library/x509_create.c

/*
 *  X.509 base functions for creating certificates / CSRs
 *
 *  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.
 */

#include "common.h"

#if defined(MBEDTLS_X509_CREATE_C)

#include "mbedtls/x509.h"
#include "mbedtls/asn1write.h"
#include "mbedtls/error.h"
#include "mbedtls/oid.h"

#include <string.h>

/* Structure linking OIDs for X.509 DN AttributeTypes to their
 * string representations and default string encodings used by Mbed TLS. */
typedef struct {
    const char *name; /* String representation of AttributeType, e.g.
                       * "CN" or "emailAddress". */
    size_t name_len; /* Length of 'name', without trailing 0 byte. */
    const char *oid; /* String representation of OID of AttributeType,
                      * as per RFC 5280, Appendix A.1. */
    int default_tag; /* The default character encoding used for the
                      * given attribute type, e.g.
                      * MBEDTLS_ASN1_UTF8_STRING for UTF-8. */
} x509_attr_descriptor_t;

#define ADD_STRLEN(s)     s, sizeof(s) - 1

/* X.509 DN attributes from RFC 5280, Appendix A.1. */
static const x509_attr_descriptor_t x509_attrs[] =
{
    { ADD_STRLEN("CN"),
      MBEDTLS_OID_AT_CN, MBEDTLS_ASN1_UTF8_STRING },
    { ADD_STRLEN("commonName"),
      MBEDTLS_OID_AT_CN, MBEDTLS_ASN1_UTF8_STRING },
    { ADD_STRLEN("C"),
      MBEDTLS_OID_AT_COUNTRY, MBEDTLS_ASN1_PRINTABLE_STRING },
    { ADD_STRLEN("countryName"),
      MBEDTLS_OID_AT_COUNTRY, MBEDTLS_ASN1_PRINTABLE_STRING },
    { ADD_STRLEN("O"),
      MBEDTLS_OID_AT_ORGANIZATION, MBEDTLS_ASN1_UTF8_STRING },
    { ADD_STRLEN("organizationName"),
      MBEDTLS_OID_AT_ORGANIZATION, MBEDTLS_ASN1_UTF8_STRING },
    { ADD_STRLEN("L"),
      MBEDTLS_OID_AT_LOCALITY, MBEDTLS_ASN1_UTF8_STRING },
    { ADD_STRLEN("locality"),
      MBEDTLS_OID_AT_LOCALITY, MBEDTLS_ASN1_UTF8_STRING },
    { ADD_STRLEN("R"),
      MBEDTLS_OID_PKCS9_EMAIL, MBEDTLS_ASN1_IA5_STRING },
    { ADD_STRLEN("OU"),
      MBEDTLS_OID_AT_ORG_UNIT, MBEDTLS_ASN1_UTF8_STRING },
    { ADD_STRLEN("organizationalUnitName"),
      MBEDTLS_OID_AT_ORG_UNIT, MBEDTLS_ASN1_UTF8_STRING },
    { ADD_STRLEN("ST"),
      MBEDTLS_OID_AT_STATE, MBEDTLS_ASN1_UTF8_STRING },
    { ADD_STRLEN("stateOrProvinceName"),
      MBEDTLS_OID_AT_STATE, MBEDTLS_ASN1_UTF8_STRING },
    { ADD_STRLEN("emailAddress"),
      MBEDTLS_OID_PKCS9_EMAIL, MBEDTLS_ASN1_IA5_STRING },
    { ADD_STRLEN("serialNumber"),
      MBEDTLS_OID_AT_SERIAL_NUMBER, MBEDTLS_ASN1_PRINTABLE_STRING },
    { ADD_STRLEN("postalAddress"),
      MBEDTLS_OID_AT_POSTAL_ADDRESS, MBEDTLS_ASN1_PRINTABLE_STRING },
    { ADD_STRLEN("postalCode"),
      MBEDTLS_OID_AT_POSTAL_CODE, MBEDTLS_ASN1_PRINTABLE_STRING },
    { ADD_STRLEN("dnQualifier"),
      MBEDTLS_OID_AT_DN_QUALIFIER, MBEDTLS_ASN1_PRINTABLE_STRING },
    { ADD_STRLEN("title"),
      MBEDTLS_OID_AT_TITLE, MBEDTLS_ASN1_UTF8_STRING },
    { ADD_STRLEN("surName"),
      MBEDTLS_OID_AT_SUR_NAME, MBEDTLS_ASN1_UTF8_STRING },
    { ADD_STRLEN("SN"),
      MBEDTLS_OID_AT_SUR_NAME, MBEDTLS_ASN1_UTF8_STRING },
    { ADD_STRLEN("givenName"),
      MBEDTLS_OID_AT_GIVEN_NAME, MBEDTLS_ASN1_UTF8_STRING },
    { ADD_STRLEN("GN"),
      MBEDTLS_OID_AT_GIVEN_NAME, MBEDTLS_ASN1_UTF8_STRING },
    { ADD_STRLEN("initials"),
      MBEDTLS_OID_AT_INITIALS, MBEDTLS_ASN1_UTF8_STRING },
    { ADD_STRLEN("pseudonym"),
      MBEDTLS_OID_AT_PSEUDONYM, MBEDTLS_ASN1_UTF8_STRING },
    { ADD_STRLEN("generationQualifier"),
      MBEDTLS_OID_AT_GENERATION_QUALIFIER, MBEDTLS_ASN1_UTF8_STRING },
    { ADD_STRLEN("domainComponent"),
      MBEDTLS_OID_DOMAIN_COMPONENT, MBEDTLS_ASN1_IA5_STRING },
    { ADD_STRLEN("DC"),
      MBEDTLS_OID_DOMAIN_COMPONENT,   MBEDTLS_ASN1_IA5_STRING },
    { NULL, 0, NULL, MBEDTLS_ASN1_NULL }
};

static const x509_attr_descriptor_t *x509_attr_descr_from_name(const char *name, size_t name_len)
{
    const x509_attr_descriptor_t *cur;

    for (cur = x509_attrs; cur->name != NULL; cur++) {
        if (cur->name_len == name_len &&
            strncmp(cur->name, name, name_len) == 0) {
            break;
        }
    }

    if (cur->name == NULL) {
        return NULL;
    }

    return cur;
}

static int x509_is_char_hex(char c)
{
    return ('0' <= c && c <= '9') || ('a' <= c && c <= 'f') || ('A' <= c && c <= 'F');
}

static int x509_hex_to_int(char c)
{
    return ((c & 0x40) ? (c + 9) : c) & 0x0F;
}

int mbedtls_x509_string_to_names(mbedtls_asn1_named_data **head, const char *name)
{
    int ret = MBEDTLS_ERR_X509_INVALID_NAME;
    const char *s = name, *c = s;
    const char *end = s + strlen(s);
    const char *oid = NULL;
    const x509_attr_descriptor_t *attr_descr = NULL;
    int in_tag = 1;
    int hexpair = 0;
    char data[MBEDTLS_X509_MAX_DN_NAME_SIZE];
    char *d = data;

    /* Clear existing chain if present */
    mbedtls_asn1_free_named_data_list(head);

    while (c <= end) {
        if (in_tag && *c == '=') {
            if ((attr_descr = x509_attr_descr_from_name(s, c - s)) == NULL) {
                ret = MBEDTLS_ERR_X509_UNKNOWN_OID;
                goto exit;
            }

            oid = attr_descr->oid;
            s = c + 1;
            in_tag = 0;
            d = data;
        }

        if (!in_tag && *c == '\\' && c != end) {
            c++;

            /* Check for valid escaped characters in RFC 4514 in Section 3*/
            if (c + 1 < end && x509_is_char_hex(*c) && x509_is_char_hex(*(c+1))) {
                hexpair = 1;
                *(d++) = (x509_hex_to_int(*c) << 4) + x509_hex_to_int(*(c+1));
                c++;
            } else if (c == end || !strchr(" ,=+<>#;\"\\+", *c)) {
                ret = MBEDTLS_ERR_X509_INVALID_NAME;
                goto exit;
            }
        } else if (!in_tag && (*c == ',' || c == end)) {
            mbedtls_asn1_named_data *cur =
                mbedtls_asn1_store_named_data(head, oid, strlen(oid),
                                              (unsigned char *) data,
                                              d - data);

            if (cur == NULL) {
                return MBEDTLS_ERR_X509_ALLOC_FAILED;
            }

            // set tagType
            cur->val.tag = attr_descr->default_tag;

            while (c < end && *(c + 1) == ' ') {
                c++;
            }

            s = c + 1;
            in_tag = 1;

            /* Successfully parsed one name, update ret to success */
            ret = 0;
        }

        if (!hexpair && !in_tag && s != c + 1) {
            *(d++) = *c;

            if (d - data == MBEDTLS_X509_MAX_DN_NAME_SIZE) {
                ret = MBEDTLS_ERR_X509_INVALID_NAME;
                goto exit;
            }
        }

        hexpair = 0;
        c++;
    }

exit:

    return ret;
}

/* The first byte of the value in the mbedtls_asn1_named_data structure is reserved
 * to store the critical boolean for us
 */
int mbedtls_x509_set_extension(mbedtls_asn1_named_data **head, const char *oid, size_t oid_len,
                               int critical, const unsigned char *val, size_t val_len)
{
    mbedtls_asn1_named_data *cur;

    if ((cur = mbedtls_asn1_store_named_data(head, oid, oid_len,
                                             NULL, val_len + 1)) == NULL) {
        return MBEDTLS_ERR_X509_ALLOC_FAILED;
    }

    cur->val.p[0] = critical;
    memcpy(cur->val.p + 1, val, val_len);

    return 0;
}

/*
 *  RelativeDistinguishedName ::=
 *    SET OF AttributeTypeAndValue
 *
 *  AttributeTypeAndValue ::= SEQUENCE {
 *    type     AttributeType,
 *    value    AttributeValue }
 *
 *  AttributeType ::= OBJECT IDENTIFIER
 *
 *  AttributeValue ::= ANY DEFINED BY AttributeType
 */
static int x509_write_name(unsigned char **p,
                           unsigned char *start,
                           mbedtls_asn1_named_data *cur_name)
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
    size_t len = 0;
    const char *oid             = (const char *) cur_name->oid.p;
    size_t oid_len              = cur_name->oid.len;
    const unsigned char *name   = cur_name->val.p;
    size_t name_len             = cur_name->val.len;

    // Write correct string tag and value
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tagged_string(p, start,
                                                               cur_name->val.tag,
                                                               (const char *) name,
                                                               name_len));
    // Write OID
    //
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_oid(p, start, oid,
                                                     oid_len));

    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));

    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_SET));

    return (int) len;
}

int mbedtls_x509_write_names(unsigned char **p, unsigned char *start,
                             mbedtls_asn1_named_data *first)
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
    size_t len = 0;
    mbedtls_asn1_named_data *cur = first;

    while (cur != NULL) {
        MBEDTLS_ASN1_CHK_ADD(len, x509_write_name(p, start, cur));
        cur = cur->next;
    }

    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;
}

int mbedtls_x509_write_sig(unsigned char **p, unsigned char *start,
                           const char *oid, size_t oid_len,
                           unsigned char *sig, size_t size,
                           mbedtls_pk_type_t pk_alg)
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
    int write_null_par;
    size_t len = 0;

    if (*p < start || (size_t) (*p - start) < size) {
        return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL;
    }

    len = size;
    (*p) -= len;
    memcpy(*p, sig, len);

    if (*p - start < 1) {
        return MBEDTLS_ERR_ASN1_BUF_TOO_SMALL;
    }

    *--(*p) = 0;
    len += 1;

    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_BIT_STRING));

    // Write OID
    //
    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_null_par = 0;
    } else {
        write_null_par = 1;
    }
    MBEDTLS_ASN1_CHK_ADD(len,
                         mbedtls_asn1_write_algorithm_identifier_ext(p, start, oid, oid_len,
                                                                     0, write_null_par));

    return (int) len;
}

static int x509_write_extension(unsigned char **p, unsigned char *start,
                                mbedtls_asn1_named_data *ext)
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
    size_t len = 0;

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_raw_buffer(p, start, ext->val.p + 1,
                                                            ext->val.len - 1));
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, ext->val.len - 1));
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start, MBEDTLS_ASN1_OCTET_STRING));

    if (ext->val.p[0] != 0) {
        MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_bool(p, start, 1));
    }

    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_raw_buffer(p, start, ext->oid.p,
                                                            ext->oid.len));
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_len(p, start, ext->oid.len));
    MBEDTLS_ASN1_CHK_ADD(len, mbedtls_asn1_write_tag(p, start, MBEDTLS_ASN1_OID));

    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;
}

/*
 * Extension  ::=  SEQUENCE  {
 *     extnID      OBJECT IDENTIFIER,
 *     critical    BOOLEAN DEFAULT FALSE,
 *     extnValue   OCTET STRING
 *                 -- contains the DER encoding of an ASN.1 value
 *                 -- corresponding to the extension type identified
 *                 -- by extnID
 *     }
 */
int mbedtls_x509_write_extensions(unsigned char **p, unsigned char *start,
                                  mbedtls_asn1_named_data *first)
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
    size_t len = 0;
    mbedtls_asn1_named_data *cur_ext = first;

    while (cur_ext != NULL) {
        MBEDTLS_ASN1_CHK_ADD(len, x509_write_extension(p, start, cur_ext));
        cur_ext = cur_ext->next;
    }

    return (int) len;
}

#endif /* MBEDTLS_X509_CREATE_C */