1 files changed, 130 insertions, 0 deletions
diff --git a/libmincrypt/tools/DumpPublicKey.java b/libmincrypt/tools/DumpPublicKey.java
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+++ b/libmincrypt/tools/DumpPublicKey.java
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+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.dumpkey;
+
+import java.io.FileInputStream;
+import java.math.BigInteger;
+import java.security.cert.CertificateFactory;
+import java.security.cert.Certificate;
+import java.security.KeyStore;
+import java.security.Key;
+import java.security.PublicKey;
+import java.security.interfaces.RSAPublicKey;
+import sun.misc.BASE64Encoder;
+
+/**
+ * Command line tool to extract RSA public keys from X.509 certificates
+ * and output source code with data initializers for the keys.
+ * @hide
+ */
+class DumpPublicKey {
+    /**
+     * @param key to perform sanity checks on
+     * @throws Exception if the key has the wrong size or public exponent
+     */
+    static void check(RSAPublicKey key) throws Exception {
+        BigInteger pubexp = key.getPublicExponent();
+        BigInteger modulus = key.getModulus();
+
+        if (!pubexp.equals(BigInteger.valueOf(3)))
+                throw new Exception("Public exponent should be 3 but is " +
+                        pubexp.toString(10) + ".");
+
+        if (modulus.bitLength() != 2048)
+             throw new Exception("Modulus should be 2048 bits long but is " +
+                        modulus.bitLength() + " bits.");
+    }
+
+    /**
+     * @param key to output
+     * @return a C initializer representing this public key.
+     */
+    static String print(RSAPublicKey key) throws Exception {
+        check(key);
+
+        BigInteger N = key.getModulus();
+
+        StringBuilder result = new StringBuilder();
+
+        int nwords = N.bitLength() / 32;    // # of 32 bit integers in modulus
+
+        result.append("{");
+        result.append(nwords);
+
+        BigInteger B = BigInteger.valueOf(0x100000000L);  // 2^32
+        BigInteger N0inv = B.subtract(N.modInverse(B));   // -1 / N[0] mod 2^32
+
+        result.append(",0x");
+        result.append(N0inv.toString(16));
+
+        BigInteger R = BigInteger.valueOf(2).pow(N.bitLength());
+        BigInteger RR = R.multiply(R).mod(N);    // 2^4096 mod N
+
+        // Write out modulus as little endian array of integers.
+        result.append(",{");
+        for (int i = 0; i < nwords; ++i) {
+            int n = N.mod(B).intValue();
+            result.append(n);
+
+            if (i != nwords - 1) {
+                result.append(",");
+            }
+
+            N = N.divide(B);
+        }
+        result.append("}");
+
+        // Write R^2 as little endian array of integers.
+        result.append(",{");
+        for (int i = 0; i < nwords; ++i) {
+            int rr = RR.mod(B).intValue();
+            result.append(rr);
+
+            if (i != nwords - 1) {
+                result.append(",");
+            }
+
+            RR = RR.divide(B);
+        }
+        result.append("}");
+
+        result.append("}");
+        return result.toString();
+    }
+
+    public static void main(String[] args) {
+        if (args.length < 1) {
+            System.err.println("Usage: DumpPublicKey certfile ... > source.c");
+            System.exit(1);
+        }
+        try {
+            for (int i = 0; i < args.length; i++) {
+                FileInputStream input = new FileInputStream(args[i]);
+                CertificateFactory cf = CertificateFactory.getInstance("X.509");
+                Certificate cert = cf.generateCertificate(input);
+                RSAPublicKey key = (RSAPublicKey) (cert.getPublicKey());
+                check(key);
+                System.out.print(print(key));
+                System.out.println(i < args.length - 1 ? "," : "");
+            }
+        } catch (Exception e) {
+            e.printStackTrace();
+            System.exit(1);
+        }
+        System.exit(0);
+    }
+}