Squashed 'lib/mbedtls/external/mbedtls/' content from commit 2ca6c285a0dd

git-subtree-dir: lib/mbedtls/external/mbedtls
git-subtree-split: 2ca6c285a0dd3f33982dd57299012dacab1ff206

1 files changed, 621 insertions, 0 deletions

diff --git a/library/pkwrite.c b/library/pkwrite.c
new file mode 100644
index 00000000000..5e009c565ea
--- /dev/null
+++ b/library/pkwrite.c
@@ -0,0 +1,621 @@
+/*
+ *  Public Key layer for writing key files and structures
+ *
+ *  Copyright The Mbed TLS Contributors
+ *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
+ */
+
+#include "common.h"
+
+#if defined(MBEDTLS_PK_WRITE_C)
+
+#include "mbedtls/pk.h"
+#include "mbedtls/asn1write.h"
+#include "mbedtls/oid.h"
+#include "mbedtls/platform_util.h"
+#include "mbedtls/error.h"
+#include "pk_internal.h"
+
+#include <string.h>
+
+#if defined(MBEDTLS_ECP_C)
+#include "mbedtls/bignum.h"
+#include "mbedtls/ecp.h"
+#include "mbedtls/platform_util.h"
+#endif
+#if defined(MBEDTLS_PK_HAVE_ECC_KEYS)
+#include "pk_internal.h"
+#endif
+#if defined(MBEDTLS_RSA_C) || defined(MBEDTLS_PK_HAVE_ECC_KEYS)
+#include "pkwrite.h"
+#endif
+#if defined(MBEDTLS_PEM_WRITE_C)
+#include "mbedtls/pem.h"
+#endif
+#if defined(MBEDTLS_RSA_C)
+#include "rsa_internal.h"
+#endif
+
+#if defined(MBEDTLS_USE_PSA_CRYPTO)
+#include "psa/crypto.h"
+#include "psa_util_internal.h"
+#endif
+#include "mbedtls/platform.h"
+
+/* Helpers for properly sizing buffers aimed at holding public keys or
+ * key-pairs based on build symbols. */
+#if defined(MBEDTLS_PK_USE_PSA_EC_DATA)
+#define PK_MAX_EC_PUBLIC_KEY_SIZE       PSA_EXPORT_PUBLIC_KEY_MAX_SIZE
+#define PK_MAX_EC_KEY_PAIR_SIZE         MBEDTLS_PSA_MAX_EC_KEY_PAIR_LENGTH
+#elif defined(MBEDTLS_USE_PSA_CRYPTO)
+#define PK_MAX_EC_PUBLIC_KEY_SIZE       PSA_EXPORT_PUBLIC_KEY_MAX_SIZE
+#define PK_MAX_EC_KEY_PAIR_SIZE         MBEDTLS_PSA_MAX_EC_KEY_PAIR_LENGTH
+#else
+#define PK_MAX_EC_PUBLIC_KEY_SIZE       MBEDTLS_ECP_MAX_PT_LEN
+#define PK_MAX_EC_KEY_PAIR_SIZE         MBEDTLS_ECP_MAX_BYTES
+#endif
+
+/******************************************************************************
+ * Internal functions for RSA keys.
+ ******************************************************************************/
+#if defined(MBEDTLS_RSA_C)
+static int pk_write_rsa_der(unsigned char **p, unsigned char *buf,
+                            const mbedtls_pk_context *pk)
+{
+#if defined(MBEDTLS_USE_PSA_CRYPTO)
+    if (mbedtls_pk_get_type(pk) == MBEDTLS_PK_OPAQUE) {
+        uint8_t tmp[PSA_EXPORT_KEY_PAIR_MAX_SIZE];
+        size_t len = 0, tmp_len = 0;
+
+        if (psa_export_key(pk->priv_id, tmp, sizeof(tmp), &tmp_len) != PSA_SUCCESS) {
+            return MBEDTLS_ERR_PK_BAD_INPUT_DATA;
+        }
+        *p -= tmp_len;
+        memcpy(*p, tmp, tmp_len);
+        len += tmp_len;
+        mbedtls_platform_zeroize(tmp, sizeof(tmp));
+
+        return (int) len;
+    }
+#endif /* MBEDTLS_USE_PSA_CRYPTO */
+    return mbedtls_rsa_write_key(mbedtls_pk_rsa(*pk), buf, p);
+}
+#endif /* MBEDTLS_RSA_C */
+
+/******************************************************************************
+ * Internal functions for EC keys.
+ ******************************************************************************/
+#if defined(MBEDTLS_PK_HAVE_ECC_KEYS)
+#if defined(MBEDTLS_PK_USE_PSA_EC_DATA)
+static int pk_write_ec_pubkey(unsigned char **p, unsigned char *start,
+                              const mbedtls_pk_context *pk)
+{
+    size_t len = 0;
+    uint8_t buf[PK_MAX_EC_PUBLIC_KEY_SIZE];
+
+    if (mbedtls_pk_get_type(pk) == MBEDTLS_PK_OPAQUE) {
+        if (psa_export_public_key(pk->priv_id, buf, sizeof(buf), &len) != PSA_SUCCESS) {
+            return MBEDTLS_ERR_PK_BAD_INPUT_DATA;
+        }
+    } else {
+        len = pk->pub_raw_len;
+        memcpy(buf, pk->pub_raw, len);
+    }
+
+    if (*p < start || (size_t) (*p - start) < len) {
+        return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL;
+    }
+
+    *p -= len;
+    memcpy(*p, buf, len);
+
+    return (int) len;
+}
+#else /* MBEDTLS_PK_USE_PSA_EC_DATA */
+static int pk_write_ec_pubkey(unsigned char **p, unsigned char *start,
+                              const mbedtls_pk_context *pk)
+{
+    size_t len = 0;
+    unsigned char buf[PK_MAX_EC_PUBLIC_KEY_SIZE];
+    mbedtls_ecp_keypair *ec = mbedtls_pk_ec(*pk);
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+
+#if defined(MBEDTLS_USE_PSA_CRYPTO)
+    if (mbedtls_pk_get_type(pk) == MBEDTLS_PK_OPAQUE) {
+        if (psa_export_public_key(pk->priv_id, buf, sizeof(buf), &len) != PSA_SUCCESS) {
+            return MBEDTLS_ERR_PK_BAD_INPUT_DATA;
+        }
+        *p -= len;
+        memcpy(*p, buf, len);
+        return (int) len;
+    } else
+#endif /* MBEDTLS_USE_PSA_CRYPTO */
+    {
+        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;
+}
+#endif /* MBEDTLS_PK_USE_PSA_EC_DATA */
+
+/*
+ * privateKey  OCTET STRING -- always of length ceil(log2(n)/8)
+ */
+#if defined(MBEDTLS_PK_USE_PSA_EC_DATA)
+static int pk_write_ec_private(unsigned char **p, unsigned char *start,
+                               const mbedtls_pk_context *pk)
+{
+    size_t byte_length;
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    unsigned char tmp[PK_MAX_EC_KEY_PAIR_SIZE];
+    psa_status_t status;
+
+    if (mbedtls_pk_get_type(pk) == MBEDTLS_PK_OPAQUE) {
+        status = psa_export_key(pk->priv_id, tmp, sizeof(tmp), &byte_length);
+        if (status != PSA_SUCCESS) {
+            ret = PSA_PK_ECDSA_TO_MBEDTLS_ERR(status);
+            return ret;
+        }
+    } else {
+        status = psa_export_key(pk->priv_id, tmp, sizeof(tmp), &byte_length);
+        if (status != PSA_SUCCESS) {
+            ret = PSA_PK_ECDSA_TO_MBEDTLS_ERR(status);
+            goto exit;
+        }
+    }
+
+    ret = mbedtls_asn1_write_octet_string(p, start, tmp, byte_length);
+exit:
+    mbedtls_platform_zeroize(tmp, sizeof(tmp));
+    return ret;
+}
+#else /* MBEDTLS_PK_USE_PSA_EC_DATA */
+static int pk_write_ec_private(unsigned char **p, unsigned char *start,
+                               const mbedtls_pk_context *pk)
+{
+    size_t byte_length;
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    unsigned char tmp[PK_MAX_EC_KEY_PAIR_SIZE];
+
+#if defined(MBEDTLS_USE_PSA_CRYPTO)
+    psa_status_t status;
+    if (mbedtls_pk_get_type(pk) == MBEDTLS_PK_OPAQUE) {
+        status = psa_export_key(pk->priv_id, tmp, sizeof(tmp), &byte_length);
+        if (status != PSA_SUCCESS) {
+            ret = PSA_PK_ECDSA_TO_MBEDTLS_ERR(status);
+            return ret;
+        }
+    } else
+#endif /* MBEDTLS_USE_PSA_CRYPTO */
+    {
+        mbedtls_ecp_keypair *ec = mbedtls_pk_ec_rw(*pk);
+        byte_length = (ec->grp.pbits + 7) / 8;
+
+        ret = mbedtls_ecp_write_key_ext(ec, &byte_length, tmp, sizeof(tmp));
+        if (ret != 0) {
+            goto exit;
+        }
+    }
+    ret = mbedtls_asn1_write_octet_string(p, start, tmp, byte_length);
+exit:
+    mbedtls_platform_zeroize(tmp, sizeof(tmp));
+    return ret;
+}
+#endif /* MBEDTLS_PK_USE_PSA_EC_DATA */
+
+/*
+ * ECParameters ::= CHOICE {
+ *   namedCurve         OBJECT IDENTIFIER
+ * }
+ */
+static int pk_write_ec_param(unsigned char **p, unsigned char *start,
+                             mbedtls_ecp_group_id grp_id)
+{
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    size_t len = 0;
+    const char *oid;
+    size_t oid_len;
+
+    if ((ret = mbedtls_oid_get_oid_by_ec_grp(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;
+}
+
+#if defined(MBEDTLS_PK_HAVE_RFC8410_CURVES)
+/*
+ * RFC8410 section 7
+ *
+ * OneAsymmetricKey ::= SEQUENCE {
+ *    version Version,
+ *    privateKeyAlgorithm PrivateKeyAlgorithmIdentifier,
+ *    privateKey PrivateKey,
+ *    attributes [0] IMPLICIT Attributes OPTIONAL,
+ *    ...,
+ *    [[2: publicKey [1] IMPLICIT PublicKey OPTIONAL ]],
+ *    ...
+ * }
+ * ...
+ * CurvePrivateKey ::= OCTET STRING
+ */
+static int pk_write_ec_rfc8410_der(unsigned char **p, unsigned char *buf,
+                                   const mbedtls_pk_context *pk)
+{
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    size_t len = 0;
+    size_t oid_len = 0;
+    const char *oid;
+    mbedtls_ecp_group_id grp_id;
+
+    /* privateKey */
+    MBEDTLS_ASN1_CHK_ADD(len, pk_write_ec_private(p, buf, pk));
+    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, buf, len));
+    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, buf, MBEDTLS_ASN1_OCTET_STRING));
+
+    grp_id = mbedtls_pk_get_ec_group_id(pk);
+    /* privateKeyAlgorithm */
+    if ((ret = mbedtls_oid_get_oid_by_ec_grp_algid(grp_id, &oid, &oid_len)) != 0) {
+        return ret;
+    }
+    MBEDTLS_ASN1_CHK_ADD(len,
+                         mbedtls_asn1_write_algorithm_identifier_ext(p, buf, oid, oid_len, 0, 0));
+
+    /* version */
+    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_int(p, buf, 0));
+
+    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, buf, len));
+    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, buf, MBEDTLS_ASN1_CONSTRUCTED |
+                                                     MBEDTLS_ASN1_SEQUENCE));
+
+    return (int) len;
+}
+#endif /* MBEDTLS_PK_HAVE_RFC8410_CURVES */
+
+/*
+ * 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
+ *    }
+ */
+static int pk_write_ec_der(unsigned char **p, unsigned char *buf,
+                           const mbedtls_pk_context *pk)
+{
+    size_t len = 0;
+    int ret;
+    size_t pub_len = 0, par_len = 0;
+    mbedtls_ecp_group_id grp_id;
+
+    /* publicKey */
+    MBEDTLS_ASN1_CHK_ADD(pub_len, pk_write_ec_pubkey(p, buf, pk));
+
+    if (*p - buf < 1) {
+        return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL;
+    }
+    (*p)--;
+    **p = 0;
+    pub_len += 1;
+
+    MBEDTLS_ASN1_CHK_ADD(pub_len, mbedtls_asn1_write_len(p, buf, pub_len));
+    MBEDTLS_ASN1_CHK_ADD(pub_len, mbedtls_asn1_write_tag(p, buf, MBEDTLS_ASN1_BIT_STRING));
+
+    MBEDTLS_ASN1_CHK_ADD(pub_len, mbedtls_asn1_write_len(p, buf, pub_len));
+    MBEDTLS_ASN1_CHK_ADD(pub_len, mbedtls_asn1_write_tag(p, buf,
+                                                         MBEDTLS_ASN1_CONTEXT_SPECIFIC |
+                                                         MBEDTLS_ASN1_CONSTRUCTED | 1));
+    len += pub_len;
+
+    /* parameters */
+    grp_id = mbedtls_pk_get_ec_group_id(pk);
+    MBEDTLS_ASN1_CHK_ADD(par_len, pk_write_ec_param(p, buf, grp_id));
+    MBEDTLS_ASN1_CHK_ADD(par_len, mbedtls_asn1_write_len(p, buf, par_len));
+    MBEDTLS_ASN1_CHK_ADD(par_len, mbedtls_asn1_write_tag(p, buf,
+                                                         MBEDTLS_ASN1_CONTEXT_SPECIFIC |
+                                                         MBEDTLS_ASN1_CONSTRUCTED | 0));
+    len += par_len;
+
+    /* privateKey */
+    MBEDTLS_ASN1_CHK_ADD(len, pk_write_ec_private(p, buf, pk));
+
+    /* version */
+    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_int(p, buf, 1));
+
+    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, buf, len));
+    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, buf, MBEDTLS_ASN1_CONSTRUCTED |
+                                                     MBEDTLS_ASN1_SEQUENCE));
+
+    return (int) len;
+}
+#endif /* MBEDTLS_PK_HAVE_ECC_KEYS */
+
+/******************************************************************************
+ * Internal functions for Opaque keys.
+ ******************************************************************************/
+#if defined(MBEDTLS_USE_PSA_CRYPTO)
+static int pk_write_opaque_pubkey(unsigned char **p, unsigned char *start,
+                                  const mbedtls_pk_context *pk)
+{
+    size_t buffer_size;
+    size_t len = 0;
+
+    if (*p < start) {
+        return MBEDTLS_ERR_PK_BAD_INPUT_DATA;
+    }
+
+    buffer_size = (size_t) (*p - start);
+    if (psa_export_public_key(pk->priv_id, start, buffer_size,
+                              &len) != PSA_SUCCESS) {
+        return MBEDTLS_ERR_PK_BAD_INPUT_DATA;
+    }
+
+    *p -= len;
+    memmove(*p, start, len);
+
+    return (int) len;
+}
+#endif /* MBEDTLS_USE_PSA_CRYPTO */
+
+/******************************************************************************
+ * Generic helpers
+ ******************************************************************************/
+
+/* Extend the public mbedtls_pk_get_type() by getting key type also in case of
+ * opaque keys. */
+static mbedtls_pk_type_t pk_get_type_ext(const mbedtls_pk_context *pk)
+{
+    mbedtls_pk_type_t pk_type = mbedtls_pk_get_type(pk);
+
+#if defined(MBEDTLS_USE_PSA_CRYPTO)
+    if (pk_type == MBEDTLS_PK_OPAQUE) {
+        psa_key_attributes_t opaque_attrs = PSA_KEY_ATTRIBUTES_INIT;
+        psa_key_type_t opaque_key_type;
+
+        if (psa_get_key_attributes(pk->priv_id, &opaque_attrs) != PSA_SUCCESS) {
+            return MBEDTLS_PK_NONE;
+        }
+        opaque_key_type = psa_get_key_type(&opaque_attrs);
+        psa_reset_key_attributes(&opaque_attrs);
+
+        if (PSA_KEY_TYPE_IS_ECC(opaque_key_type)) {
+            return MBEDTLS_PK_ECKEY;
+        } else if (PSA_KEY_TYPE_IS_RSA(opaque_key_type)) {
+            return MBEDTLS_PK_RSA;
+        } else {
+            return MBEDTLS_PK_NONE;
+        }
+    } else
+#endif
+    return pk_type;
+}
+
+/******************************************************************************
+ * Public functions for writing private/public DER keys.
+ ******************************************************************************/
+int mbedtls_pk_write_pubkey(unsigned char **p, unsigned char *start,
+                            const mbedtls_pk_context *key)
+{
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    size_t len = 0;
+
+#if defined(MBEDTLS_RSA_C)
+    if (mbedtls_pk_get_type(key) == MBEDTLS_PK_RSA) {
+        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_rsa_write_pubkey(mbedtls_pk_rsa(*key), start, p));
+    } else
+#endif
+#if defined(MBEDTLS_PK_HAVE_ECC_KEYS)
+    if (mbedtls_pk_get_type(key) == MBEDTLS_PK_ECKEY) {
+        MBEDTLS_ASN1_CHK_ADD(len, pk_write_ec_pubkey(p, start, key));
+    } else
+#endif
+#if defined(MBEDTLS_USE_PSA_CRYPTO)
+    if (mbedtls_pk_get_type(key) == MBEDTLS_PK_OPAQUE) {
+        MBEDTLS_ASN1_CHK_ADD(len, pk_write_opaque_pubkey(p, start, key));
+    } else
+#endif /* MBEDTLS_USE_PSA_CRYPTO */
+    return MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE;
+
+    return (int) len;
+}
+
+int mbedtls_pk_write_pubkey_der(const mbedtls_pk_context *key, unsigned char *buf, size_t size)
+{
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    unsigned char *c;
+    int has_par = 1;
+    size_t len = 0, par_len = 0, oid_len = 0;
+    mbedtls_pk_type_t pk_type;
+    const char *oid = NULL;
+
+    if (size == 0) {
+        return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL;
+    }
+
+    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));
+
+    pk_type = pk_get_type_ext(key);
+
+#if defined(MBEDTLS_PK_HAVE_ECC_KEYS)
+    if (pk_get_type_ext(key) == MBEDTLS_PK_ECKEY) {
+        mbedtls_ecp_group_id ec_grp_id = mbedtls_pk_get_ec_group_id(key);
+        if (MBEDTLS_PK_IS_RFC8410_GROUP_ID(ec_grp_id)) {
+            ret = mbedtls_oid_get_oid_by_ec_grp_algid(ec_grp_id, &oid, &oid_len);
+            if (ret != 0) {
+                return ret;
+            }
+            has_par = 0;
+        } else {
+            MBEDTLS_ASN1_CHK_ADD(par_len, pk_write_ec_param(&c, buf, ec_grp_id));
+        }
+    }
+#endif /* MBEDTLS_PK_HAVE_ECC_KEYS */
+
+    /* At this point oid_len is not null only for EC Montgomery keys. */
+    if (oid_len == 0) {
+        ret = mbedtls_oid_get_oid_by_pk_alg(pk_type, &oid, &oid_len);
+        if (ret != 0) {
+            return ret;
+        }
+    }
+
+    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_algorithm_identifier_ext(&c, buf, oid, oid_len,
+                                                                          par_len, has_par));
+
+    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(const mbedtls_pk_context *key, unsigned char *buf, size_t size)
+{
+    unsigned char *c;
+
+    if (size == 0) {
+        return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL;
+    }
+
+    c = buf + size;
+
+#if defined(MBEDTLS_RSA_C)
+    if (pk_get_type_ext(key) == MBEDTLS_PK_RSA) {
+        return pk_write_rsa_der(&c, buf, key);
+    } else
+#endif /* MBEDTLS_RSA_C */
+#if defined(MBEDTLS_PK_HAVE_ECC_KEYS)
+    if (pk_get_type_ext(key) == MBEDTLS_PK_ECKEY) {
+#if defined(MBEDTLS_PK_HAVE_RFC8410_CURVES)
+        if (mbedtls_pk_is_rfc8410(key)) {
+            return pk_write_ec_rfc8410_der(&c, buf, key);
+        }
+#endif /* MBEDTLS_PK_HAVE_RFC8410_CURVES */
+        return pk_write_ec_der(&c, buf, key);
+    } else
+#endif /* MBEDTLS_PK_HAVE_ECC_KEYS */
+    return MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE;
+}
+
+/******************************************************************************
+ * Public functions for wrinting private/public PEM keys.
+ ******************************************************************************/
+#if defined(MBEDTLS_PEM_WRITE_C)
+
+#define PUB_DER_MAX_BYTES                                                   \
+    (MBEDTLS_PK_RSA_PUB_DER_MAX_BYTES > MBEDTLS_PK_ECP_PUB_DER_MAX_BYTES ? \
+     MBEDTLS_PK_RSA_PUB_DER_MAX_BYTES : MBEDTLS_PK_ECP_PUB_DER_MAX_BYTES)
+#define PRV_DER_MAX_BYTES                                                   \
+    (MBEDTLS_PK_RSA_PRV_DER_MAX_BYTES > MBEDTLS_PK_ECP_PRV_DER_MAX_BYTES ? \
+     MBEDTLS_PK_RSA_PRV_DER_MAX_BYTES : MBEDTLS_PK_ECP_PRV_DER_MAX_BYTES)
+
+int mbedtls_pk_write_pubkey_pem(const mbedtls_pk_context *key, unsigned char *buf, size_t size)
+{
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    unsigned char *output_buf = NULL;
+    output_buf = mbedtls_calloc(1, PUB_DER_MAX_BYTES);
+    if (output_buf == NULL) {
+        return MBEDTLS_ERR_PK_ALLOC_FAILED;
+    }
+    size_t olen = 0;
+
+    if ((ret = mbedtls_pk_write_pubkey_der(key, output_buf,
+                                           PUB_DER_MAX_BYTES)) < 0) {
+        goto cleanup;
+    }
+
+    if ((ret = mbedtls_pem_write_buffer(PEM_BEGIN_PUBLIC_KEY "\n", PEM_END_PUBLIC_KEY "\n",
+                                        output_buf + PUB_DER_MAX_BYTES - ret,
+                                        ret, buf, size, &olen)) != 0) {
+        goto cleanup;
+    }
+
+    ret = 0;
+cleanup:
+    mbedtls_free(output_buf);
+    return ret;
+}
+
+int mbedtls_pk_write_key_pem(const mbedtls_pk_context *key, unsigned char *buf, size_t size)
+{
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+    unsigned char *output_buf = NULL;
+    output_buf = mbedtls_calloc(1, PRV_DER_MAX_BYTES);
+    if (output_buf == NULL) {
+        return MBEDTLS_ERR_PK_ALLOC_FAILED;
+    }
+    const char *begin, *end;
+    size_t olen = 0;
+
+    if ((ret = mbedtls_pk_write_key_der(key, output_buf, PRV_DER_MAX_BYTES)) < 0) {
+        goto cleanup;
+    }
+
+#if defined(MBEDTLS_RSA_C)
+    if (pk_get_type_ext(key) == MBEDTLS_PK_RSA) {
+        begin = PEM_BEGIN_PRIVATE_KEY_RSA "\n";
+        end = PEM_END_PRIVATE_KEY_RSA "\n";
+    } else
+#endif
+#if defined(MBEDTLS_PK_HAVE_ECC_KEYS)
+    if (pk_get_type_ext(key) == MBEDTLS_PK_ECKEY) {
+        if (mbedtls_pk_is_rfc8410(key)) {
+            begin = PEM_BEGIN_PRIVATE_KEY_PKCS8 "\n";
+            end = PEM_END_PRIVATE_KEY_PKCS8 "\n";
+        } else {
+            begin = PEM_BEGIN_PRIVATE_KEY_EC "\n";
+            end = PEM_END_PRIVATE_KEY_EC "\n";
+        }
+    } else
+#endif /* MBEDTLS_PK_HAVE_ECC_KEYS */
+    {
+        ret = MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE;
+        goto cleanup;
+    }
+
+    if ((ret = mbedtls_pem_write_buffer(begin, end,
+                                        output_buf + PRV_DER_MAX_BYTES - ret,
+                                        ret, buf, size, &olen)) != 0) {
+        goto cleanup;
+    }
+
+    ret = 0;
+cleanup:
+    mbedtls_zeroize_and_free(output_buf, PRV_DER_MAX_BYTES);
+    return ret;
+}
+#endif /* MBEDTLS_PEM_WRITE_C */
+
+#endif /* MBEDTLS_PK_WRITE_C */