我开发了一个在飞思卡尔FRDM-KL25Z（Cortex-M0）板上运行的嵌入式应用程序，通过ADB（Android Debug Bridge）协议连接Android手机（HTC Tattoo）。
然而，Google自v4.2.2（Jelly bean）以来通过USB ADB强制执行RSA身份验证，以提高安全性。这意味着我的设计仅支持从v1.5到v4.2.1的Android设备。
在A_CNXN消息期间，我的Galaxy Nexus回复了A_AUTH消息，将我的RSA（密钥）作为黑名单。
我无法找到有关ADB接口中使用的所有RSA身份验证的足够信息。如密钥长度，密钥存储位置。我找不到描述实现细节的相关文档。
可以在嵌入式ARM MCU上部署RSA身份验证吗？到目前为止，我发现LPC1343（cortex-M3）的实现具有有限长度整数到RSA计算（64位）。但是，RSA在商业认证算法中至少使用512位计算。
如果不是，那么我必须在同一时间更改我的设计以支持ADK / AOA和ADK。但是，在v2.3.7之前，AOA / ADK不支持旧设备。它使事情变得更复杂，至少我在Android上运行的应用程序应该在两种方法中开发。
多么糟糕。
答案 0 :(得分：0)
最近我用STM32F401（84MHz ROM上的512KB ROM / 196KB RAM M4）评估了mbed TLS（mbed-example-tls-benchmark），其基准数据显示RSA2048可以在2000ms内完成。但是它会在STM32F103RB上丢失内存malloc错误（在72MHz上为128KB ROM / 20KB RAM M3）。
因此我得出结论，M3 / M4内核可以在可接受的时间窗口内支持RSA2048，但其内存是一个瓶颈。至少我们使用32KB / 64KB RAM进行RSA / TLS。
答案 1 :(得分：-1)
Heyho，我知道，问题真的很老......但是，我发现了一些可以帮助你的东西。
这是一个用于签署ADB A_AUTH令牌的Java代码段。
希望这有助于你;）
package com.cgutman.adblib;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.math.BigInteger;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.security.GeneralSecurityException;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.EncodedKeySpec;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import javax.crypto.Cipher;
/**
* This class encapsulates the ADB cryptography functions and provides
* an interface for the storage and retrieval of keys.
* @author Cameron Gutman
*/
public class AdbCrypto
{
/** An RSA keypair encapsulated by the AdbCrypto object */
private KeyPair keyPair;
/** The base 64 conversion interface to use */
private AdbBase64 base64;
/** The ADB RSA key length in bits */
public static final int KEY_LENGTH_BITS = 2048;
/** The ADB RSA key length in bytes */
public static final int KEY_LENGTH_BYTES = KEY_LENGTH_BITS / 8;
/** The ADB RSA key length in words */
public static final int KEY_LENGTH_WORDS = KEY_LENGTH_BYTES / 4;
/** The RSA signature padding as an int array */
public static final int[] SIGNATURE_PADDING_AS_INT = new int[]
{
0x00,0x01,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,
0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0xff,0x00,
0x30,0x21,0x30,0x09,0x06,0x05,0x2b,0x0e,0x03,0x02,0x1a,0x05,0x00,
0x04,0x14
};
/** The RSA signature padding as a byte array */
public static byte[] SIGNATURE_PADDING;
static {
SIGNATURE_PADDING = new byte[SIGNATURE_PADDING_AS_INT.length];
for (int i = 0; i<SIGNATURE_PADDING.length; i++)
SIGNATURE_PADDING[i] = (byte)SIGNATURE_PADDING_AS_INT[i];
}
/**
* Converts a standard RSAPublicKey object to the special ADB format
* @param pubkey RSAPublicKey object to convert
* @return Byte array containing the converted RSAPublicKey object
*/
private static byte[] convertRsaPublicKeyToAdbFormat(RSAPublicKey pubkey)
{
/*
* ADB literally just saves the RSAPublicKey struct to a file.
*
* typedef struct RSAPublicKey {
* int len; // Length of n[] in number of uint32_t
* uint32_t n0inv; // -1 / n[0] mod 2^32
* uint32_t n[RSANUMWORDS]; // modulus as little endian array
* uint32_t rr[RSANUMWORDS]; // R^2 as little endian array
* int exponent; // 3 or 65537
* } RSAPublicKey;
*/
/* ------ This part is a Java-ified version of RSA_to_RSAPublicKey from adb_host_auth.c ------ */
BigInteger r32, r, rr, rem, n, n0inv;
r32 = BigInteger.ZERO.setBit(32);
n = pubkey.getModulus();
r = BigInteger.ZERO.setBit(KEY_LENGTH_WORDS * 32);
rr = r.modPow(BigInteger.valueOf(2), n);
rem = n.remainder(r32);
n0inv = rem.modInverse(r32);
int myN[] = new int[KEY_LENGTH_WORDS];
int myRr[] = new int[KEY_LENGTH_WORDS];
BigInteger res[];
for (int i = 0; i < KEY_LENGTH_WORDS; i++)
{
res = rr.divideAndRemainder(r32);
rr = res[0];
rem = res[1];
myRr[i] = rem.intValue();
res = n.divideAndRemainder(r32);
n = res[0];
rem = res[1];
myN[i] = rem.intValue();
}
/* ------------------------------------------------------------------------------------------- */
ByteBuffer bbuf = ByteBuffer.allocate(524).order(ByteOrder.LITTLE_ENDIAN);
bbuf.putInt(KEY_LENGTH_WORDS);
bbuf.putInt(n0inv.negate().intValue());
for (int i : myN)
bbuf.putInt(i);
for (int i : myRr)
bbuf.putInt(i);
bbuf.putInt(pubkey.getPublicExponent().intValue());
return bbuf.array();
}
/**
* Creates a new AdbCrypto object from a key pair loaded from files.
* @param base64 Implementation of base 64 conversion interface required by ADB
* @param privateKey File containing the RSA private key
* @param publicKey File containing the RSA public key
* @return New AdbCrypto object
* @throws IOException If the files cannot be read
* @throws NoSuchAlgorithmException If an RSA key factory cannot be found
* @throws InvalidKeySpecException If a PKCS8 or X509 key spec cannot be found
*/
public static AdbCrypto loadAdbKeyPair(AdbBase64 base64, File privateKey, File publicKey) throws IOException, NoSuchAlgorithmException, InvalidKeySpecException
{
AdbCrypto crypto = new AdbCrypto();
int privKeyLength = (int)privateKey.length();
int pubKeyLength = (int)publicKey.length();
byte[] privKeyBytes = new byte[privKeyLength];
byte[] pubKeyBytes = new byte[pubKeyLength];
FileInputStream privIn = new FileInputStream(privateKey);
FileInputStream pubIn = new FileInputStream(publicKey);
privIn.read(privKeyBytes);
pubIn.read(pubKeyBytes);
privIn.close();
pubIn.close();
KeyFactory keyFactory = KeyFactory.getInstance("RSA");
EncodedKeySpec privateKeySpec = new PKCS8EncodedKeySpec(privKeyBytes);
EncodedKeySpec publicKeySpec = new X509EncodedKeySpec(pubKeyBytes);
crypto.keyPair = new KeyPair(keyFactory.generatePublic(publicKeySpec),
keyFactory.generatePrivate(privateKeySpec));
crypto.base64 = base64;
return crypto;
}
/**
* Creates a new AdbCrypto object by generating a new key pair.
* @param base64 Implementation of base 64 conversion interface required by ADB
* @return A new AdbCrypto object
* @throws NoSuchAlgorithmException If an RSA key factory cannot be found
*/
public static AdbCrypto generateAdbKeyPair(AdbBase64 base64) throws NoSuchAlgorithmException
{
AdbCrypto crypto = new AdbCrypto();
KeyPairGenerator rsaKeyPg = KeyPairGenerator.getInstance("RSA");
rsaKeyPg.initialize(KEY_LENGTH_BITS);
crypto.keyPair = rsaKeyPg.genKeyPair();
crypto.base64 = base64;
return crypto;
}
/**
* Signs the ADB SHA1 payload with the private key of this object.
* @param payload SHA1 payload to sign
* @return Signed SHA1 payload
* @throws GeneralSecurityException If signing fails
*/
public byte[] signAdbTokenPayload(byte[] payload) throws GeneralSecurityException
{
Cipher c = Cipher.getInstance("RSA/ECB/NoPadding");
c.init(Cipher.ENCRYPT_MODE, keyPair.getPrivate());
c.update(SIGNATURE_PADDING);
return c.doFinal(payload);
}
/**
* Gets the RSA public key in ADB format.
* @return Byte array containing the RSA public key in ADB format.
* @throws IOException If the key cannot be retrived
*/
public byte[] getAdbPublicKeyPayload() throws IOException
{
byte[]
convertedKey = convertRsaPublicKeyToAdbFormat((RSAPublicKey)keyPair.getPublic());
StringBuilder keyString = new StringBuilder(720);
/* The key is base64 encoded with a user@host suffix and terminated with a NUL */
keyString.append(base64.encodeToString(convertedKey));
keyString.append(" unknown@unknown");
keyString.append('\0');
return keyString.toString().getBytes("UTF-8");
}
/**
* Saves the AdbCrypto's key pair to the specified files.
* @param privateKey The file to store the encoded private key
* @param publicKey The file to store the encoded public key
* @throws IOException If the files cannot be written
*/
public void saveAdbKeyPair(File privateKey, File publicKey) throws IOException
{
FileOutputStream privOut = new FileOutputStream(privateKey);
FileOutputStream pubOut = new FileOutputStream(publicKey);
privOut.write(keyPair.getPrivate().getEncoded());
pubOut.write(keyPair.getPublic().getEncoded());
privOut.close();
pubOut.close();
}
}