Web Crypto Api fails to verify signature after converting from string-CodePudding

I am storing my data, including the signature in string format, and after converting the signature to and from strings following the MDN Documentation the verification process fails every time. The relevant code bits are:

const publicKey: CryptoKey = await window.crypto.subtle.importKey("spki", str2ab(window.atob(publicKeyStr)), { name: "RSA-PSS", hash: { name: "SHA-256" } }, false, ["verify"]);
const privateKey: CryptoKey = await window.crypto.subtle.importKey("pkcs8", str2ab(window.atob(privateKeyStr)), { name: "RSA-PSS", hash: { name: "SHA-256" } }, false, ["sign"])
    
if(privateKey && publicKey) {
    try {
        const sign = await window.crypto.subtle.sign({name: "RSA-PSS", saltLength: 32}, privateKey, encodedMessage);
        const signature = window.btoa(String.fromCharCode.apply(null, [...new Uint8Array(sign)])); //the way said signature is stored and I can load it
        const res = await window.crypto.subtle.verify({name: "RSA-PSS", saltLength: 32}, publicKey, str2ab(signature), encodedMessage);
        console.log("Verifying:", signature, publicKey, res);
        return res;
        } catch (error) {
            console.error(error);
            return false;
        }
    }
    return false;

With the str2ab(str) function being:

export function str2ab(str: string): ArrayBuffer {
    const buf = new ArrayBuffer(str.length);
    const bufView = new Uint8Array(buf);
    for (let i = 0, strLen = str.length; i < strLen; i  ) {
      bufView[i] = str.charCodeAt(i);
    }
    return buf;
}

And encoded message is new TextEncoder.encode(messageString)

CodePudding user response：

You store the Base64 encoded signature, but do not perform a Base64 decoding before verification, i.e. the Base64 decoding must be added. For this, in:

const res = await window.crypto.subtle.verify({name: "RSA-PSS", saltLength: 32}, publicKey, str2ab(signature), encodedMessage);

replace str2ab(signature) with b642ab(signature), where b642ab() performs the Base64 decoding:

(async () => {

    var messageString = "The quick brown fox jumps over the lazy dog";
    var encodedMessage = new TextEncoder().encode(messageString);

    var publicKeyStr = "MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAunF5aDa6HCfLMMI/MZLT5hDk304CU ypFMFiBjowQdUMQKYHZ fklB7GpLxCatxYJ/hZ7rjfHH3Klq20/Y1EbYDRopyTSfkrTzPzwsX4Ur/l25CtdQldhHCTMgwf/Ev/buBNobfzdZE Dhdv5lQwKtjI43lDKvAi5kEet2TFwfJcJrBiRJeEcLfVgWTXGRQn7gngWKykUu5rS83eAU1xH9FLojQfyia89/EykiOO7/3UWwd MATZ9HLjSx2/Lf3g2jr81eifEmYDlri/OZp4OhZu 0Bo1LXloCTe vmIQ2YCX7EatUOuyQMt2Vwx4uV d/A3DP6PtMGBKpF8St4iGwIDAQAB";
    var privateKeyStr = "MIIEvgIBADANBgkqhkiG9w0BAQEFAASCBKgwggSkAgEAAoIBAQC6cXloNrocJ8swwj8xktPmEOTfTgJT7KkUwWIGOjBB1QxApgdn5 SUHsakvEJq3Fgn FnuuN8cfcqWrbT9jURtgNGinJNJ StPM/PCxfhSv XbkK11CV2EcJMyDB/8S/9u4E2ht/N1kT4OF2/mVDAq2MjjeUMq8CLmQR63ZMXB8lwmsGJEl4Rwt9WBZNcZFCfuCeBYrKRS7mtLzd4BTXEf0UuiNB/KJrz38TKSI47v/dRbB34wBNn0cuNLHb8t/eDaOvzV6J8SZgOWuL85mng6Fm77QGjUteWgJN76 YhDZgJfsRq1Q67JAy3ZXDHi5X538DcM/o 0wYEqkXxK3iIbAgMBAAECggEASlJj0ExIomKmmBhG8q8SM1s2sWG6gdQMjs6MEeluRT/1c2v79cq2Dum5y/ UBl8x8TUKPKSLpCLs GXkiVKgHXrFlqoN OYQArG2EUWzuODwczdYPhhupBXwR3oX4g41k/BsYfQfZBVzBFEJdWrIDLyAUFWNlfdGIj2BTiAoySfyqmamvmW8bsvc8coiGlZ28UC85/Xqx9wOzjeGoRkCH7PcTMlc9F7SxSthwX/k1VBXmNOHa HzGOgO/W3k1LDqJbq2wKjZTW3iVEg2VodjxgBLMm0MueSGoI6IuaZSPMyFEM3gGvC2 cDBI2SL/amhiTUa/VDlTVw/IKbSuar9uQKBgQDd76M0Po5Lqh8ZhQ3obhFqkfO5EBXy7HUL15cw51kVtwF6Gf/J2HNHjwsg9Nb0eJETTS6bbuVd9bn884JoRS986nVTFNZ4dnjEgKjjQ8GjfzdkpbUxsRLWiIxuOQSpIUZGdMi2ctTTtspvMsDsjRRYdYIQCe/SDsdHGT3vcUCybwKBgQDXDz6iVnY84Fh5iDDVrQOR4lYoxCL/ikCDJjC6y1mjR0eVFdBPQ4j1dDSPU9lahBLby0VyagQCDp/kxQOl0z2zBLRI4I8jUtz9/9KW6ze7U7dQJ7OTfumd5I97OyQOG9XZwKUkRgfyb/PAMBSUSLgosi38f OC3IN3qlvHFzvxFQKBgQCITpUDEmSczih5qQGIvolN1cRF5j5Ey7t7gXbnXz Umah7kJpMIvdyfMVOAXJABgi8PQwiBLM0ySXo2LpARjXLV8ilNUggBktYDNktc8DrJMgltayaj3HNd2IglD5rjfc2cKWRgOd7/GlKcHaTEnbreYhfR2sWrWLxJOyoMfuVWwKBgFalCbMV6qU0LfEo8aPlBN8ttVDPVNpntP4h0NgxPXgPK8Pg gA1UWSy4MouGg/hzkdHaj9ifyLlCX598a5JoT4S0x/ZeVHd/LNI8mtjcRzD6cMde7gdFbpLb5NSjIAyrsIAX4hxvpnqiOYRePkVIz0iLGziiaMbfMwlkrxvm/LRAoGBALPRbtSbE2pPgvOHKHTGPr7gKbmsWVbOcQA8rG801T38W/UPe1XtynMEjzzQ29OaVeQwvUN9 DxFXJ6Yvwj6ih4Wdq109i7Oo1fDnMczOQN9DKch2eNAHrNSOMyLDCBm  wbyHAsS2T0VO8 gzLABviZm5AFCQWfke4LZo5mOS10";

    const publicKey = await window.crypto.subtle.importKey("spki", str2ab(window.atob(publicKeyStr)), { name: "RSA-PSS", hash: { name: "SHA-256" } }, false, ["verify"]);
    const privateKey = await window.crypto.subtle.importKey("pkcs8", str2ab(window.atob(privateKeyStr)), { name: "RSA-PSS", hash: { name: "SHA-256" } }, false, ["sign"]);

    if(privateKey && publicKey) {
        const sign = await window.crypto.subtle.sign({name: "RSA-PSS", saltLength: 32}, privateKey, encodedMessage);
        const signature = window.btoa(String.fromCharCode.apply(null, [...new Uint8Array(sign)])); //the way said signature is stored and I can load it
        const res = await window.crypto.subtle.verify({name: "RSA-PSS", saltLength: 32}, publicKey, b642ab(signature), encodedMessage);
        console.log("Verifying:", /*signature, publicKey,*/ res);
    }
})();

function b642ab(base64_string){
    return Uint8Array.from(window.atob(base64_string), c => c.charCodeAt(0));
}

function str2ab(str) {
    const buf = new ArrayBuffer(str.length);
    const bufView = new Uint8Array(buf);
    for (let i = 0, strLen = str.length; i < strLen; i  ) {
      bufView[i] = str.charCodeAt(i);
    }
    return buf;
}

After this bug is fixed, verification is successfully performed.