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#import "XADWinZipAESHandle.h"
#import "XADException.h"
@implementation XADWinZipAESHandle
-(id)initWithHandle:(CSHandle *)handle length:(off_t)length password:(NSData *)passdata keyLength:(int)keylength
{
off_t actuallength=length-keylength/2-12;
if((self=[super initWithName:[handle name] length:actuallength]))
{
parent=[handle retain];
password=[passdata retain];
keybytes=keylength;
startoffs=[handle offsetInFile];
hmac_inited=hmac_done=hmac_correct=NO;
}
return self;
}
-(void)dealloc
{
[parent release];
[password release];
if(hmac_inited) HMAC_CTX_cleanup(&hmac);
[super dealloc];
}
static void DeriveKey(NSData *password,NSData *salt,int iterations,uint8_t *keybuffer,int keylength)
{
int blocks=(keylength+19)/20;
// memset(keybuffer,0,keylength);
for(int i=0;i<blocks;i++)
{
HMAC_CTX hmac;
uint8_t counter[4]={(i+1)>>24,(i+1)>>16,(i+1)>>8,i+1};
uint8_t buffer[20];
HMAC_CTX_init(&hmac);
HMAC_Init(&hmac,[password bytes],[password length],EVP_sha1());
HMAC_Update(&hmac,[salt bytes],[salt length]);
HMAC_Update(&hmac,counter,4);
HMAC_Final(&hmac,buffer,NULL);
HMAC_CTX_cleanup(&hmac);
int blocklen=20;
if(blocklen+i*20>keylength) blocklen=keylength-i*20;
memcpy(keybuffer,buffer,blocklen);
for(int j=1;j<iterations;j++)
{
HMAC(EVP_sha1(),[password bytes],[password length],buffer,20,buffer,NULL);
for(int k=0;k<blocklen;k++) keybuffer[k]^=buffer[k];
}
keybuffer+=20;
}
}
-(void)resetStream
{
[parent seekToFileOffset:startoffs];
uint8_t keybuf[2*keybytes+2];
DeriveKey(password,[parent readDataOfLength:keybytes/2],1000,keybuf,sizeof(keybuf));
if([parent readUInt16LE]!=keybuf[2*keybytes]+(keybuf[2*keybytes+1]<<8)) [XADException raisePasswordException];
AES_set_encrypt_key(keybuf,keybytes*8,&key);
memset(counter,0,16);
if(hmac_inited) HMAC_CTX_cleanup(&hmac);
HMAC_CTX_init(&hmac);
HMAC_Init(&hmac,keybuf+keybytes,keybytes,EVP_sha1());
hmac_inited=YES;
hmac_done=NO;
hmac_correct=NO;
}
-(int)streamAtMost:(int)num toBuffer:(void *)buffer
{
int actual=[parent readAtMost:num toBuffer:buffer];
HMAC_Update(&hmac,buffer,actual);
for(int i=0;i<actual;i++)
{
int bufoffs=(i+streampos)%16;
if(bufoffs==0)
{
for(int i=0;i<8;i++) if(++counter[i]!=0) break;
AES_encrypt(counter,aesbuffer,&key);
}
((uint8_t *)buffer)[i]^=aesbuffer[bufoffs];
}
return actual;
}
-(BOOL)hasChecksum { return YES; }
-(BOOL)isChecksumCorrect
{
if(!hmac_done && streampos==streamlength)
{
uint8_t filedigest[10],calcdigest[20];
[parent readBytes:10 toBuffer:filedigest];
HMAC_Final(&hmac,calcdigest,NULL);
hmac_correct=memcmp(calcdigest,filedigest,10)==0;
hmac_done=YES;
}
return hmac_correct;
}
@end
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