diff --git a/library/x509write_csr.c b/library/x509write_csr.c
new file mode 100644
index 0000000..8dc39e7
--- /dev/null
+++ b/library/x509write_csr.c
@@ -0,0 +1,287 @@
+/*
+ *  X.509 Certificate Signing Request writing
+ *
+ *  Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
+ *  SPDX-License-Identifier: Apache-2.0
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License"); you may
+ *  not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ *  This file is part of mbed TLS (https://tls.mbed.org)
+ */
+/*
+ * References:
+ * - CSRs: PKCS#10 v1.7 aka RFC 2986
+ * - attributes: PKCS#9 v2.0 aka RFC 2985
+ */
+
+#if !defined(MBEDTLS_CONFIG_FILE)
+#include "mbedtls/config.h"
+#else
+#include MBEDTLS_CONFIG_FILE
+#endif
+
+#if defined(MBEDTLS_X509_CSR_WRITE_C)
+
+#include "mbedtls/x509_csr.h"
+#include "mbedtls/oid.h"
+#include "mbedtls/asn1write.h"
+#include "mbedtls/platform_util.h"
+
+#if defined(MBEDTLS_USE_PSA_CRYPTO)
+#include "psa/crypto.h"
+#include "mbedtls/psa_util.h"
+#endif
+
+#include <string.h>
+#include <stdlib.h>
+
+#if defined(MBEDTLS_PEM_WRITE_C)
+#include "mbedtls/pem.h"
+#endif
+
+void mbedtls_x509write_csr_init( mbedtls_x509write_csr *ctx )
+{
+    memset( ctx, 0, sizeof( mbedtls_x509write_csr ) );
+}
+
+void mbedtls_x509write_csr_free( mbedtls_x509write_csr *ctx )
+{
+    mbedtls_asn1_free_named_data_list( &ctx->subject );
+    mbedtls_asn1_free_named_data_list( &ctx->extensions );
+
+    mbedtls_platform_zeroize( ctx, sizeof( mbedtls_x509write_csr ) );
+}
+
+void mbedtls_x509write_csr_set_md_alg( mbedtls_x509write_csr *ctx, mbedtls_md_type_t md_alg )
+{
+    ctx->md_alg = md_alg;
+}
+
+void mbedtls_x509write_csr_set_key( mbedtls_x509write_csr *ctx, mbedtls_pk_context *key )
+{
+    ctx->key = key;
+}
+
+int mbedtls_x509write_csr_set_subject_name( mbedtls_x509write_csr *ctx,
+                                    const char *subject_name )
+{
+    return mbedtls_x509_string_to_names( &ctx->subject, subject_name );
+}
+
+int mbedtls_x509write_csr_set_extension( mbedtls_x509write_csr *ctx,
+                                 const char *oid, size_t oid_len,
+                                 const unsigned char *val, size_t val_len )
+{
+    return mbedtls_x509_set_extension( &ctx->extensions, oid, oid_len,
+                               0, val, val_len );
+}
+
+int mbedtls_x509write_csr_set_key_usage( mbedtls_x509write_csr *ctx, unsigned char key_usage )
+{
+    unsigned char buf[4];
+    unsigned char *c;
+    int ret;
+
+    c = buf + 4;
+
+    ret = mbedtls_asn1_write_named_bitstring( &c, buf, &key_usage, 8 );
+    if( ret < 3 || ret > 4 )
+        return( ret );
+
+    ret = mbedtls_x509write_csr_set_extension( ctx, MBEDTLS_OID_KEY_USAGE,
+                                       MBEDTLS_OID_SIZE( MBEDTLS_OID_KEY_USAGE ),
+                                       c, (size_t)ret );
+    if( ret != 0 )
+        return( ret );
+
+    return( 0 );
+}
+
+int mbedtls_x509write_csr_set_ns_cert_type( mbedtls_x509write_csr *ctx,
+                                    unsigned char ns_cert_type )
+{
+    unsigned char buf[4];
+    unsigned char *c;
+    int ret;
+
+    c = buf + 4;
+
+    ret = mbedtls_asn1_write_named_bitstring( &c, buf, &ns_cert_type, 8 );
+    if( ret < 3 || ret > 4 )
+        return( ret );
+
+    ret = mbedtls_x509write_csr_set_extension( ctx, MBEDTLS_OID_NS_CERT_TYPE,
+                                       MBEDTLS_OID_SIZE( MBEDTLS_OID_NS_CERT_TYPE ),
+                                       c, (size_t)ret );
+    if( ret != 0 )
+        return( ret );
+
+    return( 0 );
+}
+
+int mbedtls_x509write_csr_der( mbedtls_x509write_csr *ctx, unsigned char *buf, size_t size,
+                       int (*f_rng)(void *, unsigned char *, size_t),
+                       void *p_rng )
+{
+    int ret;
+    const char *sig_oid;
+    size_t sig_oid_len = 0;
+    unsigned char *c, *c2;
+    unsigned char hash[64];
+    unsigned char sig[MBEDTLS_MPI_MAX_SIZE];
+    unsigned char tmp_buf[2048];
+    size_t pub_len = 0, sig_and_oid_len = 0, sig_len;
+    size_t len = 0;
+    mbedtls_pk_type_t pk_alg;
+#if defined(MBEDTLS_USE_PSA_CRYPTO)
+    psa_hash_operation_t hash_operation = PSA_HASH_OPERATION_INIT;
+    size_t hash_len;
+    psa_algorithm_t hash_alg = mbedtls_psa_translate_md( ctx->md_alg );
+#endif /* MBEDTLS_USE_PSA_CRYPTO */
+    /*
+     * Prepare data to be signed in tmp_buf
+     */
+    c = tmp_buf + sizeof( tmp_buf );
+
+    MBEDTLS_ASN1_CHK_ADD( len, mbedtls_x509_write_extensions( &c, tmp_buf, ctx->extensions ) );
+
+    if( len )
+    {
+        MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, tmp_buf, len ) );
+        MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, tmp_buf, MBEDTLS_ASN1_CONSTRUCTED |
+                                                        MBEDTLS_ASN1_SEQUENCE ) );
+
+        MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, tmp_buf, len ) );
+        MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, tmp_buf, MBEDTLS_ASN1_CONSTRUCTED |
+                                                        MBEDTLS_ASN1_SET ) );
+
+        MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_oid( &c, tmp_buf, MBEDTLS_OID_PKCS9_CSR_EXT_REQ,
+                                          MBEDTLS_OID_SIZE( MBEDTLS_OID_PKCS9_CSR_EXT_REQ ) ) );
+
+        MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, tmp_buf, len ) );
+        MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, tmp_buf, MBEDTLS_ASN1_CONSTRUCTED |
+                                                        MBEDTLS_ASN1_SEQUENCE ) );
+    }
+
+    MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, tmp_buf, len ) );
+    MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, tmp_buf, MBEDTLS_ASN1_CONSTRUCTED |
+                                                    MBEDTLS_ASN1_CONTEXT_SPECIFIC ) );
+
+    MBEDTLS_ASN1_CHK_ADD( pub_len, mbedtls_pk_write_pubkey_der( ctx->key,
+                                                tmp_buf, c - tmp_buf ) );
+    c -= pub_len;
+    len += pub_len;
+
+    /*
+     *  Subject  ::=  Name
+     */
+    MBEDTLS_ASN1_CHK_ADD( len, mbedtls_x509_write_names( &c, tmp_buf, ctx->subject ) );
+
+    /*
+     *  Version  ::=  INTEGER  {  v1(0), v2(1), v3(2)  }
+     */
+    MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_int( &c, tmp_buf, 0 ) );
+
+    MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c, tmp_buf, len ) );
+    MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c, tmp_buf, MBEDTLS_ASN1_CONSTRUCTED |
+                                                    MBEDTLS_ASN1_SEQUENCE ) );
+
+    /*
+     * Prepare signature
+     * Note: hash errors can happen only after an internal error
+     */
+#if defined(MBEDTLS_USE_PSA_CRYPTO)
+    if( psa_hash_setup( &hash_operation, hash_alg ) != PSA_SUCCESS )
+        return( MBEDTLS_ERR_X509_FATAL_ERROR );
+
+    if( psa_hash_update( &hash_operation, c, len ) != PSA_SUCCESS )
+        return( MBEDTLS_ERR_X509_FATAL_ERROR );
+
+    if( psa_hash_finish( &hash_operation, hash, sizeof( hash ), &hash_len )
+        != PSA_SUCCESS )
+    {
+        return( MBEDTLS_ERR_X509_FATAL_ERROR );
+    }
+#else /* MBEDTLS_USE_PSA_CRYPTO */
+    mbedtls_md( mbedtls_md_info_from_type( ctx->md_alg ), c, len, hash );
+#endif
+    if( ( ret = mbedtls_pk_sign( ctx->key, ctx->md_alg, hash, 0, sig, &sig_len,
+                                 f_rng, p_rng ) ) != 0 )
+    {
+        return( ret );
+    }
+
+    if( mbedtls_pk_can_do( ctx->key, MBEDTLS_PK_RSA ) )
+        pk_alg = MBEDTLS_PK_RSA;
+    else if( mbedtls_pk_can_do( ctx->key, MBEDTLS_PK_ECDSA ) )
+        pk_alg = MBEDTLS_PK_ECDSA;
+    else
+        return( MBEDTLS_ERR_X509_INVALID_ALG );
+
+    if( ( ret = mbedtls_oid_get_oid_by_sig_alg( pk_alg, ctx->md_alg,
+                                                &sig_oid, &sig_oid_len ) ) != 0 )
+    {
+        return( ret );
+    }
+
+    /*
+     * Write data to output buffer
+     */
+    c2 = buf + size;
+    MBEDTLS_ASN1_CHK_ADD( sig_and_oid_len, mbedtls_x509_write_sig( &c2, buf,
+                                        sig_oid, sig_oid_len, sig, sig_len ) );
+
+    if( len > (size_t)( c2 - buf ) )
+        return( MBEDTLS_ERR_ASN1_BUF_TOO_SMALL );
+
+    c2 -= len;
+    memcpy( c2, c, len );
+
+    len += sig_and_oid_len;
+    MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &c2, buf, len ) );
+    MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &c2, buf, MBEDTLS_ASN1_CONSTRUCTED |
+                                                 MBEDTLS_ASN1_SEQUENCE ) );
+
+    return( (int) len );
+}
+
+#define PEM_BEGIN_CSR           "-----BEGIN CERTIFICATE REQUEST-----\n"
+#define PEM_END_CSR             "-----END CERTIFICATE REQUEST-----\n"
+
+#if defined(MBEDTLS_PEM_WRITE_C)
+int mbedtls_x509write_csr_pem( mbedtls_x509write_csr *ctx, unsigned char *buf, size_t size,
+                       int (*f_rng)(void *, unsigned char *, size_t),
+                       void *p_rng )
+{
+    int ret;
+    unsigned char output_buf[4096];
+    size_t olen = 0;
+
+    if( ( ret = mbedtls_x509write_csr_der( ctx, output_buf, sizeof(output_buf),
+                                   f_rng, p_rng ) ) < 0 )
+    {
+        return( ret );
+    }
+
+    if( ( ret = mbedtls_pem_write_buffer( PEM_BEGIN_CSR, PEM_END_CSR,
+                                  output_buf + sizeof(output_buf) - ret,
+                                  ret, buf, size, &olen ) ) != 0 )
+    {
+        return( ret );
+    }
+
+    return( 0 );
+}
+#endif /* MBEDTLS_PEM_WRITE_C */
+
+#endif /* MBEDTLS_X509_CSR_WRITE_C */