library/x509write_csr.c - third_party/github/ARMmbed/mbedtls - Git at Google

 /*
  *  X.509 Certificate Signing Request writing
  *
  *  Copyright The Mbed TLS Contributors
  *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
  */
 /*
  * References:
  * - CSRs: PKCS#10 v1.7 aka RFC 2986
  * - attributes: PKCS#9 v2.0 aka RFC 2985
  */

 #include "common.h"

 #if defined(MBEDTLS_X509_CSR_WRITE_C)

 #include "x509_internal.h"
 #include "mbedtls/x509_csr.h"
 #include "mbedtls/asn1write.h"
 #include "mbedtls/error.h"
 #include "mbedtls/oid.h"
 #include "mbedtls/platform_util.h"

 #if defined(MBEDTLS_USE_PSA_CRYPTO)
 #include "psa/crypto.h"
 #include "psa_util_internal.h"
 #include "mbedtls/psa_util.h"
 #endif /* MBEDTLS_USE_PSA_CRYPTO */

 #include <string.h>
 #include <stdlib.h>

 #if defined(MBEDTLS_PEM_WRITE_C)
 #include "mbedtls/pem.h"
 #endif

 #include "mbedtls/platform.h"

 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,
                                         int critical,
                                         const unsigned char *val, size_t val_len)
 {
     return mbedtls_x509_set_extension(&ctx->extensions, oid, oid_len,
                                       critical, val, val_len);
 }

 int mbedtls_x509write_csr_set_subject_alternative_name(mbedtls_x509write_csr *ctx,
                                                        const mbedtls_x509_san_list *san_list)
 {
     return mbedtls_x509_write_set_san_common(&ctx->extensions, san_list);
 }

 int mbedtls_x509write_csr_set_key_usage(mbedtls_x509write_csr *ctx, unsigned char key_usage)
 {
     unsigned char buf[4] = { 0 };
     unsigned char *c;
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

     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),
                                               0, 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] = { 0 };
     unsigned char *c;
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

     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),
                                               0, c, (size_t) ret);
     if (ret != 0) {
         return ret;
     }

     return 0;
 }

 static int x509write_csr_der_internal(mbedtls_x509write_csr *ctx,
                                       unsigned char *buf,
                                       size_t size,
                                       unsigned char *sig, size_t sig_size,
                                       int (*f_rng)(void *, unsigned char *, size_t),
                                       void *p_rng)
 {
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     const char *sig_oid;
     size_t sig_oid_len = 0;
     unsigned char *c, *c2;
     unsigned char hash[MBEDTLS_MD_MAX_SIZE];
     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)
     size_t hash_len;
     psa_algorithm_t hash_alg = mbedtls_md_psa_alg_from_type(ctx->md_alg);
 #endif /* MBEDTLS_USE_PSA_CRYPTO */

     /* Write the CSR backwards starting from the end of buf */
     c = buf + size;

     MBEDTLS_ASN1_CHK_ADD(len, mbedtls_x509_write_extensions(&c, buf,
                                                             ctx->extensions));

     if (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));

         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_SET));

         MBEDTLS_ASN1_CHK_ADD(len,
                              mbedtls_asn1_write_oid(
                                  &c, 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, buf, len));
         MBEDTLS_ASN1_CHK_ADD(len,
                              mbedtls_asn1_write_tag(
                                  &c, buf,
                                  MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE));
     }

     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_CONTEXT_SPECIFIC));

     MBEDTLS_ASN1_CHK_ADD(pub_len, mbedtls_pk_write_pubkey_der(ctx->key,
                                                               buf, (size_t) (c - buf)));
     c -= pub_len;
     len += pub_len;

     /*
      *  Subject  ::=  Name
      */
     MBEDTLS_ASN1_CHK_ADD(len, mbedtls_x509_write_names(&c, buf,
                                                        ctx->subject));

     /*
      *  Version  ::=  INTEGER  {  v1(0), v2(1), v3(2)  }
      */
     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));

     /*
      * Sign the written CSR data into the sig buffer
      * Note: hash errors can happen only after an internal error
      */
 #if defined(MBEDTLS_USE_PSA_CRYPTO)
     if (psa_hash_compute(hash_alg,
                          c,
                          len,
                          hash,
                          sizeof(hash),
                          &hash_len) != PSA_SUCCESS) {
         return MBEDTLS_ERR_PLATFORM_HW_ACCEL_FAILED;
     }
 #else /* MBEDTLS_USE_PSA_CRYPTO */
     ret = mbedtls_md(mbedtls_md_info_from_type(ctx->md_alg), c, len, hash);
     if (ret != 0) {
         return ret;
     }
 #endif
     if ((ret = mbedtls_pk_sign(ctx->key, ctx->md_alg, hash, 0,
                                sig, sig_size, &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;
     }

     /*
      * Move the written CSR data to the start of buf to create space for
      * writing the signature into buf.
      */
     memmove(buf, c, len);

     /*
      * Write sig and its OID into buf backwards from the end of buf.
      * Note: mbedtls_x509_write_sig will check for c2 - ( buf + len ) < sig_len
      * and return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL if needed.
      */
     c2 = buf + size;
     MBEDTLS_ASN1_CHK_ADD(sig_and_oid_len,
                          mbedtls_x509_write_sig(&c2, buf + len, sig_oid, sig_oid_len,
                                                 sig, sig_len, pk_alg));

     /*
      * Compact the space between the CSR data and signature by moving the
      * CSR data to the start of the signature.
      */
     c2 -= len;
     memmove(c2, buf, len);

     /* ASN encode the total size and tag the CSR data with it. */
     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));

     /* Zero the unused bytes at the start of buf */
     memset(buf, 0, (size_t) (c2 - buf));

     return (int) len;
 }

 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;
     unsigned char *sig;

     if ((sig = mbedtls_calloc(1, MBEDTLS_PK_SIGNATURE_MAX_SIZE)) == NULL) {
         return MBEDTLS_ERR_X509_ALLOC_FAILED;
     }

     ret = x509write_csr_der_internal(ctx, buf, size,
                                      sig, MBEDTLS_PK_SIGNATURE_MAX_SIZE,
                                      f_rng, p_rng);

     mbedtls_free(sig);

     return ret;
 }

 #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 = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
     size_t olen = 0;

     if ((ret = mbedtls_x509write_csr_der(ctx, buf, size,
                                          f_rng, p_rng)) < 0) {
         return ret;
     }

     if ((ret = mbedtls_pem_write_buffer(PEM_BEGIN_CSR, PEM_END_CSR,
                                         buf + size - ret,
                                         ret, buf, size, &olen)) != 0) {
         return ret;
     }

     return 0;
 }
 #endif /* MBEDTLS_PEM_WRITE_C */

 #endif /* MBEDTLS_X509_CSR_WRITE_C */
	/*
	* X.509 Certificate Signing Request writing
	*
	* Copyright The Mbed TLS Contributors
	* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
	*/
	/*
	* References:
	* - CSRs: PKCS#10 v1.7 aka RFC 2986
	* - attributes: PKCS#9 v2.0 aka RFC 2985
	*/

	#include "common.h"

	#if defined(MBEDTLS_X509_CSR_WRITE_C)

	#include "x509_internal.h"
	#include "mbedtls/x509_csr.h"
	#include "mbedtls/asn1write.h"
	#include "mbedtls/error.h"
	#include "mbedtls/oid.h"
	#include "mbedtls/platform_util.h"

	#if defined(MBEDTLS_USE_PSA_CRYPTO)
	#include "psa/crypto.h"
	#include "psa_util_internal.h"
	#include "mbedtls/psa_util.h"
	#endif /* MBEDTLS_USE_PSA_CRYPTO */

	#include <string.h>
	#include <stdlib.h>

	#if defined(MBEDTLS_PEM_WRITE_C)
	#include "mbedtls/pem.h"
	#endif

	#include "mbedtls/platform.h"

	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,
	int critical,
	const unsigned char *val, size_t val_len)
	{
	return mbedtls_x509_set_extension(&ctx->extensions, oid, oid_len,
	critical, val, val_len);
	}

	int mbedtls_x509write_csr_set_subject_alternative_name(mbedtls_x509write_csr *ctx,
	const mbedtls_x509_san_list *san_list)
	{
	return mbedtls_x509_write_set_san_common(&ctx->extensions, san_list);
	}

	int mbedtls_x509write_csr_set_key_usage(mbedtls_x509write_csr *ctx, unsigned char key_usage)
	{
	unsigned char buf[4] = { 0 };
	unsigned char *c;
	int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

	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),
	0, 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] = { 0 };
	unsigned char *c;
	int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

	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),
	0, c, (size_t) ret);
	if (ret != 0) {
	return ret;
	}

	return 0;
	}

	static int x509write_csr_der_internal(mbedtls_x509write_csr *ctx,
	unsigned char *buf,
	size_t size,
	unsigned char *sig, size_t sig_size,
	int (f_rng)(void , unsigned char *, size_t),
	void *p_rng)
	{
	int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
	const char *sig_oid;
	size_t sig_oid_len = 0;
	unsigned char c, c2;
	unsigned char hash[MBEDTLS_MD_MAX_SIZE];
	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)
	size_t hash_len;
	psa_algorithm_t hash_alg = mbedtls_md_psa_alg_from_type(ctx->md_alg);
	#endif /* MBEDTLS_USE_PSA_CRYPTO */

	/* Write the CSR backwards starting from the end of buf */
	c = buf + size;

	MBEDTLS_ASN1_CHK_ADD(len, mbedtls_x509_write_extensions(&c, buf,
	ctx->extensions));

	if (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));

	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_SET));

	MBEDTLS_ASN1_CHK_ADD(len,
	mbedtls_asn1_write_oid(
	&c, 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, buf, len));
	MBEDTLS_ASN1_CHK_ADD(len,
	mbedtls_asn1_write_tag(
	&c, buf,
	MBEDTLS_ASN1_CONSTRUCTED \| MBEDTLS_ASN1_SEQUENCE));
	}

	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_CONTEXT_SPECIFIC));

	MBEDTLS_ASN1_CHK_ADD(pub_len, mbedtls_pk_write_pubkey_der(ctx->key,
	buf, (size_t) (c - buf)));
	c -= pub_len;
	len += pub_len;

	/*
	* Subject ::= Name
	*/
	MBEDTLS_ASN1_CHK_ADD(len, mbedtls_x509_write_names(&c, buf,
	ctx->subject));

	/*
	* Version ::= INTEGER { v1(0), v2(1), v3(2) }
	*/
	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));

	/*
	* Sign the written CSR data into the sig buffer
	* Note: hash errors can happen only after an internal error
	*/
	#if defined(MBEDTLS_USE_PSA_CRYPTO)
	if (psa_hash_compute(hash_alg,
	c,
	len,
	hash,
	sizeof(hash),
	&hash_len) != PSA_SUCCESS) {
	return MBEDTLS_ERR_PLATFORM_HW_ACCEL_FAILED;
	}
	#else /* MBEDTLS_USE_PSA_CRYPTO */
	ret = mbedtls_md(mbedtls_md_info_from_type(ctx->md_alg), c, len, hash);
	if (ret != 0) {
	return ret;
	}
	#endif
	if ((ret = mbedtls_pk_sign(ctx->key, ctx->md_alg, hash, 0,
	sig, sig_size, &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;
	}

	/*
	* Move the written CSR data to the start of buf to create space for
	* writing the signature into buf.
	*/
	memmove(buf, c, len);

	/*
	* Write sig and its OID into buf backwards from the end of buf.
	* Note: mbedtls_x509_write_sig will check for c2 - ( buf + len ) < sig_len
	* and return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL if needed.
	*/
	c2 = buf + size;
	MBEDTLS_ASN1_CHK_ADD(sig_and_oid_len,
	mbedtls_x509_write_sig(&c2, buf + len, sig_oid, sig_oid_len,
	sig, sig_len, pk_alg));

	/*
	* Compact the space between the CSR data and signature by moving the
	* CSR data to the start of the signature.
	*/
	c2 -= len;
	memmove(c2, buf, len);

	/* ASN encode the total size and tag the CSR data with it. */
	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));

	/* Zero the unused bytes at the start of buf */
	memset(buf, 0, (size_t) (c2 - buf));

	return (int) len;
	}

	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;
	unsigned char *sig;

	if ((sig = mbedtls_calloc(1, MBEDTLS_PK_SIGNATURE_MAX_SIZE)) == NULL) {
	return MBEDTLS_ERR_X509_ALLOC_FAILED;
	}

	ret = x509write_csr_der_internal(ctx, buf, size,
	sig, MBEDTLS_PK_SIGNATURE_MAX_SIZE,
	f_rng, p_rng);

	mbedtls_free(sig);

	return ret;
	}

	#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 = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
	size_t olen = 0;

	if ((ret = mbedtls_x509write_csr_der(ctx, buf, size,
	f_rng, p_rng)) < 0) {
	return ret;
	}

	if ((ret = mbedtls_pem_write_buffer(PEM_BEGIN_CSR, PEM_END_CSR,
	buf + size - ret,
	ret, buf, size, &olen)) != 0) {
	return ret;
	}

	return 0;
	}
	#endif /* MBEDTLS_PEM_WRITE_C */

	#endif /* MBEDTLS_X509_CSR_WRITE_C */