/* * 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 #if defined(MBEDTLS_RSA_C) #include "mbedtls/rsa.h" #endif #if defined(MBEDTLS_ECP_C) #include "mbedtls/bignum.h" #include "mbedtls/ecp.h" #include "mbedtls/platform_util.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_USE_PSA_CRYPTO) #include "psa/crypto.h" #include "mbedtls/psa_util.h" #endif #include "mbedtls/platform.h" /* Parameter validation macros based on platform_util.h */ #define PK_VALIDATE_RET(cond) \ MBEDTLS_INTERNAL_VALIDATE_RET(cond, MBEDTLS_ERR_PK_BAD_INPUT_DATA) #define PK_VALIDATE(cond) \ MBEDTLS_INTERNAL_VALIDATE(cond) #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 = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; 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 = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; 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 = 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(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; } /* * privateKey OCTET STRING -- always of length ceil(log2(n)/8) */ static int pk_write_ec_private(unsigned char **p, unsigned char *start, mbedtls_ecp_keypair *ec) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; size_t byte_length = (ec->grp.pbits + 7) / 8; unsigned char tmp[MBEDTLS_ECP_MAX_BYTES]; ret = mbedtls_ecp_write_key(ec, tmp, byte_length); if (ret != 0) { goto exit; } ret = mbedtls_asn1_write_octet_string(p, start, tmp, byte_length); exit: mbedtls_platform_zeroize(tmp, byte_length); return ret; } #endif /* MBEDTLS_ECP_C */ 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; (void) p; (void) start; (void) key; (void) ret; PK_VALIDATE_RET(p != NULL); PK_VALIDATE_RET(*p != NULL); PK_VALIDATE_RET(start != NULL); PK_VALIDATE_RET(key != NULL); #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 #if defined(MBEDTLS_USE_PSA_CRYPTO) if (mbedtls_pk_get_type(key) == MBEDTLS_PK_OPAQUE) { size_t buffer_size; psa_key_id_t *key_id = (psa_key_id_t *) key->pk_ctx; if (*p < start) { return MBEDTLS_ERR_PK_BAD_INPUT_DATA; } buffer_size = (size_t) (*p - start); if (psa_export_public_key(*key_id, start, buffer_size, &len) != PSA_SUCCESS) { return MBEDTLS_ERR_PK_BAD_INPUT_DATA; } else { *p -= len; memmove(*p, start, len); } } else #endif /* MBEDTLS_USE_PSA_CRYPTO */ 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 = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char *c; size_t len = 0, par_len = 0, oid_len; mbedtls_pk_type_t pk_type; const char *oid; PK_VALIDATE_RET(key != NULL); if (size == 0) { return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL; } PK_VALIDATE_RET(buf != NULL); 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 = mbedtls_pk_get_type(key); #if defined(MBEDTLS_ECP_C) if (pk_type == MBEDTLS_PK_ECKEY) { MBEDTLS_ASN1_CHK_ADD(par_len, pk_write_ec_param(&c, buf, mbedtls_pk_ec(*key))); } #endif #if defined(MBEDTLS_USE_PSA_CRYPTO) if (pk_type == MBEDTLS_PK_OPAQUE) { psa_key_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT; psa_key_type_t key_type; psa_key_id_t key_id; psa_ecc_family_t curve; size_t bits; key_id = *((psa_key_id_t *) key->pk_ctx); if (PSA_SUCCESS != psa_get_key_attributes(key_id, &attributes)) { return MBEDTLS_ERR_PK_HW_ACCEL_FAILED; } key_type = psa_get_key_type(&attributes); bits = psa_get_key_bits(&attributes); psa_reset_key_attributes(&attributes); curve = PSA_KEY_TYPE_ECC_GET_FAMILY(key_type); if (curve == 0) { return MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE; } ret = mbedtls_psa_get_ecc_oid_from_id(curve, bits, &oid, &oid_len); if (ret != 0) { return MBEDTLS_ERR_PK_FEATURE_UNAVAILABLE; } /* Write EC algorithm parameters; that's akin * to pk_write_ec_param() above. */ MBEDTLS_ASN1_CHK_ADD(par_len, mbedtls_asn1_write_oid(&c, buf, oid, oid_len)); /* The rest of the function works as for legacy EC contexts. */ pk_type = MBEDTLS_PK_ECKEY; } #endif /* MBEDTLS_USE_PSA_CRYPTO */ if ((ret = mbedtls_oid_get_oid_by_pk_alg(pk_type, &oid, &oid_len)) != 0) { return ret; } 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 = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char *c; size_t len = 0; (void) ret; (void) c; (void) key; PK_VALIDATE_RET(key != NULL); if (size == 0) { return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL; } PK_VALIDATE_RET(buf != NULL); c = buf + size; #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 */ MBEDTLS_ASN1_CHK_ADD(len, pk_write_ec_private(&c, buf, ec)); /* 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 = 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; PK_VALIDATE_RET(key != NULL); PK_VALIDATE_RET(buf != NULL || size == 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, PEM_END_PUBLIC_KEY, 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(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; PK_VALIDATE_RET(key != NULL); PK_VALIDATE_RET(buf != NULL || size == 0); if ((ret = mbedtls_pk_write_key_der(key, output_buf, PRV_DER_MAX_BYTES)) < 0) { goto cleanup; } #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 { 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_platform_zeroize(output_buf, PRV_DER_MAX_BYTES); mbedtls_free(output_buf); return ret; } #endif /* MBEDTLS_PEM_WRITE_C */ #endif /* MBEDTLS_PK_WRITE_C */