OLMKit: SAS: Add PK signing

(cherry picked from commit ff31d489c68d5d9e597bd55a6f6a64f3fe4c7ecc)

xcode/OLMKit/OLMKit.h

@@ -28,6 +28,7 @@
 #import <OLMKit/OLMOutboundGroupSession.h>
 #import <OLMKit/OLMPkEncryption.h>
 #import <OLMKit/OLMPkDecryption.h>
+#import <OLMKit/OLMPkSigning.h>
 #import <OLMKit/OLMSAS.h>
 
 @interface OLMKit : NSObject

xcode/OLMKit/OLMPkSigning.h

@@ -0,0 +1,49 @@
+/*
+ Copyright 2019 New Vector Ltd
+
+ 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.
+ */
+
+#import <Foundation/Foundation.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+@interface OLMPkSigning : NSObject
+
+/**
+ Initialise the signing object with a public/private keypair from a seed.
+
+ @param seed the seed.
+ @param error the error if any.
+ @return the public key
+ */
+- (NSString *)doInitWithSeed:(NSData*)seed error:(NSError* _Nullable *)error;
+
+/**
+ Sign a message.
+
+ @param message the message to sign.
+ @param error the error if any.
+ @return the signature.
+ */
+- (NSString *)sign:(NSString*)message error:(NSError* _Nullable *)error;
+
+/**
+ Generate a seed.
+
+ @return the generated seed.
+ */
++ (NSData *)generateSeed;
+
+@end
+
+NS_ASSUME_NONNULL_END

xcode/OLMKit/OLMPkSigning.m

@@ -0,0 +1,123 @@
+/*
+ Copyright 2019 New Vector Ltd
+
+ 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.
+ */
+
+#import "OLMPkSigning.h"
+
+#include "olm/olm.h"
+#include "olm/pk.h"
+#include "OLMUtility.h"
+
+@interface OLMPkSigning ()
+{
+    OlmPkSigning *sign;
+}
+@end
+
+@implementation OLMPkSigning
+
+- (void)dealloc {
+    olm_clear_pk_signing(sign);
+    free(sign);
+}
+
+
+- (instancetype)init {
+    self = [super init];
+    if (self) {
+        sign = (OlmPkSigning *)malloc(olm_pk_signing_size());
+        olm_pk_signing(sign);
+    }
+    return self;
+}
+
+- (NSString *)doInitWithSeed:(NSData *)seed error:(NSError *__autoreleasing  _Nullable *)error {
+    size_t publicKeyLength = olm_pk_signing_public_key_length();
+    NSMutableData *publicKeyData = [NSMutableData dataWithLength:publicKeyLength];
+    if (!publicKeyData) {
+        return nil;
+    }
+
+    NSMutableData *mutableSeed = [NSMutableData dataWithData:seed];
+
+    size_t result = olm_pk_signing_key_from_seed(sign,
+                                                 publicKeyData.mutableBytes, publicKeyLength,
+                                                 mutableSeed.mutableBytes, mutableSeed.length);
+    if (result == olm_error()) {
+        const char *olm_error = olm_pk_signing_last_error(sign);
+
+        NSString *errorString = [NSString stringWithUTF8String:olm_error];
+        NSLog(@"[OLMPkSigning] doInitWithSeed: olm_pk_signing_key_from_seed error: %@", errorString);
+
+        if (error && olm_error && errorString) {
+            *error = [NSError errorWithDomain:OLMErrorDomain
+                                         code:0
+                                     userInfo:@{
+                                                NSLocalizedDescriptionKey: errorString,
+                                                NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:@"olm_pk_signing_key_from_seed error: %@", errorString]
+                                                }];
+        }
+
+        return nil;
+    }
+
+    NSString *publicKey = [[NSString alloc] initWithData:publicKeyData encoding:NSUTF8StringEncoding];
+    return publicKey;
+}
+
+- (NSString *)sign:(NSString *)message error:(NSError *__autoreleasing  _Nullable *)error {
+    NSData *messageData = [message dataUsingEncoding:NSUTF8StringEncoding];
+
+    size_t signatureLength = olm_pk_signature_length();
+    NSMutableData *signatureData = [NSMutableData dataWithLength:signatureLength];
+    if (!signatureData) {
+        return nil;
+    }
+
+    size_t result = olm_pk_sign(sign,
+                                messageData.bytes, messageData.length,
+                                signatureData.mutableBytes, signatureLength);
+    if (result == olm_error()) {
+        const char *olm_error = olm_pk_signing_last_error(sign);
+
+        NSString *errorString = [NSString stringWithUTF8String:olm_error];
+        NSLog(@"[OLMPkSigning] sign: olm_pk_sign error: %@", errorString);
+
+        if (error && olm_error && errorString) {
+            *error = [NSError errorWithDomain:OLMErrorDomain
+                                         code:0
+                                     userInfo:@{
+                                                NSLocalizedDescriptionKey: errorString,
+                                                NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:@"olm_pk_sign error: %@", errorString]
+                                                }];
+        }
+
+        return nil;
+    }
+
+    NSString *signature = [[NSString alloc] initWithData:signatureData encoding:NSUTF8StringEncoding];
+    return signature;
+}
+
++ (NSData *)generateSeed {
+    size_t seedLength = olm_pk_signing_seed_length();
+    NSMutableData *seed = [OLMUtility randomBytesOfLength:seedLength];
+    if (!seed) {
+        return nil;
+    }
+
+    return seed;
+}
+
+@end

xcode/OLMKitTests/OLMKitPkTests.m

@@ -104,4 +104,39 @@
     XCTAssertEqualObjects(decrypted, TEST_TEXT);
 }
 
+- (void)testSignAndVerify {
+
+    UInt8 seedBytes[] = {
+        0x77, 0x07, 0x6D, 0x0A, 0x73, 0x18, 0xA5, 0x7D,
+        0x3C, 0x16, 0xC1, 0x72, 0x51, 0xB2, 0x66, 0x45,
+        0xDF, 0x4C, 0x2F, 0x87, 0xEB, 0xC0, 0x99, 0x2A,
+        0xB1, 0x77, 0xFB, 0xA5, 0x1D, 0xB9, 0x2C, 0x2A
+    };
+
+    NSData *seed = [NSData dataWithBytes:seedBytes length:sizeof(seedBytes)];
+
+    NSString *TEST_TEXT = @"We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness.";
+
+    OLMPkSigning *signing = [OLMPkSigning new];
+
+    NSError *error;
+    NSString *pubKey = [signing doInitWithSeed:seed error:&error];
+    XCTAssertNotNil(pubKey);
+    XCTAssertNil(error);
+
+    NSString *sig = [signing sign:TEST_TEXT error:&error];
+    XCTAssertNotNil(sig);
+    XCTAssertNil(error);
+
+    OLMUtility *util = [OLMUtility new];
+    BOOL verify = [util verifyEd25519Signature:sig key:pubKey message:[TEST_TEXT dataUsingEncoding:NSUTF8StringEncoding] error:&error];
+    XCTAssertTrue(verify);
+    XCTAssertNil(error);
+
+    NSString *badSig = [sig stringByReplacingCharactersInRange:NSMakeRange(0, 1) withString:@"p"];
+    verify = [util verifyEd25519Signature:badSig key:pubKey message:[TEST_TEXT dataUsingEncoding:NSUTF8StringEncoding] error:&error];
+    XCTAssertFalse(verify);
+    XCTAssertNotNil(error);
+}
+
 @end