diff --git a/lib/Kconfig b/lib/Kconfig
index 4d06f7e..965cf7b 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -265,6 +265,7 @@
 	  present.
 
 source lib/rsa/Kconfig
+source lib/crypto/Kconfig
 
 config TPM
 	bool "Trusted Platform Module (TPM) Support"
diff --git a/lib/Makefile b/lib/Makefile
index d5bf195..1fb650c 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -18,6 +18,7 @@
 obj-$(CONFIG_ARCH_AT91) += at91/
 obj-$(CONFIG_OPTEE) += optee/
 obj-$(CONFIG_ASN1_DECODER) += asn1_decoder.o
+obj-y += crypto/
 
 obj-$(CONFIG_AES) += aes.o
 
diff --git a/lib/crypto/Kconfig b/lib/crypto/Kconfig
index 9572ea8..aeb599c 100644
--- a/lib/crypto/Kconfig
+++ b/lib/crypto/Kconfig
@@ -27,4 +27,16 @@
 	  public key data and provides the ability to instantiate a public
 	  key.
 
+config X509_CERTIFICATE_PARSER
+	bool "X.509 certificate parser"
+	depends on ASYMMETRIC_PUBLIC_KEY_SUBTYPE
+	select ASN1_DECODER
+	select ASN1_COMPILER
+	select OID_REGISTRY
+	select LIB_DATE
+	help
+	  This option provides support for parsing X.509 format blobs for key
+	  data and provides the ability to instantiate a crypto key from a
+	  public key packet found inside the certificate.
+
 endif # ASYMMETRIC_KEY_TYPE
diff --git a/lib/crypto/Makefile b/lib/crypto/Makefile
index 69330a9..d7e27be 100644
--- a/lib/crypto/Makefile
+++ b/lib/crypto/Makefile
@@ -19,3 +19,20 @@
 
 $(obj)/rsapubkey.asn1.o: $(obj)/rsapubkey.asn1.c $(obj)/rsapubkey.asn1.h
 $(obj)/rsa_helper.o: $(obj)/rsapubkey.asn1.h
+
+#
+# X.509 Certificate handling
+#
+obj-$(CONFIG_X509_CERTIFICATE_PARSER) += x509_key_parser.o
+x509_key_parser-y := \
+	x509.asn1.o \
+	x509_akid.asn1.o \
+	x509_cert_parser.o \
+	x509_public_key.o
+
+$(obj)/x509_cert_parser.o: \
+	$(obj)/x509.asn1.h \
+	$(obj)/x509_akid.asn1.h
+
+$(obj)/x509.asn1.o: $(obj)/x509.asn1.c $(obj)/x509.asn1.h
+$(obj)/x509_akid.asn1.o: $(obj)/x509_akid.asn1.c $(obj)/x509_akid.asn1.h
diff --git a/lib/crypto/x509.asn1 b/lib/crypto/x509.asn1
new file mode 100644
index 0000000..5c9f4e4
--- /dev/null
+++ b/lib/crypto/x509.asn1
@@ -0,0 +1,60 @@
+Certificate ::= SEQUENCE {
+	tbsCertificate		TBSCertificate ({ x509_note_tbs_certificate }),
+	signatureAlgorithm	AlgorithmIdentifier,
+	signature		BIT STRING ({ x509_note_signature })
+	}
+
+TBSCertificate ::= SEQUENCE {
+	version           [ 0 ]	Version DEFAULT,
+	serialNumber		CertificateSerialNumber ({ x509_note_serial }),
+	signature		AlgorithmIdentifier ({ x509_note_pkey_algo }),
+	issuer			Name ({ x509_note_issuer }),
+	validity		Validity,
+	subject			Name ({ x509_note_subject }),
+	subjectPublicKeyInfo	SubjectPublicKeyInfo,
+	issuerUniqueID    [ 1 ]	IMPLICIT UniqueIdentifier OPTIONAL,
+	subjectUniqueID   [ 2 ]	IMPLICIT UniqueIdentifier OPTIONAL,
+	extensions        [ 3 ]	Extensions OPTIONAL
+	}
+
+Version ::= INTEGER
+CertificateSerialNumber ::= INTEGER
+
+AlgorithmIdentifier ::= SEQUENCE {
+	algorithm		OBJECT IDENTIFIER ({ x509_note_OID }),
+	parameters		ANY OPTIONAL ({ x509_note_params })
+}
+
+Name ::= SEQUENCE OF RelativeDistinguishedName
+
+RelativeDistinguishedName ::= SET OF AttributeValueAssertion
+
+AttributeValueAssertion ::= SEQUENCE {
+	attributeType		OBJECT IDENTIFIER ({ x509_note_OID }),
+	attributeValue		ANY ({ x509_extract_name_segment })
+	}
+
+Validity ::= SEQUENCE {
+	notBefore		Time ({ x509_note_not_before }),
+	notAfter		Time ({ x509_note_not_after })
+	}
+
+Time ::= CHOICE {
+	utcTime			UTCTime,
+	generalTime		GeneralizedTime
+	}
+
+SubjectPublicKeyInfo ::= SEQUENCE {
+	algorithm		AlgorithmIdentifier,
+	subjectPublicKey	BIT STRING ({ x509_extract_key_data })
+	}
+
+UniqueIdentifier ::= BIT STRING
+
+Extensions ::= SEQUENCE OF Extension
+
+Extension ::= SEQUENCE {
+	extnid			OBJECT IDENTIFIER ({ x509_note_OID }),
+	critical		BOOLEAN DEFAULT,
+	extnValue		OCTET STRING ({ x509_process_extension })
+	}
diff --git a/lib/crypto/x509_akid.asn1 b/lib/crypto/x509_akid.asn1
new file mode 100644
index 0000000..1a33231
--- /dev/null
+++ b/lib/crypto/x509_akid.asn1
@@ -0,0 +1,35 @@
+-- X.509 AuthorityKeyIdentifier
+-- rfc5280 section 4.2.1.1
+
+AuthorityKeyIdentifier ::= SEQUENCE {
+	keyIdentifier			[0] IMPLICIT KeyIdentifier		OPTIONAL,
+	authorityCertIssuer		[1] IMPLICIT GeneralNames		OPTIONAL,
+	authorityCertSerialNumber	[2] IMPLICIT CertificateSerialNumber	OPTIONAL
+	}
+
+KeyIdentifier ::= OCTET STRING ({ x509_akid_note_kid })
+
+CertificateSerialNumber ::= INTEGER ({ x509_akid_note_serial })
+
+GeneralNames ::= SEQUENCE OF GeneralName
+
+GeneralName ::= CHOICE {
+	otherName			[0] ANY,
+	rfc822Name			[1] IA5String,
+	dNSName				[2] IA5String,
+	x400Address			[3] ANY,
+	directoryName			[4] Name ({ x509_akid_note_name }),
+	ediPartyName			[5] ANY,
+	uniformResourceIdentifier	[6] IA5String,
+	iPAddress			[7] OCTET STRING,
+	registeredID			[8] OBJECT IDENTIFIER
+	}
+
+Name ::= SEQUENCE OF RelativeDistinguishedName
+
+RelativeDistinguishedName ::= SET OF AttributeValueAssertion
+
+AttributeValueAssertion ::= SEQUENCE {
+	attributeType		OBJECT IDENTIFIER ({ x509_note_OID }),
+	attributeValue		ANY ({ x509_extract_name_segment })
+	}
diff --git a/lib/crypto/x509_cert_parser.c b/lib/crypto/x509_cert_parser.c
new file mode 100644
index 0000000..e6d2a42
--- /dev/null
+++ b/lib/crypto/x509_cert_parser.c
@@ -0,0 +1,697 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* X.509 certificate parser
+ *
+ * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#define pr_fmt(fmt) "X.509: "fmt
+#include <linux/kernel.h>
+#ifndef __UBOOT__
+#include <linux/export.h>
+#include <linux/slab.h>
+#endif
+#include <linux/err.h>
+#include <linux/oid_registry.h>
+#ifdef __UBOOT__
+#include <linux/string.h>
+#endif
+#include <crypto/public_key.h>
+#include "x509_parser.h"
+#include "x509.asn1.h"
+#include "x509_akid.asn1.h"
+
+struct x509_parse_context {
+	struct x509_certificate	*cert;		/* Certificate being constructed */
+	unsigned long	data;			/* Start of data */
+	const void	*cert_start;		/* Start of cert content */
+	const void	*key;			/* Key data */
+	size_t		key_size;		/* Size of key data */
+	const void	*params;		/* Key parameters */
+	size_t		params_size;		/* Size of key parameters */
+	enum OID	key_algo;		/* Public key algorithm */
+	enum OID	last_oid;		/* Last OID encountered */
+	enum OID	algo_oid;		/* Algorithm OID */
+	unsigned char	nr_mpi;			/* Number of MPIs stored */
+	u8		o_size;			/* Size of organizationName (O) */
+	u8		cn_size;		/* Size of commonName (CN) */
+	u8		email_size;		/* Size of emailAddress */
+	u16		o_offset;		/* Offset of organizationName (O) */
+	u16		cn_offset;		/* Offset of commonName (CN) */
+	u16		email_offset;		/* Offset of emailAddress */
+	unsigned	raw_akid_size;
+	const void	*raw_akid;		/* Raw authorityKeyId in ASN.1 */
+	const void	*akid_raw_issuer;	/* Raw directoryName in authorityKeyId */
+	unsigned	akid_raw_issuer_size;
+};
+
+/*
+ * Free an X.509 certificate
+ */
+void x509_free_certificate(struct x509_certificate *cert)
+{
+	if (cert) {
+		public_key_free(cert->pub);
+		public_key_signature_free(cert->sig);
+		kfree(cert->issuer);
+		kfree(cert->subject);
+		kfree(cert->id);
+		kfree(cert->skid);
+		kfree(cert);
+	}
+}
+EXPORT_SYMBOL_GPL(x509_free_certificate);
+
+/*
+ * Parse an X.509 certificate
+ */
+struct x509_certificate *x509_cert_parse(const void *data, size_t datalen)
+{
+	struct x509_certificate *cert;
+	struct x509_parse_context *ctx;
+	struct asymmetric_key_id *kid;
+	long ret;
+
+	ret = -ENOMEM;
+	cert = kzalloc(sizeof(struct x509_certificate), GFP_KERNEL);
+	if (!cert)
+		goto error_no_cert;
+	cert->pub = kzalloc(sizeof(struct public_key), GFP_KERNEL);
+	if (!cert->pub)
+		goto error_no_ctx;
+	cert->sig = kzalloc(sizeof(struct public_key_signature), GFP_KERNEL);
+	if (!cert->sig)
+		goto error_no_ctx;
+	ctx = kzalloc(sizeof(struct x509_parse_context), GFP_KERNEL);
+	if (!ctx)
+		goto error_no_ctx;
+
+	ctx->cert = cert;
+	ctx->data = (unsigned long)data;
+
+	/* Attempt to decode the certificate */
+	ret = asn1_ber_decoder(&x509_decoder, ctx, data, datalen);
+	if (ret < 0)
+		goto error_decode;
+
+	/* Decode the AuthorityKeyIdentifier */
+	if (ctx->raw_akid) {
+		pr_devel("AKID: %u %*phN\n",
+			 ctx->raw_akid_size, ctx->raw_akid_size, ctx->raw_akid);
+		ret = asn1_ber_decoder(&x509_akid_decoder, ctx,
+				       ctx->raw_akid, ctx->raw_akid_size);
+		if (ret < 0) {
+			pr_warn("Couldn't decode AuthKeyIdentifier\n");
+			goto error_decode;
+		}
+	}
+
+	ret = -ENOMEM;
+	cert->pub->key = kmemdup(ctx->key, ctx->key_size, GFP_KERNEL);
+	if (!cert->pub->key)
+		goto error_decode;
+
+	cert->pub->keylen = ctx->key_size;
+
+	cert->pub->params = kmemdup(ctx->params, ctx->params_size, GFP_KERNEL);
+	if (!cert->pub->params)
+		goto error_decode;
+
+	cert->pub->paramlen = ctx->params_size;
+	cert->pub->algo = ctx->key_algo;
+
+	/* Grab the signature bits */
+	ret = x509_get_sig_params(cert);
+	if (ret < 0)
+		goto error_decode;
+
+	/* Generate cert issuer + serial number key ID */
+	kid = asymmetric_key_generate_id(cert->raw_serial,
+					 cert->raw_serial_size,
+					 cert->raw_issuer,
+					 cert->raw_issuer_size);
+	if (IS_ERR(kid)) {
+		ret = PTR_ERR(kid);
+		goto error_decode;
+	}
+	cert->id = kid;
+
+#ifndef __UBOOT__
+	/* Detect self-signed certificates */
+	ret = x509_check_for_self_signed(cert);
+	if (ret < 0)
+		goto error_decode;
+#endif
+
+	kfree(ctx);
+	return cert;
+
+error_decode:
+	kfree(ctx);
+error_no_ctx:
+	x509_free_certificate(cert);
+error_no_cert:
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(x509_cert_parse);
+
+/*
+ * Note an OID when we find one for later processing when we know how
+ * to interpret it.
+ */
+int x509_note_OID(void *context, size_t hdrlen,
+	     unsigned char tag,
+	     const void *value, size_t vlen)
+{
+	struct x509_parse_context *ctx = context;
+
+	ctx->last_oid = look_up_OID(value, vlen);
+	if (ctx->last_oid == OID__NR) {
+		char buffer[50];
+		sprint_oid(value, vlen, buffer, sizeof(buffer));
+		pr_debug("Unknown OID: [%lu] %s\n",
+			 (unsigned long)value - ctx->data, buffer);
+	}
+	return 0;
+}
+
+/*
+ * Save the position of the TBS data so that we can check the signature over it
+ * later.
+ */
+int x509_note_tbs_certificate(void *context, size_t hdrlen,
+			      unsigned char tag,
+			      const void *value, size_t vlen)
+{
+	struct x509_parse_context *ctx = context;
+
+	pr_debug("x509_note_tbs_certificate(,%zu,%02x,%ld,%zu)!\n",
+		 hdrlen, tag, (unsigned long)value - ctx->data, vlen);
+
+	ctx->cert->tbs = value - hdrlen;
+	ctx->cert->tbs_size = vlen + hdrlen;
+	return 0;
+}
+
+/*
+ * Record the public key algorithm
+ */
+int x509_note_pkey_algo(void *context, size_t hdrlen,
+			unsigned char tag,
+			const void *value, size_t vlen)
+{
+	struct x509_parse_context *ctx = context;
+
+	pr_debug("PubKey Algo: %u\n", ctx->last_oid);
+
+	switch (ctx->last_oid) {
+	case OID_md2WithRSAEncryption:
+	case OID_md3WithRSAEncryption:
+	default:
+		return -ENOPKG; /* Unsupported combination */
+
+	case OID_md4WithRSAEncryption:
+		ctx->cert->sig->hash_algo = "md4";
+		goto rsa_pkcs1;
+
+	case OID_sha1WithRSAEncryption:
+		ctx->cert->sig->hash_algo = "sha1";
+		goto rsa_pkcs1;
+
+	case OID_sha256WithRSAEncryption:
+		ctx->cert->sig->hash_algo = "sha256";
+		goto rsa_pkcs1;
+
+	case OID_sha384WithRSAEncryption:
+		ctx->cert->sig->hash_algo = "sha384";
+		goto rsa_pkcs1;
+
+	case OID_sha512WithRSAEncryption:
+		ctx->cert->sig->hash_algo = "sha512";
+		goto rsa_pkcs1;
+
+	case OID_sha224WithRSAEncryption:
+		ctx->cert->sig->hash_algo = "sha224";
+		goto rsa_pkcs1;
+
+	case OID_gost2012Signature256:
+		ctx->cert->sig->hash_algo = "streebog256";
+		goto ecrdsa;
+
+	case OID_gost2012Signature512:
+		ctx->cert->sig->hash_algo = "streebog512";
+		goto ecrdsa;
+	}
+
+rsa_pkcs1:
+	ctx->cert->sig->pkey_algo = "rsa";
+	ctx->cert->sig->encoding = "pkcs1";
+	ctx->algo_oid = ctx->last_oid;
+	return 0;
+ecrdsa:
+	ctx->cert->sig->pkey_algo = "ecrdsa";
+	ctx->cert->sig->encoding = "raw";
+	ctx->algo_oid = ctx->last_oid;
+	return 0;
+}
+
+/*
+ * Note the whereabouts and type of the signature.
+ */
+int x509_note_signature(void *context, size_t hdrlen,
+			unsigned char tag,
+			const void *value, size_t vlen)
+{
+	struct x509_parse_context *ctx = context;
+
+	pr_debug("Signature type: %u size %zu\n", ctx->last_oid, vlen);
+
+	if (ctx->last_oid != ctx->algo_oid) {
+		pr_warn("Got cert with pkey (%u) and sig (%u) algorithm OIDs\n",
+			ctx->algo_oid, ctx->last_oid);
+		return -EINVAL;
+	}
+
+	if (strcmp(ctx->cert->sig->pkey_algo, "rsa") == 0 ||
+	    strcmp(ctx->cert->sig->pkey_algo, "ecrdsa") == 0) {
+		/* Discard the BIT STRING metadata */
+		if (vlen < 1 || *(const u8 *)value != 0)
+			return -EBADMSG;
+
+		value++;
+		vlen--;
+	}
+
+	ctx->cert->raw_sig = value;
+	ctx->cert->raw_sig_size = vlen;
+	return 0;
+}
+
+/*
+ * Note the certificate serial number
+ */
+int x509_note_serial(void *context, size_t hdrlen,
+		     unsigned char tag,
+		     const void *value, size_t vlen)
+{
+	struct x509_parse_context *ctx = context;
+	ctx->cert->raw_serial = value;
+	ctx->cert->raw_serial_size = vlen;
+	return 0;
+}
+
+/*
+ * Note some of the name segments from which we'll fabricate a name.
+ */
+int x509_extract_name_segment(void *context, size_t hdrlen,
+			      unsigned char tag,
+			      const void *value, size_t vlen)
+{
+	struct x509_parse_context *ctx = context;
+
+	switch (ctx->last_oid) {
+	case OID_commonName:
+		ctx->cn_size = vlen;
+		ctx->cn_offset = (unsigned long)value - ctx->data;
+		break;
+	case OID_organizationName:
+		ctx->o_size = vlen;
+		ctx->o_offset = (unsigned long)value - ctx->data;
+		break;
+	case OID_email_address:
+		ctx->email_size = vlen;
+		ctx->email_offset = (unsigned long)value - ctx->data;
+		break;
+	default:
+		break;
+	}
+
+	return 0;
+}
+
+/*
+ * Fabricate and save the issuer and subject names
+ */
+static int x509_fabricate_name(struct x509_parse_context *ctx, size_t hdrlen,
+			       unsigned char tag,
+			       char **_name, size_t vlen)
+{
+	const void *name, *data = (const void *)ctx->data;
+	size_t namesize;
+	char *buffer;
+
+	if (*_name)
+		return -EINVAL;
+
+	/* Empty name string if no material */
+	if (!ctx->cn_size && !ctx->o_size && !ctx->email_size) {
+		buffer = kmalloc(1, GFP_KERNEL);
+		if (!buffer)
+			return -ENOMEM;
+		buffer[0] = 0;
+		goto done;
+	}
+
+	if (ctx->cn_size && ctx->o_size) {
+		/* Consider combining O and CN, but use only the CN if it is
+		 * prefixed by the O, or a significant portion thereof.
+		 */
+		namesize = ctx->cn_size;
+		name = data + ctx->cn_offset;
+		if (ctx->cn_size >= ctx->o_size &&
+		    memcmp(data + ctx->cn_offset, data + ctx->o_offset,
+			   ctx->o_size) == 0)
+			goto single_component;
+		if (ctx->cn_size >= 7 &&
+		    ctx->o_size >= 7 &&
+		    memcmp(data + ctx->cn_offset, data + ctx->o_offset, 7) == 0)
+			goto single_component;
+
+		buffer = kmalloc(ctx->o_size + 2 + ctx->cn_size + 1,
+				 GFP_KERNEL);
+		if (!buffer)
+			return -ENOMEM;
+
+		memcpy(buffer,
+		       data + ctx->o_offset, ctx->o_size);
+		buffer[ctx->o_size + 0] = ':';
+		buffer[ctx->o_size + 1] = ' ';
+		memcpy(buffer + ctx->o_size + 2,
+		       data + ctx->cn_offset, ctx->cn_size);
+		buffer[ctx->o_size + 2 + ctx->cn_size] = 0;
+		goto done;
+
+	} else if (ctx->cn_size) {
+		namesize = ctx->cn_size;
+		name = data + ctx->cn_offset;
+	} else if (ctx->o_size) {
+		namesize = ctx->o_size;
+		name = data + ctx->o_offset;
+	} else {
+		namesize = ctx->email_size;
+		name = data + ctx->email_offset;
+	}
+
+single_component:
+	buffer = kmalloc(namesize + 1, GFP_KERNEL);
+	if (!buffer)
+		return -ENOMEM;
+	memcpy(buffer, name, namesize);
+	buffer[namesize] = 0;
+
+done:
+	*_name = buffer;
+	ctx->cn_size = 0;
+	ctx->o_size = 0;
+	ctx->email_size = 0;
+	return 0;
+}
+
+int x509_note_issuer(void *context, size_t hdrlen,
+		     unsigned char tag,
+		     const void *value, size_t vlen)
+{
+	struct x509_parse_context *ctx = context;
+	ctx->cert->raw_issuer = value;
+	ctx->cert->raw_issuer_size = vlen;
+	return x509_fabricate_name(ctx, hdrlen, tag, &ctx->cert->issuer, vlen);
+}
+
+int x509_note_subject(void *context, size_t hdrlen,
+		      unsigned char tag,
+		      const void *value, size_t vlen)
+{
+	struct x509_parse_context *ctx = context;
+	ctx->cert->raw_subject = value;
+	ctx->cert->raw_subject_size = vlen;
+	return x509_fabricate_name(ctx, hdrlen, tag, &ctx->cert->subject, vlen);
+}
+
+/*
+ * Extract the parameters for the public key
+ */
+int x509_note_params(void *context, size_t hdrlen,
+		     unsigned char tag,
+		     const void *value, size_t vlen)
+{
+	struct x509_parse_context *ctx = context;
+
+	/*
+	 * AlgorithmIdentifier is used three times in the x509, we should skip
+	 * first and ignore third, using second one which is after subject and
+	 * before subjectPublicKey.
+	 */
+	if (!ctx->cert->raw_subject || ctx->key)
+		return 0;
+	ctx->params = value - hdrlen;
+	ctx->params_size = vlen + hdrlen;
+	return 0;
+}
+
+/*
+ * Extract the data for the public key algorithm
+ */
+int x509_extract_key_data(void *context, size_t hdrlen,
+			  unsigned char tag,
+			  const void *value, size_t vlen)
+{
+	struct x509_parse_context *ctx = context;
+
+	ctx->key_algo = ctx->last_oid;
+	if (ctx->last_oid == OID_rsaEncryption)
+		ctx->cert->pub->pkey_algo = "rsa";
+	else if (ctx->last_oid == OID_gost2012PKey256 ||
+		 ctx->last_oid == OID_gost2012PKey512)
+		ctx->cert->pub->pkey_algo = "ecrdsa";
+	else
+		return -ENOPKG;
+
+	/* Discard the BIT STRING metadata */
+	if (vlen < 1 || *(const u8 *)value != 0)
+		return -EBADMSG;
+	ctx->key = value + 1;
+	ctx->key_size = vlen - 1;
+	return 0;
+}
+
+/* The keyIdentifier in AuthorityKeyIdentifier SEQUENCE is tag(CONT,PRIM,0) */
+#define SEQ_TAG_KEYID (ASN1_CONT << 6)
+
+/*
+ * Process certificate extensions that are used to qualify the certificate.
+ */
+int x509_process_extension(void *context, size_t hdrlen,
+			   unsigned char tag,
+			   const void *value, size_t vlen)
+{
+	struct x509_parse_context *ctx = context;
+	struct asymmetric_key_id *kid;
+	const unsigned char *v = value;
+
+	pr_debug("Extension: %u\n", ctx->last_oid);
+
+	if (ctx->last_oid == OID_subjectKeyIdentifier) {
+		/* Get hold of the key fingerprint */
+		if (ctx->cert->skid || vlen < 3)
+			return -EBADMSG;
+		if (v[0] != ASN1_OTS || v[1] != vlen - 2)
+			return -EBADMSG;
+		v += 2;
+		vlen -= 2;
+
+		ctx->cert->raw_skid_size = vlen;
+		ctx->cert->raw_skid = v;
+		kid = asymmetric_key_generate_id(v, vlen, "", 0);
+		if (IS_ERR(kid))
+			return PTR_ERR(kid);
+		ctx->cert->skid = kid;
+		pr_debug("subjkeyid %*phN\n", kid->len, kid->data);
+		return 0;
+	}
+
+	if (ctx->last_oid == OID_authorityKeyIdentifier) {
+		/* Get hold of the CA key fingerprint */
+		ctx->raw_akid = v;
+		ctx->raw_akid_size = vlen;
+		return 0;
+	}
+
+	return 0;
+}
+
+/**
+ * x509_decode_time - Decode an X.509 time ASN.1 object
+ * @_t: The time to fill in
+ * @hdrlen: The length of the object header
+ * @tag: The object tag
+ * @value: The object value
+ * @vlen: The size of the object value
+ *
+ * Decode an ASN.1 universal time or generalised time field into a struct the
+ * kernel can handle and check it for validity.  The time is decoded thus:
+ *
+ *	[RFC5280 §4.1.2.5]
+ *	CAs conforming to this profile MUST always encode certificate validity
+ *	dates through the year 2049 as UTCTime; certificate validity dates in
+ *	2050 or later MUST be encoded as GeneralizedTime.  Conforming
+ *	applications MUST be able to process validity dates that are encoded in
+ *	either UTCTime or GeneralizedTime.
+ */
+int x509_decode_time(time64_t *_t,  size_t hdrlen,
+		     unsigned char tag,
+		     const unsigned char *value, size_t vlen)
+{
+	static const unsigned char month_lengths[] = { 31, 28, 31, 30, 31, 30,
+						       31, 31, 30, 31, 30, 31 };
+	const unsigned char *p = value;
+	unsigned year, mon, day, hour, min, sec, mon_len;
+
+#define dec2bin(X) ({ unsigned char x = (X) - '0'; if (x > 9) goto invalid_time; x; })
+#define DD2bin(P) ({ unsigned x = dec2bin(P[0]) * 10 + dec2bin(P[1]); P += 2; x; })
+
+	if (tag == ASN1_UNITIM) {
+		/* UTCTime: YYMMDDHHMMSSZ */
+		if (vlen != 13)
+			goto unsupported_time;
+		year = DD2bin(p);
+		if (year >= 50)
+			year += 1900;
+		else
+			year += 2000;
+	} else if (tag == ASN1_GENTIM) {
+		/* GenTime: YYYYMMDDHHMMSSZ */
+		if (vlen != 15)
+			goto unsupported_time;
+		year = DD2bin(p) * 100 + DD2bin(p);
+		if (year >= 1950 && year <= 2049)
+			goto invalid_time;
+	} else {
+		goto unsupported_time;
+	}
+
+	mon  = DD2bin(p);
+	day = DD2bin(p);
+	hour = DD2bin(p);
+	min  = DD2bin(p);
+	sec  = DD2bin(p);
+
+	if (*p != 'Z')
+		goto unsupported_time;
+
+	if (year < 1970 ||
+	    mon < 1 || mon > 12)
+		goto invalid_time;
+
+	mon_len = month_lengths[mon - 1];
+	if (mon == 2) {
+		if (year % 4 == 0) {
+			mon_len = 29;
+			if (year % 100 == 0) {
+				mon_len = 28;
+				if (year % 400 == 0)
+					mon_len = 29;
+			}
+		}
+	}
+
+	if (day < 1 || day > mon_len ||
+	    hour > 24 || /* ISO 8601 permits 24:00:00 as midnight tomorrow */
+	    min > 59 ||
+	    sec > 60) /* ISO 8601 permits leap seconds [X.680 46.3] */
+		goto invalid_time;
+
+	*_t = mktime64(year, mon, day, hour, min, sec);
+	return 0;
+
+unsupported_time:
+	pr_debug("Got unsupported time [tag %02x]: '%*phN'\n",
+		 tag, (int)vlen, value);
+	return -EBADMSG;
+invalid_time:
+	pr_debug("Got invalid time [tag %02x]: '%*phN'\n",
+		 tag, (int)vlen, value);
+	return -EBADMSG;
+}
+EXPORT_SYMBOL_GPL(x509_decode_time);
+
+int x509_note_not_before(void *context, size_t hdrlen,
+			 unsigned char tag,
+			 const void *value, size_t vlen)
+{
+	struct x509_parse_context *ctx = context;
+	return x509_decode_time(&ctx->cert->valid_from, hdrlen, tag, value, vlen);
+}
+
+int x509_note_not_after(void *context, size_t hdrlen,
+			unsigned char tag,
+			const void *value, size_t vlen)
+{
+	struct x509_parse_context *ctx = context;
+	return x509_decode_time(&ctx->cert->valid_to, hdrlen, tag, value, vlen);
+}
+
+/*
+ * Note a key identifier-based AuthorityKeyIdentifier
+ */
+int x509_akid_note_kid(void *context, size_t hdrlen,
+		       unsigned char tag,
+		       const void *value, size_t vlen)
+{
+	struct x509_parse_context *ctx = context;
+	struct asymmetric_key_id *kid;
+
+	pr_debug("AKID: keyid: %*phN\n", (int)vlen, value);
+
+	if (ctx->cert->sig->auth_ids[1])
+		return 0;
+
+	kid = asymmetric_key_generate_id(value, vlen, "", 0);
+	if (IS_ERR(kid))
+		return PTR_ERR(kid);
+	pr_debug("authkeyid %*phN\n", kid->len, kid->data);
+	ctx->cert->sig->auth_ids[1] = kid;
+	return 0;
+}
+
+/*
+ * Note a directoryName in an AuthorityKeyIdentifier
+ */
+int x509_akid_note_name(void *context, size_t hdrlen,
+			unsigned char tag,
+			const void *value, size_t vlen)
+{
+	struct x509_parse_context *ctx = context;
+
+	pr_debug("AKID: name: %*phN\n", (int)vlen, value);
+
+	ctx->akid_raw_issuer = value;
+	ctx->akid_raw_issuer_size = vlen;
+	return 0;
+}
+
+/*
+ * Note a serial number in an AuthorityKeyIdentifier
+ */
+int x509_akid_note_serial(void *context, size_t hdrlen,
+			  unsigned char tag,
+			  const void *value, size_t vlen)
+{
+	struct x509_parse_context *ctx = context;
+	struct asymmetric_key_id *kid;
+
+	pr_debug("AKID: serial: %*phN\n", (int)vlen, value);
+
+	if (!ctx->akid_raw_issuer || ctx->cert->sig->auth_ids[0])
+		return 0;
+
+	kid = asymmetric_key_generate_id(value,
+					 vlen,
+					 ctx->akid_raw_issuer,
+					 ctx->akid_raw_issuer_size);
+	if (IS_ERR(kid))
+		return PTR_ERR(kid);
+
+	pr_debug("authkeyid %*phN\n", kid->len, kid->data);
+	ctx->cert->sig->auth_ids[0] = kid;
+	return 0;
+}
diff --git a/lib/crypto/x509_parser.h b/lib/crypto/x509_parser.h
new file mode 100644
index 0000000..c233f13
--- /dev/null
+++ b/lib/crypto/x509_parser.h
@@ -0,0 +1,57 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* X.509 certificate parser internal definitions
+ *
+ * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/time.h>
+#include <crypto/public_key.h>
+#include <keys/asymmetric-type.h>
+
+struct x509_certificate {
+	struct x509_certificate *next;
+	struct x509_certificate *signer;	/* Certificate that signed this one */
+	struct public_key *pub;			/* Public key details */
+	struct public_key_signature *sig;	/* Signature parameters */
+	char		*issuer;		/* Name of certificate issuer */
+	char		*subject;		/* Name of certificate subject */
+	struct asymmetric_key_id *id;		/* Issuer + Serial number */
+	struct asymmetric_key_id *skid;		/* Subject + subjectKeyId (optional) */
+	time64_t	valid_from;
+	time64_t	valid_to;
+	const void	*tbs;			/* Signed data */
+	unsigned	tbs_size;		/* Size of signed data */
+	unsigned	raw_sig_size;		/* Size of sigature */
+	const void	*raw_sig;		/* Signature data */
+	const void	*raw_serial;		/* Raw serial number in ASN.1 */
+	unsigned	raw_serial_size;
+	unsigned	raw_issuer_size;
+	const void	*raw_issuer;		/* Raw issuer name in ASN.1 */
+	const void	*raw_subject;		/* Raw subject name in ASN.1 */
+	unsigned	raw_subject_size;
+	unsigned	raw_skid_size;
+	const void	*raw_skid;		/* Raw subjectKeyId in ASN.1 */
+	unsigned	index;
+	bool		seen;			/* Infinite recursion prevention */
+	bool		verified;
+	bool		self_signed;		/* T if self-signed (check unsupported_sig too) */
+	bool		unsupported_key;	/* T if key uses unsupported crypto */
+	bool		unsupported_sig;	/* T if signature uses unsupported crypto */
+	bool		blacklisted;
+};
+
+/*
+ * x509_cert_parser.c
+ */
+extern void x509_free_certificate(struct x509_certificate *cert);
+extern struct x509_certificate *x509_cert_parse(const void *data, size_t datalen);
+extern int x509_decode_time(time64_t *_t,  size_t hdrlen,
+			    unsigned char tag,
+			    const unsigned char *value, size_t vlen);
+
+/*
+ * x509_public_key.c
+ */
+extern int x509_get_sig_params(struct x509_certificate *cert);
+extern int x509_check_for_self_signed(struct x509_certificate *cert);
diff --git a/lib/crypto/x509_public_key.c b/lib/crypto/x509_public_key.c
new file mode 100644
index 0000000..04bdb67
--- /dev/null
+++ b/lib/crypto/x509_public_key.c
@@ -0,0 +1,292 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* Instantiate a public key crypto key from an X.509 Certificate
+ *
+ * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#define pr_fmt(fmt) "X.509: "fmt
+#ifdef __UBOOT__
+#include <common.h>
+#include <linux/compat.h>
+#include <linux/errno.h>
+#else
+#include <linux/module.h>
+#endif
+#include <linux/kernel.h>
+#ifndef __UBOOT__
+#include <linux/slab.h>
+#include <keys/asymmetric-subtype.h>
+#include <keys/asymmetric-parser.h>
+#include <keys/system_keyring.h>
+#include <crypto/hash.h>
+#include "asymmetric_keys.h"
+#endif
+#include "x509_parser.h"
+
+/*
+ * Set up the signature parameters in an X.509 certificate.  This involves
+ * digesting the signed data and extracting the signature.
+ */
+int x509_get_sig_params(struct x509_certificate *cert)
+{
+	struct public_key_signature *sig = cert->sig;
+#ifndef __UBOOT__
+	struct crypto_shash *tfm;
+	struct shash_desc *desc;
+	size_t desc_size;
+#endif
+	int ret;
+
+	pr_devel("==>%s()\n", __func__);
+
+	if (!cert->pub->pkey_algo)
+		cert->unsupported_key = true;
+
+	if (!sig->pkey_algo)
+		cert->unsupported_sig = true;
+
+	/* We check the hash if we can - even if we can't then verify it */
+	if (!sig->hash_algo) {
+		cert->unsupported_sig = true;
+		return 0;
+	}
+
+	sig->s = kmemdup(cert->raw_sig, cert->raw_sig_size, GFP_KERNEL);
+	if (!sig->s)
+		return -ENOMEM;
+
+	sig->s_size = cert->raw_sig_size;
+
+#ifdef __UBOOT__
+	/*
+	 * Note:
+	 * This part (filling sig->digest) should be implemented if
+	 * x509_check_for_self_signed() is enabled x509_cert_parse().
+	 * Currently, this check won't affect UEFI secure boot.
+	 */
+	ret = 0;
+#else
+	/* Allocate the hashing algorithm we're going to need and find out how
+	 * big the hash operational data will be.
+	 */
+	tfm = crypto_alloc_shash(sig->hash_algo, 0, 0);
+	if (IS_ERR(tfm)) {
+		if (PTR_ERR(tfm) == -ENOENT) {
+			cert->unsupported_sig = true;
+			return 0;
+		}
+		return PTR_ERR(tfm);
+	}
+
+	desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
+	sig->digest_size = crypto_shash_digestsize(tfm);
+
+	ret = -ENOMEM;
+	sig->digest = kmalloc(sig->digest_size, GFP_KERNEL);
+	if (!sig->digest)
+		goto error;
+
+	desc = kzalloc(desc_size, GFP_KERNEL);
+	if (!desc)
+		goto error;
+
+	desc->tfm = tfm;
+
+	ret = crypto_shash_digest(desc, cert->tbs, cert->tbs_size, sig->digest);
+	if (ret < 0)
+		goto error_2;
+
+	ret = is_hash_blacklisted(sig->digest, sig->digest_size, "tbs");
+	if (ret == -EKEYREJECTED) {
+		pr_err("Cert %*phN is blacklisted\n",
+		       sig->digest_size, sig->digest);
+		cert->blacklisted = true;
+		ret = 0;
+	}
+
+error_2:
+	kfree(desc);
+error:
+	crypto_free_shash(tfm);
+#endif /* __UBOOT__ */
+	pr_devel("<==%s() = %d\n", __func__, ret);
+	return ret;
+}
+
+#ifndef __UBOOT__
+/*
+ * Check for self-signedness in an X.509 cert and if found, check the signature
+ * immediately if we can.
+ */
+int x509_check_for_self_signed(struct x509_certificate *cert)
+{
+	int ret = 0;
+
+	pr_devel("==>%s()\n", __func__);
+
+	if (cert->raw_subject_size != cert->raw_issuer_size ||
+	    memcmp(cert->raw_subject, cert->raw_issuer,
+		   cert->raw_issuer_size) != 0)
+		goto not_self_signed;
+
+	if (cert->sig->auth_ids[0] || cert->sig->auth_ids[1]) {
+		/* If the AKID is present it may have one or two parts.  If
+		 * both are supplied, both must match.
+		 */
+		bool a = asymmetric_key_id_same(cert->skid, cert->sig->auth_ids[1]);
+		bool b = asymmetric_key_id_same(cert->id, cert->sig->auth_ids[0]);
+
+		if (!a && !b)
+			goto not_self_signed;
+
+		ret = -EKEYREJECTED;
+		if (((a && !b) || (b && !a)) &&
+		    cert->sig->auth_ids[0] && cert->sig->auth_ids[1])
+			goto out;
+	}
+
+	ret = -EKEYREJECTED;
+	if (strcmp(cert->pub->pkey_algo, cert->sig->pkey_algo) != 0)
+		goto out;
+
+	ret = public_key_verify_signature(cert->pub, cert->sig);
+	if (ret < 0) {
+		if (ret == -ENOPKG) {
+			cert->unsupported_sig = true;
+			ret = 0;
+		}
+		goto out;
+	}
+
+	pr_devel("Cert Self-signature verified");
+	cert->self_signed = true;
+
+out:
+	pr_devel("<==%s() = %d\n", __func__, ret);
+	return ret;
+
+not_self_signed:
+	pr_devel("<==%s() = 0 [not]\n", __func__);
+	return 0;
+}
+
+/*
+ * Attempt to parse a data blob for a key as an X509 certificate.
+ */
+static int x509_key_preparse(struct key_preparsed_payload *prep)
+{
+	struct asymmetric_key_ids *kids;
+	struct x509_certificate *cert;
+	const char *q;
+	size_t srlen, sulen;
+	char *desc = NULL, *p;
+	int ret;
+
+	cert = x509_cert_parse(prep->data, prep->datalen);
+	if (IS_ERR(cert))
+		return PTR_ERR(cert);
+
+	pr_devel("Cert Issuer: %s\n", cert->issuer);
+	pr_devel("Cert Subject: %s\n", cert->subject);
+
+	if (cert->unsupported_key) {
+		ret = -ENOPKG;
+		goto error_free_cert;
+	}
+
+	pr_devel("Cert Key Algo: %s\n", cert->pub->pkey_algo);
+	pr_devel("Cert Valid period: %lld-%lld\n", cert->valid_from, cert->valid_to);
+
+	cert->pub->id_type = "X509";
+
+	if (cert->unsupported_sig) {
+		public_key_signature_free(cert->sig);
+		cert->sig = NULL;
+	} else {
+		pr_devel("Cert Signature: %s + %s\n",
+			 cert->sig->pkey_algo, cert->sig->hash_algo);
+	}
+
+	/* Don't permit addition of blacklisted keys */
+	ret = -EKEYREJECTED;
+	if (cert->blacklisted)
+		goto error_free_cert;
+
+	/* Propose a description */
+	sulen = strlen(cert->subject);
+	if (cert->raw_skid) {
+		srlen = cert->raw_skid_size;
+		q = cert->raw_skid;
+	} else {
+		srlen = cert->raw_serial_size;
+		q = cert->raw_serial;
+	}
+
+	ret = -ENOMEM;
+	desc = kmalloc(sulen + 2 + srlen * 2 + 1, GFP_KERNEL);
+	if (!desc)
+		goto error_free_cert;
+	p = memcpy(desc, cert->subject, sulen);
+	p += sulen;
+	*p++ = ':';
+	*p++ = ' ';
+	p = bin2hex(p, q, srlen);
+	*p = 0;
+
+	kids = kmalloc(sizeof(struct asymmetric_key_ids), GFP_KERNEL);
+	if (!kids)
+		goto error_free_desc;
+	kids->id[0] = cert->id;
+	kids->id[1] = cert->skid;
+
+	/* We're pinning the module by being linked against it */
+	__module_get(public_key_subtype.owner);
+	prep->payload.data[asym_subtype] = &public_key_subtype;
+	prep->payload.data[asym_key_ids] = kids;
+	prep->payload.data[asym_crypto] = cert->pub;
+	prep->payload.data[asym_auth] = cert->sig;
+	prep->description = desc;
+	prep->quotalen = 100;
+
+	/* We've finished with the certificate */
+	cert->pub = NULL;
+	cert->id = NULL;
+	cert->skid = NULL;
+	cert->sig = NULL;
+	desc = NULL;
+	ret = 0;
+
+error_free_desc:
+	kfree(desc);
+error_free_cert:
+	x509_free_certificate(cert);
+	return ret;
+}
+
+static struct asymmetric_key_parser x509_key_parser = {
+	.owner	= THIS_MODULE,
+	.name	= "x509",
+	.parse	= x509_key_preparse,
+};
+
+/*
+ * Module stuff
+ */
+static int __init x509_key_init(void)
+{
+	return register_asymmetric_key_parser(&x509_key_parser);
+}
+
+static void __exit x509_key_exit(void)
+{
+	unregister_asymmetric_key_parser(&x509_key_parser);
+}
+
+module_init(x509_key_init);
+module_exit(x509_key_exit);
+#endif /* !__UBOOT__ */
+
+MODULE_DESCRIPTION("X.509 certificate parser");
+MODULE_AUTHOR("Red Hat, Inc.");
+MODULE_LICENSE("GPL");