signed-xml.ts

import type {
  CanonicalizationAlgorithmType,
  CanonicalizationOrTransformationAlgorithm,
  ComputeSignatureOptions,
  GetKeyInfoContentArgs,
  HashAlgorithm,
  HashAlgorithmType,
  Reference,
  SignatureAlgorithm,
  SignatureAlgorithmType,
  SignedXmlOptions,
  CanonicalizationOrTransformAlgorithmType,
  ErrorFirstCallback,
  CanonicalizationOrTransformationAlgorithmProcessOptions,
} from "./types";

import * as xpath from "xpath";
import * as xmldom from "@xmldom/xmldom";
import * as utils from "./utils";
import * as c14n from "./c14n-canonicalization";
import * as execC14n from "./exclusive-canonicalization";
import * as envelopedSignatures from "./enveloped-signature";
import * as hashAlgorithms from "./hash-algorithms";
import * as signatureAlgorithms from "./signature-algorithms";
import * as crypto from "crypto";
import * as isDomNode from "@xmldom/is-dom-node";

export class SignedXml {
  idMode?: "wssecurity";
  idAttributes: string[];
  /**
   * A {@link Buffer} or pem encoded {@link String} containing your private key
   */
  privateKey?: crypto.KeyLike;
  privateKeyPass?: string;
  publicCert?: crypto.KeyLike;
  /**
   * One of the supported signature algorithms.
   * @see {@link SignatureAlgorithmType}
   */
  signatureAlgorithm?: SignatureAlgorithmType = undefined;
  /**
   * Rules used to convert an XML document into its canonical form.
   */
  canonicalizationAlgorithm?: CanonicalizationAlgorithmType = undefined;
  /**
   * It specifies a list of namespace prefixes that should be considered "inclusive" during the canonicalization process.
   */
  inclusiveNamespacesPrefixList: string[] = [];
  namespaceResolver: XPathNSResolver = {
    lookupNamespaceURI: function (/* prefix */) {
      throw new Error("Not implemented");
    },
  };
  implicitTransforms: ReadonlyArray<CanonicalizationOrTransformAlgorithmType> = [];
  keyInfoAttributes: { [attrName: string]: string } = {};
  getKeyInfoContent = SignedXml.getKeyInfoContent;
  getCertFromKeyInfo = SignedXml.getCertFromKeyInfo;

  // Internal state
  private id = 0;
  private signedXml = "";
  private signatureXml = "";
  private signatureNode: Node | null = null;
  private signatureValue = "";
  private originalXmlWithIds = "";
  private keyInfo: Node | null = null;

  /**
   * Contains the references that were signed.
   * @see {@link Reference}
   */
  private references: Reference[] = [];

  /**
   *  To add a new transformation algorithm create a new class that implements the {@link TransformationAlgorithm} interface, and register it here. More info: {@link https://github.com/node-saml/xml-crypto#customizing-algorithms|Customizing Algorithms}
   */
  CanonicalizationAlgorithms: Record<
    CanonicalizationOrTransformAlgorithmType,
    new () => CanonicalizationOrTransformationAlgorithm
  > = {
    "http://www.w3.org/TR/2001/REC-xml-c14n-20010315": c14n.C14nCanonicalization,
    "http://www.w3.org/TR/2001/REC-xml-c14n-20010315#WithComments":
      c14n.C14nCanonicalizationWithComments,
    "http://www.w3.org/2001/10/xml-exc-c14n#": execC14n.ExclusiveCanonicalization,
    "http://www.w3.org/2001/10/xml-exc-c14n#WithComments":
      execC14n.ExclusiveCanonicalizationWithComments,
    "http://www.w3.org/2000/09/xmldsig#enveloped-signature": envelopedSignatures.EnvelopedSignature,
  };

  /**
   * To add a new hash algorithm create a new class that implements the {@link HashAlgorithm} interface, and register it here. More info: {@link https://github.com/node-saml/xml-crypto#customizing-algorithms|Customizing Algorithms}
   */
  HashAlgorithms: Record<HashAlgorithmType, new () => HashAlgorithm> = {
    "http://www.w3.org/2000/09/xmldsig#sha1": hashAlgorithms.Sha1,
    "http://www.w3.org/2001/04/xmlenc#sha256": hashAlgorithms.Sha256,
    "http://www.w3.org/2001/04/xmlenc#sha512": hashAlgorithms.Sha512,
  };

  /**
   * To add a new signature algorithm create a new class that implements the {@link SignatureAlgorithm} interface, and register it here. More info: {@link https://github.com/node-saml/xml-crypto#customizing-algorithms|Customizing Algorithms}
   */
  SignatureAlgorithms: Record<SignatureAlgorithmType, new () => SignatureAlgorithm> = {
    "http://www.w3.org/2000/09/xmldsig#rsa-sha1": signatureAlgorithms.RsaSha1,
    "http://www.w3.org/2001/04/xmldsig-more#rsa-sha256": signatureAlgorithms.RsaSha256,
    "http://www.w3.org/2001/04/xmldsig-more#rsa-sha512": signatureAlgorithms.RsaSha512,
    // Disabled by default due to key confusion concerns.
    // 'http://www.w3.org/2000/09/xmldsig#hmac-sha1': SignatureAlgorithms.HmacSha1
  };

  static defaultNsForPrefix = {
    ds: "http://www.w3.org/2000/09/xmldsig#",
  };

  static noop = () => null;

  /**
   * The SignedXml constructor provides an abstraction for sign and verify xml documents. The object is constructed using
   * @param options {@link SignedXmlOptions}
   */
  constructor(options: SignedXmlOptions = {}) {
    const {
      idMode,
      idAttribute,
      privateKey,
      publicCert,
      signatureAlgorithm,
      canonicalizationAlgorithm,
      inclusiveNamespacesPrefixList,
      implicitTransforms,
      keyInfoAttributes,
      getKeyInfoContent,
      getCertFromKeyInfo,
    } = options;

    // Options
    this.idMode = idMode;
    this.idAttributes = ["Id", "ID", "id"];
    if (idAttribute) {
      this.idAttributes.unshift(idAttribute);
    }
    this.privateKey = privateKey;
    this.publicCert = publicCert;
    this.signatureAlgorithm = signatureAlgorithm ?? this.signatureAlgorithm;
    this.canonicalizationAlgorithm = canonicalizationAlgorithm;
    if (typeof inclusiveNamespacesPrefixList === "string") {
      this.inclusiveNamespacesPrefixList = inclusiveNamespacesPrefixList.split(" ");
    } else if (utils.isArrayHasLength(inclusiveNamespacesPrefixList)) {
      this.inclusiveNamespacesPrefixList = inclusiveNamespacesPrefixList;
    }
    this.implicitTransforms = implicitTransforms ?? this.implicitTransforms;
    this.keyInfoAttributes = keyInfoAttributes ?? this.keyInfoAttributes;
    this.getKeyInfoContent = getKeyInfoContent ?? this.getKeyInfoContent;
    this.getCertFromKeyInfo = getCertFromKeyInfo ?? SignedXml.noop;
    this.CanonicalizationAlgorithms;
    this.HashAlgorithms;
    this.SignatureAlgorithms;
  }

  /**
   * Due to key-confusion issues, it's risky to have both hmac
   * and digital signature algorithms enabled at the same time.
   * This enables HMAC and disables other signing algorithms.
   */
  enableHMAC(): void {
    this.SignatureAlgorithms = {
      "http://www.w3.org/2000/09/xmldsig#hmac-sha1": signatureAlgorithms.HmacSha1,
    };
    this.getKeyInfoContent = SignedXml.noop;
  }

  /**
   * Builds the contents of a KeyInfo element as an XML string.
   *
   * For example, if the value of the prefix argument is 'foo', then
   * the resultant XML string will be "<foo:X509Data></foo:X509Data>"
   *
   * @return an XML string representation of the contents of a KeyInfo element, or `null` if no `KeyInfo` element should be included
   */
  static getKeyInfoContent({ publicCert, prefix }: GetKeyInfoContentArgs): string | null {
    if (publicCert == null) {
      return null;
    }

    prefix = prefix ? `${prefix}:` : "";

    let x509Certs = "";
    if (Buffer.isBuffer(publicCert)) {
      publicCert = publicCert.toString("latin1");
    }

    let publicCertMatches: string[] = [];
    if (typeof publicCert === "string") {
      publicCertMatches = publicCert.match(utils.EXTRACT_X509_CERTS) || [];
    }

    if (publicCertMatches.length > 0) {
      x509Certs = publicCertMatches
        .map(
          (c) =>
            `<${prefix}X509Certificate>${utils
              .pemToDer(c)
              .toString("base64")}</${prefix}X509Certificate>`,
        )
        .join("");
    }

    return `<${prefix}X509Data>${x509Certs}</${prefix}X509Data>`;
  }

  /**
   * Returns the value of the signing certificate based on the contents of the
   * specified KeyInfo.
   *
   * @param keyInfo KeyInfo element (@see https://www.w3.org/TR/2008/REC-xmldsig-core-20080610/#sec-X509Data)
   * @return the signing certificate as a string in PEM format
   */
  static getCertFromKeyInfo(keyInfo?: Node | null): string | null {
    if (keyInfo != null) {
      const cert = xpath.select1(".//*[local-name(.)='X509Certificate']", keyInfo);
      if (isDomNode.isNodeLike(cert)) {
        return utils.derToPem(cert.textContent ?? "", "CERTIFICATE");
      }
    }

    return null;
  }

  /**
   * Validates the signature of the provided XML document synchronously using the configured key info provider.
   *
   * @param xml The XML document containing the signature to be validated.
   * @returns `true` if the signature is valid
   * @throws Error if no key info resolver is provided.
   */
  checkSignature(xml: string): boolean;
  /**
   * Validates the signature of the provided XML document synchronously using the configured key info provider.
   *
   * @param xml The XML document containing the signature to be validated.
   * @param callback Callback function to handle the validation result asynchronously.
   * @throws Error if the last parameter is provided and is not a function, or if no key info resolver is provided.
   */
  checkSignature(xml: string, callback: (error: Error | null, isValid?: boolean) => void): void;
  checkSignature(
    xml: string,
    callback?: (error: Error | null, isValid?: boolean) => void,
  ): unknown {
    if (callback != null && typeof callback !== "function") {
      throw new Error("Last parameter must be a callback function");
    }

    this.signedXml = xml;

    const doc = new xmldom.DOMParser().parseFromString(xml);

    if (!this.getReferences().every((ref) => this.validateReference(ref, doc))) {
      if (callback) {
        callback(new Error("Could not validate all references"));
        return;
      }

      return false;
    }

    const signedInfoCanon = this.getCanonSignedInfoXml(doc);
    const signer = this.findSignatureAlgorithm(this.signatureAlgorithm);
    const key = this.getCertFromKeyInfo(this.keyInfo) || this.publicCert || this.getPrivateKey();
    if (key == null) {
      throw new Error("KeyInfo or publicCert or privateKey is required to validate signature");
    }
    if (callback) {
      signer.verifySignature(signedInfoCanon, key, this.signatureValue, callback);
    } else {
      const verified = signer.verifySignature(signedInfoCanon, key, this.signatureValue);

      if (verified === false) {
        throw new Error(
          `invalid signature: the signature value ${this.signatureValue} is incorrect`,
        );
      }

      return true;
    }
  }

  private getCanonSignedInfoXml(doc: Document) {
    if (this.signatureNode == null) {
      throw new Error("No signature found.");
    }
    if (typeof this.canonicalizationAlgorithm !== "string") {
      throw new Error("Missing canonicalizationAlgorithm when trying to get signed info for XML");
    }

    const signedInfo = utils.findChildren(this.signatureNode, "SignedInfo");
    if (signedInfo.length === 0) {
      throw new Error("could not find SignedInfo element in the message");
    }

    if (
      this.canonicalizationAlgorithm === "http://www.w3.org/TR/2001/REC-xml-c14n-20010315" ||
      this.canonicalizationAlgorithm ===
        "http://www.w3.org/TR/2001/REC-xml-c14n-20010315#WithComments"
    ) {
      if (!doc || typeof doc !== "object") {
        throw new Error(
          "When canonicalization method is non-exclusive, whole xml dom must be provided as an argument",
        );
      }
    }

    /**
     * Search for ancestor namespaces before canonicalization.
     */
    const ancestorNamespaces = utils.findAncestorNs(doc, "//*[local-name()='SignedInfo']");

    const c14nOptions = {
      ancestorNamespaces: ancestorNamespaces,
    };

    return this.getCanonXml([this.canonicalizationAlgorithm], signedInfo[0], c14nOptions);
  }

  private getCanonReferenceXml(doc: Document, ref: Reference, node: Node) {
    /**
     * Search for ancestor namespaces before canonicalization.
     */
    if (Array.isArray(ref.transforms)) {
      ref.ancestorNamespaces = utils.findAncestorNs(doc, ref.xpath, this.namespaceResolver);
    }

    const c14nOptions = {
      inclusiveNamespacesPrefixList: ref.inclusiveNamespacesPrefixList,
      ancestorNamespaces: ref.ancestorNamespaces,
    };

    return this.getCanonXml(ref.transforms, node, c14nOptions);
  }

  private calculateSignatureValue(doc: Document, callback?: ErrorFirstCallback<string>) {
    const signedInfoCanon = this.getCanonSignedInfoXml(doc);
    const signer = this.findSignatureAlgorithm(this.signatureAlgorithm);
    const privateKey = this.getPrivateKey();
    if (privateKey === undefined) {
      throw new Error("Private key is required to compute signature");
    }
    if (typeof callback === "function") {
      signer.getSignature(signedInfoCanon, privateKey, callback);
    } else {
      this.signatureValue = signer.getSignature(signedInfoCanon, privateKey);
    }
  }

  private findSignatureAlgorithm(name?: SignatureAlgorithmType) {
    if (name == null) {
      throw new Error("signatureAlgorithm is required");
    }
    const algo = this.SignatureAlgorithms[name];
    if (algo) {
      return new algo();
    } else {
      throw new Error(`signature algorithm '${name}' is not supported`);
    }
  }

  private findCanonicalizationAlgorithm(name: CanonicalizationOrTransformAlgorithmType) {
    if (name != null) {
      const algo = this.CanonicalizationAlgorithms[name];
      if (algo) {
        return new algo();
      }
    }

    throw new Error(`canonicalization algorithm '${name}' is not supported`);
  }

  private findHashAlgorithm(name: HashAlgorithmType) {
    const algo = this.HashAlgorithms[name];
    if (algo) {
      return new algo();
    } else {
      throw new Error(`hash algorithm '${name}' is not supported`);
    }
  }

  validateElementAgainstReferences(elemOrXpath: Element | string, doc: Document): Reference {
    let elem: Element;
    if (typeof elemOrXpath === "string") {
      const firstElem = xpath.select1(elemOrXpath, doc);
      isDomNode.assertIsElementNode(firstElem);
      elem = firstElem;
    } else {
      elem = elemOrXpath;
    }

    for (const ref of this.getReferences()) {
      const uri = ref.uri?.[0] === "#" ? ref.uri.substring(1) : ref.uri;

      for (const attr of this.idAttributes) {
        const elemId = elem.getAttribute(attr);
        if (uri === elemId) {
          ref.xpath = `//*[@*[local-name(.)='${attr}']='${uri}']`;
          break; // found the correct element, no need to check further
        }
      }

      const canonXml = this.getCanonReferenceXml(doc, ref, elem);
      const hash = this.findHashAlgorithm(ref.digestAlgorithm);
      const digest = hash.getHash(canonXml);

      if (utils.validateDigestValue(digest, ref.digestValue)) {
        return ref;
      }
    }

    throw new Error("No references passed validation");
  }

  private validateReference(ref: Reference, doc: Document) {
    const uri = ref.uri?.[0] === "#" ? ref.uri.substring(1) : ref.uri;
    let elem: xpath.SelectSingleReturnType = null;

    if (uri === "") {
      elem = xpath.select1("//*", doc);
    } else if (uri?.indexOf("'") !== -1) {
      // xpath injection
      throw new Error("Cannot validate a uri with quotes inside it");
    } else {
      let num_elements_for_id = 0;
      for (const attr of this.idAttributes) {
        const tmp_elemXpath = `//*[@*[local-name(.)='${attr}']='${uri}']`;
        const tmp_elem = xpath.select(tmp_elemXpath, doc);
        if (utils.isArrayHasLength(tmp_elem)) {
          num_elements_for_id += tmp_elem.length;

          if (num_elements_for_id > 1) {
            throw new Error(
              "Cannot validate a document which contains multiple elements with the " +
                "same value for the ID / Id / Id attributes, in order to prevent " +
                "signature wrapping attack.",
            );
          }

          elem = tmp_elem[0];
          ref.xpath = tmp_elemXpath;
        }
      }
    }

    ref.getValidatedNode = (xpathSelector?: string) => {
      xpathSelector = xpathSelector || ref.xpath;
      if (typeof xpathSelector !== "string" || ref.validationError != null) {
        return null;
      }
      const selectedValue = xpath.select1(xpathSelector, doc);
      return isDomNode.isNodeLike(selectedValue) ? selectedValue : null;
    };

    if (!isDomNode.isNodeLike(elem)) {
      const validationError = new Error(
        `invalid signature: the signature references an element with uri ${ref.uri} but could not find such element in the xml`,
      );
      ref.validationError = validationError;
      return false;
    }

    const canonXml = this.getCanonReferenceXml(doc, ref, elem);
    const hash = this.findHashAlgorithm(ref.digestAlgorithm);
    const digest = hash.getHash(canonXml);

    if (!utils.validateDigestValue(digest, ref.digestValue)) {
      const validationError = new Error(
        `invalid signature: for uri ${ref.uri} calculated digest is ${digest} but the xml to validate supplies digest ${ref.digestValue}`,
      );
      ref.validationError = validationError;

      return false;
    }

    return true;
  }

  findSignatures(doc: Node): Node[] {
    const nodes = xpath.select(
      "//*[local-name(.)='Signature' and namespace-uri(.)='http://www.w3.org/2000/09/xmldsig#']",
      doc,
    );

    return isDomNode.isArrayOfNodes(nodes) ? nodes : [];
  }

  /**
   * Loads the signature information from the provided XML node or string.
   *
   * @param signatureNode The XML node or string representing the signature.
   */
  loadSignature(signatureNode: Node | string): void {
    if (typeof signatureNode === "string") {
      this.signatureNode = signatureNode = new xmldom.DOMParser().parseFromString(signatureNode);
    } else {
      this.signatureNode = signatureNode;
    }

    this.signatureXml = signatureNode.toString();

    const node = xpath.select1(
      ".//*[local-name(.)='CanonicalizationMethod']/@Algorithm",
      signatureNode,
    );
    if (!isDomNode.isNodeLike(node)) {
      throw new Error("could not find CanonicalizationMethod/@Algorithm element");
    }

    if (isDomNode.isAttributeNode(node)) {
      this.canonicalizationAlgorithm = node.value as CanonicalizationAlgorithmType;
    }

    const signatureAlgorithm = xpath.select1(
      ".//*[local-name(.)='SignatureMethod']/@Algorithm",
      signatureNode,
    );

    if (isDomNode.isAttributeNode(signatureAlgorithm)) {
      this.signatureAlgorithm = signatureAlgorithm.value as SignatureAlgorithmType;
    }

    this.references = [];
    const references = xpath.select(
      ".//*[local-name(.)='SignedInfo']/*[local-name(.)='Reference']",
      signatureNode,
    );
    if (!utils.isArrayHasLength(references)) {
      throw new Error("could not find any Reference elements");
    }

    for (const reference of references) {
      this.loadReference(reference);
    }

    const signatureValue = xpath.select1(
      ".//*[local-name(.)='SignatureValue']/text()",
      signatureNode,
    );

    if (isDomNode.isTextNode(signatureValue)) {
      this.signatureValue = signatureValue.data.replace(/\r?\n/g, "");
    }

    const keyInfo = xpath.select1(".//*[local-name(.)='KeyInfo']", signatureNode);

    if (isDomNode.isNodeLike(keyInfo)) {
      this.keyInfo = keyInfo;
    }
  }

  /**
   * Load the reference xml node to a model
   *
   */
  private loadReference(refNode: Node) {
    let nodes = utils.findChildren(refNode, "DigestMethod");
    if (nodes.length === 0) {
      throw new Error(`could not find DigestMethod in reference ${refNode.toString()}`);
    }
    const digestAlgoNode = nodes[0];

    const attr = utils.findAttr(digestAlgoNode, "Algorithm");
    if (!attr) {
      throw new Error(`could not find Algorithm attribute in node ${digestAlgoNode.toString()}`);
    }
    const digestAlgo = attr.value;

    nodes = utils.findChildren(refNode, "DigestValue");
    if (nodes.length === 0) {
      throw new Error(`could not find DigestValue node in reference ${refNode.toString()}`);
    }
    const firstChild = nodes[0].firstChild;
    if (!firstChild || !("data" in firstChild)) {
      throw new Error(`could not find the value of DigestValue in ${nodes[0].toString()}`);
    }
    const digestValue = firstChild.data;

    const transforms: string[] = [];
    let inclusiveNamespacesPrefixList: string[] = [];
    nodes = utils.findChildren(refNode, "Transforms");
    if (nodes.length !== 0) {
      const transformsNode = nodes[0];
      const transformsAll = utils.findChildren(transformsNode, "Transform");
      for (const transform of transformsAll) {
        const transformAttr = utils.findAttr(transform, "Algorithm");

        if (transformAttr) {
          transforms.push(transformAttr.value);
        }
      }

      // This is a little strange, we are looking for children of the last child of `transformsNode`
      const inclusiveNamespaces = utils.findChildren(
        transformsAll[transformsAll.length - 1],
        "InclusiveNamespaces",
      );
      if (utils.isArrayHasLength(inclusiveNamespaces)) {
        // Should really only be one prefix list, but maybe there's some circumstances where more than one to let's handle it
        inclusiveNamespacesPrefixList = inclusiveNamespaces
          .flatMap((namespace) => (namespace.getAttribute("PrefixList") ?? "").split(" "))
          .filter((value) => value.length > 0);
      }
    }

    if (utils.isArrayHasLength(this.implicitTransforms)) {
      this.implicitTransforms.forEach(function (t) {
        transforms.push(t);
      });
    }

    /**
     * DigestMethods take an octet stream rather than a node set. If the output of the last transform is a node set, we
     * need to canonicalize the node set to an octet stream using non-exclusive canonicalization. If there are no
     * transforms, we need to canonicalize because URI dereferencing for a same-document reference will return a node-set.
     * @see:
     * https://www.w3.org/TR/xmldsig-core1/#sec-DigestMethod
     * https://www.w3.org/TR/xmldsig-core1/#sec-ReferenceProcessingModel
     * https://www.w3.org/TR/xmldsig-core1/#sec-Same-Document
     */
    if (
      transforms.length === 0 ||
      transforms[transforms.length - 1] === "http://www.w3.org/2000/09/xmldsig#enveloped-signature"
    ) {
      transforms.push("http://www.w3.org/TR/2001/REC-xml-c14n-20010315");
    }

    this.addReference({
      transforms,
      digestAlgorithm: digestAlgo,
      uri: isDomNode.isElementNode(refNode) ? utils.findAttr(refNode, "URI")?.value : undefined,
      digestValue,
      inclusiveNamespacesPrefixList,
      isEmptyUri: false,
    });
  }

  /**
   * Adds a reference to the signature.
   *
   * @param xpath The XPath expression to select the XML nodes to be referenced.
   * @param transforms An array of transform algorithms to be applied to the selected nodes.
   * @param digestAlgorithm The digest algorithm to use for computing the digest value.
   * @param uri The URI identifier for the reference. If empty, an empty URI will be used.
   * @param digestValue The expected digest value for the reference.
   * @param inclusiveNamespacesPrefixList The prefix list for inclusive namespace canonicalization.
   * @param isEmptyUri Indicates whether the URI is empty. Defaults to `false`.
   */
  addReference({
    xpath,
    transforms,
    digestAlgorithm,
    uri = "",
    digestValue,
    inclusiveNamespacesPrefixList = [],
    isEmptyUri = false,
  }: Partial<Reference> & Pick<Reference, "xpath">): void {
    if (digestAlgorithm == null) {
      throw new Error("digestAlgorithm is required");
    }

    if (!utils.isArrayHasLength(transforms)) {
      throw new Error("transforms must contain at least one transform algorithm");
    }

    this.references.push({
      xpath,
      transforms,
      digestAlgorithm,
      uri,
      digestValue,
      inclusiveNamespacesPrefixList,
      isEmptyUri,
      getValidatedNode: () => {
        throw new Error(
          "Reference has not been validated yet; Did you call `sig.checkSignature()`?",
        );
      },
    });
  }

  getReferences(): Reference[] {
    return this.references;
  }

  /**
   * Compute the signature of the given XML (using the already defined settings).
   *
   * @param xml The XML to compute the signature for.
   * @param callback A callback function to handle the signature computation asynchronously.
   * @returns void
   * @throws TypeError If the xml can not be parsed.
   */
  computeSignature(xml: string): void;

  /**
   * Compute the signature of the given XML (using the already defined settings).
   *
   * @param xml The XML to compute the signature for.
   * @param callback A callback function to handle the signature computation asynchronously.
   * @returns void
   * @throws TypeError If the xml can not be parsed.
   */
  computeSignature(xml: string, callback: ErrorFirstCallback<SignedXml>): void;

  /**
   * Compute the signature of the given XML (using the already defined settings).
   *
   * @param xml The XML to compute the signature for.
   * @param opts An object containing options for the signature computation.
   * @returns If no callback is provided, returns `this` (the instance of SignedXml).
   * @throws TypeError If the xml can not be parsed, or Error if there were invalid options passed.
   */
  computeSignature(xml: string, options: ComputeSignatureOptions): void;

  /**
   * Compute the signature of the given XML (using the already defined settings).
   *
   * @param xml The XML to compute the signature for.
   * @param opts An object containing options for the signature computation.
   * @param callback A callback function to handle the signature computation asynchronously.
   * @returns void
   * @throws TypeError If the xml can not be parsed, or Error if there were invalid options passed.
   */
  computeSignature(
    xml: string,
    options: ComputeSignatureOptions,
    callback: ErrorFirstCallback<SignedXml>,
  ): void;

  computeSignature(
    xml: string,
    options?: ComputeSignatureOptions | ErrorFirstCallback<SignedXml>,
    callbackParam?: ErrorFirstCallback<SignedXml>,
  ): void {
    let callback: ErrorFirstCallback<SignedXml>;
    if (typeof options === "function" && callbackParam == null) {
      callback = options as ErrorFirstCallback<SignedXml>;
      options = {} as ComputeSignatureOptions;
    } else {
      callback = callbackParam as ErrorFirstCallback<SignedXml>;
      options = (options ?? {}) as ComputeSignatureOptions;
    }

    const doc = new xmldom.DOMParser().parseFromString(xml);
    let xmlNsAttr = "xmlns";
    const signatureAttrs: string[] = [];
    let currentPrefix: string;

    const validActions = ["append", "prepend", "before", "after"];

    const prefix = options.prefix;
    const attrs = options.attrs || {};
    const location = options.location || {};
    const existingPrefixes = options.existingPrefixes || {};

    this.namespaceResolver = {
      lookupNamespaceURI: function (prefix) {
        return prefix ? existingPrefixes[prefix] : null;
      },
    };

    // defaults to the root node
    location.reference = location.reference || "/*";
    // defaults to append action
    location.action = location.action || "append";

    if (validActions.indexOf(location.action) === -1) {
      const err = new Error(
        `location.action option has an invalid action: ${
          location.action
        }, must be any of the following values: ${validActions.join(", ")}`,
      );
      if (!callback) {
        throw err;
      } else {
        callback(err);
        return;
      }
    }

    // automatic insertion of `:`
    if (prefix) {
      xmlNsAttr += `:${prefix}`;
      currentPrefix = `${prefix}:`;
    } else {
      currentPrefix = "";
    }

    Object.keys(attrs).forEach(function (name) {
      if (name !== "xmlns" && name !== xmlNsAttr) {
        signatureAttrs.push(`${name}="${attrs[name]}"`);
      }
    });

    // add the xml namespace attribute
    signatureAttrs.push(`${xmlNsAttr}="http://www.w3.org/2000/09/xmldsig#"`);

    let signatureXml = `<${currentPrefix}Signature ${signatureAttrs.join(" ")}>`;

    signatureXml += this.createSignedInfo(doc, prefix);
    signatureXml += this.getKeyInfo(prefix);
    signatureXml += `</${currentPrefix}Signature>`;

    this.originalXmlWithIds = doc.toString();

    let existingPrefixesString = "";
    Object.keys(existingPrefixes).forEach(function (key) {
      existingPrefixesString += `xmlns:${key}="${existingPrefixes[key]}" `;
    });

    // A trick to remove the namespaces that already exist in the xml
    // This only works if the prefix and namespace match with those in the xml
    const dummySignatureWrapper = `<Dummy ${existingPrefixesString}>${signatureXml}</Dummy>`;
    const nodeXml = new xmldom.DOMParser().parseFromString(dummySignatureWrapper);

    // Because we are using a dummy wrapper hack described above, we know there will be a `firstChild`
    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
    const signatureDoc = nodeXml.documentElement.firstChild!;

    const referenceNode = xpath.select1(location.reference, doc);

    if (!isDomNode.isNodeLike(referenceNode)) {
      const err2 = new Error(
        `the following xpath cannot be used because it was not found: ${location.reference}`,
      );
      if (!callback) {
        throw err2;
      } else {
        callback(err2);
        return;
      }
    }

    if (location.action === "append") {
      referenceNode.appendChild(signatureDoc);
    } else if (location.action === "prepend") {
      referenceNode.insertBefore(signatureDoc, referenceNode.firstChild);
    } else if (location.action === "before") {
      if (referenceNode.parentNode == null) {
        throw new Error(
          "`location.reference` refers to the root node (by default), so we can't insert `before`",
        );
      }
      referenceNode.parentNode.insertBefore(signatureDoc, referenceNode);
    } else if (location.action === "after") {
      if (referenceNode.parentNode == null) {
        throw new Error(
          "`location.reference` refers to the root node (by default), so we can't insert `after`",
        );
      }
      referenceNode.parentNode.insertBefore(signatureDoc, referenceNode.nextSibling);
    }

    this.signatureNode = signatureDoc;
    const signedInfoNodes = utils.findChildren(this.signatureNode, "SignedInfo");
    if (signedInfoNodes.length === 0) {
      const err3 = new Error("could not find SignedInfo element in the message");
      if (!callback) {
        throw err3;
      } else {
        callback(err3);
        return;
      }
    }
    const signedInfoNode = signedInfoNodes[0];

    if (typeof callback === "function") {
      // Asynchronous flow
      this.calculateSignatureValue(doc, (err, signature) => {
        if (err) {
          callback(err);
        } else {
          this.signatureValue = signature || "";
          signatureDoc.insertBefore(this.createSignature(prefix), signedInfoNode.nextSibling);
          this.signatureXml = signatureDoc.toString();
          this.signedXml = doc.toString();
          callback(null, this);
        }
      });
    } else {
      // Synchronous flow
      this.calculateSignatureValue(doc);
      signatureDoc.insertBefore(this.createSignature(prefix), signedInfoNode.nextSibling);
      this.signatureXml = signatureDoc.toString();
      this.signedXml = doc.toString();
    }
  }

  private getKeyInfo(prefix) {
    const currentPrefix = prefix ? `${prefix}:` : "";

    let keyInfoAttrs = "";
    if (this.keyInfoAttributes) {
      Object.keys(this.keyInfoAttributes).forEach((name) => {
        keyInfoAttrs += ` ${name}="${this.keyInfoAttributes[name]}"`;
      });
    }

    const keyInfoContent = this.getKeyInfoContent({ publicCert: this.publicCert, prefix });
    if (keyInfoAttrs || keyInfoContent) {
      return `<${currentPrefix}KeyInfo${keyInfoAttrs}>${keyInfoContent}</${currentPrefix}KeyInfo>`;
    }

    return "";
  }

  /**
   * Generate the Reference nodes (as part of the signature process)
   *
   */
  private createReferences(doc, prefix) {
    let res = "";

    prefix = prefix || "";
    prefix = prefix ? `${prefix}:` : prefix;

    for (const ref of this.getReferences()) {
      const nodes = xpath.selectWithResolver(ref.xpath ?? "", doc, this.namespaceResolver);

      if (!utils.isArrayHasLength(nodes)) {
        throw new Error(
          `the following xpath cannot be signed because it was not found: ${ref.xpath}`,
        );
      }

      for (const node of nodes) {
        if (ref.isEmptyUri) {
          res += `<${prefix}Reference URI="">`;
        } else {
          const id = this.ensureHasId(node);
          ref.uri = id;
          res += `<${prefix}Reference URI="#${id}">`;
        }
        res += `<${prefix}Transforms>`;
        for (const trans of ref.transforms || []) {
          const transform = this.findCanonicalizationAlgorithm(trans);
          res += `<${prefix}Transform Algorithm="${transform.getAlgorithmName()}"`;
          if (utils.isArrayHasLength(ref.inclusiveNamespacesPrefixList)) {
            res += ">";
            res += `<InclusiveNamespaces PrefixList="${ref.inclusiveNamespacesPrefixList.join(
              " ",
            )}" xmlns="${transform.getAlgorithmName()}"/>`;
            res += `</${prefix}Transform>`;
          } else {
            res += " />";
          }
        }

        const canonXml = this.getCanonReferenceXml(doc, ref, node);

        const digestAlgorithm = this.findHashAlgorithm(ref.digestAlgorithm);
        res +=
          `</${prefix}Transforms>` +
          `<${prefix}DigestMethod Algorithm="${digestAlgorithm.getAlgorithmName()}" />` +
          `<${prefix}DigestValue>${digestAlgorithm.getHash(canonXml)}</${prefix}DigestValue>` +
          `</${prefix}Reference>`;
      }
    }

    return res;
  }

  getCanonXml(
    transforms: Reference["transforms"],
    node: Node,
    options: CanonicalizationOrTransformationAlgorithmProcessOptions = {},
  ) {
    options.defaultNsForPrefix = options.defaultNsForPrefix ?? SignedXml.defaultNsForPrefix;
    options.signatureNode = this.signatureNode;

    const canonXml = node.cloneNode(true); // Deep clone
    let transformedXml: Node | string = canonXml;

    transforms.forEach((transformName) => {
      if (isDomNode.isNodeLike(transformedXml)) {
        // If, after processing, `transformedNode` is a string, we can't do anymore transforms on it
        const transform = this.findCanonicalizationAlgorithm(transformName);
        transformedXml = transform.process(transformedXml, options);
      }
      //TODO: currently transform.process may return either Node or String value (enveloped transformation returns Node, exclusive-canonicalization returns String).
      //This either needs to be more explicit in the API, or all should return the same.
      //exclusive-canonicalization returns String since it builds the Xml by hand. If it had used xmldom it would incorrectly minimize empty tags
      //to <x/> instead of <x></x> and also incorrectly handle some delicate line break issues.
      //enveloped transformation returns Node since if it would return String consider this case:
      //<x xmlns:p='ns'><p:y/></x>
      //if only y is the node to sign then a string would be <p:y/> without the definition of the p namespace. probably xmldom toString() should have added it.
    });

    return transformedXml.toString();
  }

  /**
   * Ensure an element has Id attribute. If not create it with unique value.
   * Work with both normal and wssecurity Id flavour
   */
  private ensureHasId(node) {
    let attr;

    if (this.idMode === "wssecurity") {
      attr = utils.findAttr(
        node,
        "Id",
        "http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd",
      );
    } else {
      this.idAttributes.some((idAttribute) => {
        attr = utils.findAttr(node, idAttribute);
        return !!attr; // This will break the loop as soon as a truthy attr is found.
      });
    }

    if (attr) {
      return attr.value;
    }

    //add the attribute
    const id = `_${this.id++}`;

    if (this.idMode === "wssecurity") {
      node.setAttributeNS(
        "http://www.w3.org/2000/xmlns/",
        "xmlns:wsu",
        "http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd",
      );
      node.setAttributeNS(
        "http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd",
        "wsu:Id",
        id,
      );
    } else {
      node.setAttribute("Id", id);
    }

    return id;
  }

  /**
   * Create the SignedInfo element
   *
   */
  private createSignedInfo(doc, prefix) {
    if (typeof this.canonicalizationAlgorithm !== "string") {
      throw new Error(
        "Missing canonicalizationAlgorithm when trying to create signed info for XML",
      );
    }
    const transform = this.findCanonicalizationAlgorithm(this.canonicalizationAlgorithm);
    const algo = this.findSignatureAlgorithm(this.signatureAlgorithm);
    let currentPrefix;

    currentPrefix = prefix || "";
    currentPrefix = currentPrefix ? `${currentPrefix}:` : currentPrefix;

    let res = `<${currentPrefix}SignedInfo>`;
    res += `<${currentPrefix}CanonicalizationMethod Algorithm="${transform.getAlgorithmName()}"`;
    if (utils.isArrayHasLength(this.inclusiveNamespacesPrefixList)) {
      res += ">";
      res += `<InclusiveNamespaces PrefixList="${this.inclusiveNamespacesPrefixList.join(
        " ",
      )}" xmlns="${transform.getAlgorithmName()}"/>`;
      res += `</${currentPrefix}CanonicalizationMethod>`;
    } else {
      res += " />";
    }
    res += `<${currentPrefix}SignatureMethod Algorithm="${algo.getAlgorithmName()}" />`;

    res += this.createReferences(doc, prefix);
    res += `</${currentPrefix}SignedInfo>`;
    return res;
  }

  /**
   * Create the Signature element
   *
   */
  private createSignature(prefix?: string) {
    let xmlNsAttr = "xmlns";

    if (prefix) {
      xmlNsAttr += `:${prefix}`;
      prefix += ":";
    } else {
      prefix = "";
    }

    const signatureValueXml = `<${prefix}SignatureValue>${this.signatureValue}</${prefix}SignatureValue>`;
    //the canonicalization requires to get a valid xml node.
    //we need to wrap the info in a dummy signature since it contains the default namespace.
    const dummySignatureWrapper = `<${prefix}Signature ${xmlNsAttr}="http://www.w3.org/2000/09/xmldsig#">${signatureValueXml}</${prefix}Signature>`;

    const doc = new xmldom.DOMParser().parseFromString(dummySignatureWrapper);

    // Because we are using a dummy wrapper hack described above, we know there will be a `firstChild`
    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
    return doc.documentElement.firstChild!;
  }

  /**
   * Returns just the signature part, must be called only after {@link computeSignature}
   *
   * @returns The signature XML.
   */
  getSignatureXml(): string {
    return this.signatureXml;
  }

  /**
   * Returns the original xml with Id attributes added on relevant elements (required for validation), must be called only after {@link computeSignature}
   *
   * @returns The original XML with IDs.
   */
  getOriginalXmlWithIds(): string {
    return this.originalXmlWithIds;
  }

  /**
   * Returns the original xml document with the signature in it, must be called only after {@link computeSignature}
   *
   * @returns The signed XML.
   */
  getSignedXml(): string {
    return this.signedXml;
  }

  getPrivateKey(): crypto.KeyLike | undefined {
    if (
      this.privateKeyPass &&
      (this.privateKey instanceof Buffer || typeof this.privateKey === "string")
    ) {
      return crypto.createPrivateKey({
        key: this.privateKey,
        passphrase: this.privateKeyPass,
      });
    }
    return this.privateKey;
  }
}