I am trying to implement the new VerificationController.m class that Apple released to fix the in-app purchase fraud problem.
As everything released by Apple, this is one more vague, incomplete and bad explained document with a lot of voids and unknowns that cannot be circumvented/understood by everyone.
I am trying to implement that, but at the end of the code we see these four methods:
- (NSString *)encodeBase64:(const uint8_t *)input length:(NSInteger)length
{
#warning Replace this method.
return nil;
}
- (NSString *)decodeBase64:(NSString *)input length:(NSInteger *)length
{
#warning Replace this method.
return nil;
}
#warning Implement this function.
char* base64_encode(const void* buf, size_t size)
{ return NULL; }
#warning Implement this function.
void * base64_decode(const char* s, size_t * data_len)
{ return NULL; }
You can see that Apple was lazy to implement the C functions at the end of the code. As my C/C++ abilities stink, I see I need to implement these two functions in C/C++ and that they must return char and void (???). Other people have posted routines to do that on SO, but they are either in Objective-C or not returning chars and void (??).
NOTE: this is another problem I have: how can a method return void if it is used by Apple in this form?
uint8_t *purchase_info_bytes = base64_decode([purchase_info_string cStringUsingEncoding:NSASCIIStringEncoding], &purchase_info_length);
shouldn't it be returning uint8_t?
NOTE2: another problem I have is that apple says base64_encode is required but it is not being used on the code provided by them. I think they are smoking bad stuff or my C/C++ knowledge really stink.
So, returning to my first question. Can someone post/point a method that can do the job that follows the requirements of the declared methods base64_encode and base64_decode? Please refrain from posting objective-c methods that are not compatible with these requirements imposed by Apple.
Thanks.
This solution should be pretty straight forward, which includes all the methods to populate the missing information. Tested and functional within the sandbox.
// single base64 character conversion
static int POS(char c)
{
if (c>='A' && c<='Z') return c - 'A';
if (c>='a' && c<='z') return c - 'a' + 26;
if (c>='0' && c<='9') return c - '0' + 52;
if (c == '+') return 62;
if (c == '/') return 63;
if (c == '=') return -1;
[NSException raise:@"invalid BASE64 encoding" format:@"Invalid BASE64 encoding"];
return 0;
}
- (NSString *)encodeBase64:(const uint8_t *)input length:(NSInteger)length
{
return [NSString stringWithUTF8String:base64_encode(input, (size_t)length)];
}
- (NSString *)decodeBase64:(NSString *)input length:(NSInteger *)length
{
size_t retLen;
uint8_t *retStr = base64_decode([input UTF8String], &retLen);
if (length)
*length = (NSInteger)retLen;
NSString *st = [[[NSString alloc] initWithBytes:retStr
length:retLen
encoding:NSUTF8StringEncoding] autorelease];
free(retStr); // If base64_decode returns dynamically allocated memory
return st;
}
char* base64_encode(const void* buf, size_t size)
{
static const char base64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
char* str = (char*) malloc((size+3)*4/3 + 1);
char* p = str;
unsigned char* q = (unsigned char*) buf;
size_t i = 0;
while(i < size) {
int c = q[i++];
c *= 256;
if (i < size) c += q[i];
i++;
c *= 256;
if (i < size) c += q[i];
i++;
*p++ = base64[(c & 0x00fc0000) >> 18];
*p++ = base64[(c & 0x0003f000) >> 12];
if (i > size + 1)
*p++ = '=';
else
*p++ = base64[(c & 0x00000fc0) >> 6];
if (i > size)
*p++ = '=';
else
*p++ = base64[c & 0x0000003f];
}
*p = 0;
return str;
}
void* base64_decode(const char* s, size_t* data_len_ptr)
{
size_t len = strlen(s);
if (len % 4)
[NSException raise:@"Invalid input in base64_decode" format:@"%d is an invalid length for an input string for BASE64 decoding", len];
unsigned char* data = (unsigned char*) malloc(len/4*3);
int n[4];
unsigned char* q = (unsigned char*) data;
for(const char*p=s; *p; )
{
n[0] = POS(*p++);
n[1] = POS(*p++);
n[2] = POS(*p++);
n[3] = POS(*p++);
if (n[0]==-1 || n[1]==-1)
[NSException raise:@"Invalid input in base64_decode" format:@"Invalid BASE64 encoding"];
if (n[2]==-1 && n[3]!=-1)
[NSException raise:@"Invalid input in base64_decode" format:@"Invalid BASE64 encoding"];
q[0] = (n[0] << 2) + (n[1] >> 4);
if (n[2] != -1) q[1] = ((n[1] & 15) << 4) + (n[2] >> 2);
if (n[3] != -1) q[2] = ((n[2] & 3) << 6) + n[3];
q += 3;
}
// make sure that data_len_ptr is not null
if (!data_len_ptr)
[NSException raise:@"Invalid input in base64_decode" format:@"Invalid destination for output string length"];
*data_len_ptr = q-data - (n[2]==-1) - (n[3]==-1);
return data;
}
Here is a base 64 encode function for NSString
to NSString
:
+(NSString *) encodeString:(NSString *)inString
{
NSData *data = [inString dataUsingEncoding:NSUTF8StringEncoding];
//Point to start of the data and set buffer sizes
int inLength = [data length];
int outLength = ((((inLength * 4)/3)/4)*4) + (((inLength * 4)/3)%4 ? 4 : 0);
const char *inputBuffer = [data bytes];
char *outputBuffer = malloc(outLength);
outputBuffer[outLength] = 0;
//64 digit code
static char Encode[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
//start the count
int cycle = 0;
int inpos = 0;
int outpos = 0;
char temp;
outputBuffer[outLength-1] = '=';
outputBuffer[outLength-2] = '=';
while (inpos < inLength){
switch (cycle) {
case 0:
outputBuffer[outpos++] = Encode[(inputBuffer[inpos]&0xFC)>>2];
cycle = 1;
break;
case 1:
temp = (inputBuffer[inpos++]&0x03)<<4;
outputBuffer[outpos] = Encode[temp];
cycle = 2;
break;
case 2:
outputBuffer[outpos++] = Encode[temp|(inputBuffer[inpos]&0xF0)>> 4];
temp = (inputBuffer[inpos++]&0x0F)<<2;
outputBuffer[outpos] = Encode[temp];
cycle = 3;
break;
case 3:
outputBuffer[outpos++] = Encode[temp|(inputBuffer[inpos]&0xC0)>>6];
cycle = 4;
break;
case 4:
outputBuffer[outpos++] = Encode[inputBuffer[inpos++]&0x3f];
cycle = 0;
break;
default:
cycle = 0;
break;
}
}
NSString *pictemp = [NSString stringWithUTF8String:outputBuffer];
free(outputBuffer);
return pictemp;
}
and Here is a base 64 decode function for NSString
to NSString
:
+(NSString *) decodeString:(NSString *)inString
{
const char* string = [inString cStringUsingEncoding:NSASCIIStringEncoding];
NSInteger inputLength = inString.length;
static char decodingTable[128];
static char encodingTable[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
for (NSInteger i = 0; i < 128; i++) {
decodingTable[encodingTable[i]] = i;
}
if ((string == NULL) || (inputLength % 4 != 0)) {
return nil;
}
while (inputLength > 0 && string[inputLength - 1] == '=') {
inputLength--;
}
NSInteger outputLength = inputLength * 3 / 4;
NSMutableData* data = [NSMutableData dataWithLength:outputLength];
uint8_t* output = data.mutableBytes;
NSInteger inputPoint = 0;
NSInteger outputPoint = 0;
while (inputPoint < inputLength) {
char i0 = string[inputPoint++];
char i1 = string[inputPoint++];
char i2 = inputPoint < inputLength ? string[inputPoint++] : 'A'; /* 'A' will decode to \0 */
char i3 = inputPoint < inputLength ? string[inputPoint++] : 'A';
output[outputPoint++] = (decodingTable[i0] << 2) | (decodingTable[i1] >> 4);
if (outputPoint < outputLength) {
output[outputPoint++] = ((decodingTable[i1] & 0xf) << 4) | (decodingTable[i2] >> 2);
}
if (outputPoint < outputLength) {
output[outputPoint++] = ((decodingTable[i2] & 0x3) << 6) | decodingTable[i3];
}
}
NSLog(@"%@",data);
NSString *finalString = [[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding];
return finalString;
}
These were pieced together from examples I found in various places on the internet when I was searching for them a while ago. They, may be easier for you to implement. I just created a Base64
class and placed these methods in it.
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