm);
	int rc;

	rc = s390_hmac_sha2_init(desc);
	if (rc)
		return rc;

	ctx->gr0.iimp = 0;
	kmac_sha2_set_imbl(ctx->param, len, 0,
			   crypto_shash_blocksize(desc->tfm));
	_cpacf_kmac(&ctx->gr0.reg, ctx->param, data, len);
	memcpy(out, ctx->param, ds);

	return 0;
}

static int s390_hmac_export_zero(struct shash_desc *desc, void *out)
{
	struct crypto_shash *tfm = desc->tfm;
	u8 ipad[SHA512_BLOCK_SIZE];
	struct s390_hmac_ctx *ctx;
	unsigned int bs;
	int err, i;

	ctx = crypto_shash_ctx(tfm);
	bs = crypto_shash_blocksize(tfm);
	for (i = 0; i < bs; i++)
		ipad[i] = ctx->key[i] ^ HMAC_IPAD_VALUE;

	err = hash_data(ipad, bs, out, crypto_shash_digestsize(tfm), false);
	memzero_explicit(ipad, sizeof(ipad));
	return err;
}

static int s390_hmac_export(struct shash_desc *desc, void *out)
{
	struct s390_kmac_sha2_ctx *ctx = shash_desc_ctx(desc);
	unsigned int bs = crypto_shash_blocksize(desc->tfm);
	unsigned int ds = bs / 2;
	u64 lo = ctx->buflen[0];
	union {
		u8 *u8;
		u64 *u64;
	} p = { .u8 = out };
	int err = 0;

	if (!ctx->gr0.ikp)
		err = s390_hmac_export_zero(desc, out);
	else
		memcpy(p.u8, ctx->param, ds);
	p.u8 += ds;
	lo += bs;
	put_unaligned(lo, p.u64++);
	if (ds == SHA512_DIGEST_SIZE)
		put_unaligned(ctx->buflen[1] + (lo < bs), p.u64);
	return err;
}

static int s390_hmac_import(struct shash_desc *desc, const void *in)
{
	struct s390_kmac_sha2_ctx *ctx = shash_desc_ctx(desc);
	unsigned int bs = crypto_shash_blocksize(desc->tfm);
	unsigned int ds = bs / 2;
	union {
		const u8 *u8;
		const u64 *u64;
	} p = { .u8 = in };
	u64 lo;
	int err;

	err = s390_hmac_sha2_init(desc);
	memcpy(ctx->param, p.u8, ds);
	p.u8 += ds;
	lo = get_unaligned(p.u64++);
	ctx->buflen[0] = lo - bs;
	if (ds == SHA512_DIGEST_SIZE)
		ctx->buflen[1] = get_unaligned(p.u64) - (lo < bs);
	if (ctx->buflen[0] | ctx->buflen[1])
		ctx->gr0.ikp = 1;
	return err;
}

#define S390_HMAC_SHA2_ALG(x, ss) {					\
	.fc = CPACF_KMAC_HMAC_SHA_##x,					\
	.alg = {							\
		.init = s390_hmac_sha2_init,				\
		.update = s390_hmac_sha2_update,			\
		.finup = s390_hmac_sha2_finup,				\
		.digest = s390_hmac_sha2_digest,			\
		.setkey = s390_hmac_sha2_setkey,			\
		.export = s390_hmac_export,				\
		.import = s390_hmac_import,				\
		.descsize = sizeof(struct s390_kmac_sha2_ctx),		\
		.halg = {						\
			.statesize = ss,				\
			.digestsize = SHA##x##_DIGEST_SIZE,		\
			.base = {					\
				.cra_name = "hmac(sha" #x ")",		\
				.cra_driver_name = "hmac_s390_sha" #x,	\
				.cra_blocksize = SHA##x##_BLOCK_SIZE,	\
				.cra_priority = 400,			\
				.cra_flags = CRYPTO_AHASH_ALG_BLOCK_ONLY | \
					     CRYPTO_AHASH_ALG_FINUP_MAX, \
				.cra_ctxsize = sizeof(struct s390_hmac_ctx), \
				.cra_module = THIS_MODULE,		\
			},						\
		},							\
	},								\
}

static struct s390_hmac_alg {
	bool registered;
	unsigned int fc;
	struct shash_alg alg;
} s390_hmac_algs[] = {
	S390_HMAC_SHA2_ALG(224, sizeof(struct crypto_sha256_state)),
	S390_HMAC_SHA2_ALG(256, sizeof(struct crypto_sha256_state)),
	S390_HMAC_SHA2_ALG(384, SHA512_STATE_SIZE),
	S390_HMAC_SHA2_ALG(512, SHA512_STATE_SIZE),
};

static __always_inline void _s390_hmac_algs_unregister(void)
{
	struct s390_hmac_alg *hmac;
	int i;

	for (i = ARRAY_SIZE(s390_hmac_algs) - 1; i >= 0; i--) {
		hmac = &s390_hmac_algs[i];
		if (!hmac->registered)
			continue;
		crypto_unregister_shash(&hmac->alg);
	}
}

static int __init hmac_s390_init(void)
{
	struct s390_hmac_alg *hmac;
	int i, rc = -ENODEV;

	if (!cpacf_query_func(CPACF_KLMD, CPACF_KLMD_SHA_256))
		return -ENODEV;
	if (!cpacf_query_func(CPACF_KLMD, CPACF_KLMD_SHA_512))
		return -ENODEV;

	for (i = 0; i < ARRAY_SIZE(s390_hmac_algs); i++) {
		hmac = &s390_hmac_algs[i];
		if (!cpacf_query_func(CPACF_KMAC, hmac->fc))
			continue;

		rc = crypto_register_shash(&hmac->alg);
		if (rc) {
			pr_err("unable to register %s\n",
			       hmac->alg.halg.base.cra_name);
			goto out;
		}
		hmac->registered = true;
		pr_debug("registered %s\n", hmac->alg.halg.base.cra_name);
	}
	return rc;
out:
	_s390_hmac_algs_unregister();
	return rc;
}

static void __exit hmac_s390_exit(void)
{
	_s390_hmac_algs_unregister();
}

module_cpu_feature_match(S390_CPU_FEATURE_MSA, hmac_s390_init);
module_exit(hmac_s390_exit);

MODULE_DESCRIPTION("S390 HMAC driver");
MODULE_LICENSE("GPL");