It is possible to store a NSDictionary
in the iPhone
keychain, using KeychainItemWrapper
(or without)?
If it's not possible, have you another solution?

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Yes, but when I read data, I have a reference to a empty NSString. – Michaël Mar 30 '12 at 18:51
7 Answers
You must properly serialize the NSDictionary
before storing it into the Keychain.
Using:
[dic description]
[dic propertyList]
you will end up with a NSDictionary
collection of only NSString
objects. If you want to maintain the data types of the objects, you can use NSPropertyListSerialization
.
KeychainItemWrapper *keychain = [[KeychainItemWrapper alloc] initWithIdentifier:@"arbitraryId" accessGroup:nil]
NSString *error;
//The following NSData object may be stored in the Keychain
NSData *dictionaryRep = [NSPropertyListSerialization dataFromPropertyList:dictionary format:NSPropertyListXMLFormat_v1_0 errorDescription:&error];
[keychain setObject:dictionaryRep forKey:kSecValueData];
//When the NSData object object is retrieved from the Keychain, you convert it back to NSDictionary type
dictionaryRep = [keychain objectForKey:kSecValueData];
NSDictionary *dictionary = [NSPropertyListSerialization propertyListFromData:dictionaryRep mutabilityOption:NSPropertyListImmutable format:nil errorDescription:&error];
if (error) {
NSLog(@"%@", error);
}
The NSDictionary
returned by the second call to NSPropertyListSerialization
will maintain original data types within the NSDictionary
collection.

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1I edited the code to reflect more accurately how this is used with KeychainItemWrapper. – Bret Deasy Nov 16 '12 at 01:24
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4This stores the data in `kSecAttrService`, which is not an encrypted field. I believe you meant to use `kSecValueData` here, which is the encrypted payload. – Rob Napier Apr 23 '13 at 16:57
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Your code does not work in ios7 for some reason. Would consider updating it to be more clear. For example, you say that we need to use [dic description] but in your example there is no dic variable. – user798719 Sep 02 '13 at 19:04
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1@user798719 - I'm actually saying not to use [dic description] and [dic propertyList] if you want to maintain data types in the NSDictionary object. – Bret Deasy Sep 12 '13 at 15:59
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3The code doesn't work, passing `NSData` for key `kSecValueData` breaks the `KeychainItemWrapper`, as internally it expects a value of `NSString` for this key (i.e., a password). This is because it needs to encrypt the payload of `kSecValueData`, and before it can do so it needs to convert it to `NSData`. Therefore the `KeychainItemWrapper` already does `[payloadString dataUsingEncoding:NSUTF8StringEncoding]` internally, and if you pass `NSData` as `payloadString`, you'll get an `Unrecognized selector sent to instance exception`. Check out my answer on this page for more details and a solution. – DTs Dec 18 '13 at 04:24
Using the KeychainItemWrapper
dependency requires modifying the library/sample code to accept NSData
as the encrypted payload, which is not future proof. Also, doing the NSDictionary > NSData > NSString
conversion sequence just so that you can use KeychainItemWrapper
is inefficient: KeychainItemWrapper
will convert your string back to NSData
anyway, to encrypt it.
Here's a complete solution that solves the above by utilizing the keychain library directly. It is implemented as a category so you use it like this:
// to store your dictionary
[myDict storeToKeychainWithKey:@"myStorageKey"];
// to retrieve it
NSDictionary *myDict = [NSDictionary dictionaryFromKeychainWithKey:@"myStorageKey"];
// to delete it
[myDict deleteFromKeychainWithKey:@"myStorageKey"];
and here's the Category:
@implementation NSDictionary (Keychain)
-(void) storeToKeychainWithKey:(NSString *)aKey {
// serialize dict
NSString *error;
NSData *serializedDictionary = [NSPropertyListSerialization dataFromPropertyList:self format:NSPropertyListXMLFormat_v1_0 errorDescription:&error];
// encrypt in keychain
if(!error) {
// first, delete potential existing entries with this key (it won't auto update)
[self deleteFromKeychainWithKey:aKey];
// setup keychain storage properties
NSDictionary *storageQuery = @{
(id)kSecAttrAccount: aKey,
(id)kSecValueData: serializedDictionary,
(id)kSecClass: (id)kSecClassGenericPassword,
(id)kSecAttrAccessible: (id)kSecAttrAccessibleWhenUnlocked
};
OSStatus osStatus = SecItemAdd((CFDictionaryRef)storageQuery, nil);
if(osStatus != noErr) {
// do someting with error
}
}
}
+(NSDictionary *) dictionaryFromKeychainWithKey:(NSString *)aKey {
// setup keychain query properties
NSDictionary *readQuery = @{
(id)kSecAttrAccount: aKey,
(id)kSecReturnData: (id)kCFBooleanTrue,
(id)kSecClass: (id)kSecClassGenericPassword
};
NSData *serializedDictionary = nil;
OSStatus osStatus = SecItemCopyMatching((CFDictionaryRef)readQuery, (CFTypeRef *)&serializedDictionary);
if(osStatus == noErr) {
// deserialize dictionary
NSString *error;
NSDictionary *storedDictionary = [NSPropertyListSerialization propertyListFromData:serializedDictionary mutabilityOption:NSPropertyListImmutable format:nil errorDescription:&error];
if(error) {
NSLog(@"%@", error);
}
return storedDictionary;
}
else {
// do something with error
return nil;
}
}
-(void) deleteFromKeychainWithKey:(NSString *)aKey {
// setup keychain query properties
NSDictionary *deletableItemsQuery = @{
(id)kSecAttrAccount: aKey,
(id)kSecClass: (id)kSecClassGenericPassword,
(id)kSecMatchLimit: (id)kSecMatchLimitAll,
(id)kSecReturnAttributes: (id)kCFBooleanTrue
};
NSArray *itemList = nil;
OSStatus osStatus = SecItemCopyMatching((CFDictionaryRef)deletableItemsQuery, (CFTypeRef *)&itemList);
// each item in the array is a dictionary
for (NSDictionary *item in itemList) {
NSMutableDictionary *deleteQuery = [item mutableCopy];
[deleteQuery setValue:(id)kSecClassGenericPassword forKey:(id)kSecClass];
// do delete
osStatus = SecItemDelete((CFDictionaryRef)deleteQuery);
if(osStatus != noErr) {
// do something with error
}
[deleteQuery release];
}
}
@end
In fact, you can modify it easily to store any kind of serializable object in the keychain, not just a dictionary. Just make an NSData
representation of the object you want to store.

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Made few minor changes to Dts category. Converted to ARC and using NSKeyedArchiver to store custom objects.
@implementation NSDictionary (Keychain)
-(void) storeToKeychainWithKey:(NSString *)aKey {
// serialize dict
NSData *serializedDictionary = [NSKeyedArchiver archivedDataWithRootObject:self];
// encrypt in keychain
// first, delete potential existing entries with this key (it won't auto update)
[self deleteFromKeychainWithKey:aKey];
// setup keychain storage properties
NSDictionary *storageQuery = @{
(__bridge id)kSecAttrAccount: aKey,
(__bridge id)kSecValueData: serializedDictionary,
(__bridge id)kSecClass: (__bridge id)kSecClassGenericPassword,
(__bridge id)kSecAttrAccessible: (__bridge id)kSecAttrAccessibleWhenUnlocked
};
OSStatus osStatus = SecItemAdd((__bridge CFDictionaryRef)storageQuery, nil);
if(osStatus != noErr) {
// do someting with error
}
}
+(NSDictionary *) dictionaryFromKeychainWithKey:(NSString *)aKey {
// setup keychain query properties
NSDictionary *readQuery = @{
(__bridge id)kSecAttrAccount: aKey,
(__bridge id)kSecReturnData: (id)kCFBooleanTrue,
(__bridge id)kSecClass: (__bridge id)kSecClassGenericPassword
};
CFDataRef serializedDictionary = NULL;
OSStatus osStatus = SecItemCopyMatching((__bridge CFDictionaryRef)readQuery, (CFTypeRef *)&serializedDictionary);
if(osStatus == noErr) {
// deserialize dictionary
NSData *data = (__bridge NSData *)serializedDictionary;
NSDictionary *storedDictionary = [NSKeyedUnarchiver unarchiveObjectWithData:data];
return storedDictionary;
}
else {
// do something with error
return nil;
}
}
-(void) deleteFromKeychainWithKey:(NSString *)aKey {
// setup keychain query properties
NSDictionary *deletableItemsQuery = @{
(__bridge id)kSecAttrAccount: aKey,
(__bridge id)kSecClass: (__bridge id)kSecClassGenericPassword,
(__bridge id)kSecMatchLimit: (__bridge id)kSecMatchLimitAll,
(__bridge id)kSecReturnAttributes: (id)kCFBooleanTrue
};
CFArrayRef itemList = nil;
OSStatus osStatus = SecItemCopyMatching((__bridge CFDictionaryRef)deletableItemsQuery, (CFTypeRef *)&itemList);
// each item in the array is a dictionary
NSArray *itemListArray = (__bridge NSArray *)itemList;
for (NSDictionary *item in itemListArray) {
NSMutableDictionary *deleteQuery = [item mutableCopy];
[deleteQuery setValue:(__bridge id)kSecClassGenericPassword forKey:(__bridge id)kSecClass];
// do delete
osStatus = SecItemDelete((__bridge CFDictionaryRef)deleteQuery);
if(osStatus != noErr) {
// do something with error
}
}
}
@end

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Looks good. I used yours except I made deleteFromKeychainWithKey a class method so I could also perform general cleanup without having the dictionary. – Fervus Apr 09 '15 at 14:38
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Works like a charm. I added the best parts from the KeychainItemWrapper. – dogsgod Feb 11 '16 at 20:02
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You can store anything, you just need to serialize it.
NSData *data = [NSKeyedArchiver archivedDataWithRootObject:dictionary];
You should be able to store that data in the keychain.

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2*** Assertion failure in -[KeychainItemWrapper writeToKeychain] 'Couldn't add the Keychain Item.' – Michaël Mar 30 '12 at 19:50
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You'll have to provide more details, then. There could be many reasons for 'Couldn't add the Keychain Item.' – wbyoung Mar 30 '12 at 20:48
I found that the keychain wrapper only wants strings. Not even NSData. So to store a dictionary you'll have to do as Bret suggested, but with an extra step to convert the NSData serialization to a string. Like this:
NSString *error;
KeychainItemWrapper *keychain = [[KeychainItemWrapper alloc] initWithIdentifier:MY_STRING accessGroup:nil];
NSData *dictionaryRep = [NSPropertyListSerialization dataFromPropertyList:dictToSave format:NSPropertyListXMLFormat_v1_0 errorDescription:&error];
NSString *xml = [[NSString alloc] initWithBytes:[dictionaryRep bytes] length:[dictionaryRep length] encoding:NSUTF8StringEncoding];
[keychain setObject:xml forKey:(__bridge id)(kSecValueData)];
Reading it back:
NSError *error;
NSString *xml = [keychain objectForKey:(__bridge id)(kSecValueData)];
if (xml && xml.length) {
NSData *dictionaryRep = [xml dataUsingEncoding:NSUTF8StringEncoding];
dict = [NSPropertyListSerialization propertyListWithData:dictionaryRep options:NSPropertyListImmutable format:nil error:&error];
if (error) {
NSLog(@"%@", error);
}
}

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Not all data is valid UTF-8 so this will not work. The best option is to encode to Base64. – zaph Jan 09 '15 at 04:02
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It might work; after all the XML starts out by claiming UTF-8 encoding, . I believe that Apple encodes data as Base64 in the XML (See https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/PropertyLists/SerializePlist/SerializePlist.html for an example). If that does fail, your fallback to Base64 is a good idea. – Graham Perks Jan 09 '15 at 15:49
I added access group support and simulator safety to Amols solution:
//
// NSDictionary+SharedKeyChain.h
// LHSharedKeyChain
//
#import <Foundation/Foundation.h>
@interface NSDictionary (SharedKeyChain)
/**
* Returns a previously stored dictionary from the KeyChain.
*
* @param key NSString The name of the dictionary. There can be multiple dictionaries stored in the KeyChain.
* @param accessGroup NSString Access group for shared KeyChains, set to nil for no group.
*
* @return NSDictionary A dictionary that has been stored in the Keychain, nil if no dictionary for the key and accessGroup exist.
*/
+ (NSDictionary *)dictionaryFromKeychainWithKey:(NSString *)key accessGroup:(NSString *)accessGroup;
/**
* Deletes a previously stored dictionary from the KeyChain.
*
* @param key NSString The name of the dictionary. There can be multiple dictionaries stored in the KeyChain.
* @param accessGroup NSString Access group for shared KeyChains, set to nil for no group.
*/
+ (void)deleteFromKeychainWithKey:(NSString *)key accessGroup:(NSString *)accessGroup;
/**
* Save dictionary instance to the KeyChain. Any previously existing data with the same key and accessGroup will be overwritten.
*
* @param key NSString The name of the dictionary. There can be multiple dictionaries stored in the KeyChain.
* @param accessGroup NSString Access group for shared KeyChains, set to nil for no group.
*/
- (void)storeToKeychainWithKey:(NSString *)key accessGroup:(NSString *)accessGroup;
@end
//
// NSDictionary+SharedKeyChain.m
// LHSharedKeyChain
//
#import "NSDictionary+SharedKeyChain.h"
@implementation NSDictionary (SharedKeyChain)
- (void)storeToKeychainWithKey:(NSString *)key accessGroup:(NSString *)accessGroup;
{
// serialize dict
NSData *serializedDictionary = [NSKeyedArchiver archivedDataWithRootObject:self];
// encrypt in keychain
// first, delete potential existing entries with this key (it won't auto update)
[NSDictionary deleteFromKeychainWithKey:key accessGroup:accessGroup];
// setup keychain storage properties
NSDictionary *storageQuery = @{
(__bridge id)kSecAttrAccount: key,
#if TARGET_IPHONE_SIMULATOR
// Ignore the access group if running on the iPhone simulator.
//
// Apps that are built for the simulator aren't signed, so there's no keychain access group
// for the simulator to check. This means that all apps can see all keychain items when run
// on the simulator.
//
// If a SecItem contains an access group attribute, SecItemAdd and SecItemUpdate on the
// simulator will return -25243 (errSecNoAccessForItem).
#else
(__bridge id)kSecAttrAccessGroup: accessGroup,
#endif
(__bridge id)kSecValueData: serializedDictionary,
(__bridge id)kSecClass: (__bridge id)kSecClassGenericPassword,
(__bridge id)kSecAttrAccessible: (__bridge id)kSecAttrAccessibleWhenUnlocked
};
OSStatus status = SecItemAdd ((__bridge CFDictionaryRef)storageQuery, nil);
if (status != noErr)
{
NSLog (@"%d %@", (int)status, @"Couldn't save to Keychain.");
}
}
+ (NSDictionary *)dictionaryFromKeychainWithKey:(NSString *)key accessGroup:(NSString *)accessGroup;
{
// setup keychain query properties
NSDictionary *readQuery = @{
(__bridge id)kSecAttrAccount: key,
#if TARGET_IPHONE_SIMULATOR
// Ignore the access group if running on the iPhone simulator.
//
// Apps that are built for the simulator aren't signed, so there's no keychain access group
// for the simulator to check. This means that all apps can see all keychain items when run
// on the simulator.
//
// If a SecItem contains an access group attribute, SecItemAdd and SecItemUpdate on the
// simulator will return -25243 (errSecNoAccessForItem).
#else
(__bridge id)kSecAttrAccessGroup: accessGroup,
#endif
(__bridge id)kSecReturnData: (id)kCFBooleanTrue,
(__bridge id)kSecClass: (__bridge id)kSecClassGenericPassword
};
CFDataRef serializedDictionary = NULL;
OSStatus status = SecItemCopyMatching ((__bridge CFDictionaryRef)readQuery, (CFTypeRef *)&serializedDictionary);
if (status == noErr)
{
// deserialize dictionary
NSData *data = (__bridge NSData *)serializedDictionary;
NSDictionary *storedDictionary = [NSKeyedUnarchiver unarchiveObjectWithData:data];
return storedDictionary;
}
else
{
NSLog (@"%d %@", (int)status, @"Couldn't read from Keychain.");
return nil;
}
}
+ (void)deleteFromKeychainWithKey:(NSString *)key accessGroup:(NSString *)accessGroup;
{
// setup keychain query properties
NSDictionary *deletableItemsQuery = @{
(__bridge id)kSecAttrAccount: key,
#if TARGET_IPHONE_SIMULATOR
// Ignore the access group if running on the iPhone simulator.
//
// Apps that are built for the simulator aren't signed, so there's no keychain access group
// for the simulator to check. This means that all apps can see all keychain items when run
// on the simulator.
//
// If a SecItem contains an access group attribute, SecItemAdd and SecItemUpdate on the
// simulator will return -25243 (errSecNoAccessForItem).
#else
(__bridge id)kSecAttrAccessGroup: accessGroup,
#endif
(__bridge id)kSecClass: (__bridge id)kSecClassGenericPassword,
(__bridge id)kSecMatchLimit: (__bridge id)kSecMatchLimitAll,
(__bridge id)kSecReturnAttributes: (id)kCFBooleanTrue
};
CFArrayRef itemList = nil;
OSStatus status = SecItemCopyMatching ((__bridge CFDictionaryRef)deletableItemsQuery, (CFTypeRef *)&itemList);
// each item in the array is a dictionary
NSArray *itemListArray = (__bridge NSArray *)itemList;
for (NSDictionary *item in itemListArray)
{
NSMutableDictionary *deleteQuery = [item mutableCopy];
[deleteQuery setValue:(__bridge id)kSecClassGenericPassword forKey:(__bridge id)kSecClass];
// do delete
status = SecItemDelete ((__bridge CFDictionaryRef)deleteQuery);
if (status != noErr)
{
NSLog (@"%d %@", (int)status, @"Couldn't delete from Keychain.");
}
}
}
@end

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