/* * X.509 certificate writing * * Copyright The Mbed TLS Contributors * 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. */ /* * References: * - certificates: RFC 5280, updated by RFC 6818 * - CSRs: PKCS#10 v1.7 aka RFC 2986 * - attributes: PKCS#9 v2.0 aka RFC 2985 */ #include "common.h" #if defined(MBEDTLS_X509_CRT_WRITE_C) #include "mbedtls/x509_crt.h" #include "mbedtls/asn1write.h" #include "mbedtls/error.h" #include "mbedtls/oid.h" #include "mbedtls/platform_util.h" #include "mbedtls/sha1.h" #include #if defined(MBEDTLS_PEM_WRITE_C) #include "mbedtls/pem.h" #endif /* MBEDTLS_PEM_WRITE_C */ void mbedtls_x509write_crt_init(mbedtls_x509write_cert *ctx) { memset(ctx, 0, sizeof(mbedtls_x509write_cert)); mbedtls_mpi_init(&ctx->serial); ctx->version = MBEDTLS_X509_CRT_VERSION_3; } void mbedtls_x509write_crt_free(mbedtls_x509write_cert *ctx) { mbedtls_mpi_free(&ctx->serial); mbedtls_asn1_free_named_data_list(&ctx->subject); mbedtls_asn1_free_named_data_list(&ctx->issuer); mbedtls_asn1_free_named_data_list(&ctx->extensions); mbedtls_platform_zeroize(ctx, sizeof(mbedtls_x509write_cert)); } void mbedtls_x509write_crt_set_version(mbedtls_x509write_cert *ctx, int version) { ctx->version = version; } void mbedtls_x509write_crt_set_md_alg(mbedtls_x509write_cert *ctx, mbedtls_md_type_t md_alg) { ctx->md_alg = md_alg; } void mbedtls_x509write_crt_set_subject_key(mbedtls_x509write_cert *ctx, mbedtls_pk_context *key) { ctx->subject_key = key; } void mbedtls_x509write_crt_set_issuer_key(mbedtls_x509write_cert *ctx, mbedtls_pk_context *key) { ctx->issuer_key = key; } int mbedtls_x509write_crt_set_subject_name(mbedtls_x509write_cert *ctx, const char *subject_name) { return mbedtls_x509_string_to_names(&ctx->subject, subject_name); } int mbedtls_x509write_crt_set_issuer_name(mbedtls_x509write_cert *ctx, const char *issuer_name) { return mbedtls_x509_string_to_names(&ctx->issuer, issuer_name); } int mbedtls_x509write_crt_set_serial(mbedtls_x509write_cert *ctx, const mbedtls_mpi *serial) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; if (mbedtls_mpi_size(serial) > MBEDTLS_X509_RFC5280_MAX_SERIAL_LEN) { return MBEDTLS_ERR_X509_BAD_INPUT_DATA; } if ((ret = mbedtls_mpi_copy(&ctx->serial, serial)) != 0) { return ret; } return 0; } int mbedtls_x509write_crt_set_validity(mbedtls_x509write_cert *ctx, const char *not_before, const char *not_after) { if (strlen(not_before) != MBEDTLS_X509_RFC5280_UTC_TIME_LEN - 1 || strlen(not_after) != MBEDTLS_X509_RFC5280_UTC_TIME_LEN - 1) { return MBEDTLS_ERR_X509_BAD_INPUT_DATA; } strncpy(ctx->not_before, not_before, MBEDTLS_X509_RFC5280_UTC_TIME_LEN); strncpy(ctx->not_after, not_after, MBEDTLS_X509_RFC5280_UTC_TIME_LEN); ctx->not_before[MBEDTLS_X509_RFC5280_UTC_TIME_LEN - 1] = 'Z'; ctx->not_after[MBEDTLS_X509_RFC5280_UTC_TIME_LEN - 1] = 'Z'; return 0; } int mbedtls_x509write_crt_set_extension(mbedtls_x509write_cert *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_crt_set_basic_constraints(mbedtls_x509write_cert *ctx, int is_ca, int max_pathlen) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char buf[9]; unsigned char *c = buf + sizeof(buf); size_t len = 0; memset(buf, 0, sizeof(buf)); if (is_ca && max_pathlen > 127) { return MBEDTLS_ERR_X509_BAD_INPUT_DATA; } if (is_ca) { if (max_pathlen >= 0) { MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_int(&c, buf, max_pathlen)); } MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_bool(&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)); return mbedtls_x509write_crt_set_extension(ctx, MBEDTLS_OID_BASIC_CONSTRAINTS, MBEDTLS_OID_SIZE(MBEDTLS_OID_BASIC_CONSTRAINTS), is_ca, buf + sizeof(buf) - len, len); } #if defined(MBEDTLS_SHA1_C) int mbedtls_x509write_crt_set_subject_key_identifier(mbedtls_x509write_cert *ctx) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char buf[MBEDTLS_MPI_MAX_SIZE * 2 + 20]; /* tag, length + 2xMPI */ unsigned char *c = buf + sizeof(buf); size_t len = 0; memset(buf, 0, sizeof(buf)); MBEDTLS_ASN1_CHK_ADD(len, mbedtls_pk_write_pubkey(&c, buf, ctx->subject_key)); ret = mbedtls_sha1_ret(buf + sizeof(buf) - len, len, buf + sizeof(buf) - 20); if (ret != 0) { return ret; } c = buf + sizeof(buf) - 20; len = 20; 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_OCTET_STRING)); return mbedtls_x509write_crt_set_extension(ctx, MBEDTLS_OID_SUBJECT_KEY_IDENTIFIER, MBEDTLS_OID_SIZE(MBEDTLS_OID_SUBJECT_KEY_IDENTIFIER), 0, buf + sizeof(buf) - len, len); } int mbedtls_x509write_crt_set_authority_key_identifier(mbedtls_x509write_cert *ctx) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char buf[MBEDTLS_MPI_MAX_SIZE * 2 + 20]; /* tag, length + 2xMPI */ unsigned char *c = buf + sizeof(buf); size_t len = 0; memset(buf, 0, sizeof(buf)); MBEDTLS_ASN1_CHK_ADD(len, mbedtls_pk_write_pubkey(&c, buf, ctx->issuer_key)); ret = mbedtls_sha1_ret(buf + sizeof(buf) - len, len, buf + sizeof(buf) - 20); if (ret != 0) { return ret; } c = buf + sizeof(buf) - 20; len = 20; 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_CONTEXT_SPECIFIC | 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)); return mbedtls_x509write_crt_set_extension( ctx, MBEDTLS_OID_AUTHORITY_KEY_IDENTIFIER, MBEDTLS_OID_SIZE(MBEDTLS_OID_AUTHORITY_KEY_IDENTIFIER), 0, buf + sizeof(buf) - len, len); } #endif /* MBEDTLS_SHA1_C */ int mbedtls_x509write_crt_set_key_usage(mbedtls_x509write_cert *ctx, unsigned int key_usage) { unsigned char buf[5] = { 0 }, ku[2] = { 0 }; unsigned char *c; int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; const unsigned int allowed_bits = MBEDTLS_X509_KU_DIGITAL_SIGNATURE | MBEDTLS_X509_KU_NON_REPUDIATION | MBEDTLS_X509_KU_KEY_ENCIPHERMENT | MBEDTLS_X509_KU_DATA_ENCIPHERMENT | MBEDTLS_X509_KU_KEY_AGREEMENT | MBEDTLS_X509_KU_KEY_CERT_SIGN | MBEDTLS_X509_KU_CRL_SIGN | MBEDTLS_X509_KU_ENCIPHER_ONLY | MBEDTLS_X509_KU_DECIPHER_ONLY; /* Check that nothing other than the allowed flags is set */ if ((key_usage & ~allowed_bits) != 0) { return MBEDTLS_ERR_X509_FEATURE_UNAVAILABLE; } c = buf + 5; MBEDTLS_PUT_UINT16_LE(key_usage, ku, 0); ret = mbedtls_asn1_write_named_bitstring(&c, buf, ku, 9); if (ret < 0) { return ret; } else if (ret < 3 || ret > 5) { return MBEDTLS_ERR_X509_INVALID_FORMAT; } ret = mbedtls_x509write_crt_set_extension(ctx, MBEDTLS_OID_KEY_USAGE, MBEDTLS_OID_SIZE(MBEDTLS_OID_KEY_USAGE), 1, c, (size_t) ret); if (ret != 0) { return ret; } return 0; } int mbedtls_x509write_crt_set_ns_cert_type(mbedtls_x509write_cert *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_crt_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 x509_write_time(unsigned char **p, unsigned char *start, const char *t, size_t size) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; size_t len = 0; /* * write MBEDTLS_ASN1_UTC_TIME if year < 2050 (2 bytes shorter) */ if (t[0] < '2' || (t[0] == '2' && t[1] == '0' && t[2] < '5')) { MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_raw_buffer(p, start, (const unsigned char *) t + 2, size - 2)); 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_UTC_TIME)); } else { MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_raw_buffer(p, start, (const unsigned char *) t, size)); 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_GENERALIZED_TIME)); } return (int) len; } int mbedtls_x509write_crt_der(mbedtls_x509write_cert *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; const char *sig_oid; size_t sig_oid_len = 0; unsigned char *c, *c2; unsigned char hash[64]; unsigned char sig[MBEDTLS_PK_SIGNATURE_MAX_SIZE]; size_t sub_len = 0, pub_len = 0, sig_and_oid_len = 0, sig_len; size_t len = 0; mbedtls_pk_type_t pk_alg; int write_sig_null_par; /* * Prepare data to be signed at the end of the target buffer */ c = buf + size; /* Signature algorithm needed in TBS, and later for actual signature */ /* There's no direct way of extracting a signature algorithm * (represented as an element of mbedtls_pk_type_t) from a PK instance. */ if (mbedtls_pk_can_do(ctx->issuer_key, MBEDTLS_PK_RSA)) { pk_alg = MBEDTLS_PK_RSA; } else if (mbedtls_pk_can_do(ctx->issuer_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; } /* * Extensions ::= SEQUENCE SIZE (1..MAX) OF Extension */ /* Only for v3 */ if (ctx->version == MBEDTLS_X509_CRT_VERSION_3) { MBEDTLS_ASN1_CHK_ADD(len, mbedtls_x509_write_extensions(&c, buf, ctx->extensions)); 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_CONTEXT_SPECIFIC | MBEDTLS_ASN1_CONSTRUCTED | 3)); } /* * SubjectPublicKeyInfo */ MBEDTLS_ASN1_CHK_ADD(pub_len, mbedtls_pk_write_pubkey_der(ctx->subject_key, buf, c - buf)); c -= pub_len; len += pub_len; /* * Subject ::= Name */ MBEDTLS_ASN1_CHK_ADD(len, mbedtls_x509_write_names(&c, buf, ctx->subject)); /* * Validity ::= SEQUENCE { * notBefore Time, * notAfter Time } */ sub_len = 0; MBEDTLS_ASN1_CHK_ADD(sub_len, x509_write_time(&c, buf, ctx->not_after, MBEDTLS_X509_RFC5280_UTC_TIME_LEN)); MBEDTLS_ASN1_CHK_ADD(sub_len, x509_write_time(&c, buf, ctx->not_before, MBEDTLS_X509_RFC5280_UTC_TIME_LEN)); len += sub_len; MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, sub_len)); MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(&c, buf, MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE)); /* * Issuer ::= Name */ MBEDTLS_ASN1_CHK_ADD(len, mbedtls_x509_write_names(&c, buf, ctx->issuer)); /* * Signature ::= AlgorithmIdentifier */ if (pk_alg == MBEDTLS_PK_ECDSA) { /* * The AlgorithmIdentifier's parameters field must be absent for DSA/ECDSA signature * algorithms, see https://www.rfc-editor.org/rfc/rfc5480#page-17 and * https://www.rfc-editor.org/rfc/rfc5758#section-3. */ write_sig_null_par = 0; } else { write_sig_null_par = 1; } MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_algorithm_identifier_ext(&c, buf, sig_oid, strlen(sig_oid), 0, write_sig_null_par)); /* * Serial ::= INTEGER */ MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_mpi(&c, buf, &ctx->serial)); /* * Version ::= INTEGER { v1(0), v2(1), v3(2) } */ /* Can be omitted for v1 */ if (ctx->version != MBEDTLS_X509_CRT_VERSION_1) { sub_len = 0; MBEDTLS_ASN1_CHK_ADD(sub_len, mbedtls_asn1_write_int(&c, buf, ctx->version)); len += sub_len; MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(&c, buf, sub_len)); MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(&c, buf, MBEDTLS_ASN1_CONTEXT_SPECIFIC | MBEDTLS_ASN1_CONSTRUCTED | 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)); /* * Make signature */ /* Compute hash of CRT. */ if ((ret = mbedtls_md(mbedtls_md_info_from_type(ctx->md_alg), c, len, hash)) != 0) { return ret; } if ((ret = mbedtls_pk_sign(ctx->issuer_key, ctx->md_alg, hash, 0, sig, &sig_len, f_rng, p_rng)) != 0) { return ret; } /* Move CRT to the front of the buffer to have space * for the signature. */ memmove(buf, c, len); c = buf + len; /* Add signature at the end of the buffer, * making sure that it doesn't underflow * into the CRT buffer. */ c2 = buf + size; MBEDTLS_ASN1_CHK_ADD(sig_and_oid_len, mbedtls_x509_write_sig(&c2, c, sig_oid, sig_oid_len, sig, sig_len, pk_alg)); /* * Memory layout after this step: * * buf c=buf+len c2 buf+size * [CRT0,...,CRTn, UNUSED, ..., UNUSED, SIG0, ..., SIGm] */ /* Move raw CRT to just before the signature. */ c = c2 - len; memmove(c, buf, len); len += sig_and_oid_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; } #define PEM_BEGIN_CRT "-----BEGIN CERTIFICATE-----\n" #define PEM_END_CRT "-----END CERTIFICATE-----\n" #if defined(MBEDTLS_PEM_WRITE_C) int mbedtls_x509write_crt_pem(mbedtls_x509write_cert *crt, 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; if ((ret = mbedtls_x509write_crt_der(crt, buf, size, f_rng, p_rng)) < 0) { return ret; } if ((ret = mbedtls_pem_write_buffer(PEM_BEGIN_CRT, PEM_END_CRT, buf + size - ret, ret, buf, size, &olen)) != 0) { return ret; } return 0; } #endif /* MBEDTLS_PEM_WRITE_C */ #endif /* MBEDTLS_X509_CRT_WRITE_C */