510Connectbot: src/com/trilead/ssh2/KnownHosts.java comparison

comparison src/com/trilead/ssh2/KnownHosts.java @ 0:0ce5cc452d02

initial version

author	Carl Byington <carl@five-ten-sg.com>
date	Thu, 22 May 2014 10:41:19 -0700
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--1:000000000000
+:0ce5cc452d02
+package com.trilead.ssh2;
+import java.io.BufferedReader;
+import java.io.CharArrayReader;
+import java.io.CharArrayWriter;
+import java.io.File;
+import java.io.FileReader;
+import java.io.IOException;
+import java.io.RandomAccessFile;
+import java.io.UnsupportedEncodingException;
+import java.net.InetAddress;
+import java.net.UnknownHostException;
+import java.security.InvalidKeyException;
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+import java.security.PublicKey;
+import java.security.SecureRandom;
+import java.security.interfaces.DSAPublicKey;
+import java.security.interfaces.ECPublicKey;
+import java.security.interfaces.RSAPublicKey;
+import java.util.Iterator;
+import java.util.LinkedList;
+import java.util.Locale;
+import java.util.Vector;
+import javax.crypto.Mac;
+import javax.crypto.spec.SecretKeySpec;
+import com.trilead.ssh2.crypto.Base64;
+import com.trilead.ssh2.signature.DSASHA1Verify;
+import com.trilead.ssh2.signature.ECDSASHA2Verify;
+import com.trilead.ssh2.signature.RSASHA1Verify;
+/**
+* The <code>KnownHosts</code> class is a handy tool to verify received server hostkeys
+* based on the information in <code>known_hosts</code> files (the ones used by OpenSSH).
+* <p>
+* It offers basically an in-memory database for known_hosts entries, as well as some
+* helper functions. Entries from a <code>known_hosts</code> file can be loaded at construction time.
+* It is also possible to add more keys later (e.g., one can parse different
+* <code>known_hosts<code> files).
+* <p>
+* It is a thread safe implementation, therefore, you need only to instantiate one
+* <code>KnownHosts</code> for your whole application.
+*
+* @author Christian Plattner, plattner@trilead.com
+* @version $Id: KnownHosts.java,v 1.2 2008/04/01 12:38:09 cplattne Exp $
+*/
+public class KnownHosts {
+public static final int HOSTKEY_IS_OK = 0;
+public static final int HOSTKEY_IS_NEW = 1;
+public static final int HOSTKEY_HAS_CHANGED = 2;
+private class KnownHostsEntry {
+String[] patterns;
+PublicKey key;
+KnownHostsEntry(String[] patterns, PublicKey key) {
+this.patterns = patterns;
+this.key = key;
+}
+}
+private LinkedList<KnownHostsEntry> publicKeys = new LinkedList<KnownHostsEntry>();
+public KnownHosts() {
+}
+public KnownHosts(char[] knownHostsData) throws IOException {
+initialize(knownHostsData);
+}
+public KnownHosts(File knownHosts) throws IOException {
+initialize(knownHosts);
+}
+/**
+* Adds a single public key entry to the database. Note: this will NOT add the public key
+* to any physical file (e.g., "~/.ssh/known_hosts") - use <code>addHostkeyToFile()</code> for that purpose.
+* This method is designed to be used in a {@link ServerHostKeyVerifier}.
+*
+* @param hostnames a list of hostname patterns - at least one most be specified. Check out the
+*        OpenSSH sshd man page for a description of the pattern matching algorithm.
+* @param serverHostKeyAlgorithm as passed to the {@link ServerHostKeyVerifier}.
+* @param serverHostKey as passed to the {@link ServerHostKeyVerifier}.
+* @throws IOException
+*/
+public void addHostkey(String hostnames[], String serverHostKeyAlgorithm, byte[] serverHostKey) throws IOException {
+if (hostnames == null)
+throw new IllegalArgumentException("hostnames may not be null");
+if ("ssh-rsa".equals(serverHostKeyAlgorithm)) {
+RSAPublicKey rpk = RSASHA1Verify.decodeSSHRSAPublicKey(serverHostKey);
+synchronized (publicKeys) {
+publicKeys.add(new KnownHostsEntry(hostnames, rpk));
+}
+}
+else if ("ssh-dss".equals(serverHostKeyAlgorithm)) {
+DSAPublicKey dpk = DSASHA1Verify.decodeSSHDSAPublicKey(serverHostKey);
+synchronized (publicKeys) {
+publicKeys.add(new KnownHostsEntry(hostnames, dpk));
+}
+}
+else if (serverHostKeyAlgorithm.startsWith(ECDSASHA2Verify.ECDSA_SHA2_PREFIX)) {
+ECPublicKey epk = ECDSASHA2Verify.decodeSSHECDSAPublicKey(serverHostKey);
+synchronized (publicKeys) {
+publicKeys.add(new KnownHostsEntry(hostnames, epk));
+}
+}
+else
+throw new IOException("Unknwon host key type (" + serverHostKeyAlgorithm + ")");
+}
+/**
+* Parses the given known_hosts data and adds entries to the database.
+*
+* @param knownHostsData
+* @throws IOException
+*/
+public void addHostkeys(char[] knownHostsData) throws IOException {
+initialize(knownHostsData);
+}
+/**
+* Parses the given known_hosts file and adds entries to the database.
+*
+* @param knownHosts
+* @throws IOException
+*/
+public void addHostkeys(File knownHosts) throws IOException {
+initialize(knownHosts);
+}
+/**
+* Generate the hashed representation of the given hostname. Useful for adding entries
+* with hashed hostnames to a known_hosts file. (see -H option of OpenSSH key-gen).
+*
+* @param hostname
+* @return the hashed representation, e.g., "|1|cDhrv7zwEUV3k71CEPHnhHZezhA=|Xo+2y6rUXo2OIWRAYhBOIijbJMA="
+*/
+public static final String createHashedHostname(String hostname) {
+MessageDigest sha1;
+try {
+sha1 = MessageDigest.getInstance("SHA1");
+}
+catch (NoSuchAlgorithmException e) {
+throw new RuntimeException("VM doesn't support SHA1", e);
+}
+byte[] salt = new byte[sha1.getDigestLength()];
+new SecureRandom().nextBytes(salt);
+byte[] hash = hmacSha1Hash(salt, hostname);
+String base64_salt = new String(Base64.encode(salt));
+String base64_hash = new String(Base64.encode(hash));
+return new String("|1|" + base64_salt + "|" + base64_hash);
+}
+private static final byte[] hmacSha1Hash(byte[] salt, String hostname) {
+Mac hmac;
+try {
+hmac = Mac.getInstance("HmacSHA1");
+if (salt.length != hmac.getMacLength())
+throw new IllegalArgumentException("Salt has wrong length (" + salt.length + ")");
+hmac.init(new SecretKeySpec(salt, "HmacSHA1"));
+}
+catch (NoSuchAlgorithmException e) {
+throw new RuntimeException("Unable to HMAC-SHA1", e);
+}
+catch (InvalidKeyException e) {
+throw new RuntimeException("Unable to create SecretKey", e);
+}
+try {
+hmac.update(hostname.getBytes("ISO-8859-1"));
+}
+catch (UnsupportedEncodingException ignore) {
+/* Actually, ISO-8859-1 is supported by all correct
+* Java implementations. But... you never know. */
+hmac.update(hostname.getBytes());
+}
+return hmac.doFinal();
+}
+private final boolean checkHashed(String entry, String hostname) {
+if (entry.startsWith("|1|") == false)
+return false;
+int delim_idx = entry.indexOf('|', 3);
+if (delim_idx == -1)
+return false;
+String salt_base64 = entry.substring(3, delim_idx);
+String hash_base64 = entry.substring(delim_idx + 1);
+byte[] salt = null;
+byte[] hash = null;
+try {
+salt = Base64.decode(salt_base64.toCharArray());
+hash = Base64.decode(hash_base64.toCharArray());
+}
+catch (IOException e) {
+return false;
+}
+try {
+MessageDigest sha1 = MessageDigest.getInstance("SHA1");
+if (salt.length != sha1.getDigestLength())
+return false;
+}
+catch (NoSuchAlgorithmException e) {
+throw new RuntimeException("VM does not support SHA1", e);
+}
+byte[] dig = hmacSha1Hash(salt, hostname);
+for (int i = 0; i < dig.length; i++)
+if (dig[i] != hash[i])
+return false;
+return true;
+}
+private int checkKey(String remoteHostname, PublicKey remoteKey) {
+int result = HOSTKEY_IS_NEW;
+synchronized (publicKeys) {
+Iterator<KnownHostsEntry> i = publicKeys.iterator();
+while (i.hasNext()) {
+KnownHostsEntry ke = i.next();
+if (hostnameMatches(ke.patterns, remoteHostname) == false)
+continue;
+boolean res = matchKeys(ke.key, remoteKey);
+if (res == true)
+return HOSTKEY_IS_OK;
+result = HOSTKEY_HAS_CHANGED;
+}
+}
+return result;
+}
+private Vector<PublicKey> getAllKeys(String hostname) {
+Vector<PublicKey> keys = new Vector<PublicKey>();
+synchronized (publicKeys) {
+Iterator<KnownHostsEntry> i = publicKeys.iterator();
+while (i.hasNext()) {
+KnownHostsEntry ke = i.next();
+if (hostnameMatches(ke.patterns, hostname) == false)
+continue;
+keys.addElement(ke.key);
+}
+}
+return keys;
+}
+/**
+* Try to find the preferred order of hostkey algorithms for the given hostname.
+* Based on the type of hostkey that is present in the internal database
+* (i.e., either <code>ssh-rsa</code> or <code>ssh-dss</code>)
+* an ordered list of hostkey algorithms is returned which can be passed
+* to <code>Connection.setServerHostKeyAlgorithms</code>.
+*
+* @param hostname
+* @return <code>null</code> if no key for the given hostname is present or
+* there are keys of multiple types present for the given hostname. Otherwise,
+* an array with hostkey algorithms is returned (i.e., an array of length 2).
+*/
+public String[] getPreferredServerHostkeyAlgorithmOrder(String hostname) {
+String[] algos = recommendHostkeyAlgorithms(hostname);
+if (algos != null)
+return algos;
+InetAddress[] ipAdresses = null;
+try {
+ipAdresses = InetAddress.getAllByName(hostname);
+}
+catch (UnknownHostException e) {
+return null;
+}
+for (int i = 0; i < ipAdresses.length; i++) {
+algos = recommendHostkeyAlgorithms(ipAdresses[i].getHostAddress());
+if (algos != null)
+return algos;
+}
+return null;
+}
+private final boolean hostnameMatches(String[] hostpatterns, String hostname) {
+boolean isMatch = false;
+boolean negate = false;
+hostname = hostname.toLowerCase(Locale.US);
+for (int k = 0; k < hostpatterns.length; k++) {
+if (hostpatterns[k] == null)
+continue;
+String pattern = null;
+/* In contrast to OpenSSH we also allow negated hash entries (as well as hashed
+* entries in lines with multiple entries).
+*/
+if ((hostpatterns[k].length() > 0) && (hostpatterns[k].charAt(0) == '!')) {
+pattern = hostpatterns[k].substring(1);
+negate = true;
+}
+else {
+pattern = hostpatterns[k];
+negate = false;
+}
+/* Optimize, no need to check this entry */
+if ((isMatch) && (negate == false))
+continue;
+/* Now compare */
+if (pattern.charAt(0) == '|') {
+if (checkHashed(pattern, hostname)) {
+if (negate)
+return false;
+isMatch = true;
+}
+}
+else {
+pattern = pattern.toLowerCase(Locale.US);
+if ((pattern.indexOf('?') != -1) || (pattern.indexOf('*') != -1)) {
+if (pseudoRegex(pattern.toCharArray(), 0, hostname.toCharArray(), 0)) {
+if (negate)
+return false;
+isMatch = true;
+}
+}
+else if (pattern.compareTo(hostname) == 0) {
+if (negate)
+return false;
+isMatch = true;
+}
+}
+}
+return isMatch;
+}
+private void initialize(char[] knownHostsData) throws IOException {
+BufferedReader br = new BufferedReader(new CharArrayReader(knownHostsData));
+while (true) {
+String line = br.readLine();
+if (line == null)
+break;
+line = line.trim();
+if (line.startsWith("#"))
+continue;
+String[] arr = line.split(" ");
+if (arr.length >= 3) {
+if ((arr[1].compareTo("ssh-rsa") == 0) || (arr[1].compareTo("ssh-dss") == 0)) {
+String[] hostnames = arr[0].split(",");
+byte[] msg = Base64.decode(arr[2].toCharArray());
+addHostkey(hostnames, arr[1], msg);
+}
+}
+}
+}
+private void initialize(File knownHosts) throws IOException {
+char[] buff = new char[512];
+CharArrayWriter cw = new CharArrayWriter();
+knownHosts.createNewFile();
+FileReader fr = new FileReader(knownHosts);
+while (true) {
+int len = fr.read(buff);
+if (len < 0)
+break;
+cw.write(buff, 0, len);
+}
+fr.close();
+initialize(cw.toCharArray());
+}
+private final boolean matchKeys(PublicKey key1, PublicKey key2) {
+return key1.equals(key2);
+}
+private final boolean pseudoRegex(char[] pattern, int i, char[] match, int j) {
+/* This matching logic is equivalent to the one present in OpenSSH 4.1 */
+while (true) {
+/* Are we at the end of the pattern? */
+if (pattern.length == i)
+return (match.length == j);
+if (pattern[i] == '*') {
+i++;
+if (pattern.length == i)
+return true;
+if ((pattern[i] != '*') && (pattern[i] != '?')) {
+while (true) {
+if ((pattern[i] == match[j]) && pseudoRegex(pattern, i + 1, match, j + 1))
+return true;
+j++;
+if (match.length == j)
+return false;
+}
+}
+while (true) {
+if (pseudoRegex(pattern, i, match, j))
+return true;
+j++;
+if (match.length == j)
+return false;
+}
+}
+if (match.length == j)
+return false;
+if ((pattern[i] != '?') && (pattern[i] != match[j]))
+return false;
+i++;
+j++;
+}
+}
+private String[] recommendHostkeyAlgorithms(String hostname) {
+String preferredAlgo = null;
+Vector<PublicKey> keys = getAllKeys(hostname);
+for (int i = 0; i < keys.size(); i++) {
+String thisAlgo = null;
+if (keys.elementAt(i) instanceof RSAPublicKey)
+thisAlgo = "ssh-rsa";
+else if (keys.elementAt(i) instanceof DSAPublicKey)
+thisAlgo = "ssh-dss";
+else
+continue;
+if (preferredAlgo != null) {
+/* If we find different key types, then return null */
+if (preferredAlgo.compareTo(thisAlgo) != 0)
+return null;
+/* OK, we found the same algo again, optimize */
+continue;
+}
+}
+/* If we did not find anything that we know of, return null */
+if (preferredAlgo == null)
+return null;
+/* Now put the preferred algo to the start of the array.
+* You may ask yourself why we do it that way - basically, we could just
+* return only the preferred algorithm: since we have a saved key of that
+* type (sent earlier from the remote host), then that should work out.
+* However, imagine that the server is (for whatever reasons) not offering
+* that type of hostkey anymore (e.g., "ssh-rsa" was disabled and
+* now "ssh-dss" is being used). If we then do not let the server send us
+* a fresh key of the new type, then we shoot ourself into the foot:
+* the connection cannot be established and hence the user cannot decide
+* if he/she wants to accept the new key.
+*/
+if (preferredAlgo.equals("ssh-rsa"))
+return new String[] { "ssh-rsa", "ssh-dss" };
+return new String[] { "ssh-dss", "ssh-rsa" };
+}
+/**
+* Checks the internal hostkey database for the given hostkey.
+* If no matching key can be found, then the hostname is resolved to an IP address
+* and the search is repeated using that IP address.
+*
+* @param hostname the server's hostname, will be matched with all hostname patterns
+* @param serverHostKeyAlgorithm type of hostkey, either <code>ssh-rsa</code> or <code>ssh-dss</code>
+* @param serverHostKey the key blob
+* @return <ul>
+*         <li><code>HOSTKEY_IS_OK</code>: the given hostkey matches an entry for the given hostname</li>
+*         <li><code>HOSTKEY_IS_NEW</code>: no entries found for this hostname and this type of hostkey</li>
+*         <li><code>HOSTKEY_HAS_CHANGED</code>: hostname is known, but with another key of the same type
+*         (man-in-the-middle attack?)</li>
+*         </ul>
+* @throws IOException if the supplied key blob cannot be parsed or does not match the given hostkey type.
+*/
+public int verifyHostkey(String hostname, String serverHostKeyAlgorithm, byte[] serverHostKey) throws IOException {
+PublicKey remoteKey = null;
+if ("ssh-rsa".equals(serverHostKeyAlgorithm)) {
+remoteKey = RSASHA1Verify.decodeSSHRSAPublicKey(serverHostKey);
+}
+else if ("ssh-dss".equals(serverHostKeyAlgorithm)) {
+remoteKey = DSASHA1Verify.decodeSSHDSAPublicKey(serverHostKey);
+}
+else if (serverHostKeyAlgorithm.startsWith("ecdsa-sha2-")) {
+remoteKey = ECDSASHA2Verify.decodeSSHECDSAPublicKey(serverHostKey);
+}
+else
+throw new IllegalArgumentException("Unknown hostkey type " + serverHostKeyAlgorithm);
+int result = checkKey(hostname, remoteKey);
+if (result == HOSTKEY_IS_OK)
+return result;
+InetAddress[] ipAdresses = null;
+try {
+ipAdresses = InetAddress.getAllByName(hostname);
+}
+catch (UnknownHostException e) {
+return result;
+}
+for (int i = 0; i < ipAdresses.length; i++) {
+int newresult = checkKey(ipAdresses[i].getHostAddress(), remoteKey);
+if (newresult == HOSTKEY_IS_OK)
+return newresult;
+if (newresult == HOSTKEY_HAS_CHANGED)
+result = HOSTKEY_HAS_CHANGED;
+}
+return result;
+}
+/**
+* Adds a single public key entry to the a known_hosts file.
+* This method is designed to be used in a {@link ServerHostKeyVerifier}.
+*
+* @param knownHosts the file where the publickey entry will be appended.
+* @param hostnames a list of hostname patterns - at least one most be specified. Check out the
+*        OpenSSH sshd man page for a description of the pattern matching algorithm.
+* @param serverHostKeyAlgorithm as passed to the {@link ServerHostKeyVerifier}.
+* @param serverHostKey as passed to the {@link ServerHostKeyVerifier}.
+* @throws IOException
+*/
+public final static void addHostkeyToFile(File knownHosts, String[] hostnames, String serverHostKeyAlgorithm,
+byte[] serverHostKey) throws IOException {
+if ((hostnames == null) || (hostnames.length == 0))
+throw new IllegalArgumentException("Need at least one hostname specification");
+if ((serverHostKeyAlgorithm == null) || (serverHostKey == null))
+throw new IllegalArgumentException();
+CharArrayWriter writer = new CharArrayWriter();
+for (int i = 0; i < hostnames.length; i++) {
+if (i != 0)
+writer.write(',');
+writer.write(hostnames[i]);
+}
+writer.write(' ');
+writer.write(serverHostKeyAlgorithm);
+writer.write(' ');
+writer.write(Base64.encode(serverHostKey));
+writer.write("\n");
+char[] entry = writer.toCharArray();
+RandomAccessFile raf = new RandomAccessFile(knownHosts, "rw");
+long len = raf.length();
+if (len > 0) {
+raf.seek(len - 1);
+int last = raf.read();
+if (last != '\n')
+raf.write('\n');
+}
+raf.write(new String(entry).getBytes("ISO-8859-1"));
+raf.close();
+}
+/**
+* Generates a "raw" fingerprint of a hostkey.
+*
+* @param type either "md5" or "sha1"
+* @param keyType either "ssh-rsa" or "ssh-dss"
+* @param hostkey the hostkey
+* @return the raw fingerprint
+*/
+static final private byte[] rawFingerPrint(String type, String keyType, byte[] hostkey) {
+MessageDigest dig = null;
+try {
+if ("md5".equals(type)) {
+dig = MessageDigest.getInstance("MD5");
+}
+else if ("sha1".equals(type)) {
+dig = MessageDigest.getInstance("SHA1");
+}
+else {
+throw new IllegalArgumentException("Unknown hash type " + type);
+}
+}
+catch (NoSuchAlgorithmException e) {
+throw new IllegalArgumentException("Unknown hash type " + type);
+}
+if (keyType.startsWith("ecdsa-sha2-")) {
+}
+else if ("ssh-rsa".equals(keyType)) {
+}
+else if ("ssh-dss".equals(keyType)) {
+}
+else
+throw new IllegalArgumentException("Unknown key type " + keyType);
+if (hostkey == null)
+throw new IllegalArgumentException("hostkey is null");
+dig.update(hostkey);
+return dig.digest();
+}
+/**
+* Convert a raw fingerprint to hex representation (XX:YY:ZZ...).
+* @param fingerprint raw fingerprint
+* @return the hex representation
+*/
+static final private String rawToHexFingerprint(byte[] fingerprint) {
+final char[] alpha = "0123456789abcdef".toCharArray();
+StringBuffer sb = new StringBuffer();
+for (int i = 0; i < fingerprint.length; i++) {
+if (i != 0)
+sb.append(':');
+int b = fingerprint[i] & 0xff;
+sb.append(alpha[b >> 4]);
+sb.append(alpha[b & 15]);
+}
+return sb.toString();
+}
+/**
+* Convert a raw fingerprint to bubblebabble representation.
+* @param raw raw fingerprint
+* @return the bubblebabble representation
+*/
+static final private String rawToBubblebabbleFingerprint(byte[] raw) {
+final char[] v = "aeiouy".toCharArray();
+final char[] c = "bcdfghklmnprstvzx".toCharArray();
+StringBuffer sb = new StringBuffer();
+int seed = 1;
+int rounds = (raw.length / 2) + 1;
+sb.append('x');
+for (int i = 0; i < rounds; i++) {
+if (((i + 1) < rounds) || ((raw.length) % 2 != 0)) {
+sb.append(v[(((raw[2 * i] >> 6) & 3) + seed) % 6]);
+sb.append(c[(raw[2 * i] >> 2) & 15]);
+sb.append(v[((raw[2 * i] & 3) + (seed / 6)) % 6]);
+if ((i + 1) < rounds) {
+sb.append(c[(((raw[(2 * i) + 1])) >> 4) & 15]);
+sb.append('-');
+sb.append(c[(((raw[(2 * i) + 1]))) & 15]);
+// As long as seed >= 0, seed will be >= 0 afterwards
+seed = ((seed * 5) + (((raw[2 * i] & 0xff) * 7) + (raw[(2 * i) + 1] & 0xff))) % 36;
+}
+}
+else {
+sb.append(v[seed % 6]); // seed >= 0, therefore index positive
+sb.append('x');
+sb.append(v[seed / 6]);
+}
+}
+sb.append('x');
+return sb.toString();
+}
+/**
+* Convert a ssh2 key-blob into a human readable hex fingerprint.
+* Generated fingerprints are identical to those generated by OpenSSH.
+* <p>
+* Example fingerprint: d0:cb:76:19:99:5a:03:fc:73:10:70:93:f2:44:63:47.
+* @param keytype either "ssh-rsa" or "ssh-dss"
+* @param publickey key blob
+* @return Hex fingerprint
+*/
+public final static String createHexFingerprint(String keytype, byte[] publickey) {
+byte[] raw = rawFingerPrint("md5", keytype, publickey);
+return rawToHexFingerprint(raw);
+}
+/**
+* Convert a ssh2 key-blob into a human readable bubblebabble fingerprint.
+* The used bubblebabble algorithm (taken from OpenSSH) generates fingerprints
+* that are easier to remember for humans.
+* <p>
+* Example fingerprint: xofoc-bubuz-cazin-zufyl-pivuk-biduk-tacib-pybur-gonar-hotat-lyxux.
+*
+* @param keytype either "ssh-rsa" or "ssh-dss"
+* @param publickey key data
+* @return Bubblebabble fingerprint
+*/
+public final static String createBubblebabbleFingerprint(String keytype, byte[] publickey) {
+byte[] raw = rawFingerPrint("sha1", keytype, publickey);
+return rawToBubblebabbleFingerprint(raw);
+}
+}

Mercurial > 510Connectbot

comparison src/com/trilead/ssh2/KnownHosts.java @ 0:0ce5cc452d02