EXC_BAD_ACCESS when using string declared in header file

Question

I've declared a string in my header file like so:

@property (nonatomic, retain) NSString *resultOfHash;

I call my getHash method like so:

 NSString *hash = [self getHash];

My getHash method is:

-(NSString *) getHash
{
//Get username form Keychain
KeychainItemWrapper *keyChain = [[KeychainItemWrapper alloc]    initWithIdentifier:KeyChainName accessGroup:nil];
username = [keyChain objectForKey:(__bridge id)kSecAttrAccount];

//get token from NSUserDefauls
NSString *token = [[NSUserDefaults standardUserDefaults]objectForKey:@"Token"];

NSString *toHash = [[username stringByAppendingString:HashExtra] stringByAppendingString:token];

const char *s = [toHash cStringUsingEncoding:NSASCIIStringEncoding];

NSData *keyData = [NSData dataWithBytes:s length:strlen(s)];

uint8_t digest[CC_SHA1_DIGEST_LENGTH] = {0};

CC_SHA512(keyData.bytes, keyData.length, digest);

NSData *out = [NSData dataWithBytes:digest length:CC_SHA1_DIGEST_LENGTH];

//convert to string
resultOfHash = [out description];
//App crashed out above

// get rid of unwanted characters
resultOfHash = [resultOfHash stringByReplacingOccurrencesOfString:@" " withString:@""];
resultOfHash = [resultOfHash stringByReplacingOccurrencesOfString:@"<" withString:@""];
resultOfHash = [resultOfHash stringByReplacingOccurrencesOfString:@">" withString:@""];

//log to make sure it works
NSLog(@"hash is: %@", resultOfHash);

return resultOfHash;
}

My code crashes out at the line: ResultOfHash = [out description]; but I'm not sure why.

When I use a local variable the conversion works fine but then I cannot return the local variable from the getHash method. Example:

Replace ResultOfHash = [out description];

with

NSString *local = [out description];
return local;

and the conversion works fine and when I debug line by line, the debugger will go to my closing bracket on my method and then produce the EXC_BAD_ACCESS error.

I've tried running NSZombie but that didn't find anything at all.

Any help in trying to sort this out would be greatly appreciated.

did you have synthesize the string resultOfHash ??? – DShah Jan 06 '12 at 16:08 — DShah, Jan 06 '12 at 16:08

score 1 · Answer 1 · edited May 23 '17 at 11:48

1

Have a look at the answer in this question. Try converting to NSString using

[NSString *local = [[[NSString alloc] initWithData:out encoding:NSASCIIStringEncoding];

I haven't tested this code with this encoding, but it's similar to something I already use.

Update -

I corrected an error in the code above. I somehow left the method signiture out in a distracted copy and paste.

edited May 23 '17 at 11:48

Community

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answered Jan 06 '12 at 15:33

Draco

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Thanks for pointing this out Draco. I didn't know using the description part of NSData was wrong. I'll change that. – user1134552 Jan 09 '12 at 10:12

score 0 · Answer 2 · answered Jan 06 '12 at 15:32

0

It's crashing because out is unretained. You should add retain:

resultOfHash = [[out description] retain];

or use retained property:

self.resultOfHash = [out description];

Check this, it should be work.

answered Jan 06 '12 at 15:32

Tomasz Wojtkowiak

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The author seems to be using ARC. – tia Jan 06 '12 at 15:44
In the fact, he didn't write about it. – Tomasz Wojtkowiak Jan 06 '12 at 16:05

score 0 · Answer 3 · edited Jan 06 '12 at 15:54

0

You probably need to use an NSMutableString.

edited Jan 06 '12 at 15:54

axel22

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answered Jan 06 '12 at 15:33

Krishna K

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score 0 · Accepted Answer · answered Jan 06 '12 at 15:47

0

I think the problem is here:

uint8_t digest[CC_SHA1_DIGEST_LENGTH] = {0};
CC_SHA512(keyData.bytes, keyData.length, digest);
NSData *out = [NSData dataWithBytes:digest length:CC_SHA1_DIGEST_LENGTH];

You are using CC_SHA512, but only allocate array of size CC_SHA1_DIGEST_LENGTH, which is smaller and will lead to the buffer overrunning.

To correct this, you should use CC_SHA512_DIGEST_LENGTH instead.

answered Jan 06 '12 at 15:47

tia

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Spot on Tia. This code was originally setup for SHA512 and I converted to SHA1 but missed that line. When I changed it to SHA1 and changed resultsofHash to NSMutableString, the code worked. Thanks for that – user1134552 Jan 09 '12 at 10:09

EXC_BAD_ACCESS when using string declared in header file

4 Answers4