//

//  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);

}