ObjXMPP  Documentation

/*
 * Copyright (c) 2011, Florian Zeitz <florob@babelmonkeys.de>
 * Copyright (c) 2011, Jonathan Schleifer <js@webkeks.org>
 *
 * https://webkeks.org/hg/objxmpp/
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice is present in all copies.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <string.h>

#import "XMPPSCRAMAuth.h"
#import "XMPPExceptions.h"

#define HMAC_IPAD 0x36
#define HMAC_OPAD 0x5c

#ifndef HAVE_ARC4RANDOM_UNIFORM
extern uint32_t arc4random_uniform(uint32_t);
#endif

@interface XMPPSCRAMAuth ()
- (OFString*)XMPP_genNonce;
- (uint8_t*)XMPP_HMACWithKey: (OFDataArray*)key
			data: (OFDataArray*)data;
- (OFDataArray*)XMPP_hiWithData: (OFDataArray *)str
			   salt: (OFDataArray *)salt_
		 iterationCount: (intmax_t)i;
@end

@implementation XMPPSCRAMAuth
+ SCRAMAuthWithAuthcid: (OFString*)authcid
	      password: (OFString*)password
		  hash: (Class)hash;
{
	return [[[self alloc] initWithAuthcid: authcid
				     password: password
					 hash: hash] autorelease];
}

+ SCRAMAuthWithAuthzid: (OFString*)authzid
	       authcid: (OFString*)authcid
	      password: (OFString*)password
		  hash: (Class)hash;
{
	return [[[self alloc] initWithAuthzid: authzid
				      authcid: authcid
				     password: password
					 hash: hash] autorelease];
}

- initWithAuthcid: (OFString*)authcid_
	 password: (OFString*)password_
	     hash: (Class)hash;
{
	return [self initWithAuthzid: nil
			     authcid: authcid_
			    password: password_
				hash: hash];
}

- initWithAuthzid: (OFString*)authzid_
	  authcid: (OFString*)authcid_
	 password: (OFString*)password_
	     hash: (Class)hash;
{
	self = [super initWithAuthzid: authzid_
			      authcid: authcid_
			     password: password_];

	hashType = hash;

	return self;
}

- (void)dealloc
{
	[GS2Header release];
	[clientFirstMessageBare release];
	[serverSignature release];
	[cNonce release];

	[super dealloc];
}

- (void)setAuthzid: (OFString*)authzid_
{
	OFString *old = authzid;

	if (authzid_) {
		OFMutableString *new = [[authzid_ mutableCopy] autorelease];
		[new replaceOccurrencesOfString: @"="
				     withString: @"=3D"];
		[new replaceOccurrencesOfString: @","
				     withString: @"=2C"];
		authzid = [new retain];
	} else
		authzid = nil;

	[old release];
}

- (void)setAuthcid: (OFString*)authcid_
{
	OFString *old = authcid;

	if (authcid_) {
		OFMutableString *new = [[authcid_ mutableCopy] autorelease];
		[new replaceOccurrencesOfString: @"="
				     withString: @"=3D"];
		[new replaceOccurrencesOfString: @","
				     withString: @"=2C"];
		authcid = [new retain];
	} else
		authcid = nil;

	[old release];
}

- (OFDataArray*)clientFirstMessage
{
	OFDataArray *ret = [OFDataArray dataArrayWithItemSize: 1];

	[GS2Header release];
	GS2Header = nil;

	if (authzid)
		GS2Header = [[OFString alloc] initWithFormat: @"n,a=%@,",
							      authzid];
	else
		GS2Header = @"n,,";

	[cNonce release];
	cNonce = nil;
	cNonce = [[self XMPP_genNonce] retain];

	[clientFirstMessageBare release];
	clientFirstMessageBare = nil;
	clientFirstMessageBare = [[OFString alloc] initWithFormat: @"n=%@,r=%@",
								   authcid,
								   cNonce];

	[ret addNItems: [GS2Header cStringLength]
	    fromCArray: [GS2Header cString]];

	[ret addNItems: [clientFirstMessageBare cStringLength]
	    fromCArray: [clientFirstMessageBare cString]];

	return ret;
}

- (OFDataArray*)calculateResponseWithChallenge: (OFDataArray*)challenge
{
	size_t i;
	uint8_t *clientKey, *serverKey, *clientSignature;
	intmax_t iterCount;
	OFHash *hash;
	OFDataArray *ret, *authMessage, *tmpArray, *salt, *saltedPassword;
	OFString *tmpString, *sNonce;
	OFAutoreleasePool *pool = [[OFAutoreleasePool alloc] init];
	enum {
		GOT_SNONCE, GOT_SALT, GOT_ITERCOUNT
	} got = 0;

	hash = [[[hashType alloc] init] autorelease];
	ret = [OFDataArray dataArrayWithItemSize: 1];
	authMessage = [OFDataArray dataArrayWithItemSize: 1];

	OFString *chal = [OFString stringWithCString: [challenge cArray]
					      length: [challenge count] *
						      [challenge itemSize]];

	for (OFString *comp in [chal componentsSeparatedByString: @","]) {
		OFString *entry = [comp substringFromIndex: 2
						   toIndex: [comp length]];

		if ([comp hasPrefix: @"r="]) {
			if (![entry hasPrefix: cNonce])
				@throw [XMPPAuthFailedException
				    newWithClass: isa
				      connection: nil
					  reason: @"Received wrong nonce"];

			sNonce = entry;
			got |= GOT_SNONCE;
		} else if ([comp hasPrefix: @"s="]) {
			salt = [OFDataArray
			    dataArrayWithBase64EncodedString: entry];
			got |= GOT_SALT;
		} else if ([comp hasPrefix: @"i="]) {
			iterCount = [entry decimalValue];
			got |= GOT_ITERCOUNT;
		}
	}

	if (got != (GOT_SNONCE | GOT_SALT | GOT_ITERCOUNT))
		@throw [OFInvalidServerReplyException newWithClass: isa];

	// Add c=<base64(GS2Header+channelBindingData)>
	// XXX: No channel binding for now
	tmpArray = [OFDataArray dataArrayWithItemSize: 1];
	[tmpArray addNItems: [GS2Header cStringLength]
		 fromCArray: [GS2Header cString]];
	tmpString = [tmpArray stringByBase64Encoding];
	[ret addNItems: 2
	    fromCArray: "c="];
	[ret addNItems: [tmpString cStringLength]
	    fromCArray: [tmpString cString]];

	// Add r=<nonce>
	[ret addItem: ","];
	[ret addNItems: 2
	    fromCArray: "r="];
	[ret addNItems: [sNonce cStringLength]
	    fromCArray: [sNonce cString]];

	tmpArray = [OFDataArray dataArrayWithItemSize: 1];
	[tmpArray addNItems: [password cStringLength]
		 fromCArray: [password cString]];

	/*
	 * IETF RFC 5802:
	 * SaltedPassword := Hi(Normalize(password), salt, i)
	 */
	saltedPassword = [self XMPP_hiWithData: tmpArray
					  salt: salt
				iterationCount: iterCount];

	/*
	 * IETF RFC 5802:
	 * AuthMessage := client-first-message-bare + "," +
	 *		  server-first-message + "," +
	 *		  client-final-message-without-proof
	 */
	[authMessage addNItems: [clientFirstMessageBare cStringLength]
		    fromCArray: [clientFirstMessageBare cString]];
	[authMessage addItem: ","];
	[authMessage addNItems: [challenge count] * [challenge itemSize]
		    fromCArray: [challenge cArray]];
	[authMessage addItem: ","];
	[authMessage addNItems: [ret count]
		    fromCArray: [ret cArray]];

	/*
	 * IETF RFC 5802:
	 * ClientKey := HMAC(SaltedPassword, "Client Key")
	 */
	tmpArray = [OFDataArray dataArrayWithItemSize: 1];
	[tmpArray addNItems: 10
		 fromCArray: "Client Key"];
	clientKey = [self XMPP_HMACWithKey: saltedPassword
				      data: tmpArray];

	/*
	 * IETF RFC 5802:
	 * StoredKey := H(ClientKey)
	 */
	[hash updateWithBuffer: (void*) clientKey
			ofSize: [hashType digestSize]];
	tmpArray = [OFDataArray dataArrayWithItemSize: 1];
	[tmpArray addNItems: [hashType digestSize]
		 fromCArray: [hash digest]];

	/*
	 * IETF RFC 5802:
	 * ClientSignature := HMAC(StoredKey, AuthMessage)
	 */
	clientSignature = [self XMPP_HMACWithKey: tmpArray
					    data: authMessage];

	/*
	 * IETF RFC 5802:
	 * ServerKey := HMAC(SaltedPassword, "Server Key")
	 */
	tmpArray = [OFDataArray dataArrayWithItemSize: 1];
	[tmpArray addNItems: 10
		 fromCArray: "Server Key"];
	serverKey = [self XMPP_HMACWithKey: saltedPassword
				      data: tmpArray];

	/*
	 * IETF RFC 5802:
	 * ServerSignature := HMAC(ServerKey, AuthMessage)
	 */
	tmpArray = [OFDataArray dataArrayWithItemSize: 1];
	[tmpArray addNItems: [hashType digestSize]
		 fromCArray: serverKey];
	serverSignature = [[OFDataArray alloc] initWithItemSize: 1];
	[serverSignature addNItems: [hashType digestSize]
			fromCArray: [self XMPP_HMACWithKey: tmpArray
						      data: authMessage]];

	/*
	 * IETF RFC 5802:
	 * ClientProof := ClientKey XOR ClientSignature
	 */
	tmpArray = [OFDataArray dataArrayWithItemSize: 1];
	for (i = 0; i < [hashType digestSize]; i++) {
		uint8_t c = clientKey[i] ^ clientSignature[i];
		[tmpArray addItem: &c];
	}

	// Add p=<base64(ClientProof)>
	[ret addItem: ","];
	[ret addNItems: 2
	    fromCArray: "p="];
	tmpString = [tmpArray stringByBase64Encoding];
	[ret addNItems: [tmpString cStringLength]
	    fromCArray: [tmpString cString]];

	[ret retain];
	[pool release];

	return [ret autorelease];
}

- (void)parseServerFinalMessage: (OFDataArray*)message
{
	OFAutoreleasePool *pool = [[OFAutoreleasePool alloc] init];
	OFString *mess = [OFString stringWithCString: [message cArray]
					      length: [message count] *
						      [message itemSize]];
	OFString *value = [mess substringFromIndex: 2
					   toIndex: [mess length]];

	if ([mess hasPrefix: @"v="]) {
		if (![value isEqual: [serverSignature stringByBase64Encoding]])
			@throw [XMPPAuthFailedException
			    newWithClass: isa
			      connection: nil
				  reason: @"Received wrong ServerSignature"];
	} else
		@throw [XMPPAuthFailedException newWithClass: isa
						  connection: nil
						      reason: value];

	[pool release];
}

- (OFString*)XMPP_genNonce
{
	OFMutableString *nonce = [OFMutableString string];
	uint32_t res, i;

	for (i = 0; i < 64; i++) {
		while ((res = arc4random_uniform('~' - '!' + 1) + '!') == ',');
		[nonce appendFormat: @"%c", res];
	}

	return nonce;
}

- (uint8_t*)XMPP_HMACWithKey: (OFDataArray*)key
			data: (OFDataArray*)data
{
	OFAutoreleasePool *pool = [[OFAutoreleasePool alloc] init];
	OFDataArray *k = [OFDataArray dataArrayWithItemSize: 1];
	size_t i, kSize, blockSize = [hashType blockSize];
	uint8_t *kCArray, *kI = NULL, *kO = NULL;
	OFHash *hash;

	if (key.itemSize * key.count > blockSize) {
		hash = [[[hashType alloc] init] autorelease];
		[hash updateWithBuffer: [key cArray]
				ofSize: key.itemSize * key.count];
		[k addNItems: [hashType digestSize]
		  fromCArray: [hash digest]];
	} else
		[k addNItems: key.itemSize * key.count
		  fromCArray: [key cArray]];

	@try {
		kI = [self allocMemoryWithSize: blockSize * sizeof(uint8_t)];
		memset(kI, HMAC_IPAD, blockSize * sizeof(uint8_t));

		kO = [self allocMemoryWithSize: blockSize * sizeof(uint8_t)];
		memset(kO, HMAC_OPAD, blockSize * sizeof(uint8_t));

		kCArray = [k cArray];
		kSize = k.count;
		for (i = 0; i < kSize; i++) {
			kI[i] ^= kCArray[i];
			kO[i] ^= kCArray[i];
		}

		k = [OFDataArray dataArrayWithItemSize: 1];
		[k addNItems: blockSize
		  fromCArray: kI];
		[k addNItems: data.itemSize * data.count
		  fromCArray: [data cArray]];

		hash = [[[hashType alloc] init] autorelease];
		[hash updateWithBuffer: [k cArray]
				ofSize: k.count];
		k = [OFDataArray dataArrayWithItemSize: 1];
		[k addNItems: blockSize
		  fromCArray: kO];
		[k addNItems: [hashType digestSize]
		   fromCArray: [hash digest]];
	} @finally {
		[self freeMemory: kI];
		[self freeMemory: kO];
	}

	hash = [[[hashType alloc] init] autorelease];
	[hash updateWithBuffer: [k cArray]
			ofSize: k.count];

	[hash retain];
	[pool release];

	return [hash digest];
}

- (OFDataArray*)XMPP_hiWithData: (OFDataArray *)str
			   salt: (OFDataArray *)salt_
		 iterationCount: (intmax_t)i
{
	OFAutoreleasePool *pool = [[OFAutoreleasePool alloc] init];
	size_t digestSize = [hashType digestSize];
	uint8_t *result = NULL, *u, *uOld;
	intmax_t j, k;
	OFDataArray *salty, *tmp, *ret;

	result = [self allocMemoryWithSize: digestSize];

	@try {
		memset(result, 0, digestSize);

		salty = [[salt_ copy] autorelease];
		[salty addNItems: 4
		      fromCArray: "\0\0\0\1"];

		uOld = [self XMPP_HMACWithKey: str
					 data: salty];

		for (j = 0; j < digestSize; j++)
			result[j] ^= uOld[j];

		for (j = 0; j < i - 1; j++) {
			tmp = [OFDataArray dataArrayWithItemSize: 1];
			[tmp addNItems: digestSize
			    fromCArray: uOld];

			u = [self XMPP_HMACWithKey: str
					      data: tmp];

			for (k = 0; k < digestSize; k++)
				result[k] ^= u[k];

			uOld = u;

			[pool releaseObjects];
		}

		ret = [OFDataArray dataArrayWithItemSize: 1];
		[ret addNItems: digestSize
		    fromCArray: result];
	} @finally {
		[self freeMemory: result];
	}

	[ret retain];
	[pool release];

	return [ret autorelease];
}
@end