//

 //  MYBERParser.m

 //  MYCrypto

 //

 //  Created by Jens Alfke on 6/2/09.

 //  Copyright 2009 Jens Alfke. All rights reserved.

 //

 // Reference:

 // <http://www.columbia.edu/~ariel/ssleay/layman.html> "Layman's Guide To ASN.1/BER/DER"

 #import "MYBERParser.h"

 #import "MYASN1Object.h"

 #import "MYOID.h"

 #import "MYErrorUtils.h"

 #import "CollectionUtils.h"

 #import "Test.h"

 #define MYBERParserException @"MYBERParserException"

 typedef struct {

     unsigned tag            :5;

     unsigned isConstructed  :1;

     unsigned tagClass       :2;

     unsigned length         :7;

     unsigned isLengthLong   :1;

 } BERHeader;

 typedef struct {

     const uint8_t *nextChar;

     size_t length;

 } InputData;

 static void requireLength (size_t length, size_t expectedLength) {

     if (length != expectedLength)

         [NSException raise: MYBERParserException format: @"Unexpected value length"];

 }

 static const void* readOrDie (InputData *input, size_t len) {

     if (len > input->length)

         [NSException raise: MYBERParserException format: @"Unexpected EOF on input"];

     const void *bytes = input->nextChar;

     input->nextChar += len;

     input->length -= len;

     return bytes;

 }

 static NSData* readDataOrDie(InputData *input, size_t length) {

     return [NSMutableData dataWithBytes: readOrDie(input,length) length: length];

 }

 static NSString* readStringOrDie(InputData *input, size_t length, NSStringEncoding encoding) {

     NSString *str = [[NSString alloc] initWithBytes: readOrDie(input,length) 

                                              length: length

                                            encoding: encoding];

     if (!str)

         [NSException raise: MYBERParserException format: @"Unparseable string"];

     return [str autorelease];

 }    

 static uint32_t readBigEndianUnsignedInteger (InputData *input, size_t length) {

     if (length == 0 || length > 4)

         [NSException raise: MYBERParserException format: @"Invalid integer length"];

     uint32_t result = 0;

     memcpy(((uint8_t*)&result)+(4-length), readOrDie(input, length), length);

     return result;

 }

 static int32_t readBigEndianSignedInteger (InputData *input, size_t length) {

     int32_t result = (int32_t) readBigEndianUnsignedInteger(input,length);

     uint8_t *dst = ((uint8_t*)&result)+(4-length);

     if (*dst & 0x80) { // sign-extend negative value

         while (--dst >= (uint8_t*)&result)

             *dst = 0xFF;

     }

     return result;

 }

 NSDateFormatter* MYBERGeneralizedTimeFormatter() {

     static NSDateFormatter *sFmt;

     if (!sFmt) {

         sFmt = [[NSDateFormatter alloc] init];

         sFmt.dateFormat = @"yyyyMMddHHmmss'Z'";

         sFmt.timeZone = [NSTimeZone timeZoneWithName: @"GMT"];

     }

     return sFmt;

 }

 NSDateFormatter* MYBERUTCTimeFormatter() {

     static NSDateFormatter *sFmt;

     if (!sFmt) {

         sFmt = [[NSDateFormatter alloc] init];

         sFmt.dateFormat = @"yyMMddHHmmss'Z'";

         sFmt.timeZone = [NSTimeZone timeZoneWithName: @"GMT"];

     }

     return sFmt;

 }

 static NSDate* parseDate (NSString *dateStr, unsigned tag) {

     //FIX: There are more date formats possible; need to try them all. (see "Layman's Guide", 5.17)

     NSDateFormatter *fmt = (tag==23 ?MYBERUTCTimeFormatter() :MYBERGeneralizedTimeFormatter());

     NSDate *date = [fmt dateFromString: dateStr];

     if (!date)

         [NSException raise: MYBERParserException format: @"Unparseable date '%@'", dateStr];

     return date;

 }

 static size_t readHeader(InputData *input, BERHeader *header) {

     memcpy(header, readOrDie(input,2), 2);

     if (header->tag == 0x1F)

         [NSException raise: MYBERParserException format: @"Long tags not supported"];

     if (!header->isLengthLong)

         return header->length;

     else {

         if (header->length == 0)

             [NSException raise: MYBERParserException format: @"Indefinite length not supported"];

         return NSSwapBigIntToHost(readBigEndianUnsignedInteger(input,header->length));

     }

 }

 static id parseBER(InputData *input) {

     BERHeader header;

     size_t length = readHeader(input,&header);

     Class defaultClass = [MYASN1Object class];

     // Tag values can be found in <Security/x509defs.h>. I'm not using them here because that

     // header does not exist on iPhone!

     if (header.isConstructed) {

         // Constructed:

         NSMutableArray *items = $marray();

         InputData subInput = {input->nextChar, length};

         while (subInput.length > 0) {

             [items addObject: parseBER(&subInput)];

         }

         input->nextChar += length;

         input->length -= length;

         switch (header.tag) {

             case 16: // sequence

                 return items;

             case 17: // set

                 return [NSSet setWithArray: items];

             default:

                 return [[[MYASN1Object alloc] initWithTag: header.tag

                                                   ofClass: header.tagClass

                                                components: items] autorelease];

         }

     } else {

         // Primitive:

         switch (header.tag) {

             case 1: { // boolean

                 requireLength(length,1);

                 return *(const uint8_t*)readOrDie(input, 1) ?$true :$false;

             }

             case 2: // integer

             case 10: // enum

             {

                 if (length <= 4) {

                     int32_t value = NSSwapBigIntToHost(readBigEndianSignedInteger(input,length));

                     return [NSNumber numberWithInteger: value];

                 } else {

                     // Big integer!

                     defaultClass = [MYASN1BigInteger class];

                     break;

                 }

             }

             case 3: // bitstring

             {

                 UInt8 unusedBits = *(const UInt8*) readOrDie(input, 1);

                 if (unusedBits)

                     Log(@"Bit-string has %u unused bits", (unsigned)unusedBits);

                 if (unusedBits > 7 || length < 1)

                     [NSException raise: MYBERParserException format: @"Bogus bit-string"];

                 return [[[MYBitString alloc] initWithBits: readDataOrDie(input, length-1)

                                                     count: 8*(length-1) - unusedBits] autorelease];

             }

             case 4: // octetstring

                 return readDataOrDie(input, length);

             case 5: // null

                 requireLength(length,0);

                 return [NSNull null];

             case 6: // OID

                 return [[[MYOID alloc] initWithBEREncoding: readDataOrDie(input, length)] autorelease];

             case 12: // UTF8String

                 return readStringOrDie(input,length,NSUTF8StringEncoding);

             case 18: // numeric string

             case 19: // printable string:

             case 22: // IA5 string:

             case 20: // T61 string:

             {

                 NSString *string = readStringOrDie(input,length,NSASCIIStringEncoding);

                 if (string)

                     return string;

                 else

                     break;  // if decoding fails, fall back to generic MYASN1Object

             }

             case 23: // UTC time:

             case 24: // Generalized time:

                 return parseDate(readStringOrDie(input,length,NSASCIIStringEncoding), header.tag);

             default:

                 break;

         }

     }

     // Generic case -- create and return a MYASN1Object:

     NSData *value = readDataOrDie(input, length);

     id result = [[[defaultClass alloc] initWithTag: header.tag

                                            ofClass: header.tagClass 

                                        constructed: header.isConstructed

                                              value: value] autorelease];

     if( defaultClass == [MYASN1Object class])

         Warn(@"parseBER: Returning default %@", result);

     return result;

 }

 static void exceptionToError (NSException *x, NSError **outError) {

     if ($equal(x.name, MYBERParserException)) {

         if (outError)

             *outError = MYError(1,MYASN1ErrorDomain, @"%@", x.reason);

     } else {

         @throw(x);

     }

 }

 id MYBERParse (NSData *ber, NSError **outError) {

     @try{

         InputData input = {ber.bytes, ber.length};

         return parseBER(&input);

     }@catch (NSException *x) {

         exceptionToError(x,outError);

     }

     return nil;

 }

 size_t MYBERGetLength (NSData *ber, NSError **outError) {

     @try{

         InputData input = {ber.bytes, ber.length};

         BERHeader header;

         return readHeader(&input,&header);

     }@catch (NSException *x) {

         exceptionToError(x,outError);

     }

     return 0;

 }

 const void* MYBERGetContents (NSData *ber, NSError **outError) {

     @try{

         InputData input = {ber.bytes, ber.length};

         BERHeader header;

         readHeader(&input,&header);

         return input.nextChar;

     }@catch (NSException *x) {

         exceptionToError(x,outError);

     }

     return NULL;

 }

 #pragma mark -

 #pragma mark TEST CASES:

 #define $data(BYTES...)    ({const uint8_t bytes[] = {BYTES}; [NSData dataWithBytes: bytes length: sizeof(bytes)];})

 TestCase(ParseBER) {

     CAssertEqual(MYBERParse($data(0x05, 0x00), nil),

                  [NSNull null]);

     CAssertEqual(MYBERParse($data(0x01, 0x01, 0xFF), nil),

                  $true);

     CAssertEqual(MYBERParse($data(0x01, 0x01, 0x00), nil),

                  $false);

     // integers:

     CAssertEqual(MYBERParse($data(0x02, 0x01, 0x00), nil),

                  $object(0));

     CAssertEqual(MYBERParse($data(0x02, 0x01, 0x48), nil),

                  $object(72));

     CAssertEqual(MYBERParse($data(0x02, 0x01, 0x80), nil),

                  $object(-128));

     CAssertEqual(MYBERParse($data(0x02, 0x02, 0x00, 0x80), nil),

                  $object(128));

     CAssertEqual(MYBERParse($data(0x02, 0x02, 0x30,0x39), nil),

                  $object(12345));

     CAssertEqual(MYBERParse($data(0x02, 0x02, 0xCF, 0xC7), nil),

                  $object(-12345));

     CAssertEqual(MYBERParse($data(0x02, 0x04, 0x07, 0x5B, 0xCD, 0x15), nil),

                  $object(123456789));

     CAssertEqual(MYBERParse($data(0x02, 0x04, 0xF8, 0xA4, 0x32, 0xEB), nil),

                  $object(-123456789));

     CAssertEqual(MYBERParse($data(0x02, 0x04, 0xF8, 0xA4, 0x32, 0xEB), nil),

                  $object(-123456789));

     // octet strings:

     CAssertEqual(MYBERParse($data(0x04, 0x05, 'h', 'e', 'l', 'l', 'o'), nil),

                  [@"hello" dataUsingEncoding: NSASCIIStringEncoding]);

     CAssertEqual(MYBERParse($data(0x04, 0x00), nil),

                  [NSData data]);

     CAssertEqual(MYBERParse($data(0x0C, 0x05, 'h', 'e', 'l', 'l', 'o'), nil),

                  @"hello");

     // sequences:

     CAssertEqual(MYBERParse($data(0x30, 0x06,  0x02, 0x01, 0x48,  0x01, 0x01, 0xFF), nil),

                  $array($object(72), $true));

     CAssertEqual(MYBERParse($data(0x30, 0x10,  

                                   0x30, 0x06,  0x02, 0x01, 0x48,  0x01, 0x01, 0xFF,

                                   0x30, 0x06,  0x02, 0x01, 0x48,  0x01, 0x01, 0xFF), nil),

                  $array( $array($object(72), $true), $array($object(72), $true)));

 }

 #import "MYCertificate.h"

 #import "MYPublicKey.h"

 TestCase(ParseCert) {

     NSData *cert = [NSData dataWithContentsOfFile: @"../../Tests/selfsigned.cer"];

     NSError *error = nil;

     id parsed = MYBERParse(cert,&error);

     CAssert(parsed);

     CAssertNil(error);

     NSString *dump = [MYASN1Object dump: parsed];

     CAssert(dump);

     Log(@"Parsed selfsigned.cer:\n%@", dump);

     MYCertificate *myCert = [[MYCertificate alloc] initWithCertificateData: cert];

     CAssert(myCert);

     id parsedPubKey = MYBERParse(myCert.publicKey.keyData, NULL);

     Log(@"Parsed public key:\n%@", [MYASN1Object dump: parsedPubKey]);

     cert = [NSData dataWithContentsOfFile: @"../../Tests/iphonedev.cer"];

     parsed = MYBERParse(cert,&error);

     CAssert(parsed);

     CAssertNil(error);

     dump = [MYASN1Object dump: parsed];

     CAssert(dump);

 }