I have to remove an NSString (containing some confidential data) from memory but not only by setting it to nil, but by nullifying it's bytes. What I've tried so far is:
NSString *str = #"test";
NSLog(#"original string:%#", str);
CFStringRef ref = (__bridge CFStringRef)str;
const char * strPtr = CFStringGetCStringPtr(ref, kCFStringEncodingUTF8);
memset(strPtr, 0, [str lengthOfBytesUsingEncoding:NSUTF8StringEncoding]);
NSLog(#"cleared string:%#", str);
but the function CFStringGetCStringPtr is returning NULL so it crashes at the line with the memset. Apple says here that in some cases it is normal for that function to return NULL, but then I don't know how to solve this.
Thanks in advance
Don't store confident data as strings. You can't remove them from memory easily.
If possible, use NSMutableData to store confident data, instead.
Try This:
NSMutableString *str = [NSMutableString stringWithString:#"test"];
NSLog(#"original string:%#", str);
CFStringRef ref = ( CFStringRef)str;
CFIndex stringLength = CFStringGetLength(ref), usedBytes = 0L;
const char * strPtr = NULL;
strPtr = CFStringGetCStringPtr(ref, kCFStringEncodingUTF8);
char *freeUTF8StringPtr = NULL;
for(CFIndex idx = 0L; (strPtr != NULL) && (strPtr[idx] != 0); idx++)
{
if(strPtr[idx] >= 128) { strPtr = NULL; }
}
if((strPtr == NULL) && ((freeUTF8StringPtr = malloc(stringLength + 1L)) != NULL))
{
CFStringGetBytes(ref, CFRangeMake(0L, stringLength), kCFStringEncodingUTF8, '?', false, (UInt8*)freeUTF8StringPtr, stringLength, &usedBytes);
freeUTF8StringPtr[usedBytes] = 0;
strPtr = (const char *)freeUTF8StringPtr;
}
NSUInteger memorySize=[str lengthOfBytesUsingEncoding:NSUTF8StringEncoding];
NSLog(#"cleared string:%#", str);
I have tried something like this below:-
NSMutableString *str = #"test";
NSLog(#"original string:%#", str);
CFStringRef ref = (__bridge CFStringRef)str;//kCFStringEncodingUTF16
const char * strPtr = CFStringGetCStringPtr(ref, kCFStringEncodingUTF16);
NSUInteger memorySize=[str lengthOfBytesUsingEncoding:NSUTF8StringEncoding];
NSLog(#"cleared string:%d", memorySize);
Output := 4
Related
I have a string variable in iOS and I would like to convert that to a character array and then to a hex bytes like 0xD6, 0xD6 etc.
It will be great if there is a library in Objective-C that I can use for this
swift 4
string to byte:
let strChar = "A"
let data1 = [UInt8](self.strChar.utf8)
may be answer is here:
string to chars:
NSString *s = #"Some string";
const char *c = [s UTF8String];
chars to hex:
- (NSData *)dataFromHexString {
const char *chars = [self UTF8String];
int i = 0, len = self.length;
NSMutableData *data = [NSMutableData dataWithCapacity:len / 2];
char byteChars[3] = {'\0','\0','\0'};
unsigned long wholeByte;
while (i < len) {
byteChars[0] = chars[i++];
byteChars[1] = chars[i++];
wholeByte = strtoul(byteChars, NULL, 16);
[data appendBytes:&wholeByte length:1];
}
return data;
}
reference:NSString (hex) to bytes
Is there any method in Objective-C that converts a hex string to bytes? For example #"1156FFCD3430AA22" to an unsigned char array {0x11, 0x56, 0xFF, ...}.
Fastest NSString category implementation that I could think of (cocktail of some examples):
- (NSData *)dataFromHexString {
const char *chars = [self UTF8String];
int i = 0, len = self.length;
NSMutableData *data = [NSMutableData dataWithCapacity:len / 2];
char byteChars[3] = {'\0','\0','\0'};
unsigned long wholeByte;
while (i < len) {
byteChars[0] = chars[i++];
byteChars[1] = chars[i++];
wholeByte = strtoul(byteChars, NULL, 16);
[data appendBytes:&wholeByte length:1];
}
return data;
}
It is close to 8 times faster than wookay's solution. NSScanner is quite slow.
#interface NSString (NSStringHexToBytes)
-(NSData*) hexToBytes ;
#end
#implementation NSString (NSStringHexToBytes)
-(NSData*) hexToBytes {
NSMutableData* data = [NSMutableData data];
int idx;
for (idx = 0; idx+2 <= self.length; idx+=2) {
NSRange range = NSMakeRange(idx, 2);
NSString* hexStr = [self substringWithRange:range];
NSScanner* scanner = [NSScanner scannerWithString:hexStr];
unsigned int intValue;
[scanner scanHexInt:&intValue];
[data appendBytes:&intValue length:1];
}
return data;
}
#end
/// example
unsigned char bytes[] = { 0x11, 0x56, 0xFF, 0xCD, 0x34, 0x30, 0xAA, 0x22 };
NSData* expectedData = [NSData dataWithBytes:bytes length:sizeof(bytes)];
NSLog(#"data %#", [#"1156FFCD3430AA22" hexToBytes]);
NSLog(#"expectedData isEqual:%d", [expectedData isEqual:[#"1156FFCD3430AA22" hexToBytes]]);
The scanHexInt: and similar methods of NSScanner might be helpful in doing what you want, but you'd probably need to break the string up into smaller chunks first, in which case doing the translation manually might be simpler than using NSScanner.
Not in the way you are doing it. You'll need to write your own method to take every two characters, interpret them as an int, and store them in an array.
Modified approach,
/* Converts a hex string to bytes.
Precondition:
. The hex string can be separated by space or not.
. the string length without space or 0x, must be even. 2 symbols for one byte/char
. sample input: 23 3A F1 OR 233AF1, 0x23 0X231f 2B
*/
+ (NSData *) dataFromHexString:(NSString*)hexString
{
NSString * cleanString = [Util cleanNonHexCharsFromHexString:hexString];
if (cleanString == nil) {
return nil;
}
NSMutableData *result = [[NSMutableData alloc] init];
int i = 0;
for (i = 0; i+2 <= cleanString.length; i+=2) {
NSRange range = NSMakeRange(i, 2);
NSString* hexStr = [cleanString substringWithRange:range];
NSScanner* scanner = [NSScanner scannerWithString:hexStr];
unsigned int intValue;
[scanner scanHexInt:&intValue];
unsigned char uc = (unsigned char) intValue;
[result appendBytes:&uc length:1];
}
NSData * data = [NSData dataWithData:result];
[result release];
return data;
}
/* Clean a hex string by removing spaces and 0x chars.
. The hex string can be separated by space or not.
. sample input: 23 3A F1; 233AF1; 0x23 0x3A 0xf1
*/
+ (NSString *) cleanNonHexCharsFromHexString:(NSString *)input
{
if (input == nil) {
return nil;
}
NSString * output = [input stringByReplacingOccurrencesOfString:#"0x" withString:#""
options:NSCaseInsensitiveSearch range:NSMakeRange(0, input.length)];
NSString * hexChars = #"0123456789abcdefABCDEF";
NSCharacterSet *hexc = [NSCharacterSet characterSetWithCharactersInString:hexChars];
NSCharacterSet *invalidHexc = [hexc invertedSet];
NSString * allHex = [[output componentsSeparatedByCharactersInSet:invalidHexc] componentsJoinedByString:#""];
return allHex;
}
First attempt in Swift 2.2:
func hexStringToBytes(hexString: String) -> NSData? {
guard let chars = hexString.cStringUsingEncoding(NSUTF8StringEncoding) else { return nil}
var i = 0
let length = hexString.characters.count
let data = NSMutableData(capacity: length/2)
var byteChars: [CChar] = [0, 0, 0]
var wholeByte: CUnsignedLong = 0
while i < length {
byteChars[0] = chars[i]
i+=1
byteChars[1] = chars[i]
i+=1
wholeByte = strtoul(byteChars, nil, 16)
data?.appendBytes(&wholeByte, length: 1)
}
return data
}
Or, as an extension on String:
extension String {
func dataFromHexString() -> NSData? {
guard let chars = cStringUsingEncoding(NSUTF8StringEncoding) else { return nil}
var i = 0
let length = characters.count
let data = NSMutableData(capacity: length/2)
var byteChars: [CChar] = [0, 0, 0]
var wholeByte: CUnsignedLong = 0
while i < length {
byteChars[0] = chars[i]
i+=1
byteChars[1] = chars[i]
i+=1
wholeByte = strtoul(byteChars, nil, 16)
data?.appendBytes(&wholeByte, length: 1)
}
return data
}
}
This is a continuous work-in-progress, but appears to work well so far.
Further optimizations and a more in-depth discussion can be found on Code Review.
Several solution is returned wrong value if the string like this
"DBA"
The correct data for "DBA" string is "\x0D\xBA" (int value : 3514)
if you got a data is not like this "\x0D\xBA" it mean you got a wrong byte because the value will be different, for example you got data like this "\xDB\x0A" the int value is 56074
Here is rewrite the solution:
+ (NSData *)dataFromHexString:(NSString *) string {
if([string length] % 2 == 1){
string = [#"0"stringByAppendingString:string];
}
const char *chars = [string UTF8String];
int i = 0, len = (int)[string length];
NSMutableData *data = [NSMutableData dataWithCapacity:len / 2];
char byteChars[3] = {'\0','\0','\0'};
unsigned long wholeByte;
while (i < len) {
byteChars[0] = chars[i++];
byteChars[1] = chars[i++];
wholeByte = strtoul(byteChars, NULL, 16);
[data appendBytes:&wholeByte length:1];
}
return data;
}
Is there any method in Objective-C that converts a hex string to bytes? For example #"1156FFCD3430AA22" to an unsigned char array {0x11, 0x56, 0xFF, ...}.
Fastest NSString category implementation that I could think of (cocktail of some examples):
- (NSData *)dataFromHexString {
const char *chars = [self UTF8String];
int i = 0, len = self.length;
NSMutableData *data = [NSMutableData dataWithCapacity:len / 2];
char byteChars[3] = {'\0','\0','\0'};
unsigned long wholeByte;
while (i < len) {
byteChars[0] = chars[i++];
byteChars[1] = chars[i++];
wholeByte = strtoul(byteChars, NULL, 16);
[data appendBytes:&wholeByte length:1];
}
return data;
}
It is close to 8 times faster than wookay's solution. NSScanner is quite slow.
#interface NSString (NSStringHexToBytes)
-(NSData*) hexToBytes ;
#end
#implementation NSString (NSStringHexToBytes)
-(NSData*) hexToBytes {
NSMutableData* data = [NSMutableData data];
int idx;
for (idx = 0; idx+2 <= self.length; idx+=2) {
NSRange range = NSMakeRange(idx, 2);
NSString* hexStr = [self substringWithRange:range];
NSScanner* scanner = [NSScanner scannerWithString:hexStr];
unsigned int intValue;
[scanner scanHexInt:&intValue];
[data appendBytes:&intValue length:1];
}
return data;
}
#end
/// example
unsigned char bytes[] = { 0x11, 0x56, 0xFF, 0xCD, 0x34, 0x30, 0xAA, 0x22 };
NSData* expectedData = [NSData dataWithBytes:bytes length:sizeof(bytes)];
NSLog(#"data %#", [#"1156FFCD3430AA22" hexToBytes]);
NSLog(#"expectedData isEqual:%d", [expectedData isEqual:[#"1156FFCD3430AA22" hexToBytes]]);
The scanHexInt: and similar methods of NSScanner might be helpful in doing what you want, but you'd probably need to break the string up into smaller chunks first, in which case doing the translation manually might be simpler than using NSScanner.
Not in the way you are doing it. You'll need to write your own method to take every two characters, interpret them as an int, and store them in an array.
Modified approach,
/* Converts a hex string to bytes.
Precondition:
. The hex string can be separated by space or not.
. the string length without space or 0x, must be even. 2 symbols for one byte/char
. sample input: 23 3A F1 OR 233AF1, 0x23 0X231f 2B
*/
+ (NSData *) dataFromHexString:(NSString*)hexString
{
NSString * cleanString = [Util cleanNonHexCharsFromHexString:hexString];
if (cleanString == nil) {
return nil;
}
NSMutableData *result = [[NSMutableData alloc] init];
int i = 0;
for (i = 0; i+2 <= cleanString.length; i+=2) {
NSRange range = NSMakeRange(i, 2);
NSString* hexStr = [cleanString substringWithRange:range];
NSScanner* scanner = [NSScanner scannerWithString:hexStr];
unsigned int intValue;
[scanner scanHexInt:&intValue];
unsigned char uc = (unsigned char) intValue;
[result appendBytes:&uc length:1];
}
NSData * data = [NSData dataWithData:result];
[result release];
return data;
}
/* Clean a hex string by removing spaces and 0x chars.
. The hex string can be separated by space or not.
. sample input: 23 3A F1; 233AF1; 0x23 0x3A 0xf1
*/
+ (NSString *) cleanNonHexCharsFromHexString:(NSString *)input
{
if (input == nil) {
return nil;
}
NSString * output = [input stringByReplacingOccurrencesOfString:#"0x" withString:#""
options:NSCaseInsensitiveSearch range:NSMakeRange(0, input.length)];
NSString * hexChars = #"0123456789abcdefABCDEF";
NSCharacterSet *hexc = [NSCharacterSet characterSetWithCharactersInString:hexChars];
NSCharacterSet *invalidHexc = [hexc invertedSet];
NSString * allHex = [[output componentsSeparatedByCharactersInSet:invalidHexc] componentsJoinedByString:#""];
return allHex;
}
First attempt in Swift 2.2:
func hexStringToBytes(hexString: String) -> NSData? {
guard let chars = hexString.cStringUsingEncoding(NSUTF8StringEncoding) else { return nil}
var i = 0
let length = hexString.characters.count
let data = NSMutableData(capacity: length/2)
var byteChars: [CChar] = [0, 0, 0]
var wholeByte: CUnsignedLong = 0
while i < length {
byteChars[0] = chars[i]
i+=1
byteChars[1] = chars[i]
i+=1
wholeByte = strtoul(byteChars, nil, 16)
data?.appendBytes(&wholeByte, length: 1)
}
return data
}
Or, as an extension on String:
extension String {
func dataFromHexString() -> NSData? {
guard let chars = cStringUsingEncoding(NSUTF8StringEncoding) else { return nil}
var i = 0
let length = characters.count
let data = NSMutableData(capacity: length/2)
var byteChars: [CChar] = [0, 0, 0]
var wholeByte: CUnsignedLong = 0
while i < length {
byteChars[0] = chars[i]
i+=1
byteChars[1] = chars[i]
i+=1
wholeByte = strtoul(byteChars, nil, 16)
data?.appendBytes(&wholeByte, length: 1)
}
return data
}
}
This is a continuous work-in-progress, but appears to work well so far.
Further optimizations and a more in-depth discussion can be found on Code Review.
Several solution is returned wrong value if the string like this
"DBA"
The correct data for "DBA" string is "\x0D\xBA" (int value : 3514)
if you got a data is not like this "\x0D\xBA" it mean you got a wrong byte because the value will be different, for example you got data like this "\xDB\x0A" the int value is 56074
Here is rewrite the solution:
+ (NSData *)dataFromHexString:(NSString *) string {
if([string length] % 2 == 1){
string = [#"0"stringByAppendingString:string];
}
const char *chars = [string UTF8String];
int i = 0, len = (int)[string length];
NSMutableData *data = [NSMutableData dataWithCapacity:len / 2];
char byteChars[3] = {'\0','\0','\0'};
unsigned long wholeByte;
while (i < len) {
byteChars[0] = chars[i++];
byteChars[1] = chars[i++];
wholeByte = strtoul(byteChars, NULL, 16);
[data appendBytes:&wholeByte length:1];
}
return data;
}
perhaps I'm blind but I cant figure out what I am doing wrong.
after the 2 runs (there are only 2 values in the database) I get 2 different values like it should be. Then I write it into the NSMutableArray.
But there is only the 2nd value twice. Shouldnt it add to the end of the array? What do I do wrong?
- (NSMutableArray *)getItemsFromDatabaseWithName:(NSString *)databaseName fromTable:(NSString *)tableName andConstraint:(NSString *)constraint
{
NSString *absolutePath = [[NSBundle mainBundle].resourcePath stringByAppendingPathComponent:databaseName];
NSLog(#"%#", absolutePath);
//Datenbank öffnen --- "**" bedeuten "&" verwenden
sqlite3_open([absolutePath UTF8String], &_database);
//check if there is a constraint and if not take 2nd statement
if (![constraint isEqualToString:#""])
{
_statement = [NSString stringWithFormat:#"select * from %# where %#",tableName, constraint];
}
else
{
_statement = [NSString stringWithFormat:#"select * from %#",tableName];
}
const char *charStatement = [_statement cStringUsingEncoding:NSUTF8StringEncoding];
sqlite3_stmt *results;
//new array to return values
_mutableItemArray = [NSMutableArray new];
//new ItemModel
ItemModel *tmpItem = [ItemModel new];
if (sqlite3_prepare_v2(_database, charStatement, -1, &results, NULL)== SQLITE_OK)
{
while (sqlite3_step(results) == SQLITE_ROW)
{
_charItemName = (char *)sqlite3_column_text(results, 1);
[tmpItem setItemName:[NSString stringWithUTF8String:_charItemName]];
_charItemDescription = (char *)sqlite3_column_text(results, 2);
[tmpItem setItemDescription:[NSString stringWithUTF8String:_charItemDescription]];
_charItemYear = (char *)sqlite3_column_text(results, 3);
[tmpItem setItemYear:[_dateFormat dateFromString:[NSString stringWithUTF8String:_charItemYear]]];
_charItemRecommendedBy = (char *)sqlite3_column_text(results, 4);
[tmpItem setItemRecommendedBy:[NSString stringWithUTF8String:_charItemRecommendedBy]];
_charItemImage = (char *)sqlite3_column_text(results, 5);
[tmpItem setItemImage:[NSString stringWithUTF8String:_charItemImage]];
[_mutableItemArray addObject:tmpItem];
#warning here I get the 2 items correct
NSLog(#"ItemName: %#",[tmpItem getItemName]);
NSLog(#"ItemName: %#",[tmpItem getItemDescription]);
}
}
sqlite3_close(_database);
#warning here I get 2 times the same item ???
NSLog(#"ItemName: %#",[_mutableItemArray objectAtIndex:0]);
NSLog(#"ItemName: %#",[_mutableItemArray objectAtIndex:1]);
return _mutableItemArray;
}
You just create one object tmpItem.
This will be added to the array and in the next run of the while loop you're not creating a new tmpItem but modifying the old one and add it to the array.
Therefore you will end up with an Array containing two pointers to the same object tmpItem (with the latest state).
Solution: create your tmpItem within the while loop.
If you go through your code you will see inside the while loop you are setting the same object (tmpItem) again and again,that is why your array has last updated values of the same object.
Now see below code you will notice in the while loop, we are creating new object and storing it in an NSArray.
- (NSMutableArray *)getItemsFromDatabaseWithName:(NSString *)databaseName fromTable:(NSString *)tableName andConstraint:(NSString *)constraint
{
NSString *absolutePath = [[NSBundle mainBundle].resourcePath stringByAppendingPathComponent:databaseName];
NSLog(#"%#", absolutePath);
//Datenbank öffnen --- "**" bedeuten "&" verwenden
sqlite3_open([absolutePath UTF8String], &_database);
//check if there is a constraint and if not take 2nd statement
if (![constraint isEqualToString:#""])
{
_statement = [NSString stringWithFormat:#"select * from %# where %#",tableName, constraint];
}
else
{
_statement = [NSString stringWithFormat:#"select * from %#",tableName];
}
const char *charStatement = [_statement cStringUsingEncoding:NSUTF8StringEncoding];
sqlite3_stmt *results;
//new array to return values
_mutableItemArray = [NSMutableArray new];
//new ItemModel
if (sqlite3_prepare_v2(_database, charStatement, -1, &results, NULL)== SQLITE_OK)
{
while (sqlite3_step(results) == SQLITE_ROW)
{
ItemModel *tmpItem = [ItemModel new];
_charItemName = (char *)sqlite3_column_text(results, 1);
[tmpItem setItemName:[NSString stringWithUTF8String:_charItemName]];
_charItemDescription = (char *)sqlite3_column_text(results, 2);
[tmpItem setItemDescription:[NSString stringWithUTF8String:_charItemDescription]];
_charItemYear = (char *)sqlite3_column_text(results, 3);
[tmpItem setItemYear:[_dateFormat dateFromString:[NSString stringWithUTF8String:_charItemYear]]];
_charItemRecommendedBy = (char *)sqlite3_column_text(results, 4);
[tmpItem setItemRecommendedBy:[NSString stringWithUTF8String:_charItemRecommendedBy]];
_charItemImage = (char *)sqlite3_column_text(results, 5);
[tmpItem setItemImage:[NSString stringWithUTF8String:_charItemImage]];
[_mutableItemArray addObject:tmpItem];
NSLog(#"ItemName: %#",[tmpItem getItemName]);
NSLog(#"ItemName: %#",[tmpItem getItemDescription]);
}
}
sqlite3_close(_database);
NSLog(#"ItemName: %#",[_mutableItemArray objectAtIndex:0]);
NSLog(#"ItemName: %#",[_mutableItemArray objectAtIndex:1]);
return _mutableItemArray;
}
I have a requirement to integrate with a web service that serves as a login. The hash needs to be generated on the client. I am able to produce the correct hash as NSMutableData, but then I need to convert it to a string, without the spaces or brackets produced when the NSMutableData object is rendered as a string in the output console. I have read several posts, all seeming to say the same thing:
NSString *newstring = [[NSString alloc] initWithDSata:dataToConvert encoding:NSUTF8StringEncoding];
Unfortunately, this doesnt work for me. Using NSUTF8StringEncoding returns null. NSASCIIStringEncoding is even worse.
Here is my code:
NSString *password = [NSString stringWithFormat:#"%#%#", kPrefix, [self.txtPassword text]];
NSLog(#"PLAIN: %#", password);
NSData *data = [password dataUsingEncoding:NSASCIIStringEncoding];
NSMutableData *sha256Out = [NSMutableData dataWithLength:CC_SHA256_DIGEST_LENGTH];
CC_SHA256(data.bytes, data.length, sha256Out.mutableBytes);
NSString *preppedPassword = [[NSString alloc] initWithData:sha256Out encoding:NSASCIIStringEncoding];
NSLog(#"HASH: %#\n", preppedPassword);
How can I convert the NSMutableData to string?
My problem is that I need to from this
<7e8df5b3 17c99263 e4fe6220 bb75b798 4a41de45 44464ba8 06266397 f165742e>
to this
7e8df5b317c99263e4fe6220bb75b7984a41de4544464ba806266397f165742e
See How to convert an NSData into an NSString Hex string?
I use a slightly modified version myself:
#implementation NSData (Hex)
- (NSString *)hexRepresentationWithSpaces:(BOOL)spaces uppercase:(BOOL)uppercase {
const unsigned char *bytes = (const unsigned char *)[self bytes];
NSUInteger nbBytes = [self length];
// If spaces is true, insert a space every this many input bytes (twice this many output characters).
static const NSUInteger spaceEveryThisManyBytes = 4UL;
// If spaces is true, insert a line-break instead of a space every this many spaces.
static const NSUInteger lineBreakEveryThisManySpaces = 4UL;
const NSUInteger lineBreakEveryThisManyBytes = spaceEveryThisManyBytes * lineBreakEveryThisManySpaces;
NSUInteger strLen = 2 * nbBytes + (spaces ? nbBytes / spaceEveryThisManyBytes : 0);
NSMutableString *hex = [[NSMutableString alloc] initWithCapacity:strLen];
for (NSUInteger i = 0; i < nbBytes; ) {
if (uppercase) {
[hex appendFormat:#"%02X", bytes[i]];
} else {
[hex appendFormat:#"%02x", bytes[i]];
}
// We need to increment here so that the every-n-bytes computations are right.
++i;
if (spaces) {
if (i % lineBreakEveryThisManyBytes == 0) {
[hex appendString:#"\n"];
} else if (i % spaceEveryThisManyBytes == 0) {
[hex appendString:#" "];
}
}
}
return hex;
}
#end