Resolve XML-encoded carriage returns during signature validation

src/node-saml/saml.ts

@@ -738,6 +738,8 @@ class SAML {
     if (totalReferencedNodes.length > 1) {
       return false;
     }
+    // normalize XML to replace XML-encoded carriage returns with actual carriage returns
+    fullXml = this.normalizeXml(fullXml);
     fullXml = this.normalizeNewlines(fullXml);
     return sig.checkSignature(fullXml);
   }
@@ -1465,6 +1467,12 @@ class SAML {
     // https://github.com/node-saml/passport-saml/issues/431#issuecomment-718132752
     return xml.replace(/\r\n?/g, "\n");
   }
+
+  normalizeXml(xml: string): string {
+    // we can use this utility to parse and re-stringify XML
+    // `DOMParser` will take care of normalization tasks, like replacing XML-encoded carriage returns with actual carriage returns
+    return new xmldom.DOMParser({}).parseFromString(xml).toString();
+  }
 }
 
 export { SAML };

test/node-saml/test-signatures.spec.ts

@@ -279,4 +279,26 @@ describe("Signatures", function () {
       await testOneResponseBody(body, false, 1);
     });
   });
+
+  describe("Signature on saml:Response with XML-encoded carriage returns", () => {
+    const samlResponseXml = fs
+      .readFileSync(
+        __dirname + "/../static/signatures/valid/response.root-unsigned.assertion-signed.xml"
+      )
+      .toString();
+    const makeBody = (str: string) => ({ SAMLResponse: Buffer.from(str).toString("base64") });
+
+    const insertChars = (str: string, where: string, chars: string) =>
+      str.replace(new RegExp(`(<ds:${where}>)(.{10})(.{10})`), `$1$2${chars}$3`);
+
+    it("SignatureValue with &#13;", async () => {
+      const body = makeBody(insertChars(samlResponseXml, "SignatureValue", "&#13;"));
+      await testOneResponseBody(body, false, 2);
+    });
+
+    it("SignatureValue with &#xd;", async () => {
+      const body = makeBody(insertChars(samlResponseXml, "SignatureValue", "&#xd;"));
+      await testOneResponseBody(body, false, 2);
+    });
+  });
 });