library/x509_crl.c

/*
 *  X.509 Certidicate Revocation List (CRL) parsing
 *
 *  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.
 */
/*
 *  The ITU-T X.509 standard defines a certificate format for PKI.
 *
 *  http://www.ietf.org/rfc/rfc5280.txt (Certificates and CRLs)
 *  http://www.ietf.org/rfc/rfc3279.txt (Alg IDs for CRLs)
 *  http://www.ietf.org/rfc/rfc2986.txt (CSRs, aka PKCS#10)
 *
 *  http://www.itu.int/ITU-T/studygroups/com17/languages/X.680-0207.pdf
 *  http://www.itu.int/ITU-T/studygroups/com17/languages/X.690-0207.pdf
 */

#include "common.h"

#if defined(MBEDTLS_X509_CRL_PARSE_C)

#    include "mbedtls/x509_crl.h"
#    include "mbedtls/error.h"
#    include "mbedtls/oid.h"
#    include "mbedtls/platform_util.h"

#    include <string.h>

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

#    if defined(MBEDTLS_PLATFORM_C)
#        include "mbedtls/platform.h"
#    else
#        include <stdlib.h>
#        include <stdio.h>
#        define mbedtls_free     free
#        define mbedtls_calloc   calloc
#        define mbedtls_snprintf snprintf
#    endif

#    if defined(_WIN32) && !defined(EFIX64) && !defined(EFI32)
#        include <windows.h>
#    else
#        include <time.h>
#    endif

#    if defined(MBEDTLS_FS_IO) || defined(EFIX64) || defined(EFI32)
#        include <stdio.h>
#    endif

/*
 *  Version  ::=  INTEGER  {  v1(0), v2(1)  }
 */
static int
x509_crl_get_version(unsigned char **p, const unsigned char *end, int *ver)
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

    if ((ret = mbedtls_asn1_get_int(p, end, ver)) != 0) {
        if (ret == MBEDTLS_ERR_ASN1_UNEXPECTED_TAG) {
            *ver = 0;
            return 0;
        }

        return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_VERSION, ret);
    }

    return 0;
}

/*
 * X.509 CRL v2 extensions
 *
 * We currently don't parse any extension's content, but we do check that the
 * list of extensions is well-formed and abort on critical extensions (that
 * are unsupported as we don't support any extension so far)
 */
static int x509_get_crl_ext(unsigned char **p,
                            const unsigned char *end,
                            mbedtls_x509_buf *ext)
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

    if (*p == end)
        return 0;

    /*
     * crlExtensions           [0]  EXPLICIT Extensions OPTIONAL
     *                              -- if present, version MUST be v2
     */
    if ((ret = mbedtls_x509_get_ext(p, end, ext, 0)) != 0)
        return ret;

    end = ext->p + ext->len;

    while (*p < end) {
        /*
         * Extension  ::=  SEQUENCE  {
         *      extnID      OBJECT IDENTIFIER,
         *      critical    BOOLEAN DEFAULT FALSE,
         *      extnValue   OCTET STRING  }
         */
        int is_critical = 0;
        const unsigned char *end_ext_data;
        size_t len;

        /* Get enclosing sequence tag */
        if ((ret = mbedtls_asn1_get_tag(p, end, &len,
                                        MBEDTLS_ASN1_CONSTRUCTED |
                                            MBEDTLS_ASN1_SEQUENCE)) != 0)
            return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret);

        end_ext_data = *p + len;

        /* Get OID (currently ignored) */
        if ((ret = mbedtls_asn1_get_tag(p, end_ext_data, &len,
                                        MBEDTLS_ASN1_OID)) != 0) {
            return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret);
        }
        *p += len;

        /* Get optional critical */
        if ((ret = mbedtls_asn1_get_bool(p, end_ext_data, &is_critical)) != 0 &&
            (ret != MBEDTLS_ERR_ASN1_UNEXPECTED_TAG)) {
            return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret);
        }

        /* Data should be octet string type */
        if ((ret = mbedtls_asn1_get_tag(p, end_ext_data, &len,
                                        MBEDTLS_ASN1_OCTET_STRING)) != 0)
            return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret);

        /* Ignore data so far and just check its length */
        *p += len;
        if (*p != end_ext_data)
            return (MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
                                      MBEDTLS_ERR_ASN1_LENGTH_MISMATCH));

        /* Abort on (unsupported) critical extensions */
        if (is_critical)
            return (MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
                                      MBEDTLS_ERR_ASN1_UNEXPECTED_TAG));
    }

    if (*p != end)
        return (MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
                                  MBEDTLS_ERR_ASN1_LENGTH_MISMATCH));

    return 0;
}

/*
 * X.509 CRL v2 entry extensions (no extensions parsed yet.)
 */
static int x509_get_crl_entry_ext(unsigned char **p,
                                  const unsigned char *end,
                                  mbedtls_x509_buf *ext)
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
    size_t len = 0;

    /* OPTIONAL */
    if (end <= *p)
        return 0;

    ext->tag = **p;
    ext->p = *p;

    /*
     * Get CRL-entry extension sequence header
     * crlEntryExtensions      Extensions OPTIONAL  -- if present, MUST be v2
     */
    if ((ret = mbedtls_asn1_get_tag(p, end, &ext->len,
                                    MBEDTLS_ASN1_CONSTRUCTED |
                                        MBEDTLS_ASN1_SEQUENCE)) != 0) {
        if (ret == MBEDTLS_ERR_ASN1_UNEXPECTED_TAG) {
            ext->p = NULL;
            return 0;
        }
        return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret);
    }

    end = *p + ext->len;

    if (end != *p + ext->len)
        return (MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
                                  MBEDTLS_ERR_ASN1_LENGTH_MISMATCH));

    while (*p < end) {
        if ((ret = mbedtls_asn1_get_tag(p, end, &len,
                                        MBEDTLS_ASN1_CONSTRUCTED |
                                            MBEDTLS_ASN1_SEQUENCE)) != 0)
            return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS, ret);

        *p += len;
    }

    if (*p != end)
        return (MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_EXTENSIONS,
                                  MBEDTLS_ERR_ASN1_LENGTH_MISMATCH));

    return 0;
}

/*
 * X.509 CRL Entries
 */
static int x509_get_entries(unsigned char **p,
                            const unsigned char *end,
                            mbedtls_x509_crl_entry *entry)
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
    size_t entry_len;
    mbedtls_x509_crl_entry *cur_entry = entry;

    if (*p == end)
        return 0;

    if ((ret = mbedtls_asn1_get_tag(p, end, &entry_len,
                                    MBEDTLS_ASN1_SEQUENCE |
                                        MBEDTLS_ASN1_CONSTRUCTED)) != 0) {
        if (ret == MBEDTLS_ERR_ASN1_UNEXPECTED_TAG)
            return 0;

        return ret;
    }

    end = *p + entry_len;

    while (*p < end) {
        size_t len2;
        const unsigned char *end2;

        cur_entry->raw.tag = **p;
        if ((ret = mbedtls_asn1_get_tag(p, end, &len2,
                                        MBEDTLS_ASN1_SEQUENCE |
                                            MBEDTLS_ASN1_CONSTRUCTED)) != 0) {
            return ret;
        }

        cur_entry->raw.p = *p;
        cur_entry->raw.len = len2;
        end2 = *p + len2;

        if ((ret = mbedtls_x509_get_serial(p, end2, &cur_entry->serial)) != 0)
            return ret;

        if ((ret = mbedtls_x509_get_time(p, end2,
                                         &cur_entry->revocation_date)) != 0)
            return ret;

        if ((ret = x509_get_crl_entry_ext(p, end2, &cur_entry->entry_ext)) != 0)
            return ret;

        if (*p < end) {
            cur_entry->next = mbedtls_calloc(1, sizeof(mbedtls_x509_crl_entry));

            if (cur_entry->next == NULL)
                return MBEDTLS_ERR_X509_ALLOC_FAILED;

            cur_entry = cur_entry->next;
        }
    }

    return 0;
}

/*
 * Parse one  CRLs in DER format and append it to the chained list
 */
int mbedtls_x509_crl_parse_der(mbedtls_x509_crl *chain,
                               const unsigned char *buf,
                               size_t buflen)
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
    size_t len;
    unsigned char *p = NULL, *end = NULL;
    mbedtls_x509_buf sig_params1, sig_params2, sig_oid2;
    mbedtls_x509_crl *crl = chain;

    /*
     * Check for valid input
     */
    if (crl == NULL || buf == NULL)
        return MBEDTLS_ERR_X509_BAD_INPUT_DATA;

    memset(&sig_params1, 0, sizeof(mbedtls_x509_buf));
    memset(&sig_params2, 0, sizeof(mbedtls_x509_buf));
    memset(&sig_oid2, 0, sizeof(mbedtls_x509_buf));

    /*
     * Add new CRL on the end of the chain if needed.
     */
    while (crl->version != 0 && crl->next != NULL)
        crl = crl->next;

    if (crl->version != 0 && crl->next == NULL) {
        crl->next = mbedtls_calloc(1, sizeof(mbedtls_x509_crl));

        if (crl->next == NULL) {
            mbedtls_x509_crl_free(crl);
            return MBEDTLS_ERR_X509_ALLOC_FAILED;
        }

        mbedtls_x509_crl_init(crl->next);
        crl = crl->next;
    }

    /*
     * Copy raw DER-encoded CRL
     */
    if (buflen == 0)
        return MBEDTLS_ERR_X509_INVALID_FORMAT;

    p = mbedtls_calloc(1, buflen);
    if (p == NULL)
        return MBEDTLS_ERR_X509_ALLOC_FAILED;

    memcpy(p, buf, buflen);

    crl->raw.p = p;
    crl->raw.len = buflen;

    end = p + buflen;

    /*
     * CertificateList  ::=  SEQUENCE  {
     *      tbsCertList          TBSCertList,
     *      signatureAlgorithm   AlgorithmIdentifier,
     *      signatureValue       BIT STRING  }
     */
    if ((ret = mbedtls_asn1_get_tag(&p, end, &len,
                                    MBEDTLS_ASN1_CONSTRUCTED |
                                        MBEDTLS_ASN1_SEQUENCE)) != 0) {
        mbedtls_x509_crl_free(crl);
        return MBEDTLS_ERR_X509_INVALID_FORMAT;
    }

    if (len != (size_t)(end - p)) {
        mbedtls_x509_crl_free(crl);
        return (MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_FORMAT,
                                  MBEDTLS_ERR_ASN1_LENGTH_MISMATCH));
    }

    /*
     * TBSCertList  ::=  SEQUENCE  {
     */
    crl->tbs.p = p;

    if ((ret = mbedtls_asn1_get_tag(&p, end, &len,
                                    MBEDTLS_ASN1_CONSTRUCTED |
                                        MBEDTLS_ASN1_SEQUENCE)) != 0) {
        mbedtls_x509_crl_free(crl);
        return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_FORMAT, ret);
    }

    end = p + len;
    crl->tbs.len = end - crl->tbs.p;

    /*
     * Version  ::=  INTEGER  OPTIONAL {  v1(0), v2(1)  }
     *               -- if present, MUST be v2
     *
     * signature            AlgorithmIdentifier
     */
    if ((ret = x509_crl_get_version(&p, end, &crl->version)) != 0 ||
        (ret = mbedtls_x509_get_alg(&p, end, &crl->sig_oid, &sig_params1)) !=
            0) {
        mbedtls_x509_crl_free(crl);
        return ret;
    }

    if (crl->version < 0 || crl->version > 1) {
        mbedtls_x509_crl_free(crl);
        return MBEDTLS_ERR_X509_UNKNOWN_VERSION;
    }

    crl->version++;

    if ((ret = mbedtls_x509_get_sig_alg(&crl->sig_oid, &sig_params1,
                                        &crl->sig_md, &crl->sig_pk,
                                        &crl->sig_opts)) != 0) {
        mbedtls_x509_crl_free(crl);
        return MBEDTLS_ERR_X509_UNKNOWN_SIG_ALG;
    }

    /*
     * issuer               Name
     */
    crl->issuer_raw.p = p;

    if ((ret = mbedtls_asn1_get_tag(&p, end, &len,
                                    MBEDTLS_ASN1_CONSTRUCTED |
                                        MBEDTLS_ASN1_SEQUENCE)) != 0) {
        mbedtls_x509_crl_free(crl);
        return MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_FORMAT, ret);
    }

    if ((ret = mbedtls_x509_get_name(&p, p + len, &crl->issuer)) != 0) {
        mbedtls_x509_crl_free(crl);
        return ret;
    }

    crl->issuer_raw.len = p - crl->issuer_raw.p;

    /*
     * thisUpdate          Time
     * nextUpdate          Time OPTIONAL
     */
    if ((ret = mbedtls_x509_get_time(&p, end, &crl->this_update)) != 0) {
        mbedtls_x509_crl_free(crl);
        return ret;
    }

    if ((ret = mbedtls_x509_get_time(&p, end, &crl->next_update)) != 0) {
        if (ret != (MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_DATE,
                                      MBEDTLS_ERR_ASN1_UNEXPECTED_TAG)) &&
            ret != (MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_DATE,
                                      MBEDTLS_ERR_ASN1_OUT_OF_DATA))) {
            mbedtls_x509_crl_free(crl);
            return ret;
        }
    }

    /*
     * revokedCertificates    SEQUENCE OF SEQUENCE   {
     *      userCertificate        CertificateSerialNumber,
     *      revocationDate         Time,
     *      crlEntryExtensions     Extensions OPTIONAL
     *                                   -- if present, MUST be v2
     *                        } OPTIONAL
     */
    if ((ret = x509_get_entries(&p, end, &crl->entry)) != 0) {
        mbedtls_x509_crl_free(crl);
        return ret;
    }

    /*
     * crlExtensions          EXPLICIT Extensions OPTIONAL
     *                              -- if present, MUST be v2
     */
    if (crl->version == 2) {
        ret = x509_get_crl_ext(&p, end, &crl->crl_ext);

        if (ret != 0) {
            mbedtls_x509_crl_free(crl);
            return ret;
        }
    }

    if (p != end) {
        mbedtls_x509_crl_free(crl);
        return (MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_FORMAT,
                                  MBEDTLS_ERR_ASN1_LENGTH_MISMATCH));
    }

    end = crl->raw.p + crl->raw.len;

    /*
     *  signatureAlgorithm   AlgorithmIdentifier,
     *  signatureValue       BIT STRING
     */
    if ((ret = mbedtls_x509_get_alg(&p, end, &sig_oid2, &sig_params2)) != 0) {
        mbedtls_x509_crl_free(crl);
        return ret;
    }

    if (crl->sig_oid.len != sig_oid2.len ||
        memcmp(crl->sig_oid.p, sig_oid2.p, crl->sig_oid.len) != 0 ||
        sig_params1.len != sig_params2.len ||
        (sig_params1.len != 0 &&
         memcmp(sig_params1.p, sig_params2.p, sig_params1.len) != 0)) {
        mbedtls_x509_crl_free(crl);
        return MBEDTLS_ERR_X509_SIG_MISMATCH;
    }

    if ((ret = mbedtls_x509_get_sig(&p, end, &crl->sig)) != 0) {
        mbedtls_x509_crl_free(crl);
        return ret;
    }

    if (p != end) {
        mbedtls_x509_crl_free(crl);
        return (MBEDTLS_ERROR_ADD(MBEDTLS_ERR_X509_INVALID_FORMAT,
                                  MBEDTLS_ERR_ASN1_LENGTH_MISMATCH));
    }

    return 0;
}

/*
 * Parse one or more CRLs and add them to the chained list
 */
int mbedtls_x509_crl_parse(mbedtls_x509_crl *chain,
                           const unsigned char *buf,
                           size_t buflen)
{
#    if defined(MBEDTLS_PEM_PARSE_C)
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
    size_t use_len = 0;
    mbedtls_pem_context pem;
    int is_pem = 0;

    if (chain == NULL || buf == NULL)
        return MBEDTLS_ERR_X509_BAD_INPUT_DATA;

    do {
        mbedtls_pem_init(&pem);

        // Avoid calling mbedtls_pem_read_buffer() on non-null-terminated
        // string
        if (buflen == 0 || buf[buflen - 1] != '\0')
            ret = MBEDTLS_ERR_PEM_NO_HEADER_FOOTER_PRESENT;
        else
            ret = mbedtls_pem_read_buffer(&pem, "-----BEGIN X509 CRL-----",
                                          "-----END X509 CRL-----", buf, NULL,
                                          0, &use_len);

        if (ret == 0) {
            /*
             * Was PEM encoded
             */
            is_pem = 1;

            buflen -= use_len;
            buf += use_len;

            if ((ret = mbedtls_x509_crl_parse_der(chain, pem.buf,
                                                  pem.buflen)) != 0) {
                mbedtls_pem_free(&pem);
                return ret;
            }
        } else if (is_pem) {
            mbedtls_pem_free(&pem);
            return ret;
        }

        mbedtls_pem_free(&pem);
    }
    /* In the PEM case, buflen is 1 at the end, for the terminated NULL byte.
     * And a valid CRL cannot be less than 1 byte anyway. */
    while (is_pem && buflen > 1);

    if (is_pem)
        return 0;
    else
#    endif /* MBEDTLS_PEM_PARSE_C */
        return mbedtls_x509_crl_parse_der(chain, buf, buflen);
}

#    if defined(MBEDTLS_FS_IO)
/*
 * Load one or more CRLs and add them to the chained list
 */
int mbedtls_x509_crl_parse_file(mbedtls_x509_crl *chain, const char *path)
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
    size_t n;
    unsigned char *buf;

    if ((ret = mbedtls_pk_load_file(path, &buf, &n)) != 0)
        return ret;

    ret = mbedtls_x509_crl_parse(chain, buf, n);

    mbedtls_platform_zeroize(buf, n);
    mbedtls_free(buf);

    return ret;
}
#    endif /* MBEDTLS_FS_IO */

#    if !defined(MBEDTLS_X509_REMOVE_INFO)
/*
 * Return an informational string about the certificate.
 */
#        define BEFORE_COLON 14
#        define BC           "14"
/*
 * Return an informational string about the CRL.
 */
int mbedtls_x509_crl_info(char *buf,
                          size_t size,
                          const char *prefix,
                          const mbedtls_x509_crl *crl)
{
    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
    size_t n;
    char *p;
    const mbedtls_x509_crl_entry *entry;

    p = buf;
    n = size;

    ret = mbedtls_snprintf(p, n, "%sCRL version   : %d", prefix, crl->version);
    MBEDTLS_X509_SAFE_SNPRINTF;

    ret = mbedtls_snprintf(p, n, "\n%sissuer name   : ", prefix);
    MBEDTLS_X509_SAFE_SNPRINTF;
    ret = mbedtls_x509_dn_gets(p, n, &crl->issuer);
    MBEDTLS_X509_SAFE_SNPRINTF;

    ret = mbedtls_snprintf(p, n,
                           "\n%sthis update   : "
                           "%04d-%02d-%02d %02d:%02d:%02d",
                           prefix, crl->this_update.year, crl->this_update.mon,
                           crl->this_update.day, crl->this_update.hour,
                           crl->this_update.min, crl->this_update.sec);
    MBEDTLS_X509_SAFE_SNPRINTF;

    ret = mbedtls_snprintf(p, n,
                           "\n%snext update   : "
                           "%04d-%02d-%02d %02d:%02d:%02d",
                           prefix, crl->next_update.year, crl->next_update.mon,
                           crl->next_update.day, crl->next_update.hour,
                           crl->next_update.min, crl->next_update.sec);
    MBEDTLS_X509_SAFE_SNPRINTF;

    entry = &crl->entry;

    ret = mbedtls_snprintf(p, n, "\n%sRevoked certificates:", prefix);
    MBEDTLS_X509_SAFE_SNPRINTF;

    while (entry != NULL && entry->raw.len != 0) {
        ret = mbedtls_snprintf(p, n, "\n%sserial number: ", prefix);
        MBEDTLS_X509_SAFE_SNPRINTF;

        ret = mbedtls_x509_serial_gets(p, n, &entry->serial);
        MBEDTLS_X509_SAFE_SNPRINTF;

        ret = mbedtls_snprintf(
            p, n,
            " revocation date: "
            "%04d-%02d-%02d %02d:%02d:%02d",
            entry->revocation_date.year, entry->revocation_date.mon,
            entry->revocation_date.day, entry->revocation_date.hour,
            entry->revocation_date.min, entry->revocation_date.sec);
        MBEDTLS_X509_SAFE_SNPRINTF;

        entry = entry->next;
    }

    ret = mbedtls_snprintf(p, n, "\n%ssigned using  : ", prefix);
    MBEDTLS_X509_SAFE_SNPRINTF;

    ret = mbedtls_x509_sig_alg_gets(p, n, &crl->sig_oid, crl->sig_pk,
                                    crl->sig_md, crl->sig_opts);
    MBEDTLS_X509_SAFE_SNPRINTF;

    ret = mbedtls_snprintf(p, n, "\n");
    MBEDTLS_X509_SAFE_SNPRINTF;

    return ((int)(size - n));
}
#    endif /* MBEDTLS_X509_REMOVE_INFO */

/*
 * Initialize a CRL chain
 */
void mbedtls_x509_crl_init(mbedtls_x509_crl *crl)
{
    memset(crl, 0, sizeof(mbedtls_x509_crl));
}

/*
 * Unallocate all CRL data
 */
void mbedtls_x509_crl_free(mbedtls_x509_crl *crl)
{
    mbedtls_x509_crl *crl_cur = crl;
    mbedtls_x509_crl *crl_prv;
    mbedtls_x509_name *name_cur;
    mbedtls_x509_name *name_prv;
    mbedtls_x509_crl_entry *entry_cur;
    mbedtls_x509_crl_entry *entry_prv;

    if (crl == NULL)
        return;

    do {
#    if defined(MBEDTLS_X509_RSASSA_PSS_SUPPORT)
        mbedtls_free(crl_cur->sig_opts);
#    endif

        name_cur = crl_cur->issuer.next;
        while (name_cur != NULL) {
            name_prv = name_cur;
            name_cur = name_cur->next;
            mbedtls_platform_zeroize(name_prv, sizeof(mbedtls_x509_name));
            mbedtls_free(name_prv);
        }

        entry_cur = crl_cur->entry.next;
        while (entry_cur != NULL) {
            entry_prv = entry_cur;
            entry_cur = entry_cur->next;
            mbedtls_platform_zeroize(entry_prv, sizeof(mbedtls_x509_crl_entry));
            mbedtls_free(entry_prv);
        }

        if (crl_cur->raw.p != NULL) {
            mbedtls_platform_zeroize(crl_cur->raw.p, crl_cur->raw.len);
            mbedtls_free(crl_cur->raw.p);
        }

        crl_cur = crl_cur->next;
    } while (crl_cur != NULL);

    crl_cur = crl;
    do {
        crl_prv = crl_cur;
        crl_cur = crl_cur->next;

        mbedtls_platform_zeroize(crl_prv, sizeof(mbedtls_x509_crl));
        if (crl_prv != crl)
            mbedtls_free(crl_prv);
    } while (crl_cur != NULL);
}

#endif /* MBEDTLS_X509_CRL_PARSE_C */