crypto: dh - Add DH software implementation

* Implement MPI based Diffie-Hellman under kpp API
 * Test provided uses data generad by OpenSSL
Signed-off-by: Salvatore Benedetto <salvatore.benedetto@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

CVE-2018-5383

(cherry picked from commit 802c7f1c)
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

crypto/Kconfig

@@ -119,6 +119,14 @@ config CRYPTO_RSA
 	help
 	  Generic implementation of the RSA public key algorithm.
 
+config CRYPTO_DH
+	tristate "Diffie-Hellman algorithm"
+	select CRYPTO_KPP
+	select MPILIB
+	help
+	  Generic implementation of the Diffie-Hellman algorithm.
+
+
 config CRYPTO_MANAGER
 	tristate "Cryptographic algorithm manager"
 	select CRYPTO_MANAGER2

crypto/Makefile

@@ -32,6 +32,10 @@ obj-$(CONFIG_CRYPTO_PCOMP2) += pcompress.o
 obj-$(CONFIG_CRYPTO_AKCIPHER2) += akcipher.o
 obj-$(CONFIG_CRYPTO_KPP2) += kpp.o
 
+dh_generic-y := dh.o
+dh_generic-y += dh_helper.o
+obj-$(CONFIG_CRYPTO_DH) += dh_generic.o
+
 $(obj)/rsapubkey-asn1.o: $(obj)/rsapubkey-asn1.c $(obj)/rsapubkey-asn1.h
 $(obj)/rsaprivkey-asn1.o: $(obj)/rsaprivkey-asn1.c $(obj)/rsaprivkey-asn1.h
 $(obj)/rsa_helper.o: $(obj)/rsapubkey-asn1.h $(obj)/rsaprivkey-asn1.h

crypto/dh.c

+/*  Diffie-Hellman Key Agreement Method [RFC2631]
+ *
+ * Copyright (c) 2016, Intel Corporation
+ * Authors: Salvatore Benedetto <salvatore.benedetto@intel.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#include <linux/module.h>
+#include <crypto/internal/kpp.h>
+#include <crypto/kpp.h>
+#include <crypto/dh.h>
+#include <linux/mpi.h>
+
+struct dh_ctx {
+	MPI p;
+	MPI g;
+	MPI xa;
+};
+
+static inline void dh_clear_params(struct dh_ctx *ctx)
+{
+	mpi_free(ctx->p);
+	mpi_free(ctx->g);
+	ctx->p = NULL;
+	ctx->g = NULL;
+}
+
+static void dh_free_ctx(struct dh_ctx *ctx)
+{
+	dh_clear_params(ctx);
+	mpi_free(ctx->xa);
+	ctx->xa = NULL;
+}
+
+/*
+ * If base is g we compute the public key
+ *	ya = g^xa mod p; [RFC2631 sec 2.1.1]
+ * else if base if the counterpart public key we compute the shared secret
+ *	ZZ = yb^xa mod p; [RFC2631 sec 2.1.1]
+ */
+static int _compute_val(const struct dh_ctx *ctx, MPI base, MPI val)
+{
+	/* val = base^xa mod p */
+	return mpi_powm(val, base, ctx->xa, ctx->p);
+}
+
+static inline struct dh_ctx *dh_get_ctx(struct crypto_kpp *tfm)
+{
+	return kpp_tfm_ctx(tfm);
+}
+
+static int dh_check_params_length(unsigned int p_len)
+{
+	return (p_len < 1536) ? -EINVAL : 0;
+}
+
+static int dh_set_params(struct dh_ctx *ctx, struct dh *params)
+{
+	if (unlikely(!params->p || !params->g))
+		return -EINVAL;
+
+	if (dh_check_params_length(params->p_size << 3))
+		return -EINVAL;
+
+	ctx->p = mpi_read_raw_data(params->p, params->p_size);
+	if (!ctx->p)
+		return -EINVAL;
+
+	ctx->g = mpi_read_raw_data(params->g, params->g_size);
+	if (!ctx->g) {
+		mpi_free(ctx->p);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int dh_set_secret(struct crypto_kpp *tfm, void *buf, unsigned int len)
+{
+	struct dh_ctx *ctx = dh_get_ctx(tfm);
+	struct dh params;
+
+	if (crypto_dh_decode_key(buf, len, &params) < 0)
+		return -EINVAL;
+
+	if (dh_set_params(ctx, &params) < 0)
+		return -EINVAL;
+
+	ctx->xa = mpi_read_raw_data(params.key, params.key_size);
+	if (!ctx->xa) {
+		dh_clear_params(ctx);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int dh_compute_value(struct kpp_request *req)
+{
+	struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
+	struct dh_ctx *ctx = dh_get_ctx(tfm);
+	MPI base, val = mpi_alloc(0);
+	int ret = 0;
+	int sign;
+
+	if (!val)
+		return -ENOMEM;
+
+	if (unlikely(!ctx->xa)) {
+		ret = -EINVAL;
+		goto err_free_val;
+	}
+
+	if (req->src) {
+		base = mpi_read_raw_from_sgl(req->src, req->src_len);
+		if (!base) {
+			ret = EINVAL;
+			goto err_free_val;
+		}
+	} else {
+		base = ctx->g;
+	}
+
+	ret = _compute_val(ctx, base, val);
+	if (ret)
+		goto err_free_base;
+
+	ret = mpi_write_to_sgl(val, req->dst, &req->dst_len, &sign);
+	if (ret)
+		goto err_free_base;
+
+	if (sign < 0)
+		ret = -EBADMSG;
+err_free_base:
+	if (req->src)
+		mpi_free(base);
+err_free_val:
+	mpi_free(val);
+	return ret;
+}
+
+static int dh_max_size(struct crypto_kpp *tfm)
+{
+	struct dh_ctx *ctx = dh_get_ctx(tfm);
+
+	return mpi_get_size(ctx->p);
+}
+
+static void dh_exit_tfm(struct crypto_kpp *tfm)
+{
+	struct dh_ctx *ctx = dh_get_ctx(tfm);
+
+	dh_free_ctx(ctx);
+}
+
+static struct kpp_alg dh = {
+	.set_secret = dh_set_secret,
+	.generate_public_key = dh_compute_value,
+	.compute_shared_secret = dh_compute_value,
+	.max_size = dh_max_size,
+	.exit = dh_exit_tfm,
+	.base = {
+		.cra_name = "dh",
+		.cra_driver_name = "dh-generic",
+		.cra_priority = 100,
+		.cra_module = THIS_MODULE,
+		.cra_ctxsize = sizeof(struct dh_ctx),
+	},
+};
+
+static int dh_init(void)
+{
+	return crypto_register_kpp(&dh);
+}
+
+static void dh_exit(void)
+{
+	crypto_unregister_kpp(&dh);
+}
+
+module_init(dh_init);
+module_exit(dh_exit);
+MODULE_ALIAS_CRYPTO("dh");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("DH generic algorithm");

crypto/dh_helper.c

+/*
+ * Copyright (c) 2016, Intel Corporation
+ * Authors: Salvatore Benedetto <salvatore.benedetto@intel.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+#include <linux/kernel.h>
+#include <linux/export.h>
+#include <linux/err.h>
+#include <linux/string.h>
+#include <crypto/dh.h>
+#include <crypto/kpp.h>
+
+#define DH_KPP_SECRET_MIN_SIZE (sizeof(struct kpp_secret) + 3 * sizeof(int))
+
+static inline u8 *dh_pack_data(void *dst, const void *src, size_t size)
+{
+	memcpy(dst, src, size);
+	return dst + size;
+}
+
+static inline const u8 *dh_unpack_data(void *dst, const void *src, size_t size)
+{
+	memcpy(dst, src, size);
+	return src + size;
+}
+
+static inline int dh_data_size(const struct dh *p)
+{
+	return p->key_size + p->p_size + p->g_size;
+}
+
+int crypto_dh_key_len(const struct dh *p)
+{
+	return DH_KPP_SECRET_MIN_SIZE + dh_data_size(p);
+}
+EXPORT_SYMBOL_GPL(crypto_dh_key_len);
+
+int crypto_dh_encode_key(char *buf, unsigned int len, const struct dh *params)
+{
+	u8 *ptr = buf;
+	struct kpp_secret secret = {
+		.type = CRYPTO_KPP_SECRET_TYPE_DH,
+		.len = len
+	};
+
+	if (unlikely(!buf))
+		return -EINVAL;
+
+	if (len != crypto_dh_key_len(params))
+		return -EINVAL;
+
+	ptr = dh_pack_data(ptr, &secret, sizeof(secret));
+	ptr = dh_pack_data(ptr, &params->key_size, sizeof(params->key_size));
+	ptr = dh_pack_data(ptr, &params->p_size, sizeof(params->p_size));
+	ptr = dh_pack_data(ptr, &params->g_size, sizeof(params->g_size));
+	ptr = dh_pack_data(ptr, params->key, params->key_size);
+	ptr = dh_pack_data(ptr, params->p, params->p_size);
+	dh_pack_data(ptr, params->g, params->g_size);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(crypto_dh_encode_key);
+
+int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params)
+{
+	const u8 *ptr = buf;
+	struct kpp_secret secret;
+
+	if (unlikely(!buf || len < DH_KPP_SECRET_MIN_SIZE))
+		return -EINVAL;
+
+	ptr = dh_unpack_data(&secret, ptr, sizeof(secret));
+	if (secret.type != CRYPTO_KPP_SECRET_TYPE_DH)
+		return -EINVAL;
+
+	ptr = dh_unpack_data(&params->key_size, ptr, sizeof(params->key_size));
+	ptr = dh_unpack_data(&params->p_size, ptr, sizeof(params->p_size));
+	ptr = dh_unpack_data(&params->g_size, ptr, sizeof(params->g_size));
+	if (secret.len != crypto_dh_key_len(params))
+		return -EINVAL;
+
+	/* Don't allocate memory. Set pointers to data within
+	 * the given buffer
+	 */
+	params->key = (void *)ptr;
+	params->p = (void *)(ptr + params->key_size);
+	params->g = (void *)(ptr + params->key_size + params->p_size);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(crypto_dh_decode_key);

crypto/testmgr.c

@@ -32,6 +32,7 @@
 #include <crypto/rng.h>
 #include <crypto/drbg.h>
 #include <crypto/akcipher.h>
+#include <crypto/kpp.h>
 
 #include "internal.h"
 
@@ -123,6 +124,11 @@ struct akcipher_test_suite {
 	unsigned int count;
 };
 
+struct kpp_test_suite {
+	struct kpp_testvec *vecs;
+	unsigned int count;
+};
+
 struct alg_test_desc {
 	const char *alg;
 	int (*test)(const struct alg_test_desc *desc, const char *driver,
@@ -138,6 +144,7 @@ struct alg_test_desc {
 		struct cprng_test_suite cprng;
 		struct drbg_test_suite drbg;
 		struct akcipher_test_suite akcipher;
+		struct kpp_test_suite kpp;
 	} suite;
 };
 
@@ -1847,6 +1854,133 @@ static int alg_test_drbg(const struct alg_test_desc *desc, const char *driver,
 
 }
 
+static int do_test_kpp(struct crypto_kpp *tfm, struct kpp_testvec *vec,
+		       const char *alg)
+{
+	struct kpp_request *req;
+	void *input_buf = NULL;
+	void *output_buf = NULL;
+	struct tcrypt_result result;
+	unsigned int out_len_max;
+	int err = -ENOMEM;
+	struct scatterlist src, dst;
+
+	req = kpp_request_alloc(tfm, GFP_KERNEL);
+	if (!req)
+		return err;
+
+	init_completion(&result.completion);
+
+	err = crypto_kpp_set_secret(tfm, vec->secret, vec->secret_size);
+	if (err < 0)
+		goto free_req;
+
+	out_len_max = crypto_kpp_maxsize(tfm);
+	output_buf = kzalloc(out_len_max, GFP_KERNEL);
+	if (!output_buf) {
+		err = -ENOMEM;
+		goto free_req;
+	}
+
+	/* Use appropriate parameter as base */
+	kpp_request_set_input(req, NULL, 0);
+	sg_init_one(&dst, output_buf, out_len_max);
+	kpp_request_set_output(req, &dst, out_len_max);
+	kpp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
+				 tcrypt_complete, &result);
+
+	/* Compute public key */
+	err = wait_async_op(&result, crypto_kpp_generate_public_key(req));
+	if (err) {
+		pr_err("alg: %s: generate public key test failed. err %d\n",
+		       alg, err);
+		goto free_output;
+	}
+	/* Verify calculated public key */
+	if (memcmp(vec->expected_a_public, sg_virt(req->dst),
+		   vec->expected_a_public_size)) {
+		pr_err("alg: %s: generate public key test failed. Invalid output\n",
+		       alg);
+		err = -EINVAL;
+		goto free_output;
+	}
+
+	/* Calculate shared secret key by using counter part (b) public key. */
+	input_buf = kzalloc(vec->b_public_size, GFP_KERNEL);
+	if (!input_buf) {
+		err = -ENOMEM;
+		goto free_output;
+	}
+
+	memcpy(input_buf, vec->b_public, vec->b_public_size);
+	sg_init_one(&src, input_buf, vec->b_public_size);
+	sg_init_one(&dst, output_buf, out_len_max);
+	kpp_request_set_input(req, &src, vec->b_public_size);
+	kpp_request_set_output(req, &dst, out_len_max);
+	kpp_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
+				 tcrypt_complete, &result);
+	err = wait_async_op(&result, crypto_kpp_compute_shared_secret(req));
+	if (err) {
+		pr_err("alg: %s: compute shard secret test failed. err %d\n",
+		       alg, err);
+		goto free_all;
+	}
+	/*
+	 * verify shared secret from which the user will derive
+	 * secret key by executing whatever hash it has chosen
+	 */
+	if (memcmp(vec->expected_ss, sg_virt(req->dst),
+		   vec->expected_ss_size)) {
+		pr_err("alg: %s: compute shared secret test failed. Invalid output\n",
+		       alg);
+		err = -EINVAL;
+	}
+
+free_all:
+	kfree(input_buf);
+free_output:
+	kfree(output_buf);
+free_req:
+	kpp_request_free(req);
+	return err;
+}
+
+static int test_kpp(struct crypto_kpp *tfm, const char *alg,
+		    struct kpp_testvec *vecs, unsigned int tcount)
+{
+	int ret, i;
+
+	for (i = 0; i < tcount; i++) {
+		ret = do_test_kpp(tfm, vecs++, alg);
+		if (ret) {
+			pr_err("alg: %s: test failed on vector %d, err=%d\n",
+			       alg, i + 1, ret);
+			return ret;
+		}
+	}
+	return 0;
+}
+
+static int alg_test_kpp(const struct alg_test_desc *desc, const char *driver,
+			u32 type, u32 mask)
+{
+	struct crypto_kpp *tfm;
+	int err = 0;
+
+	tfm = crypto_alloc_kpp(driver, type | CRYPTO_ALG_INTERNAL, mask);
+	if (IS_ERR(tfm)) {
+		pr_err("alg: kpp: Failed to load tfm for %s: %ld\n",
+		       driver, PTR_ERR(tfm));
+		return PTR_ERR(tfm);
+	}
+	if (desc->suite.kpp.vecs)
+		err = test_kpp(tfm, desc->alg, desc->suite.kpp.vecs,
+			       desc->suite.kpp.count);
+
+	crypto_free_kpp(tfm);
+	return err;
+}
+
 static int do_test_rsa(struct crypto_akcipher *tfm,
 		       struct akcipher_testvec *vecs)
 {
@@ -2760,6 +2894,16 @@ static const struct alg_test_desc alg_test_descs[] = {
 				}
 			}
 		}
+	}, {
+		.alg = "dh",
+		.test = alg_test_kpp,
+		.fips_allowed = 1,
+		.suite = {
+			.kpp = {
+				.vecs = dh_tv_template,
+				.count = DH_TEST_VECTORS
+			}
+		}
 	}, {
 		.alg = "digest_null",
 		.test = alg_test_null,

include/crypto/dh.h

+/*
+ * Diffie-Hellman secret to be used with kpp API along with helper functions
+ *
+ * Copyright (c) 2016, Intel Corporation
+ * Authors: Salvatore Benedetto <salvatore.benedetto@intel.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ */
+#ifndef _CRYPTO_DH_
+#define _CRYPTO_DH_
+
+struct dh {
+	void *key;
+	void *p;
+	void *g;
+	unsigned int key_size;
+	unsigned int p_size;
+	unsigned int g_size;
+};
+
+int crypto_dh_key_len(const struct dh *params);
+int crypto_dh_encode_key(char *buf, unsigned int len, const struct dh *params);
+int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params);
+
+#endif

include/crypto/kpp.h

@@ -242,6 +242,7 @@ static inline void kpp_request_set_output(struct kpp_request *req,
 
 enum {
 	CRYPTO_KPP_SECRET_TYPE_UNKNOWN,
+	CRYPTO_KPP_SECRET_TYPE_DH,
 };
 
 /**