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Follow some of coorus recommendations: better selection of algo whitelist, ignore recipients preferred algos

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This commit is contained in:
Dominik Schürmann
2015-07-30 22:46:36 +02:00
parent 57378be1c0
commit dba145f5df
5 changed files with 53 additions and 40 deletions
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1
OpenKeychain/src/main/java/org/sufficientlysecure/keychain/operations/results/OperationResult.java
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@@ -660,7 +660,6 @@ public abstract class OperationResult implements Parcelable {
MSG_PSE_COMPRESSING (LogLevel.DEBUG, R.string.msg_pse_compressing),
MSG_PSE_ENCRYPTING (LogLevel.DEBUG, R.string.msg_pse_encrypting),
MSG_PSE_ERROR_BAD_PASSPHRASE (LogLevel.ERROR, R.string.msg_pse_error_bad_passphrase),
MSG_PSE_ERROR_HASH_ALGO (LogLevel.ERROR, R.string.msg_pse_error_hash_algo),
MSG_PSE_ERROR_IO (LogLevel.ERROR, R.string.msg_pse_error_io),
MSG_PSE_ERROR_SIGN_KEY(LogLevel.ERROR, R.string.msg_pse_error_sign_key),
MSG_PSE_ERROR_KEY_SIGN (LogLevel.ERROR, R.string.msg_pse_error_key_sign),

10
OpenKeychain/src/main/java/org/sufficientlysecure/keychain/pgp/CanonicalizedSecretKey.java
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@@ -177,16 +177,6 @@ public class CanonicalizedSecretKey extends CanonicalizedPublicKey {
return true;
}
/**
* Returns a list of all supported hash algorithms.
*/
public ArrayList<Integer> getSupportedHashAlgorithms() {
// TODO: intersection between preferred hash algos of this key and PgpConstants.PREFERRED_HASH_ALGORITHMS
// choose best algo
return new ArrayList<>();
}
private PGPContentSignerBuilder getContentSignerBuilder(int hashAlgo,
Map<ByteBuffer,byte[]> signedHashes) {
if (mPrivateKeyState == PRIVATE_KEY_STATE_DIVERT_TO_CARD) {

68
OpenKeychain/src/main/java/org/sufficientlysecure/keychain/pgp/PgpConstants.java
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@@ -29,6 +29,8 @@ import java.util.HashSet;
* - ECC: 224 bit
* - Symmetric: 3TDEA
* - Digital Signature (hash A): SHA-224 - SHA-512
*
* Many decisions are based on https://gist.github.com/coruus/68a8c65571e2b4225a69
*/
public class PgpConstants {
@@ -39,26 +41,36 @@ public class PgpConstants {
// }
// https://tools.ietf.org/html/rfc6637#section-13
/*
PgpDecryptVerify: Secure Algorithms Whitelist
all other algorithms will be rejected with OpenPgpDecryptionResult.RESULT_INSECURE
// PgpDecryptVerify: Secure Algorithms Whitelist
// all other algorithms will be rejected with OpenPgpDecryptionResult.RESULT_INSECURE
No broken ciphers or ciphers with key length smaller than 128 bit are allowed!
*/
public static HashSet<Integer> sSymmetricAlgorithmsWhitelist = new HashSet<>();
static {
sSymmetricAlgorithmsWhitelist.add(SymmetricKeyAlgorithmTags.AES_256);
sSymmetricAlgorithmsWhitelist.add(SymmetricKeyAlgorithmTags.AES_192);
sSymmetricAlgorithmsWhitelist.add(SymmetricKeyAlgorithmTags.AES_128);
sSymmetricAlgorithmsWhitelist.add(SymmetricKeyAlgorithmTags.TWOFISH);
sSymmetricAlgorithmsWhitelist.add(SymmetricKeyAlgorithmTags.TWOFISH); // 128 bit
}
// all other algorithms will be rejected with OpenPgpSignatureResult.RESULT_INVALID_INSECURE
public static HashSet<Integer> sHashAlgorithmsWhitelist = new HashSet<>();
static {
sHashAlgorithmsWhitelist.add(HashAlgorithmTags.SHA256);
sHashAlgorithmsWhitelist.add(HashAlgorithmTags.SHA512);
sHashAlgorithmsWhitelist.add(HashAlgorithmTags.SHA384);
/*
TODO: SHA256 and SHA224 are still allowed even though
coruus advises against it, to enable better backward compatibility
coruus:
Implementations MUST NOT sign SHA-224 hashes. They SHOULD NOT accept signatures over SHA-224 hashes.
((collision resistance of 112-bits))
Implementations SHOULD NOT sign SHA-256 hashes. They MUST NOT default to signing SHA-256 hashes.
*/
sHashAlgorithmsWhitelist.add(HashAlgorithmTags.SHA256);
sHashAlgorithmsWhitelist.add(HashAlgorithmTags.SHA224);
sHashAlgorithmsWhitelist.add(HashAlgorithmTags.SHA1);
sHashAlgorithmsWhitelist.add(HashAlgorithmTags.RIPEMD160);
}
/*
@@ -70,15 +82,15 @@ public class PgpConstants {
SymmetricKeyAlgorithmTags.AES_256,
SymmetricKeyAlgorithmTags.AES_192,
SymmetricKeyAlgorithmTags.AES_128,
SymmetricKeyAlgorithmTags.TWOFISH
};
// NOTE: some implementations do not support SHA512, thus we choose SHA256 as default (Mailvelope?)
/*
coorus:
Implementations SHOULD use SHA-512 for RSA or DSA signatures. They SHOULD NOT use SHA-384.
((cite to affine padding attacks; unproven status of RSA-PKCSv15))
*/
public static final int[] PREFERRED_HASH_ALGORITHMS = new int[]{
HashAlgorithmTags.SHA256,
HashAlgorithmTags.SHA512,
HashAlgorithmTags.SHA384,
HashAlgorithmTags.SHA224,
};
/*
@@ -89,19 +101,41 @@ public class PgpConstants {
*/
public static final int[] PREFERRED_COMPRESSION_ALGORITHMS = new int[]{
CompressionAlgorithmTags.ZIP,
CompressionAlgorithmTags.ZLIB,
CompressionAlgorithmTags.BZIP2
};
public static final int CERTIFY_HASH_ALGO = HashAlgorithmTags.SHA256;
public static final int CERTIFY_HASH_ALGO = HashAlgorithmTags.SHA512;
/*
Always use AES-256! Ignore the preferred encryption algos of the recipient!
coorus:
Implementations SHOULD ignore the symmetric algorithm preferences of a recipient's public key;
in particular, implementations MUST NOT choose an algorithm forbidden by this
document because a recipient prefers it.
NEEDCITE downgrade attacks on TLS, other protocols
*/
public static final int DEFAULT_SYMMETRIC_ALGORITHM = SymmetricKeyAlgorithmTags.AES_256;
public interface OpenKeychainSymmetricKeyAlgorithmTags extends SymmetricKeyAlgorithmTags {
int USE_DEFAULT = -1;
}
public static final int DEFAULT_HASH_ALGORITHM = HashAlgorithmTags.SHA256;
/*
Always use SHA-512! Ignore the preferred hash algos of the recipient!
coorus:
Implementations MUST ignore the hash algorithm preferences of a recipient when signing
a message to a recipient. The difficulty of forging a signature under a given key,
using generic attacks on hash functions, is the difficulty of the weakest hash signed by that key.
Implementations MUST default to using SHA-512 for RSA signatures,
and either SHA-512 or the matched instance of SHA-2 for ECDSA signatures.
TODO: Ed25519
CITE: zooko's hash function table CITE: distinguishers on SHA-256
*/
public static final int DEFAULT_HASH_ALGORITHM = HashAlgorithmTags.SHA512;
public interface OpenKeychainHashAlgorithmTags extends HashAlgorithmTags {
int USE_DEFAULT = -1;
}
@@ -130,9 +164,9 @@ public class PgpConstants {
* OpenKeychain: 0x90
*/
public static final int SECRET_KEY_ENCRYPTOR_S2K_COUNT = 0x90;
public static final int SECRET_KEY_ENCRYPTOR_HASH_ALGO = HashAlgorithmTags.SHA256;
public static final int SECRET_KEY_ENCRYPTOR_HASH_ALGO = HashAlgorithmTags.SHA512;
public static final int SECRET_KEY_ENCRYPTOR_SYMMETRIC_ALGO = SymmetricKeyAlgorithmTags.AES_256;
public static final int SECRET_KEY_BINDING_SIGNATURE_HASH_ALGO = HashAlgorithmTags.SHA256;
public static final int SECRET_KEY_BINDING_SIGNATURE_HASH_ALGO = HashAlgorithmTags.SHA512;
// NOTE: only SHA1 is supported for key checksum calculations in OpenPGP,
// see http://tools.ietf.org/html/rfc488 0#section-5.5.3
public static final int SECRET_KEY_SIGNATURE_CHECKSUM_HASH_ALGO = HashAlgorithmTags.SHA1;

13
OpenKeychain/src/main/java/org/sufficientlysecure/keychain/pgp/PgpSignEncryptOperation.java
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@@ -226,17 +226,10 @@ public class PgpSignEncryptOperation extends BaseOperation {
return new PgpSignEncryptResult(PgpSignEncryptResult.RESULT_ERROR, log);
}
// Use preferred hash algo
// Use requested hash algo
int requestedAlgorithm = input.getSignatureHashAlgorithm();
ArrayList<Integer> supported = signingKey.getSupportedHashAlgorithms();
if (requestedAlgorithm == PgpConstants.OpenKeychainHashAlgorithmTags.USE_DEFAULT) {
input.setSignatureHashAlgorithm(PgpConstants.DEFAULT_HASH_ALGORITHM);
// TODO
// get most preferred
// input.setSignatureHashAlgorithm(supported.get(0));
} else if (!supported.contains(requestedAlgorithm)) {
log.add(LogType.MSG_PSE_ERROR_HASH_ALGO, indent);
return new PgpSignEncryptResult(PgpSignEncryptResult.RESULT_ERROR, log);
}
}
updateProgress(R.string.progress_preparing_streams, 2, 100);
@@ -245,11 +238,9 @@ public class PgpSignEncryptOperation extends BaseOperation {
PGPEncryptedDataGenerator cPk = null;
if (enableEncryption) {
// Use preferred encryption algo
// Use requested encryption algo
int algo = input.getSymmetricEncryptionAlgorithm();
if (algo == PgpConstants.OpenKeychainSymmetricKeyAlgorithmTags.USE_DEFAULT) {
// get most preferred
// TODO: get from recipients
algo = PgpConstants.DEFAULT_SYMMETRIC_ALGORITHM;
}
// has Integrity packet enabled!

1
OpenKeychain/src/main/res/values/strings.xml
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@@ -1196,7 +1196,6 @@
<string name="msg_pse_compressing">"Preparing compression"</string>
<string name="msg_pse_encrypting">"Encrypting data"</string>
<string name="msg_pse_error_bad_passphrase">"Bad password!"</string>
<string name="msg_pse_error_hash_algo">"Requested hashing algorithm is not supported by this key!"</string>
<string name="msg_pse_error_io">"Encountered IO Exception during operation!"</string>
<string name="msg_pse_error_key_sign">"Selected signing key cannot sign data!"</string>
<string name="msg_pse_error_sign_key">"Error fetching signing key!"</string>