diff --git a/crypto/dh.c b/crypto/dh.c
index 5659fe7f446d..8f79269db2b7 100644
--- a/crypto/dh.c
+++ b/crypto/dh.c
@@ -16,14 +16,16 @@
 #include <linux/mpi.h>
 
 struct dh_ctx {
-	MPI p;
-	MPI g;
-	MPI xa;
+	MPI p;	/* Value is guaranteed to be set. */
+	MPI q;	/* Value is optional. */
+	MPI g;	/* Value is guaranteed to be set. */
+	MPI xa;	/* Value is guaranteed to be set. */
 };
 
 static void dh_clear_ctx(struct dh_ctx *ctx)
 {
 	mpi_free(ctx->p);
+	mpi_free(ctx->q);
 	mpi_free(ctx->g);
 	mpi_free(ctx->xa);
 	memset(ctx, 0, sizeof(*ctx));
@@ -60,6 +62,12 @@ static int dh_set_params(struct dh_ctx *ctx, struct dh *params)
 	if (!ctx->p)
 		return -EINVAL;
 
+	if (params->q && params->q_size) {
+		ctx->q = mpi_read_raw_data(params->q, params->q_size);
+		if (!ctx->q)
+			return -EINVAL;
+	}
+
 	ctx->g = mpi_read_raw_data(params->g, params->g_size);
 	if (!ctx->g)
 		return -EINVAL;
@@ -93,6 +101,55 @@ err_clear_ctx:
 	return -EINVAL;
 }
 
+/*
+ * SP800-56A public key verification:
+ *
+ * * If Q is provided as part of the domain paramenters, a full validation
+ *   according to SP800-56A section 5.6.2.3.1 is performed.
+ *
+ * * If Q is not provided, a partial validation according to SP800-56A section
+ *   5.6.2.3.2 is performed.
+ */
+static int dh_is_pubkey_valid(struct dh_ctx *ctx, MPI y)
+{
+	if (unlikely(!ctx->p))
+		return -EINVAL;
+
+	/*
+	 * Step 1: Verify that 2 <= y <= p - 2.
+	 *
+	 * The upper limit check is actually y < p instead of y < p - 1
+	 * as the mpi_sub_ui function is yet missing.
+	 */
+	if (mpi_cmp_ui(y, 1) < 1 || mpi_cmp(y, ctx->p) >= 0)
+		return -EINVAL;
+
+	/* Step 2: Verify that 1 = y^q mod p */
+	if (ctx->q) {
+		MPI val = mpi_alloc(0);
+		int ret;
+
+		if (!val)
+			return -ENOMEM;
+
+		ret = mpi_powm(val, y, ctx->q, ctx->p);
+
+		if (ret) {
+			mpi_free(val);
+			return ret;
+		}
+
+		ret = mpi_cmp_ui(val, 1);
+
+		mpi_free(val);
+
+		if (ret != 0)
+			return -EINVAL;
+	}
+
+	return 0;
+}
+
 static int dh_compute_value(struct kpp_request *req)
 {
 	struct crypto_kpp *tfm = crypto_kpp_reqtfm(req);
@@ -115,6 +172,9 @@ static int dh_compute_value(struct kpp_request *req)
 			ret = -EINVAL;
 			goto err_free_val;
 		}
+		ret = dh_is_pubkey_valid(ctx, base);
+		if (ret)
+			goto err_free_val;
 	} else {
 		base = ctx->g;
 	}
diff --git a/crypto/dh_helper.c b/crypto/dh_helper.c
index 24fdb2ecaa85..a7de3d9ce5ac 100644
--- a/crypto/dh_helper.c
+++ b/crypto/dh_helper.c
@@ -30,7 +30,7 @@ static inline const u8 *dh_unpack_data(void *dst, const void *src, size_t size)
 
 static inline unsigned int dh_data_size(const struct dh *p)
 {
-	return p->key_size + p->p_size + p->g_size;
+	return p->key_size + p->p_size + p->q_size + p->g_size;
 }
 
 unsigned int crypto_dh_key_len(const struct dh *p)
@@ -56,9 +56,11 @@ int crypto_dh_encode_key(char *buf, unsigned int len, const struct dh *params)
 	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->q_size, sizeof(params->q_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);
+	ptr = dh_pack_data(ptr, params->q, params->q_size);
 	dh_pack_data(ptr, params->g, params->g_size);
 
 	return 0;
@@ -79,6 +81,7 @@ int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params)
 
 	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->q_size, ptr, sizeof(params->q_size));
 	ptr = dh_unpack_data(&params->g_size, ptr, sizeof(params->g_size));
 	if (secret.len != crypto_dh_key_len(params))
 		return -EINVAL;
@@ -88,7 +91,7 @@ int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params)
 	 * some drivers assume otherwise.
 	 */
 	if (params->key_size > params->p_size ||
-	    params->g_size > params->p_size)
+	    params->g_size > params->p_size || params->q_size > params->p_size)
 		return -EINVAL;
 
 	/* Don't allocate memory. Set pointers to data within
@@ -96,7 +99,9 @@ int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params)
 	 */
 	params->key = (void *)ptr;
 	params->p = (void *)(ptr + params->key_size);
-	params->g = (void *)(ptr + params->key_size + params->p_size);
+	params->q = (void *)(ptr + params->key_size + params->p_size);
+	params->g = (void *)(ptr + params->key_size + params->p_size +
+			     params->q_size);
 
 	/*
 	 * Don't permit 'p' to be 0.  It's not a prime number, and it's subject
@@ -106,6 +111,10 @@ int crypto_dh_decode_key(const char *buf, unsigned int len, struct dh *params)
 	if (memchr_inv(params->p, 0, params->p_size) == NULL)
 		return -EINVAL;
 
+	/* It is permissible to not provide Q. */
+	if (params->q_size == 0)
+		params->q = NULL;
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(crypto_dh_decode_key);
diff --git a/include/crypto/dh.h b/include/crypto/dh.h
index 71e1bb24d79f..7e0dad94cb2b 100644
--- a/include/crypto/dh.h
+++ b/include/crypto/dh.h
@@ -29,17 +29,21 @@
  *
  * @key:	Private DH key
  * @p:		Diffie-Hellman parameter P
+ * @q:		Diffie-Hellman parameter Q
  * @g:		Diffie-Hellman generator G
  * @key_size:	Size of the private DH key
  * @p_size:	Size of DH parameter P
+ * @q_size:	Size of DH parameter Q
  * @g_size:	Size of DH generator G
  */
 struct dh {
 	void *key;
 	void *p;
+	void *q;
 	void *g;
 	unsigned int key_size;
 	unsigned int p_size;
+	unsigned int q_size;
 	unsigned int g_size;
 };