/* Provenance: curl/curl servercert (fixed).
 * repo: curl/curl
 * commit: 5ea3145850ebff1dc2b13d17440300a01ca38161
 * parent: fd9b40bf8dfd43edcbc0d254d613d95a11061c05
 * commit_url: https://github.com/curl/curl/commit/5ea3145850ebff1dc2b13d17440300a01ca38161
 * cve: CVE-2021-22924
 * license: curl
 * function: servercert
 * relpath: lib/vtls/openssl.c
 * provenance: human
 * mechanism: other
 */

static CURLcode servercert(struct Curl_easy *data,
                           struct connectdata *conn,
                           struct ssl_connect_data *connssl,
                           bool strict)
{
  CURLcode result = CURLE_OK;
  int rc;
  long lerr;
  X509 *issuer;
  BIO *fp = NULL;
  char error_buffer[256]="";
  char buffer[2048];
  const char *ptr;
  BIO *mem = BIO_new(BIO_s_mem());
  struct ssl_backend_data *backend = connssl->backend;

  if(data->set.ssl.certinfo)
    /* we've been asked to gather certificate info! */
    (void)get_cert_chain(data, connssl);

  backend->server_cert = SSL_get_peer_certificate(backend->handle);
  if(!backend->server_cert) {
    BIO_free(mem);
    if(!strict)
      return CURLE_OK;

    failf(data, "SSL: couldn't get peer certificate!");
    return CURLE_PEER_FAILED_VERIFICATION;
  }

  infof(data, "%s certificate:", SSL_IS_PROXY() ? "Proxy" : "Server");

  rc = x509_name_oneline(X509_get_subject_name(backend->server_cert),
                         buffer, sizeof(buffer));
  infof(data, " subject: %s", rc?"[NONE]":buffer);

#ifndef CURL_DISABLE_VERBOSE_STRINGS
  {
    long len;
    ASN1_TIME_print(mem, X509_get0_notBefore(backend->server_cert));
    len = BIO_get_mem_data(mem, (char **) &ptr);
    infof(data, " start date: %.*s", (int)len, ptr);
    (void)BIO_reset(mem);

    ASN1_TIME_print(mem, X509_get0_notAfter(backend->server_cert));
    len = BIO_get_mem_data(mem, (char **) &ptr);
    infof(data, " expire date: %.*s", (int)len, ptr);
    (void)BIO_reset(mem);
  }
#endif

  BIO_free(mem);

  if(SSL_CONN_CONFIG(verifyhost)) {
    result = verifyhost(data, conn, backend->server_cert);
    if(result) {
      X509_free(backend->server_cert);
      backend->server_cert = NULL;
      return result;
    }
  }

  rc = x509_name_oneline(X509_get_issuer_name(backend->server_cert),
                         buffer, sizeof(buffer));
  if(rc) {
    if(strict)
      failf(data, "SSL: couldn't get X509-issuer name!");
    result = CURLE_PEER_FAILED_VERIFICATION;
  }
  else {
    infof(data, " issuer: %s", buffer);

    /* We could do all sorts of certificate verification stuff here before
       deallocating the certificate. */

    /* e.g. match issuer name with provided issuer certificate */
    if(SSL_CONN_CONFIG(issuercert) || SSL_CONN_CONFIG(issuercert_blob)) {
      if(SSL_CONN_CONFIG(issuercert_blob))
        fp = BIO_new_mem_buf(SSL_CONN_CONFIG(issuercert_blob)->data,
                             (int)SSL_CONN_CONFIG(issuercert_blob)->len);
      else {
        fp = BIO_new(BIO_s_file());
        if(!fp) {
          failf(data,
                "BIO_new return NULL, " OSSL_PACKAGE
                " error %s",
                ossl_strerror(ERR_get_error(), error_buffer,
                              sizeof(error_buffer)) );
          X509_free(backend->server_cert);
          backend->server_cert = NULL;
          return CURLE_OUT_OF_MEMORY;
        }

        if(BIO_read_filename(fp, SSL_CONN_CONFIG(issuercert)) <= 0) {
          if(strict)
            failf(data, "SSL: Unable to open issuer cert (%s)",
                  SSL_CONN_CONFIG(issuercert));
          BIO_free(fp);
          X509_free(backend->server_cert);
          backend->server_cert = NULL;
          return CURLE_SSL_ISSUER_ERROR;
        }
      }

      issuer = PEM_read_bio_X509(fp, NULL, ZERO_NULL, NULL);
      if(!issuer) {
        if(strict)
          failf(data, "SSL: Unable to read issuer cert (%s)",
                SSL_CONN_CONFIG(issuercert));
        BIO_free(fp);
        X509_free(issuer);
        X509_free(backend->server_cert);
        backend->server_cert = NULL;
        return CURLE_SSL_ISSUER_ERROR;
      }

      if(X509_check_issued(issuer, backend->server_cert) != X509_V_OK) {
        if(strict)
          failf(data, "SSL: Certificate issuer check failed (%s)",
                SSL_CONN_CONFIG(issuercert));
        BIO_free(fp);
        X509_free(issuer);
        X509_free(backend->server_cert);
        backend->server_cert = NULL;
        return CURLE_SSL_ISSUER_ERROR;
      }

      infof(data, " SSL certificate issuer check ok (%s)",
            SSL_CONN_CONFIG(issuercert));
      BIO_free(fp);
      X509_free(issuer);
    }

    lerr = SSL_get_verify_result(backend->handle);
    SSL_SET_OPTION_LVALUE(certverifyresult) = lerr;
    if(lerr != X509_V_OK) {
      if(SSL_CONN_CONFIG(verifypeer)) {
        /* We probably never reach this, because SSL_connect() will fail
           and we return earlier if verifypeer is set? */
        if(strict)
          failf(data, "SSL certificate verify result: %s (%ld)",
                X509_verify_cert_error_string(lerr), lerr);
        result = CURLE_PEER_FAILED_VERIFICATION;
      }
      else
        infof(data, " SSL certificate verify result: %s (%ld),"
              " continuing anyway.",
              X509_verify_cert_error_string(lerr), lerr);
    }
    else
      infof(data, " SSL certificate verify ok.");
  }

#if (OPENSSL_VERSION_NUMBER >= 0x0090808fL) && !defined(OPENSSL_NO_TLSEXT) && \
    !defined(OPENSSL_NO_OCSP)
  if(SSL_CONN_CONFIG(verifystatus)) {
    result = verifystatus(data, connssl);
    if(result) {
      X509_free(backend->server_cert);
      backend->server_cert = NULL;
      return result;
    }
  }
#endif

  if(!strict)
    /* when not strict, we don't bother about the verify cert problems */
    result = CURLE_OK;

  ptr = SSL_PINNED_PUB_KEY();
  if(!result && ptr) {
    result = pkp_pin_peer_pubkey(data, backend->server_cert, ptr);
    if(result)
      failf(data, "SSL: public key does not match pinned public key!");
  }

  X509_free(backend->server_cert);
  backend->server_cert = NULL;
  connssl->connecting_state = ssl_connect_done;

  return result;
}