Class Crypto

java.lang.Object

com.codename1.backend.Crypto

public final class Crypto
extends Object

The crypto a server needs to authenticate a request. Every primitive comes from OpenSSL, which the backend already links for outbound TLS - none of it is implemented here, because hand-rolled HMAC and hand-rolled password hashing are the two most reliable ways to ship an authentication system that looks correct and is not.

Field Summary

Fields

Modifier and Type	Field	Description
static final String	ES256	ECDSA over P-256 with SHA-256, and over P-384 with SHA-384.
static final String	ES384
static final int	PASSWORD_ITERATIONS	PBKDF2 iterations for a stored password.
static final String	PS256	RSASSA-PSS over SHA-256 with MGF1-SHA-256 and a 32 byte salt.
static final String	RS256	RSASSA-PKCS1-v1_5 over SHA-256, SHA-384 and SHA-512: the same bytes for the same key and message, every time.
static final String	RS384
static final String	RS512
static final String	SHA1	The digest names hmac(String, byte[], byte[]) and pbkdf2(String, byte[], byte[], int, int) take.
static final String	SHA256
static final String	SHA384
static final String	SHA512

Method Summary

Modifier and Type	Method	Description
static byte[]	aesGcmDecrypt(byte[] key, byte[] iv, byte[] aad, byte[] sealed)	Opens what aesGcmEncrypt(byte[], byte[], byte[], byte[]) sealed.
static byte[]	aesGcmEncrypt(byte[] key, byte[] iv, byte[] aad, byte[] plaintext)	AES-GCM.
static boolean	equalsConstantTime(byte[] a, byte[] b)	Compares without leaking where two values first differ.
static byte[]	generateRsaKey(int bits)	A new RSA private key as PKCS#8 DER, with the public exponent 65537.
static String	hashPassword(String password)	Hashes a password for storage.
static byte[]	hmac(String digest, byte[] key, byte[] data)	HMAC over one of SHA1, SHA256, SHA384 and SHA512.
static byte[]	hmacSha256(byte[] key, byte[] data)
static byte[]	md5(byte[] data)	MD5, for PostgreSQL's md5 authentication method.
static byte[]	pbkdf2(String digest, byte[] password, byte[] salt, int iterations, int length)	PBKDF2 over HMAC with one of SHA1, SHA256, SHA384 and SHA512, on the password's bytes as they are given.
static byte[]	pbkdf2Sha256(byte[] password, byte[] salt, int iterations, int length)	PBKDF2-HMAC-SHA-256.
static byte[]	randomBytes(int length)	Cryptographically secure bytes.
static byte[]	sha1(byte[] data)	SHA-1, for the wire protocols that specify it by name: MySQL's mysql_native_password, and the RFC 6455 4.2.2 websocket handshake, where the digest of the client key and a fixed GUID becomes Sec-WebSocket-Accept.
static byte[]	sha256(byte[] data)
static byte[]	sha384(byte[] data)	SHA-384; null for null.
static byte[]	sha512(byte[] data)	SHA-512; null for null.
static byte[]	sign(String algorithm, byte[] privateKey, byte[] data)	Signs data with a private key in PKCS#8 DER, under one of RS256, RS384, RS512, PS256, ES256 and ES384.
static boolean	verify(String algorithm, byte[] publicKey, byte[] data, byte[] signature)	Checks a signature against a public key in SubjectPublicKeyInfo DER.
static boolean	verifyPassword(String password, String stored)	False for any malformed stored value rather than throwing.

Methods inherited from class Object

clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

PASSWORD_ITERATIONS

public static final int PASSWORD_ITERATIONS

PBKDF2 iterations for a stored password. Deliberately expensive: the cost is paid once per login and multiplied by every guess an attacker makes against a stolen table.

See Also:

• Constant Field Values

SHA1

public static final String SHA1

The digest names hmac(String, byte[], byte[]) and pbkdf2(String, byte[], byte[], int, int) take.

See Also:

• Constant Field Values

SHA256

public static final String SHA256

See Also:

• Constant Field Values

SHA384

public static final String SHA384

See Also:

• Constant Field Values

SHA512

public static final String SHA512

See Also:

• Constant Field Values

RS256

public static final String RS256

RSASSA-PKCS1-v1_5 over SHA-256, SHA-384 and SHA-512: the same bytes for the same key and message, every time.

See Also:

• Constant Field Values

RS384

public static final String RS384

See Also:

• Constant Field Values

RS512

public static final String RS512

See Also:

• Constant Field Values

PS256

public static final String PS256

RSASSA-PSS over SHA-256 with MGF1-SHA-256 and a 32 byte salt.

See Also:

• Constant Field Values

ES256

public static final String ES256

ECDSA over P-256 with SHA-256, and over P-384 with SHA-384.

See Also:

• Constant Field Values

ES384

public static final String ES384

See Also:

• Constant Field Values

Method Details

sha256

public static byte[] sha256(byte[] data)

sha1

public static byte[] sha1(byte[] data)

SHA-1, for the wire protocols that specify it by name: MySQL's mysql_native_password, and the RFC 6455 4.2.2 websocket handshake, where the digest of the client key and a fixed GUID becomes Sec-WebSocket-Accept.

Never for anything this code CHOOSES: passwords go through hashPassword(String) and tokens through hmacSha256(byte[], byte[]). Both callers here are standards quoting the algorithm, and in neither is the result standing in for a signature -- the handshake value is a replay guard against caches and proxies, not an authenticator.

md5

public static byte[] md5(byte[] data)

MD5, for PostgreSQL's md5 authentication method. See sha1(byte[]).

pbkdf2Sha256

public static byte[] pbkdf2Sha256(byte[] password,
 byte[] salt,
 int iterations,
 int length)
                           throws IOException

PBKDF2-HMAC-SHA-256. Exposed because SCRAM-SHA-256 -- how PostgreSQL authenticates by default -- is defined in terms of it with the server's iteration count, which hashPassword(String) does not let a caller choose.

Throws:

IOException

hmacSha256

public static byte[] hmacSha256(byte[] key,
 byte[] data)

randomBytes

public static byte[] randomBytes(int length)
                          throws IOException

Cryptographically secure bytes. Throws rather than returning weak ones.

Throws:

IOException

equalsConstantTime

public static boolean equalsConstantTime(byte[] a,
 byte[] b)

Compares without leaking where two values first differ. An early exit on the first differing byte lets a MAC be forged one byte at a time.

hashPassword

public static String hashPassword(String password)
                           throws IOException

Hashes a password for storage. Returns "pbkdf2$iterations$salt$hash" with both binary parts base64url-encoded, so the iteration count travels with the hash and can be raised later without invalidating existing rows.

Throws:

IOException

verifyPassword

public static boolean verifyPassword(String password,
 String stored)

False for any malformed stored value rather than throwing.

sha384

public static byte[] sha384(byte[] data)

SHA-384; null for null.

sha512

public static byte[] sha512(byte[] data)

SHA-512; null for null.

hmac

public static byte[] hmac(String digest,
 byte[] key,
 byte[] data)

HMAC over one of SHA1, SHA256, SHA384 and SHA512. SHA-1 is here for what specifies it by name -- a TOTP secret an authenticator application already holds, Spring's oldest password format -- and not for anything new.

Returns:

the tag, or null when key or data is null

Throws:

IllegalArgumentException - for a digest that is not one of the four

pbkdf2

public static byte[] pbkdf2(String digest,
 byte[] password,
 byte[] salt,
 int iterations,
 int length)
                     throws IOException

PBKDF2 over HMAC with one of SHA1, SHA256, SHA384 and SHA512, on the password's bytes as they are given.

Throws:

IOException - when a count is not positive or derivation fails

sign

public static byte[] sign(String algorithm,
 byte[] privateKey,
 byte[] data)
                   throws IOException

Signs data with a private key in PKCS#8 DER, under one of RS256, RS384, RS512, PS256, ES256 and ES384.

The key has to be of the kind the algorithm is defined over: an RSA key for the first four, a P-256 key for ES256, a P-384 key for ES384. Any other pairing is refused rather than adapted to.

An ECDSA signature is returned as ASN.1 DER, the SEQUENCE of r and s both OpenSSL and the JDK produce. JOSE wants the two numbers side by side instead; com.codename1.backend.security.crypto.Der converts.

Throws:

IOException - when the key cannot be read, does not fit the algorithm, or signing fails

verify

public static boolean verify(String algorithm,
 byte[] publicKey,
 byte[] data,
 byte[] signature)
                      throws IOException

Checks a signature against a public key in SubjectPublicKeyInfo DER. The algorithms and the pairing of key and algorithm are those of sign(String, byte[], byte[]), and an ECDSA signature is given as ASN.1 DER.

Returns:

true when signature is that key's signature of data; false when it is not, whatever is wrong with it

Throws:

IOException - when the question could not be asked: the key cannot be read or does not fit the algorithm. A key that is broken is never reported as a signature that is forged.

generateRsaKey

public static byte[] generateRsaKey(int bits)
                             throws IOException

A new RSA private key as PKCS#8 DER, with the public exponent 65537.

For a development profile, so a server that signs tokens starts without a key file. A key made at start-up is gone at the next one, and every token signed with it stops verifying: a deployed server loads its key.

Parameters:

bits - 2048 to 8192

Throws:

IOException

aesGcmEncrypt

public static byte[] aesGcmEncrypt(byte[] key,
 byte[] iv,
 byte[] aad,
 byte[] plaintext)
                            throws IOException

AES-GCM. The result is the ciphertext followed by the 16 byte tag.

The nonce must never repeat under one key: 12 bytes from randomBytes(int) for each call is the ordinary way, stored beside the result.

Parameters:

key - 16, 24 or 32 bytes

iv - the nonce; 12 bytes unless a protocol says otherwise

aad - data that is authenticated and not encrypted; null for none

Throws:

IOException

aesGcmDecrypt

public static byte[] aesGcmDecrypt(byte[] key,
 byte[] iv,
 byte[] aad,
 byte[] sealed)
                            throws IOException

Opens what aesGcmEncrypt(byte[], byte[], byte[], byte[]) sealed.

Returns:

the plaintext, or null when the tag does not match: the key, the nonce, the associated data or the sealed bytes are not the ones it was made with

Throws:

IOException - when the sizes are not ones AES-GCM has