GetAndroidSig

Main.java

import java.io.IOException;
import java.io.InputStream;
import java.lang.ref.WeakReference;
import java.security.cert.CertificateEncodingException;
import java.util.Enumeration;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;
import java.util.logging.Level;
import java.util.logging.Logger;

public class Main {

    private static final Object mSync = new Object();
    private static WeakReference<byte[]> mReadBuffer;

    public static void main(String[] args) {
        if (args.length < 1) {
            System.out.println("Usage: java -jar GetAndroidSig.jar <apk/jar>");
            System.exit(-1);
        }

        System.out.println(args[0]);

        String mArchiveSourcePath = args[0];

        WeakReference<byte[]> readBufferRef;
        byte[] readBuffer = null;
        synchronized (mSync) {
            readBufferRef = mReadBuffer;
            if (readBufferRef != null) {
                mReadBuffer = null;
                readBuffer = readBufferRef.get();
            }
            if (readBuffer == null) {
                readBuffer = new byte[8192];
                readBufferRef = new WeakReference<byte[]>(readBuffer);
            }
        }

        try {
            JarFile jarFile = new JarFile(mArchiveSourcePath);
            java.security.cert.Certificate[] certs = null;

            Enumeration entries = jarFile.entries();
            while (entries.hasMoreElements()) {
                JarEntry je = (JarEntry) entries.nextElement();
                if (je.isDirectory()) {
                    continue;
                }
                if (je.getName().startsWith("META-INF/")) {
                    continue;
                }
                java.security.cert.Certificate[] localCerts = loadCertificates(jarFile, je, readBuffer);
                if (false) {
                    System.out.println("File " + mArchiveSourcePath + " entry " + je.getName()
                            + ": certs=" + certs + " ("
                            + (certs != null ? certs.length : 0) + ")");
                }
                if (localCerts == null) {
                    System.err.println("Package has no certificates at entry "
                            + je.getName() + "; ignoring!");
                    jarFile.close();
                    return;
                } else if (certs == null) {
                    certs = localCerts;
                } else {
                    // Ensure all certificates match.
                    for (int i = 0; i < certs.length; i++) {
                        boolean found = false;
                        for (int j = 0; j < localCerts.length; j++) {
                            if (certs[i] != null
                                    && certs[i].equals(localCerts[j])) {
                                found = true;
                                break;
                            }
                        }
                        if (!found || certs.length != localCerts.length) {
                            System.err.println("Package has mismatched certificates at entry "
                                    + je.getName() + "; ignoring!");
                            jarFile.close();
                            return; // false
                        }
                    }
                }
            }

            jarFile.close();

            synchronized (mSync) {
                mReadBuffer = readBufferRef;
            }

            if (certs != null && certs.length > 0) {
                final int N = certs.length;

                for (int i = 0; i < N; i++) {
                    String charSig = new String(toChars(certs[i].getEncoded()));
                    System.out.println("Cert#: " + i + "  Type:" + certs[i].getType()
                            + "\nPublic key: " + certs[i].getPublicKey()
                            + "\nHash code: " + certs[i].hashCode()
                            + " / 0x" + Integer.toHexString(certs[i].hashCode())
                            + "\nTo char: " + charSig);
                }
            } else {
                System.err.println("Package has no certificates; ignoring!");
                return;
            }
        } catch (CertificateEncodingException ex) {
            Logger.getLogger(Main.class.getName()).log(Level.SEVERE, null, ex);
        } catch (IOException e) {
            System.err.println("Exception reading " + mArchiveSourcePath + "\n" + e);
            return;
        } catch (RuntimeException e) {
            System.err.println("Exception reading " + mArchiveSourcePath + "\n" + e);
            return;
        }
    }

    private static char[] toChars(byte[] mSignature) {
        byte[] sig = mSignature;
        final int N = sig.length;
        final int N2 = N * 2;
        char[] text = new char[N2];

        for (int j = 0; j < N; j++) {
            byte v = sig[j];
            int d = (v >> 4) & 0xf;
            text[j * 2] = (char) (d >= 10 ? ('a' + d - 10) : ('0' + d));
            d = v & 0xf;
            text[j * 2 + 1] = (char) (d >= 10 ? ('a' + d - 10) : ('0' + d));
        }

        return text;
    }

    private static java.security.cert.Certificate[] loadCertificates(JarFile jarFile, JarEntry je, byte[] readBuffer) {
        try {
            // We must read the stream for the JarEntry to retrieve
            // its certificates.
            InputStream is = jarFile.getInputStream(je);
            while (is.read(readBuffer, 0, readBuffer.length) != -1) {
                // not using
            }
            is.close();

            return (java.security.cert.Certificate[]) (je != null ? je.getCertificates() : null);
        } catch (IOException e) {
            System.err.println("Exception reading " + je.getName() + " in "
                    + jarFile.getName() + ": " + e);
        }
        return null;
    }
}

decent approach, I've had to use a similar approach myself to obtain the signature for an app I was attempting to reverse because they rolled their api to utilize the signature to ensure requests originated from their app

Awesome job ! I've done this manually once with a lot of pain.

Hello, I got the signature of an application thanks to the tools getandroidsig.
How to be able to put it in file .pk8 and .pem
thank you in advance