CKT CKT - 2 months ago 17
Objective-C Question

CFRelease crash in iOS10

Below is my code, which used to work fine till iOS 9.

- (NSData *)encryptWithDataPublicKey:(NSString*)data keyTag:(NSString*)tag
{

SecKeyRef publicKey = NULL;
NSData *publicTag = [NSData dataWithBytes:[tag UTF8String] length:[tag length]];

NSMutableDictionary *queryPublicKey =
[[NSMutableDictionary alloc] init];

[queryPublicKey setObject:(__bridge id)kSecClassKey forKey:(__bridge id)kSecClass];

[queryPublicKey setObject:publicTag forKey:(__bridge id)kSecAttrApplicationTag];

[queryPublicKey setObject:(__bridge id)kSecAttrKeyTypeRSA forKey:(__bridge id)kSecAttrKeyType];

[queryPublicKey setObject:[NSNumber numberWithBool:YES] forKey:(__bridge id)kSecReturnRef];

OSStatus status = SecItemCopyMatching
((__bridge CFDictionaryRef)queryPublicKey, (CFTypeRef *)&publicKey);

NSData *encodedData = nil;

if (status == noErr && publicKey) {
NSData *dataToEncrypt = [data dataUsingEncoding:NSUTF8StringEncoding];
encodedData = [self encryptData:dataToEncrypt withKeyRef:publicKey];
CFRelease(publicKey);
}
return encodedData;
}


This method used to work fine till iOS 9.x, But today when I have updated my XCode to 8 and run on iOS 10 device. Application is getting crashed at

CFRelease(publicKey).

Before crashing below is the log from console.


could not load any Objective-C class information. This will
significantly reduce the quality of type information available


enter image description here

Could not able to get the issue exactly.

When I enabled Zombie, and reproduce the crash. Below is the log from console.

*** -[Not A Type release]: message sent to deallocated instance 0x170225880

Thanks in advance.

I got the Issue.
there is an inner method encodedData = [self encryptData:dataToEncrypt withKeyRef:publicKey];

where SecKeyRef object is getting released.

But I wonder how this worked till iOS9???????

-(NSData *)encryptData:(NSData *)data withKeyRef:(SecKeyRef) keyRef{
const uint8_t *srcbuf = (const uint8_t *)[data bytes];
size_t srclen = (size_t)data.length;

size_t block_size = SecKeyGetBlockSize(keyRef) * sizeof(uint8_t);
void *outbuf = malloc(block_size);
size_t src_block_size = block_size - 11;

NSMutableData *ret = [[NSMutableData alloc] init];
for(int idx=0; idx<srclen; idx+=src_block_size){
size_t data_len = srclen - idx;
if(data_len > src_block_size){
data_len = src_block_size;
}

size_t outlen = block_size;
OSStatus status = noErr;
status = SecKeyEncrypt(keyRef,
kSecPaddingPKCS1,
srcbuf + idx,
data_len,
outbuf,
&outlen
);
if (status != 0) {
ret = nil;
break;
}else{
[ret appendBytes:outbuf length:outlen];
}
}

free(outbuf);
CFRelease(keyRef);
return ret;
}

Answer

In encryptData:withKeyRef: you have an unbalanced CFRelease at the end of the method. Nothing in that method retained keyRef, but you release it. Remove that call.

Why didn't it crash before? Because something else was likely retaining it internally previously, possibly a cache, possibly something else. Cocoa makes no promises that an over-release will immediately (or ever) lead to a crash. You were into undefined behavior.

It's very distressing, though, that the static analyzer isn't detecting this. I would open a bug report about that (bugreport.apple.com). You have a very clear memory management violation and the analyzer should have caught it.