fido commands hash checks works.

client/Makefile

@@ -107,6 +107,7 @@ CMDSRCS =	crapto1/crapto1.c \
 			crapto1/crypto1.c \
 			mfkey.c \
 			tea.c \
+			fido/additional_ca.c \
 			polarssl/des.c \
 			crypto/libpcrypto.c\
 			crypto/asn1utils.c\

client/cmdhffido.c

@@ -41,6 +41,10 @@
 #include "cliparser/cliparser.h"
 #include "crypto/asn1utils.h"
 #include "crypto/libpcrypto.h"
+#include "fido/additional_ca.h"
+#include "mbedtls/x509_crt.h"
+#include "mbedtls/x509.h"
+#include "mbedtls/pk.h"
 
 static int CmdHelp(const char *Cmd);
 
@@ -203,7 +207,7 @@ int CmdHFFidoRegister(const char *cmd) {
 	void* argtable[] = {
 		arg_param_begin,
 		arg_lit0("aA",  "apdu",     "show APDU reqests and responses"),
-		arg_lit0("vV",  "verbose",  "show technical data"),
+		arg_lit0("vV",  "verbose",  "show technical data. vv - show full certificates data"),
 		arg_lit0("pP",  "plain",    "send plain ASCII to challenge and application parameters instead of HEX"),
 		arg_str0("jJ",  "json",		"fido.json", "JSON input / output file name for parameters."),
 		arg_str0(NULL,  NULL,       "<HEX/ASCII challenge parameter (32b HEX/1..16 chars)>", NULL),
@@ -214,6 +218,7 @@ int CmdHFFidoRegister(const char *cmd) {
 	
 	bool APDULogging = arg_get_lit(1);
 	bool verbose = arg_get_lit(2);
+	bool verbose2 = arg_get_lit(2) > 1;
 	bool paramsPlain = arg_get_lit(3);
 
 	char fname[250] = {0};
@@ -304,7 +309,7 @@ int CmdHFFidoRegister(const char *cmd) {
 	if (APDULogging)
 		PrintAndLog("---------------------------------------------------------------");
 	PrintAndLog("data len: %d", len);
-	if (verbose) {
+	if (verbose2) {
 		PrintAndLog("--------------data----------------------");
 		dump_buffer((const unsigned char *)buf, len, NULL, 0);
 		PrintAndLog("--------------data----------------------");
@@ -321,8 +326,7 @@ int CmdHFFidoRegister(const char *cmd) {
 	
 	int derp = 67 + keyHandleLen;
 	int derLen = (buf[derp + 2] << 8) + buf[derp + 3] + 4;
-	// needs to decode DER certificate
+	if (verbose2) {
-	if (verbose) {
 		PrintAndLog("DER certificate[%d]:------------------DER-------------------", derLen);
 		dump_buffer_simple((const unsigned char *)&buf[67 + keyHandleLen], derLen, NULL);
 		PrintAndLog("\n----------------DER---------------------");
@@ -331,7 +335,56 @@ int CmdHFFidoRegister(const char *cmd) {
 	}
 	
 	// check and print DER certificate
-	uint8_t public_key[65] = {0}; 
+	uint8_t public_key[65] = {0};
+	
+	// TODO: print DER certificate in DER view
+	
+	// load CA's
+	mbedtls_x509_crt cacert;
+	mbedtls_x509_crt_init(&cacert);
+	res = mbedtls_x509_crt_parse(&cacert, (const unsigned char *) additional_ca_pem, additional_ca_pem_len);
+	if (res < 0) {
+		PrintAndLog("ERROR: CA parse certificate returned -0x%x - %s", -res, ecdsa_get_error(res));
+	}
+	if (verbose) 
+		PrintAndLog("CA load OK. %d skipped", res);
+	
+	// load DER certificate from authenticator's data
+	mbedtls_x509_crt cert;
+	mbedtls_x509_crt_init(&cert);
+	res = mbedtls_x509_crt_parse_der(&cert, &buf[67 + keyHandleLen], derLen);
+	if (res) {
+		PrintAndLog("ERROR: DER parse returned 0x%x - %s", (res<0)?-res:res, ecdsa_get_error(res));
+	}
+	
+	// get certificate info
+	char linfo[300] = {0};
+	mbedtls_x509_crt_info(linfo, sizeof(linfo), "  ", &cert);
+	PrintAndLog("DER certificate info:\n%s", linfo);
+	
+	// verify certificate
+	uint32_t verifyflags = 0;
+	memset(linfo, 0x00, sizeof(linfo));
+
+	res = mbedtls_x509_crt_verify(&cert, &cacert, NULL, NULL, &verifyflags, NULL, NULL);
+	if (res) {
+		PrintAndLog("ERROR: DER verify returned 0x%x - %s", (res<0)?-res:res, ecdsa_get_error(res));
+	}
+	
+	mbedtls_x509_crt_verify_info(linfo, sizeof(linfo), "  ", verifyflags);
+	PrintAndLog("Verification info:\n%s", linfo);
+	
+	// get public key
+	res = ecdsa_public_key_from_pk(&cert.pk, public_key, sizeof(public_key));
+	if (res) {
+		PrintAndLog("ERROR: getting public key from certificate 0x%x - %s", (res<0)?-res:res, ecdsa_get_error(res));
+	} else {
+		if (verbose)
+			PrintAndLog("Got a public key from certificate.");
+	}
+
+	mbedtls_x509_crt_free(&cert);
+	mbedtls_x509_crt_free(&cacert);
 	
 	// get hash
 	int hashp = 1 + 65 + 1 + keyHandleLen + derLen;
@@ -351,8 +404,8 @@ int CmdHFFidoRegister(const char *cmd) {
 		size_t xbuflen = 0;
 		res = FillBuffer(xbuf, sizeof(xbuf), &xbuflen,
 			"\x00", 1,
-			adata, 32, 
+			&data[32], 32,           // application parameter  
-			cdata, 32, 
+			&data[0], 32,            // challenge parameter
 			&buf[67], keyHandleLen,  // keyHandle
 			&buf[1], 65,             // user public key
 			NULL, 0);

client/crypto/libpcrypto.c

@@ -16,6 +16,7 @@
 #include <mbedtls/asn1.h>
 #include <mbedtls/aes.h>
 #include <mbedtls/cmac.h>
+#include <mbedtls/pk.h>
 #include <mbedtls/ecdsa.h>
 #include <mbedtls/sha256.h>
 #include <mbedtls/ctr_drbg.h>
@@ -208,6 +209,31 @@ char *ecdsa_get_error(int ret) {
 	return retstr;
 }
 
+int ecdsa_public_key_from_pk(mbedtls_pk_context *pk, uint8_t *key, size_t keylen) {
+	int res = 0;
+	size_t realkeylen = 0;
+	if (keylen < 65) 
+		return 1;
+	
+	mbedtls_ecdsa_context ctx;
+	mbedtls_ecdsa_init(&ctx);
+	
+	res = mbedtls_ecp_group_load(&ctx.grp, MBEDTLS_ECP_DP_SECP256R1); // secp256r1
+	if (res)
+		goto exit;
+	
+	res = mbedtls_ecdsa_from_keypair(&ctx, mbedtls_pk_ec(*pk) );
+	if (res)
+		goto exit;
+	
+	res = mbedtls_ecp_point_write_binary(&ctx.grp, &ctx.Q, MBEDTLS_ECP_PF_UNCOMPRESSED, &realkeylen, key, keylen);
+	if (realkeylen != 65)
+		res = 2;
+exit:
+	mbedtls_ecdsa_free(&ctx);
+	return res;
+}
+
 int ecdsa_signature_create(uint8_t *key_d, uint8_t *key_xy, uint8_t *input, int length, uint8_t *signature, size_t *signaturelen) {
 	int res;
 	*signaturelen = 0;

client/crypto/libpcrypto.h

@@ -14,6 +14,7 @@
 #include <stdint.h>
 #include <stdbool.h>
 #include <stddef.h>
+#include <mbedtls/pk.h>
 
 extern int aes_encode(uint8_t *iv, uint8_t *key, uint8_t *input, uint8_t *output, int length);
 extern int aes_decode(uint8_t *iv, uint8_t *key, uint8_t *input, uint8_t *output, int length);
@@ -23,6 +24,7 @@ extern int aes_cmac8(uint8_t *iv, uint8_t *key, uint8_t *input, uint8_t *mac, in
 extern int sha256hash(uint8_t *input, int length, uint8_t *hash);
 
 extern int ecdsa_key_create(uint8_t * key_d, uint8_t *key_xy);
+extern int ecdsa_public_key_from_pk(mbedtls_pk_context *pk, uint8_t *key, size_t keylen);
 extern int ecdsa_signature_create(uint8_t *key_d, uint8_t *key_xy, uint8_t *input, int length, uint8_t *signature, size_t *signaturelen);
 extern int ecdsa_signature_verify(uint8_t *key_xy, uint8_t *input, int length, uint8_t *signature, size_t signaturelen);
 extern char *ecdsa_get_error(int ret);

client/fido/additional_ca.c

@@ -0,0 +1,63 @@
+//-----------------------------------------------------------------------------
+// Copyright (C) 2018 Merlok
+//
+// This code is licensed to you under the terms of the GNU GPL, version 2 or,
+// at your option, any later version. See the LICENSE.txt file for the text of
+// the license.
+//-----------------------------------------------------------------------------
+// CA PEM certificates 
+//-----------------------------------------------------------------------------
+//
+
+#include "additional_ca.h"
+#include "mbedtls/certs.h"
+
+#define GLOBALSIGN_CA				\
+"-----BEGIN CERTIFICATE-----\r\n"	\
+"MIIDdTCCAl2gAwIBAgILBAAAAAABFUtaw5QwDQYJKoZIhvcNAQEFBQAwVzELMAkG\r\n"	\
+"A1UEBhMCQkUxGTAXBgNVBAoTEEdsb2JhbFNpZ24gbnYtc2ExEDAOBgNVBAsTB1Jv\r\n"	\
+"b3QgQ0ExGzAZBgNVBAMTEkdsb2JhbFNpZ24gUm9vdCBDQTAeFw05ODA5MDExMjAw\r\n"	\
+"MDBaFw0yODAxMjgxMjAwMDBaMFcxCzAJBgNVBAYTAkJFMRkwFwYDVQQKExBHbG9i\r\n"	\
+"YWxTaWduIG52LXNhMRAwDgYDVQQLEwdSb290IENBMRswGQYDVQQDExJHbG9iYWxT\r\n"	\
+"aWduIFJvb3QgQ0EwggEiMA0GCSqGSIb3DQEBAQUAA4IBDwAwggEKAoIBAQDaDuaZ\r\n"	\
+"jc6j40+Kfvvxi4Mla+pIH/EqsLmVEQS98GPR4mdmzxzdzxtIK+6NiY6arymAZavp\r\n"	\
+"xy0Sy6scTHAHoT0KMM0VjU/43dSMUBUc71DuxC73/OlS8pF94G3VNTCOXkNz8kHp\r\n"	\
+"1Wrjsok6Vjk4bwY8iGlbKk3Fp1S4bInMm/k8yuX9ifUSPJJ4ltbcdG6TRGHRjcdG\r\n"	\
+"snUOhugZitVtbNV4FpWi6cgKOOvyJBNPc1STE4U6G7weNLWLBYy5d4ux2x8gkasJ\r\n"	\
+"U26Qzns3dLlwR5EiUWMWea6xrkEmCMgZK9FGqkjWZCrXgzT/LCrBbBlDSgeF59N8\r\n"	\
+"9iFo7+ryUp9/k5DPAgMBAAGjQjBAMA4GA1UdDwEB/wQEAwIBBjAPBgNVHRMBAf8E\r\n"	\
+"BTADAQH/MB0GA1UdDgQWBBRge2YaRQ2XyolQL30EzTSo//z9SzANBgkqhkiG9w0B\r\n"	\
+"AQUFAAOCAQEA1nPnfE920I2/7LqivjTFKDK1fPxsnCwrvQmeU79rXqoRSLblCKOz\r\n"	\
+"yj1hTdNGCbM+w6DjY1Ub8rrvrTnhQ7k4o+YviiY776BQVvnGCv04zcQLcFGUl5gE\r\n"	\
+"38NflNUVyRRBnMRddWQVDf9VMOyGj/8N7yy5Y0b2qvzfvGn9LhJIZJrglfCm7ymP\r\n"	\
+"AbEVtQwdpf5pLGkkeB6zpxxxYu7KyJesF12KwvhHhm4qxFYxldBniYUr+WymXUad\r\n"	\
+"DKqC5JlR3XC321Y9YeRq4VzW9v493kHMB65jUr9TU/Qr6cf9tveCX4XSQRjbgbME\r\n"	\
+"HMUfpIBvFSDJ3gyICh3WZlXi/EjJKSZp4A==\r\n"	\
+"-----END CERTIFICATE-----\r\n"
+
+// Name: Yubico U2F Root CA Serial 457200631
+// Issued: 2014-08-01
+#define YUBICO_CA	\
+"-----BEGIN CERTIFICATE-----" \
+"MIIDHjCCAgagAwIBAgIEG0BT9zANBgkqhkiG9w0BAQsFADAuMSwwKgYDVQQDEyNZ" \
+"dWJpY28gVTJGIFJvb3QgQ0EgU2VyaWFsIDQ1NzIwMDYzMTAgFw0xNDA4MDEwMDAw" \
+"MDBaGA8yMDUwMDkwNDAwMDAwMFowLjEsMCoGA1UEAxMjWXViaWNvIFUyRiBSb290" \
+"IENBIFNlcmlhbCA0NTcyMDA2MzEwggEiMA0GCSqGSIb3DQEBAQUAA4IBDwAwggEK" \
+"AoIBAQC/jwYuhBVlqaiYWEMsrWFisgJ+PtM91eSrpI4TK7U53mwCIawSDHy8vUmk" \
+"5N2KAj9abvT9NP5SMS1hQi3usxoYGonXQgfO6ZXyUA9a+KAkqdFnBnlyugSeCOep" \
+"8EdZFfsaRFtMjkwz5Gcz2Py4vIYvCdMHPtwaz0bVuzneueIEz6TnQjE63Rdt2zbw" \
+"nebwTG5ZybeWSwbzy+BJ34ZHcUhPAY89yJQXuE0IzMZFcEBbPNRbWECRKgjq//qT" \
+"9nmDOFVlSRCt2wiqPSzluwn+v+suQEBsUjTGMEd25tKXXTkNW21wIWbxeSyUoTXw" \
+"LvGS6xlwQSgNpk2qXYwf8iXg7VWZAgMBAAGjQjBAMB0GA1UdDgQWBBQgIvz0bNGJ" \
+"hjgpToksyKpP9xv9oDAPBgNVHRMECDAGAQH/AgEAMA4GA1UdDwEB/wQEAwIBBjAN" \
+"BgkqhkiG9w0BAQsFAAOCAQEAjvjuOMDSa+JXFCLyBKsycXtBVZsJ4Ue3LbaEsPY4" \
+"MYN/hIQ5ZM5p7EjfcnMG4CtYkNsfNHc0AhBLdq45rnT87q/6O3vUEtNMafbhU6kt" \
+"hX7Y+9XFN9NpmYxr+ekVY5xOxi8h9JDIgoMP4VB1uS0aunL1IGqrNooL9mmFnL2k" \
+"LVVee6/VR6C5+KSTCMCWppMuJIZII2v9o4dkoZ8Y7QRjQlLfYzd3qGtKbw7xaF1U" \
+"sG/5xUb/Btwb2X2g4InpiB/yt/3CpQXpiWX/K4mBvUKiGn05ZsqeY1gx4g0xLBqc" \
+"U9psmyPzK+Vsgw2jeRQ5JlKDyqE0hebfC1tvFu0CCrJFcw==" \
+"-----END CERTIFICATE-----"
+
+/* Concatenation of all additional CA certificates in PEM format if available */
+const char   additional_ca_pem[] = YUBICO_CA; ///GLOBALSIGN_CA
+const size_t additional_ca_pem_len = sizeof(additional_ca_pem);

client/fido/additional_ca.h

@@ -0,0 +1,21 @@
+//-----------------------------------------------------------------------------
+// Copyright (C) 2018 Merlok
+//
+// This code is licensed to you under the terms of the GNU GPL, version 2 or,
+// at your option, any later version. See the LICENSE.txt file for the text of
+// the license.
+//-----------------------------------------------------------------------------
+// CA PEM certificates 
+//-----------------------------------------------------------------------------
+//
+
+#ifndef __ADDITIONAL_CA_H__
+#define __ADDITIONAL_CA_H__
+
+#include <stddef.h>
+
+// Concatenation of all CA certificates in PEM format if available 
+extern const char   additional_ca_pem[];
+extern const size_t additional_ca_pem_len;
+
+#endif /* __ADDITIONAL_CA_H__ */

common/mbedtls/Makefile

@@ -29,6 +29,7 @@ mbedtls_SOURCES = \
 	arc4.c \
 	pk.c \
 	pk_wrap.c \
+	pkwrite.c \
 	pkcs5.c \
 	pkcs12.c \
 	pkparse.c \

common/mbedtls/pkwrite.c

@@ -0,0 +1,517 @@
+/*
+ *  Public Key layer for writing key files and structures
+ *
+ *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
+ *  SPDX-License-Identifier: GPL-2.0
+ *
+ *  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.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with this program; if not, write to the Free Software Foundation, Inc.,
+ *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ *  This file is part of mbed TLS (https://tls.mbed.org)
+ */
+
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "mbedtls/config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
+#if defined(MBEDTLS_PK_WRITE_C)
+
+#include "mbedtls/pk.h"
+#include "mbedtls/asn1write.h"
+#include "mbedtls/oid.h"
+
+#include <string.h>
+
+#if defined(MBEDTLS_RSA_C)
+#include "mbedtls/rsa.h"
+#endif
+#if defined(MBEDTLS_ECP_C)
+#include "mbedtls/ecp.h"
+#endif
+#if defined(MBEDTLS_ECDSA_C)
+#include "mbedtls/ecdsa.h"
+#endif
+#if defined(MBEDTLS_PEM_WRITE_C)
+#include "mbedtls/pem.h"
+#endif
+
+#if defined(MBEDTLS_PLATFORM_C)
+#include "mbedtls/platform.h"
+#else
+#include <stdlib.h>
+#define mbedtls_calloc    calloc
+#define mbedtls_free       free
+#endif
+
+#if defined(MBEDTLS_RSA_C)
+/*
+ *  RSAPublicKey ::= SEQUENCE {
+ *      modulus           INTEGER,  -- n
+ *      publicExponent    INTEGER   -- e
+ *  }
+ */
+static int pk_write_rsa_pubkey( unsigned char **p, unsigned char *start,
+                                mbedtls_rsa_context *rsa )
+{
+    int ret;
+    size_t len = 0;
+    mbedtls_mpi T;
+
+    mbedtls_mpi_init( &T );
+
+    /* Export E */
+    if ( ( ret = mbedtls_rsa_export( rsa, NULL, NULL, NULL, NULL, &T ) ) != 0 ||
+         ( ret = mbedtls_asn1_write_mpi( p, start, &T ) ) < 0 )
+        goto end_of_export;
+    len += ret;
+
+    /* Export N */
+    if ( ( ret = mbedtls_rsa_export( rsa, &T, NULL, NULL, NULL, NULL ) ) != 0 ||
+         ( ret = mbedtls_asn1_write_mpi( p, start, &T ) ) < 0 )
+        goto end_of_export;
+    len += ret;
+
+end_of_export:
+
+    mbedtls_mpi_free( &T );
+    if( ret < 0 )
+        return( ret );
+
+    MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( p, start, len ) );
+    MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( p, start, MBEDTLS_ASN1_CONSTRUCTED |
+                                                 MBEDTLS_ASN1_SEQUENCE ) );
+
+    return( (int) len );
+}
+#endif /* MBEDTLS_RSA_C */
+
+#if defined(MBEDTLS_ECP_C)
+/*
+ * EC public key is an EC point
+ */
+static int pk_write_ec_pubkey( unsigned char **p, unsigned char *start,
+                               mbedtls_ecp_keypair *ec )
+{
+    int ret;
+    size_t len = 0;
+    unsigned char buf[MBEDTLS_ECP_MAX_PT_LEN];
+
+    if( ( ret = mbedtls_ecp_point_write_binary( &ec->grp, &ec->Q,
+                                        MBEDTLS_ECP_PF_UNCOMPRESSED,
+                                        &len, buf, sizeof( buf ) ) ) != 0 )
+    {
+        return( ret );
+    }
+
+    if( *p < start || (size_t)( *p - start ) < len )
+        return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
+
+    *p -= len;
+    memcpy( *p, buf, len );
+
+    return( (int) len );
+}
+
+/*
+ * ECParameters ::= CHOICE {
+ *   namedCurve         OBJECT IDENTIFIER
+ * }
+ */
+static int pk_write_ec_param( unsigned char **p, unsigned char *start,
+                              mbedtls_ecp_keypair *ec )
+{
+    int ret;
+    size_t len = 0;
+    const char *oid;
+    size_t oid_len;
+
+    if( ( ret = mbedtls_oid_get_oid_by_ec_grp( ec->grp.id, &oid, &oid_len ) ) != 0 )
+        return( ret );
+
+    MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_oid( p, start, oid, oid_len ) );
+
+    return( (int) len );
+}
+#endif /* MBEDTLS_ECP_C */
+
+int mbedtls_pk_write_pubkey( unsigned char **p, unsigned char *start,
+                             const mbedtls_pk_context *key )
+{
+    int ret;
+    size_t len = 0;
+
+#if defined(MBEDTLS_RSA_C)
+    if( mbedtls_pk_get_type( key ) == MBEDTLS_PK_RSA )
+        MBEDTLS_ASN1_CHK_ADD( len, pk_write_rsa_pubkey( p, start, mbedtls_pk_rsa( *key ) ) );
+    else
+#endif
+#if defined(MBEDTLS_ECP_C)
+    if( mbedtls_pk_get_type( key ) == MBEDTLS_PK_ECKEY )
+        MBEDTLS_ASN1_CHK_ADD( len, pk_write_ec_pubkey( p, start, mbedtls_pk_ec( *key ) ) );
+    else
+#endif
+        return( MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE );
+
+    return( (int) len );
+}
+
+int mbedtls_pk_write_pubkey_der( mbedtls_pk_context *key, unsigned char *buf, size_t size )
+{
+    int ret;
+    unsigned char *c;
+    size_t len = 0, par_len = 0, oid_len;
+    const char *oid;
+
+    c = buf + size;
+
+    MBEDTLS_ASN1_CHK_ADD( len, mbedtls_pk_write_pubkey( &c, buf, key ) );
+
+    if( c - buf < 1 )
+        return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
+
+    /*
+     *  SubjectPublicKeyInfo  ::=  SEQUENCE  {
+     *       algorithm            AlgorithmIdentifier,
+     *       subjectPublicKey     BIT STRING }
+     */
+    *--c = 0;
+    len += 1;
+
+    MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) );
+    MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, buf, MBEDTLS_ASN1_BIT_STRING ) );
+
+    if( ( ret = mbedtls_oid_get_oid_by_pk_alg( mbedtls_pk_get_type( key ),
+                                       &oid, &oid_len ) ) != 0 )
+    {
+        return( ret );
+    }
+
+#if defined(MBEDTLS_ECP_C)
+    if( mbedtls_pk_get_type( key ) == MBEDTLS_PK_ECKEY )
+    {
+        MBEDTLS_ASN1_CHK_ADD( par_len, pk_write_ec_param( &c, buf, mbedtls_pk_ec( *key ) ) );
+    }
+#endif
+
+    MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_algorithm_identifier( &c, buf, oid, oid_len,
+                                                        par_len ) );
+
+    MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) );
+    MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, buf, MBEDTLS_ASN1_CONSTRUCTED |
+                                                MBEDTLS_ASN1_SEQUENCE ) );
+
+    return( (int) len );
+}
+
+int mbedtls_pk_write_key_der( mbedtls_pk_context *key, unsigned char *buf, size_t size )
+{
+    int ret;
+    unsigned char *c = buf + size;
+    size_t len = 0;
+
+#if defined(MBEDTLS_RSA_C)
+    if( mbedtls_pk_get_type( key ) == MBEDTLS_PK_RSA )
+    {
+        mbedtls_mpi T; /* Temporary holding the exported parameters */
+        mbedtls_rsa_context *rsa = mbedtls_pk_rsa( *key );
+
+        /*
+         * Export the parameters one after another to avoid simultaneous copies.
+         */
+
+        mbedtls_mpi_init( &T );
+
+        /* Export QP */
+        if( ( ret = mbedtls_rsa_export_crt( rsa, NULL, NULL, &T ) ) != 0 ||
+            ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 )
+            goto end_of_export;
+        len += ret;
+
+        /* Export DQ */
+        if( ( ret = mbedtls_rsa_export_crt( rsa, NULL, &T, NULL ) ) != 0 ||
+            ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 )
+            goto end_of_export;
+        len += ret;
+
+        /* Export DP */
+        if( ( ret = mbedtls_rsa_export_crt( rsa, &T, NULL, NULL ) ) != 0 ||
+            ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 )
+            goto end_of_export;
+        len += ret;
+
+        /* Export Q */
+        if ( ( ret = mbedtls_rsa_export( rsa, NULL, NULL,
+                                         &T, NULL, NULL ) ) != 0 ||
+             ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 )
+            goto end_of_export;
+        len += ret;
+
+        /* Export P */
+        if ( ( ret = mbedtls_rsa_export( rsa, NULL, &T,
+                                         NULL, NULL, NULL ) ) != 0 ||
+             ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 )
+            goto end_of_export;
+        len += ret;
+
+        /* Export D */
+        if ( ( ret = mbedtls_rsa_export( rsa, NULL, NULL,
+                                         NULL, &T, NULL ) ) != 0 ||
+             ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 )
+            goto end_of_export;
+        len += ret;
+
+        /* Export E */
+        if ( ( ret = mbedtls_rsa_export( rsa, NULL, NULL,
+                                         NULL, NULL, &T ) ) != 0 ||
+             ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 )
+            goto end_of_export;
+        len += ret;
+
+        /* Export N */
+        if ( ( ret = mbedtls_rsa_export( rsa, &T, NULL,
+                                         NULL, NULL, NULL ) ) != 0 ||
+             ( ret = mbedtls_asn1_write_mpi( &c, buf, &T ) ) < 0 )
+            goto end_of_export;
+        len += ret;
+
+    end_of_export:
+
+        mbedtls_mpi_free( &T );
+        if( ret < 0 )
+            return( ret );
+
+        MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_int( &c, buf, 0 ) );
+        MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) );
+        MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c,
+                                               buf, MBEDTLS_ASN1_CONSTRUCTED |
+                                               MBEDTLS_ASN1_SEQUENCE ) );
+    }
+    else
+#endif /* MBEDTLS_RSA_C */
+#if defined(MBEDTLS_ECP_C)
+    if( mbedtls_pk_get_type( key ) == MBEDTLS_PK_ECKEY )
+    {
+        mbedtls_ecp_keypair *ec = mbedtls_pk_ec( *key );
+        size_t pub_len = 0, par_len = 0;
+
+        /*
+         * RFC 5915, or SEC1 Appendix C.4
+         *
+         * ECPrivateKey ::= SEQUENCE {
+         *      version        INTEGER { ecPrivkeyVer1(1) } (ecPrivkeyVer1),
+         *      privateKey     OCTET STRING,
+         *      parameters [0] ECParameters {{ NamedCurve }} OPTIONAL,
+         *      publicKey  [1] BIT STRING OPTIONAL
+         *    }
+         */
+
+        /* publicKey */
+        MBEDTLS_ASN1_CHK_ADD( pub_len, pk_write_ec_pubkey( &c, buf, ec ) );
+
+        if( c - buf < 1 )
+            return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
+        *--c = 0;
+        pub_len += 1;
+
+        MBEDTLS_ASN1_CHK_ADD( pub_len, mbedtls_asn1_write_len( &c, buf, pub_len ) );
+        MBEDTLS_ASN1_CHK_ADD( pub_len, mbedtls_asn1_write_tag( &c, buf, MBEDTLS_ASN1_BIT_STRING ) );
+
+        MBEDTLS_ASN1_CHK_ADD( pub_len, mbedtls_asn1_write_len( &c, buf, pub_len ) );
+        MBEDTLS_ASN1_CHK_ADD( pub_len, mbedtls_asn1_write_tag( &c, buf,
+                            MBEDTLS_ASN1_CONTEXT_SPECIFIC | MBEDTLS_ASN1_CONSTRUCTED | 1 ) );
+        len += pub_len;
+
+        /* parameters */
+        MBEDTLS_ASN1_CHK_ADD( par_len, pk_write_ec_param( &c, buf, ec ) );
+
+        MBEDTLS_ASN1_CHK_ADD( par_len, mbedtls_asn1_write_len( &c, buf, par_len ) );
+        MBEDTLS_ASN1_CHK_ADD( par_len, mbedtls_asn1_write_tag( &c, buf,
+                            MBEDTLS_ASN1_CONTEXT_SPECIFIC | MBEDTLS_ASN1_CONSTRUCTED | 0 ) );
+        len += par_len;
+
+        /* privateKey: write as MPI then fix tag */
+        MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_mpi( &c, buf, &ec->d ) );
+        *c = MBEDTLS_ASN1_OCTET_STRING;
+
+        /* version */
+        MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_int( &c, buf, 1 ) );
+
+        MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, buf, len ) );
+        MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, buf, MBEDTLS_ASN1_CONSTRUCTED |
+                                                    MBEDTLS_ASN1_SEQUENCE ) );
+    }
+    else
+#endif /* MBEDTLS_ECP_C */
+        return( MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE );
+
+    return( (int) len );
+}
+
+#if defined(MBEDTLS_PEM_WRITE_C)
+
+#define PEM_BEGIN_PUBLIC_KEY    "-----BEGIN PUBLIC KEY-----\n"
+#define PEM_END_PUBLIC_KEY      "-----END PUBLIC KEY-----\n"
+
+#define PEM_BEGIN_PRIVATE_KEY_RSA   "-----BEGIN RSA PRIVATE KEY-----\n"
+#define PEM_END_PRIVATE_KEY_RSA     "-----END RSA PRIVATE KEY-----\n"
+#define PEM_BEGIN_PRIVATE_KEY_EC    "-----BEGIN EC PRIVATE KEY-----\n"
+#define PEM_END_PRIVATE_KEY_EC      "-----END EC PRIVATE KEY-----\n"
+
+/*
+ * Max sizes of key per types. Shown as tag + len (+ content).
+ */
+
+#if defined(MBEDTLS_RSA_C)
+/*
+ * RSA public keys:
+ *  SubjectPublicKeyInfo  ::=  SEQUENCE  {          1 + 3
+ *       algorithm            AlgorithmIdentifier,  1 + 1 (sequence)
+ *                                                + 1 + 1 + 9 (rsa oid)
+ *                                                + 1 + 1 (params null)
+ *       subjectPublicKey     BIT STRING }          1 + 3 + (1 + below)
+ *  RSAPublicKey ::= SEQUENCE {                     1 + 3
+ *      modulus           INTEGER,  -- n            1 + 3 + MPI_MAX + 1
+ *      publicExponent    INTEGER   -- e            1 + 3 + MPI_MAX + 1
+ *  }
+ */
+#define RSA_PUB_DER_MAX_BYTES   38 + 2 * MBEDTLS_MPI_MAX_SIZE
+
+/*
+ * RSA private keys:
+ *  RSAPrivateKey ::= SEQUENCE {                    1 + 3
+ *      version           Version,                  1 + 1 + 1
+ *      modulus           INTEGER,                  1 + 3 + MPI_MAX + 1
+ *      publicExponent    INTEGER,                  1 + 3 + MPI_MAX + 1
+ *      privateExponent   INTEGER,                  1 + 3 + MPI_MAX + 1
+ *      prime1            INTEGER,                  1 + 3 + MPI_MAX / 2 + 1
+ *      prime2            INTEGER,                  1 + 3 + MPI_MAX / 2 + 1
+ *      exponent1         INTEGER,                  1 + 3 + MPI_MAX / 2 + 1
+ *      exponent2         INTEGER,                  1 + 3 + MPI_MAX / 2 + 1
+ *      coefficient       INTEGER,                  1 + 3 + MPI_MAX / 2 + 1
+ *      otherPrimeInfos   OtherPrimeInfos OPTIONAL  0 (not supported)
+ *  }
+ */
+#define MPI_MAX_SIZE_2          MBEDTLS_MPI_MAX_SIZE / 2 + \
+                                MBEDTLS_MPI_MAX_SIZE % 2
+#define RSA_PRV_DER_MAX_BYTES   47 + 3 * MBEDTLS_MPI_MAX_SIZE \
+                                   + 5 * MPI_MAX_SIZE_2
+
+#else /* MBEDTLS_RSA_C */
+
+#define RSA_PUB_DER_MAX_BYTES   0
+#define RSA_PRV_DER_MAX_BYTES   0
+
+#endif /* MBEDTLS_RSA_C */
+
+#if defined(MBEDTLS_ECP_C)
+/*
+ * EC public keys:
+ *  SubjectPublicKeyInfo  ::=  SEQUENCE  {      1 + 2
+ *    algorithm         AlgorithmIdentifier,    1 + 1 (sequence)
+ *                                            + 1 + 1 + 7 (ec oid)
+ *                                            + 1 + 1 + 9 (namedCurve oid)
+ *    subjectPublicKey  BIT STRING              1 + 2 + 1               [1]
+ *                                            + 1 (point format)        [1]
+ *                                            + 2 * ECP_MAX (coords)    [1]
+ *  }
+ */
+#define ECP_PUB_DER_MAX_BYTES   30 + 2 * MBEDTLS_ECP_MAX_BYTES
+
+/*
+ * EC private keys:
+ * ECPrivateKey ::= SEQUENCE {                  1 + 2
+ *      version        INTEGER ,                1 + 1 + 1
+ *      privateKey     OCTET STRING,            1 + 1 + ECP_MAX
+ *      parameters [0] ECParameters OPTIONAL,   1 + 1 + (1 + 1 + 9)
+ *      publicKey  [1] BIT STRING OPTIONAL      1 + 2 + [1] above
+ *    }
+ */
+#define ECP_PRV_DER_MAX_BYTES   29 + 3 * MBEDTLS_ECP_MAX_BYTES
+
+#else /* MBEDTLS_ECP_C */
+
+#define ECP_PUB_DER_MAX_BYTES   0
+#define ECP_PRV_DER_MAX_BYTES   0
+
+#endif /* MBEDTLS_ECP_C */
+
+#define PUB_DER_MAX_BYTES   RSA_PUB_DER_MAX_BYTES > ECP_PUB_DER_MAX_BYTES ? \
+                            RSA_PUB_DER_MAX_BYTES : ECP_PUB_DER_MAX_BYTES
+#define PRV_DER_MAX_BYTES   RSA_PRV_DER_MAX_BYTES > ECP_PRV_DER_MAX_BYTES ? \
+                            RSA_PRV_DER_MAX_BYTES : ECP_PRV_DER_MAX_BYTES
+
+int mbedtls_pk_write_pubkey_pem( mbedtls_pk_context *key, unsigned char *buf, size_t size )
+{
+    int ret;
+    unsigned char output_buf[PUB_DER_MAX_BYTES];
+    size_t olen = 0;
+
+    if( ( ret = mbedtls_pk_write_pubkey_der( key, output_buf,
+                                     sizeof(output_buf) ) ) < 0 )
+    {
+        return( ret );
+    }
+
+    if( ( ret = mbedtls_pem_write_buffer( PEM_BEGIN_PUBLIC_KEY, PEM_END_PUBLIC_KEY,
+                                  output_buf + sizeof(output_buf) - ret,
+                                  ret, buf, size, &olen ) ) != 0 )
+    {
+        return( ret );
+    }
+
+    return( 0 );
+}
+
+int mbedtls_pk_write_key_pem( mbedtls_pk_context *key, unsigned char *buf, size_t size )
+{
+    int ret;
+    unsigned char output_buf[PRV_DER_MAX_BYTES];
+    const char *begin, *end;
+    size_t olen = 0;
+
+    if( ( ret = mbedtls_pk_write_key_der( key, output_buf, sizeof(output_buf) ) ) < 0 )
+        return( ret );
+
+#if defined(MBEDTLS_RSA_C)
+    if( mbedtls_pk_get_type( key ) == MBEDTLS_PK_RSA )
+    {
+        begin = PEM_BEGIN_PRIVATE_KEY_RSA;
+        end = PEM_END_PRIVATE_KEY_RSA;
+    }
+    else
+#endif
+#if defined(MBEDTLS_ECP_C)
+    if( mbedtls_pk_get_type( key ) == MBEDTLS_PK_ECKEY )
+    {
+        begin = PEM_BEGIN_PRIVATE_KEY_EC;
+        end = PEM_END_PRIVATE_KEY_EC;
+    }
+    else
+#endif
+        return( MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE );
+
+    if( ( ret = mbedtls_pem_write_buffer( begin, end,
+                                  output_buf + sizeof(output_buf) - ret,
+                                  ret, buf, size, &olen ) ) != 0 )
+    {
+        return( ret );
+    }
+
+    return( 0 );
+}
+#endif /* MBEDTLS_PEM_WRITE_C */
+
+#endif /* MBEDTLS_PK_WRITE_C */