/*
 * Copyright (c) 2003, 2019, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */


// common infrastructure for SunPKCS11 tests

import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.StringReader;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.security.AlgorithmParameters;
import java.security.InvalidAlgorithmParameterException;
import java.security.KeyPairGenerator;
import java.security.NoSuchProviderException;
import java.security.Policy;
import java.security.Provider;
import java.security.ProviderException;
import java.security.Security;
import java.security.spec.ECGenParameterSpec;
import java.security.spec.ECParameterSpec;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.Properties;
import java.util.ServiceConfigurationError;
import java.util.ServiceLoader;
import java.util.Set;

import jdk.test.lib.artifacts.Artifact;
import jdk.test.lib.artifacts.ArtifactResolver;
import jdk.test.lib.artifacts.ArtifactResolverException;

public abstract class PKCS11Test {

    private boolean enableSM = false;

    static final Properties props = System.getProperties();

    static final String PKCS11 = "PKCS11";

    // directory of the test source
    static final String BASE = System.getProperty("test.src", ".");

    static final char SEP = File.separatorChar;

    private static final String DEFAULT_POLICY =
            BASE + SEP + ".." + SEP + "policy";

    // directory corresponding to BASE in the /closed hierarchy
    static final String CLOSED_BASE;

    static {
        // hack
        String absBase = new File(BASE).getAbsolutePath();
        int k = absBase.indexOf(SEP + "test" + SEP + "sun" + SEP);
        if (k < 0) k = 0;
        String p1 = absBase.substring(0, k + 6);
        String p2 = absBase.substring(k + 5);
        CLOSED_BASE = p1 + "closed" + p2;

        // set it as a system property to make it available in policy file
        System.setProperty("closed.base", CLOSED_BASE);
    }

    // NSS version info
    public static enum ECCState { None, Basic, Extended };
    static double nss_version = -1;
    static ECCState nss_ecc_status = ECCState.Extended;

    // The NSS library we need to search for in getNSSLibDir()
    // Default is "libsoftokn3.so", listed as "softokn3"
    // The other is "libnss3.so", listed as "nss3".
    static String nss_library = "softokn3";

    // NSS versions of each library.  It is simplier to keep nss_version
    // for quick checking for generic testing than many if-else statements.
    static double softoken3_version = -1;
    static double nss3_version = -1;
    static Provider pkcs11;

    // Goes through ServiceLoader instead of Provider.getInstance() since it
    // works on all platforms
    static {
        ServiceLoader sl = ServiceLoader.load(java.security.Provider.class);
        Iterator<Provider> iter = sl.iterator();
        Provider p = null;
        boolean found = false;
        while (iter.hasNext()) {
            try {
                p = iter.next();
                if (p.getName().equals("SunPKCS11")) {
                    found = true;
                    break;
                }
            } catch (Exception | ServiceConfigurationError e) {
                // ignore and move on to the next one
            }
        }
        // Nothing found through ServiceLoader; fall back to reflection
        if (!found) {
            try {
                Class clazz = Class.forName("sun.security.pkcs11.SunPKCS11");
                p = (Provider) clazz.newInstance();
            } catch (Exception ex) {
                ex.printStackTrace();
            }
        }
        pkcs11 = p;
    }

    /*
     * Use Solaris SPARC 11.2 or later to avoid an intermittent failure
     * when running SunPKCS11-Solaris (8044554)
     */
    static boolean isBadSolarisSparc(Provider p) {
        if ("SunPKCS11-Solaris".equals(p.getName()) && badSolarisSparc) {
            System.out.println("SunPKCS11-Solaris provider requires " +
                "Solaris SPARC 11.2 or later, skipping");
            return true;
        }
        return false;
    }

    // Return a SunPKCS11 provider configured with the specified config file
    static Provider getSunPKCS11(String config) throws Exception {
        if (pkcs11 == null) {
            throw new NoSuchProviderException("No PKCS11 provider available");
        }
        return pkcs11.configure(config);
    }

    public abstract void main(Provider p) throws Exception;

    protected boolean skipTest(Provider p) {
        return false;
    }

    private void premain(Provider p) throws Exception {
        if (skipTest(p)) {
            return;
        }

        // set a security manager and policy before a test case runs,
        // and disable them after the test case finished
        try {
            if (enableSM) {
                System.setSecurityManager(new SecurityManager());
            }
            long start = System.currentTimeMillis();
            System.out.printf(
                    "Running test with provider %s (security manager %s) ...%n",
                        p.getName(), enableSM ? "enabled" : "disabled");
            main(p);
            long stop = System.currentTimeMillis();
            System.out.println("Completed test with provider " + p.getName() +
                " (" + (stop - start) + " ms).");
        } finally {
            if (enableSM) {
                System.setSecurityManager(null);
            }
        }
    }

    public static void main(PKCS11Test test) throws Exception {
        main(test, null);
    }

    public static void main(PKCS11Test test, String[] args) throws Exception {
        if (args != null) {
            if (args.length > 0) {
                if ("sm".equals(args[0])) {
                    test.enableSM = true;
                } else {
                    throw new RuntimeException("Unknown Command, use 'sm' as "
                            + "first arguemtn to enable security manager");
                }
            }
            if (test.enableSM) {
                System.setProperty("java.security.policy",
                        (args.length > 1) ? BASE + SEP + args[1]
                                : DEFAULT_POLICY);
            }
        }

        Provider[] oldProviders = Security.getProviders();
        try {
            System.out.println("Beginning test run " + test.getClass().getName() + "...");
            testDefault(test);
            testNSS(test);
            testDeimos(test);
        } finally {
            // NOTE: Do not place a 'return' in any finally block
            // as it will suppress exceptions and hide test failures.
            Provider[] newProviders = Security.getProviders();
            boolean found = true;
            // Do not restore providers if nothing changed. This is especailly
            // useful for ./Provider/Login.sh, where a SecurityManager exists.
            if (oldProviders.length == newProviders.length) {
                found = false;
                for (int i = 0; i<oldProviders.length; i++) {
                    if (oldProviders[i] != newProviders[i]) {
                        found = true;
                        break;
                    }
                }
            }
            if (found) {
                for (Provider p: newProviders) {
                    Security.removeProvider(p.getName());
                }
                for (Provider p: oldProviders) {
                    Security.addProvider(p);
                }
            }
        }
    }

    public static void testDeimos(PKCS11Test test) throws Exception {
        if (new File("/opt/SUNWconn/lib/libpkcs11.so").isFile() == false ||
            "true".equals(System.getProperty("NO_DEIMOS"))) {
            return;
        }
        String base = getBase();
        String p11config = base + SEP + "nss" + SEP + "p11-deimos.txt";
        Provider p = getSunPKCS11(p11config);
        test.premain(p);
    }

    public static void testDefault(PKCS11Test test) throws Exception {
        // run test for default configured PKCS11 providers (if any)

        if ("true".equals(System.getProperty("NO_DEFAULT"))) {
            return;
        }

        Provider[] providers = Security.getProviders();
        for (int i = 0; i < providers.length; i++) {
            Provider p = providers[i];
            if (p.getName().startsWith("SunPKCS11-")) {
                test.premain(p);
            }
        }
    }

    private static String PKCS11_BASE;
    static {
        try {
            PKCS11_BASE = getBase();
        } catch (Exception e) {
            // ignore
        }
    }

    private final static String PKCS11_REL_PATH = "sun/security/pkcs11";

    public static String getBase() throws Exception {
        if (PKCS11_BASE != null) {
            return PKCS11_BASE;
        }
        File cwd = new File(System.getProperty("test.src", ".")).getCanonicalFile();
        while (true) {
            File file = new File(cwd, "TEST.ROOT");
            if (file.isFile()) {
                break;
            }
            cwd = cwd.getParentFile();
            if (cwd == null) {
                throw new Exception("Test root directory not found");
            }
        }
        PKCS11_BASE = new File(cwd, PKCS11_REL_PATH.replace('/', SEP)).getAbsolutePath();
        return PKCS11_BASE;
    }

    public static String getNSSLibDir() throws Exception {
        return getNSSLibDir(nss_library);
    }

    static String getNSSLibDir(String library) throws Exception {
        Path libPath = getNSSLibPath(library);
        if (libPath == null) {
            return null;
        }

        String libDir = String.valueOf(libPath.getParent()) + File.separatorChar;
        System.out.println("nssLibDir: " + libDir);
        System.setProperty("pkcs11test.nss.libdir", libDir);
        return libDir;
    }

    private static Path getNSSLibPath() throws Exception {
        return getNSSLibPath(nss_library);
    }

    static Path getNSSLibPath(String library) throws Exception {
        String osid = getOsId();
        String[] nssLibDirs = getNssLibPaths(osid);
        if (nssLibDirs == null) {
            System.out.println("Warning: unsupported OS: " + osid
                    + ", please initialize NSS librarys location firstly, skipping test");
            return null;
        }
        if (nssLibDirs.length == 0) {
            System.out.println("Warning: NSS not supported on this platform, skipping test");
            return null;
        }

        Path nssLibPath = null;
        for (String dir : nssLibDirs) {
            Path libPath = Paths.get(dir).resolve(System.mapLibraryName(library));
            if (Files.exists(libPath)) {
                nssLibPath = libPath;
                break;
            }
        }
        if (nssLibPath == null) {
            System.out.println("Warning: can't find NSS librarys on this machine, skipping test");
            return null;
        }
        return nssLibPath;
    }

    private static String getOsId() {
        String osName = props.getProperty("os.name");
        if (osName.startsWith("Win")) {
            osName = "Windows";
        } else if (osName.equals("Mac OS X")) {
            osName = "MacOSX";
        }
        String osid = osName + "-" + props.getProperty("os.arch") + "-"
                + props.getProperty("sun.arch.data.model");
        return osid;
    }

    static boolean isBadNSSVersion(Provider p) {
        double nssVersion = getNSSVersion();
        if (isNSS(p) && nssVersion >= 3.11 && nssVersion < 3.12) {
            System.out.println("NSS 3.11 has a DER issue that recent " +
                    "version do not, skipping");
            return true;
        }
        return false;
    }

    protected static void safeReload(String lib) throws Exception {
        try {
            System.load(lib);
        } catch (UnsatisfiedLinkError e) {
            if (e.getMessage().contains("already loaded")) {
                return;
            }
        }
    }

    static boolean loadNSPR(String libdir) throws Exception {
        // load NSS softoken dependencies in advance to avoid resolver issues
        String dir = libdir.endsWith(File.separator)
                     ? libdir
                     : libdir + File.separator;
        safeReload(dir + System.mapLibraryName("nspr4"));
        safeReload(dir + System.mapLibraryName("plc4"));
        safeReload(dir + System.mapLibraryName("plds4"));
        safeReload(dir + System.mapLibraryName("sqlite3"));
        safeReload(dir + System.mapLibraryName("nssutil3"));
        return true;
    }

    // Check the provider being used is NSS
    public static boolean isNSS(Provider p) {
        return p.getName().toUpperCase().equals("SUNPKCS11-NSS");
    }

    static double getNSSVersion() {
        if (nss_version == -1)
            getNSSInfo();
        return nss_version;
    }

    static ECCState getNSSECC() {
        if (nss_version == -1)
            getNSSInfo();
        return nss_ecc_status;
    }

    public static double getLibsoftokn3Version() {
        if (softoken3_version == -1)
            return getNSSInfo("softokn3");
        return softoken3_version;
    }

    public static double getLibnss3Version() {
        if (nss3_version == -1)
            return getNSSInfo("nss3");
        return nss3_version;
    }

    /* Read the library to find out the verison */
    static void getNSSInfo() {
        getNSSInfo(nss_library);
    }

    // Try to parse the version for the specified library.
    // Assuming the library contains either of the following patterns:
    // $Header: NSS <version>
    // Version: NSS <version>
    // Here, <version> stands for NSS version.
    static double getNSSInfo(String library) {
        // look for two types of headers in NSS libraries
        String nssHeader1 = "$Header: NSS";
        String nssHeader2 = "Version: NSS";
        boolean found = false;
        String s = null;
        int i = 0;
        Path libfile = null;

        if (library.compareTo("softokn3") == 0 && softoken3_version > -1)
            return softoken3_version;
        if (library.compareTo("nss3") == 0 && nss3_version > -1)
            return nss3_version;

        try {
            libfile = getNSSLibPath();
            if (libfile == null) {
                return 0.0;
            }
            try (InputStream is = Files.newInputStream(libfile)) {
                byte[] data = new byte[1000];
                int read = 0;

                while (is.available() > 0) {
                    if (read == 0) {
                        read = is.read(data, 0, 1000);
                    } else {
                        // Prepend last 100 bytes in case the header was split
                        // between the reads.
                        System.arraycopy(data, 900, data, 0, 100);
                        read = 100 + is.read(data, 100, 900);
                    }

                    s = new String(data, 0, read, StandardCharsets.US_ASCII);
                    i = s.indexOf(nssHeader1);
                    if (i > 0 || (i = s.indexOf(nssHeader2)) > 0) {
                        found = true;
                        // If the nssHeader is before 920 we can break, otherwise
                        // we may not have the whole header so do another read.  If
                        // no bytes are in the stream, that is ok, found is true.
                        if (i < 920) {
                            break;
                        }
                    }
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

        if (!found) {
            System.out.println("lib" + library +
                    " version not found, set to 0.0: " + libfile);
            nss_version = 0.0;
            return nss_version;
        }

        // the index after whitespace after nssHeader
        int afterheader = s.indexOf("NSS", i) + 4;
        String version = String.valueOf(s.charAt(afterheader));
        for (char c = s.charAt(++afterheader);
                c == '.' || (c >= '0' && c <= '9');
                c = s.charAt(++afterheader)) {
            version += c;
        }

        // If a "dot dot" release, strip the extra dots for double parsing
        String[] dot = version.split("\\.");
        if (dot.length > 2) {
            version = dot[0]+"."+dot[1];
            for (int j = 2; dot.length > j; j++) {
                version += dot[j];
            }
        }

        // Convert to double for easier version value checking
        try {
            nss_version = Double.parseDouble(version);
        } catch (NumberFormatException e) {
            System.out.println("===== Content start =====");
            System.out.println(s);
            System.out.println("===== Content end =====");
            System.out.println("Failed to parse lib" + library +
                    " version. Set to 0.0");
            e.printStackTrace();
        }

        System.out.print("lib" + library + " version = "+version+".  ");

        // Check for ECC
        if (s.indexOf("Basic") > 0) {
            nss_ecc_status = ECCState.Basic;
            System.out.println("ECC Basic.");
        } else if (s.indexOf("Extended") > 0) {
            nss_ecc_status = ECCState.Extended;
            System.out.println("ECC Extended.");
        } else {
            System.out.println("ECC None.");
        }

        if (library.compareTo("softokn3") == 0) {
            softoken3_version = nss_version;
        } else if (library.compareTo("nss3") == 0) {
            nss3_version = nss_version;
        }

        return nss_version;
    }

    // Used to set the nss_library file to search for libsoftokn3.so
    public static void useNSS() {
        nss_library = "nss3";
    }

    public static void testNSS(PKCS11Test test) throws Exception {
        String libdir = getNSSLibDir();
        if (libdir == null) {
            return;
        }
        String base = getBase();

        if (loadNSPR(libdir) == false) {
            return;
        }

        String libfile = libdir + System.mapLibraryName(nss_library);

        String customDBdir = System.getProperty("CUSTOM_DB_DIR");
        String dbdir = (customDBdir != null) ?
                                customDBdir :
                                base + SEP + "nss" + SEP + "db";
        // NSS always wants forward slashes for the config path
        dbdir = dbdir.replace('\\', '/');

        String customConfig = System.getProperty("CUSTOM_P11_CONFIG");
        String customConfigName = System.getProperty("CUSTOM_P11_CONFIG_NAME", "p11-nss.txt");
        String p11config = (customConfig != null) ?
                                customConfig :
                                base + SEP + "nss" + SEP + customConfigName;

        System.setProperty("pkcs11test.nss.lib", libfile);
        System.setProperty("pkcs11test.nss.db", dbdir);
        Provider p = getSunPKCS11(p11config);
        test.premain(p);
    }

    // Generate a vector of supported elliptic curves of a given provider
    static List<ECParameterSpec> getKnownCurves(Provider p) throws Exception {
        int index;
        int begin;
        int end;
        String curve;

        List<ECParameterSpec> results = new ArrayList<>();
        // Get Curves to test from SunEC.
        String kcProp = Security.getProvider("SunEC").
                getProperty("AlgorithmParameters.EC SupportedCurves");

        if (kcProp == null) {
            throw new RuntimeException(
            "\"AlgorithmParameters.EC SupportedCurves property\" not found");
        }

        System.out.println("Finding supported curves using list from SunEC\n");
        index = 0;
        for (;;) {
            // Each set of curve names is enclosed with brackets.
            begin = kcProp.indexOf('[', index);
            end = kcProp.indexOf(']', index);
            if (begin == -1 || end == -1) {
                break;
            }

            /*
             * Each name is separated by a comma.
             * Just get the first name in the set.
             */
            index = end + 1;
            begin++;
            end = kcProp.indexOf(',', begin);
            if (end == -1) {
                // Only one name in the set.
                end = index -1;
            }

            curve = kcProp.substring(begin, end);
            getSupportedECParameterSpec(curve, p)
                .ifPresent(spec -> results.add(spec));
        }

        if (results.size() == 0) {
            throw new RuntimeException("No supported EC curves found");
        }

        return results;
    }

    static Optional<ECParameterSpec> getSupportedECParameterSpec(String curve,
            Provider p) throws Exception {
        ECParameterSpec e = getECParameterSpec(p, curve);
        System.out.print("\t "+ curve + ": ");
        try {
            KeyPairGenerator kpg = KeyPairGenerator.getInstance("EC", p);
            kpg.initialize(e);
            kpg.generateKeyPair();
            System.out.println("Supported");
            return Optional.of(e);
        } catch (ProviderException ex) {
            System.out.println("Unsupported: PKCS11: " +
                    ex.getCause().getMessage());
            return Optional.empty();
        } catch (InvalidAlgorithmParameterException ex) {
            System.out.println("Unsupported: Key Length: " +
                    ex.getMessage());
            return Optional.empty();
        }
    }

    private static ECParameterSpec getECParameterSpec(Provider p, String name)
            throws Exception {

        AlgorithmParameters parameters =
            AlgorithmParameters.getInstance("EC", p);

        parameters.init(new ECGenParameterSpec(name));

        return parameters.getParameterSpec(ECParameterSpec.class);
    }

    // Check support for a curve with a provided Vector of EC support
    boolean checkSupport(List<ECParameterSpec> supportedEC,
            ECParameterSpec curve) {
        for (ECParameterSpec ec: supportedEC) {
            if (ec.equals(curve)) {
                return true;
            }
        }
        return false;
    }

    private static Map<String,String[]> osMap;

    // Location of the NSS libraries on each supported platform
    private static Map<String, String[]> getOsMap() {
        if (osMap != null) {
            return osMap;
        }

        osMap = new HashMap<>();
        osMap.put("SunOS-sparc-32", new String[] { "/usr/lib/mps/" });
        osMap.put("SunOS-sparcv9-64", new String[] { "/usr/lib/mps/64/" });
        osMap.put("SunOS-x86-32", new String[] { "/usr/lib/mps/" });
        osMap.put("SunOS-amd64-64", new String[] { "/usr/lib/mps/64/" });
        osMap.put("Linux-i386-32", new String[] {
                "/usr/lib/i386-linux-gnu/",
                "/usr/lib32/",
                "/usr/lib/" });
        osMap.put("Linux-amd64-64", new String[] {
                "/usr/lib/x86_64-linux-gnu/",
                "/usr/lib/x86_64-linux-gnu/nss/",
                "/usr/lib64/" });
        osMap.put("Linux-ppc64-64", new String[] { "/usr/lib64/" });
        osMap.put("Linux-ppc64le-64", new String[] { "/usr/lib64/" });
        osMap.put("Linux-s390x-64", new String[] { "/usr/lib64/" });
        osMap.put("Windows-x86-32", new String[] {});
        osMap.put("Windows-amd64-64", new String[] {});
        osMap.put("MacOSX-x86_64-64", new String[] {});
        osMap.put("Linux-arm-32", new String[] {
                "/usr/lib/arm-linux-gnueabi/nss/",
                "/usr/lib/arm-linux-gnueabihf/nss/" });
        osMap.put("Linux-aarch64-64", new String[] {
                "/usr/lib/aarch64-linux-gnu/",
                "/usr/lib/aarch64-linux-gnu/nss/" });
        return osMap;
    }

    private static String[] getNssLibPaths(String osId) {
        String[] preferablePaths = getPreferableNssLibPaths(osId);
        if (preferablePaths.length != 0) {
            return preferablePaths;
        } else {
            return getOsMap().get(osId);
        }
    }

    private static String[] getPreferableNssLibPaths(String osId) {
        List<String> nssLibPaths = new ArrayList<>();

        String customNssLibPaths = System.getProperty("test.nss.lib.paths");
        if (customNssLibPaths == null) {
            // If custom local NSS lib path is not provided,
            // try to download NSS libs from artifactory
            String path = fetchNssLib(osId);
            if (path != null) {
                nssLibPaths.add(path);
            }
        } else {
            String[] paths = customNssLibPaths.split(",");
            for (String path : paths) {
                if (!path.endsWith(File.separator)) {
                    nssLibPaths.add(path + File.separator);
                } else {
                    nssLibPaths.add(path);
                }
            }
        }

        return nssLibPaths.toArray(new String[nssLibPaths.size()]);
    }

    private final static char[] hexDigits = "0123456789abcdef".toCharArray();

    private static final String distro = distro();

    static final boolean badSolarisSparc =
            System.getProperty("os.name").equals("SunOS") &&
            System.getProperty("os.arch").equals("sparcv9") &&
            System.getProperty("os.version").compareTo("5.11") <= 0 &&
            getDistro().compareTo("11.2") < 0;

    public static String toString(byte[] b) {
        if (b == null) {
            return "(null)";
        }
        StringBuilder sb = new StringBuilder(b.length * 3);
        for (int i = 0; i < b.length; i++) {
            int k = b[i] & 0xff;
            if (i != 0) {
                sb.append(':');
            }
            sb.append(hexDigits[k >>> 4]);
            sb.append(hexDigits[k & 0xf]);
        }
        return sb.toString();
    }

    public static byte[] parse(String s) {
        if (s.equals("(null)")) {
            return null;
        }
        try {
            int n = s.length();
            ByteArrayOutputStream out = new ByteArrayOutputStream(n / 3);
            StringReader r = new StringReader(s);
            while (true) {
                int b1 = nextNibble(r);
                if (b1 < 0) {
                    break;
                }
                int b2 = nextNibble(r);
                if (b2 < 0) {
                    throw new RuntimeException("Invalid string " + s);
                }
                int b = (b1 << 4) | b2;
                out.write(b);
            }
            return out.toByteArray();
        } catch (IOException e) {
            throw new RuntimeException(e);
        }
    }

    private static int nextNibble(StringReader r) throws IOException {
        while (true) {
            int ch = r.read();
            if (ch == -1) {
                return -1;
            } else if ((ch >= '0') && (ch <= '9')) {
                return ch - '0';
            } else if ((ch >= 'a') && (ch <= 'f')) {
                return ch - 'a' + 10;
            } else if ((ch >= 'A') && (ch <= 'F')) {
                return ch - 'A' + 10;
            }
        }
    }

    <T> T[] concat(T[] a, T[] b) {
        if ((b == null) || (b.length == 0)) {
            return a;
        }
        T[] r = Arrays.copyOf(a, a.length + b.length);
        System.arraycopy(b, 0, r, a.length, b.length);
        return r;
    }

    /**
     * Returns supported algorithms of specified type.
     */
    static List<String> getSupportedAlgorithms(String type, String alg,
            Provider p) {
        // prepare a list of supported algorithms
        List<String> algorithms = new ArrayList<>();
        Set<Provider.Service> services = p.getServices();
        for (Provider.Service service : services) {
            if (service.getType().equals(type)
                    && service.getAlgorithm().startsWith(alg)) {
                algorithms.add(service.getAlgorithm());
            }
        }
        return algorithms;
    }

    /**
     * Get the identifier for the operating system distribution
     */
    static String getDistro() {
        return distro;
    }

    private static String distro() {
        if (props.getProperty("os.name").equals("SunOS")) {
            try (BufferedReader in =
                         new BufferedReader(new InputStreamReader(
                                 Runtime.getRuntime().exec("uname -v").getInputStream()))) {

                return in.readLine();
            } catch (Exception e) {
                throw new RuntimeException("Failed to determine distro.", e);
            }
        } else {
            // Not used outside Solaris
            return null;
        }
    }

    static byte[] generateData(int length) {
        byte data[] = new byte[length];
        for (int i=0; i<data.length; i++) {
            data[i] = (byte) (i % 256);
        }
        return data;
    }

    private static String fetchNssLib(String osId) {
        switch (osId) {
        case "Windows-x86-32":
            return fetchNssLib(WINDOWS_X86.class);

        case "Windows-amd64-64":
            return fetchNssLib(WINDOWS_X64.class);

        case "MacOSX-x86_64-64":
            return fetchNssLib(MACOSX_X64.class);

        case "Linux-amd64-64":
            return fetchNssLib(LINUX_X64.class);

        default:
            return null;
        }
    }

    private static String fetchNssLib(Class<?> clazz) {
        String path = null;
        try {
            path = ArtifactResolver.resolve(clazz).entrySet().stream()
                    .findAny().get().getValue() + File.separator + "nsslib"
                    + File.separator;
        } catch (ArtifactResolverException e) {
            Throwable cause = e.getCause();
            if (cause == null) {
                System.out.println("Cannot resolve artifact, "
                        + "please check if JIB jar is present in classpath.");
            } else {
                throw new RuntimeException("Fetch artifact failed: " + clazz
                        + "\nPlease make sure the artifact is available.");
            }
        }
        Policy.setPolicy(null); // Clear the policy created by JIB if any
        return path;
    }

    @Artifact(
            organization = "jpg.tests.jdk.nsslib",
            name = "nsslib-windows_x64",
            revision = "3.46-VS2017",
            extension = "zip")
    private static class WINDOWS_X64 { }

    @Artifact(
            organization = "jpg.tests.jdk.nsslib",
            name = "nsslib-windows_x86",
            revision = "3.46-VS2017",
            extension = "zip")
    private static class WINDOWS_X86 { }

    @Artifact(
            organization = "jpg.tests.jdk.nsslib",
            name = "nsslib-macosx_x64",
            revision = "3.46",
            extension = "zip")
    private static class MACOSX_X64 { }

    @Artifact(
            organization = "jpg.tests.jdk.nsslib",
            name = "nsslib-linux_x64",
            revision = "3.46",
            extension = "zip")
    private static class LINUX_X64 { }
}