OLMKit: add Short Authentication String verification

(cherry picked from commit 3e954ca2729d3333ea853c878602d1696f616573)

3 files changed, 200 insertions, 0 deletions

diff --git a/xcode/OLMKit/OLMKit.h b/xcode/OLMKit/OLMKit.h
index 6f79399..2ed6ebd 100644
--- a/xcode/OLMKit/OLMKit.h
+++ b/xcode/OLMKit/OLMKit.h
@@ -28,6 +28,7 @@
 #import <OLMKit/OLMOutboundGroupSession.h>
 #import <OLMKit/OLMPkEncryption.h>
 #import <OLMKit/OLMPkDecryption.h>
+#import <OLMKit/OLMSAS.h>
 
 @interface OLMKit : NSObject
 
diff --git a/xcode/OLMKit/OLMSAS.h b/xcode/OLMKit/OLMSAS.h
new file mode 100644
index 0000000..454c8e0
--- /dev/null
+++ b/xcode/OLMKit/OLMSAS.h
@@ -0,0 +1,59 @@
+/*
+ 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
+
+/**
+ Short Authentication String verification utility class.
+ */
+@interface OLMSAS : NSObject
+
+/**
+ Get the public key of the SAS object.
+ */
+- (NSString * _Nullable)publicKey;
+
+/**
+ Set the public key of other user.
+
+ @param theirPublicKey the other user's public key.
+ @return error the error if any.
+ */
+- (NSError* _Nullable)setTheirPublicKey:(NSString*)theirPublicKey;
+
+/**
+ Generate bytes to use for the short authentication string.
+
+ @param info extra information to mix in when generating the bytes, as per the Matrix spec.
+ @param length the size of the output buffer. For hex-based SAS as in the Matrix spec, this will be 5.
+ @return generated bytes
+ */
+- (NSData *)generateBytes:(NSString*)info length:(NSUInteger)length;
+
+/**
+ Generate a message authentication code (MAC) based on the shared secret.
+
+ @param input the message to produce the authentication code for.
+ @param info extra information to mix in when generating the MAC, as per the Matrix spec.
+ @param error the error if any.
+ @return the MAC.
+ */
+- (NSString *)calculateMac:(NSString*)input info:(NSString*)info error:(NSError* _Nullable *)error; // TODO: NSError?
+
+@end
+
+NS_ASSUME_NONNULL_END
diff --git a/xcode/OLMKit/OLMSAS.m b/xcode/OLMKit/OLMSAS.m
new file mode 100644
index 0000000..d95f948
--- /dev/null
+++ b/xcode/OLMKit/OLMSAS.m
@@ -0,0 +1,140 @@
+/*
+ Copyright 2018 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 "OLMSAS.h"
+
+#include "olm/olm.h"
+#include "olm/sas.h"
+#include "OLMUtility.h"
+
+@interface OLMSAS () {
+    void *olmSASbuffer;
+    OlmSAS *olmSAS;
+}
+@end
+
+@implementation OLMSAS
+
+- (void)dealloc {
+    olm_clear_sas(olmSAS);
+    free(olmSASbuffer);
+}
+
+- (instancetype)init {
+    self = [super init];
+    if (self) {
+        olmSASbuffer = malloc(olm_sas_size());
+        olmSAS = olm_sas(olmSASbuffer);
+
+        size_t randomLength = olm_create_sas_random_length(olmSAS);
+        NSMutableData *random = [OLMUtility randomBytesOfLength:randomLength];
+        if (!random) {
+            return nil;
+        }
+
+        olm_create_sas(olmSAS, random.mutableBytes, randomLength);
+
+        [random resetBytesInRange:NSMakeRange(0, randomLength)];
+    }
+    return self;
+}
+
+- (NSString * _Nullable)publicKey {
+    size_t publicKeyLength = olm_sas_pubkey_length(olmSAS);
+    NSMutableData *publicKeyData = [NSMutableData dataWithLength:publicKeyLength];
+    if (!publicKeyData) {
+        return nil;
+    }
+
+    size_t result = olm_sas_get_pubkey(olmSAS, publicKeyData.mutableBytes, publicKeyLength);
+    if (result == olm_error()) {
+        const char *olm_error = olm_sas_last_error(olmSAS);
+        NSLog(@"[OLMSAS] publicKey: olm_sas_get_pubkey error: %s", olm_error);
+        return nil;
+    }
+
+    NSString *publicKey = [[NSString alloc] initWithData:publicKeyData encoding:NSUTF8StringEncoding];
+    return publicKey;
+}
+
+- (NSError * _Nullable)setTheirPublicKey:(NSString*)theirPublicKey {
+    NSMutableData *theirPublicKeyData = [theirPublicKey dataUsingEncoding:NSUTF8StringEncoding].mutableCopy;
+
+    size_t result = olm_sas_set_their_key(olmSAS, theirPublicKeyData.mutableBytes, theirPublicKeyData.length);
+    if (result == olm_error()) {
+        const char *olm_error = olm_sas_last_error(olmSAS);
+        NSLog(@"[OLMSAS] setTheirPublicKey: olm_sas_set_their_key error: %s", olm_error);
+
+        NSString *errorString = [NSString stringWithUTF8String:olm_error];
+        if (olm_error && errorString) {
+            return [NSError errorWithDomain:OLMErrorDomain
+                                       code:0
+                                   userInfo:@{
+                                              NSLocalizedDescriptionKey: errorString,
+                                              NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:@"olm_sas_set_their_key error: %@", errorString]
+                                              }];
+        }
+    }
+
+    return nil;
+}
+
+- (NSData *)generateBytes:(NSString *)info length:(NSUInteger)length {
+    NSData *infoData = [info dataUsingEncoding:NSUTF8StringEncoding];
+
+    NSMutableData *bytes = [NSMutableData dataWithLength:length];
+    if (!bytes) {
+        return nil;
+    }
+
+    olm_sas_generate_bytes(olmSAS, infoData.bytes, infoData.length, bytes.mutableBytes, length);
+    return bytes;
+}
+
+- (NSString *)calculateMac:(NSString *)input info:(NSString *)info error:(NSError *__autoreleasing  _Nullable *)error {
+    NSMutableData *inputData = [input dataUsingEncoding:NSUTF8StringEncoding].mutableCopy;
+    NSData *infoData = [info dataUsingEncoding:NSUTF8StringEncoding];
+
+    size_t macLength = olm_sas_mac_length(olmSAS);
+    NSMutableData *macData = [NSMutableData dataWithLength:macLength];
+    if (!macData) {
+        return nil;
+    }
+
+    size_t result = olm_sas_calculate_mac(olmSAS,
+                                          inputData.mutableBytes, inputData.length,
+                                          infoData.bytes, infoData.length,
+                                          macData.mutableBytes, macLength);
+    if (result == olm_error()) {
+        const char *olm_error = olm_sas_last_error(olmSAS);
+        NSLog(@"[OLMSAS] calculateMac: olm_sas_calculate_mac error: %s", olm_error);
+
+        NSString *errorString = [NSString stringWithUTF8String:olm_error];
+        if (error && olm_error && errorString) {
+            *error = [NSError errorWithDomain:OLMErrorDomain
+                                         code:0
+                                     userInfo:@{
+                                                NSLocalizedDescriptionKey: errorString,
+                                                NSLocalizedFailureReasonErrorKey: [NSString stringWithFormat:@"olm_sas_calculate_mac error: %@", errorString]
+                                                }];
+        }
+        return nil;
+    }
+
+    NSString *mac = [[NSString alloc] initWithData:macData encoding:NSUTF8StringEncoding];
+    return mac;
+}
+
+@end