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/*
* Skype Login
*
* Based on:
* FakeSkype : Skype reverse engineering proof-of-concept client
* Ouanilo MEDEGAN (c) 2006 http://www.oklabs.net
* pyskype : Skype login Python script by uunicorn
*
* Written by: leecher@dose.0wnz.at (c) 2015
*
* Module: Credentials handling, reads/writes old Skype credentials format
*
*/
#include "common.h"
#include "objects.h"
#include "random.h"
#include "crc.h"
#include "credentials.h"
#ifdef _WIN32
#define CRC_SIZE sizeof(short)
#else
#define CRC_SIZE 0
#endif
Memory_U Credentials_Write(Skype_Inst *pInst)
{
Memory_U creds;
uchar *Browser;
uint Crc;
creds.MsZ = sizeof(pInst->LoginD.LoginHash) + MODULUS_SZ + pInst->LoginD.SignedCredentials.MsZ + CRC_SIZE;
if (!(Browser = creds.Memory = malloc(creds.MsZ)))
{
creds.MsZ = 0;
return creds;
}
memcpy(Browser, pInst->LoginD.LoginHash, sizeof(pInst->LoginD.LoginHash));
Browser+=sizeof(pInst->LoginD.LoginHash);
BN_bn2bin(pInst->LoginD.RSAKeys->d, Browser);
Browser+=MODULUS_SZ;
memcpy(Browser, pInst->LoginD.SignedCredentials.Memory, pInst->LoginD.SignedCredentials.MsZ);
Browser+=pInst->LoginD.SignedCredentials.MsZ;
#ifdef _WIN32
Crc = crc32(creds.Memory, Browser-creds.Memory, -1);
*Browser++ = *((uchar *)(&Crc) + 0);
*Browser++ = *((uchar *)(&Crc) + 1);
#endif
return creds;
}
/*
0 - OK
-1 - Invalid size of credentials blob
-2 - Invalid CRC
-3 - Out of memory
-4 - Unable to parse Signed credentials
-5 - RSA public key not found
*/
int Credentials_Read(Skype_Inst *pInst, Memory_U creds, SResponse *LoginDatas)
{
uchar *Browser;
uint Crc, Idx;
RSA *Keys;
if (creds.MsZ < sizeof(pInst->LoginD.LoginHash) + MODULUS_SZ + 16 + CRC_SIZE)
return -1;
#ifdef _WIN32
Crc = crc32(creds.Memory, creds.MsZ-2, -1);
if (*((uchar *)(&Crc) + 0) != *((uchar*)creds.Memory+creds.MsZ-2) ||
*((uchar *)(&Crc) + 1) != *((uchar*)creds.Memory+creds.MsZ-1))
{
pInst->pfLog(pInst->pLogStream, "Credentials: Bad CRC!");
return -2;
}
#endif
Browser = creds.Memory;
memcpy (pInst->LoginD.LoginHash, Browser, sizeof(pInst->LoginD.LoginHash));
Browser+=sizeof(pInst->LoginD.LoginHash);
Keys=RSA_new();
BN_hex2bn(&(Keys->e), "010001");
Keys->d = BN_bin2bn(Browser, MODULUS_SZ, NULL);
Browser+=MODULUS_SZ;
if (pInst->LoginD.SignedCredentials.Memory) free(pInst->LoginD.SignedCredentials.Memory);
pInst->LoginD.SignedCredentials.MsZ = creds.MsZ - CRC_SIZE - (Browser-creds.Memory);
if (!(pInst->LoginD.SignedCredentials.Memory = malloc(pInst->LoginD.SignedCredentials.MsZ)))
{
pInst->LoginD.SignedCredentials.MsZ = 0;
RSA_free(Keys);
return -3;
}
memcpy(pInst->LoginD.SignedCredentials.Memory, Browser, pInst->LoginD.SignedCredentials.MsZ);
// Now credentials are read, but we need to finish LoginD.RSAKeys by unpacking Signed Credentials
if (Credentials_Parse(pInst, pInst->LoginD.SignedCredentials, LoginDatas)<0)
{
RSA_free(Keys);
return -4;
}
for (Idx = 0; Idx < LoginDatas->NbObj; Idx++)
{
if (LoginDatas->Objs[Idx].Id == OBJ_ID_LDMODULUS)
{
Keys->n = BN_bin2bn(LoginDatas->Objs[Idx].Value.Memory.Memory,
LoginDatas->Objs[Idx].Value.Memory.MsZ, NULL);
if (pInst->LoginD.RSAKeys) RSA_free(pInst->LoginD.RSAKeys);
pInst->LoginD.RSAKeys = Keys;
return 0;
}
}
RSA_free(Keys);
return -5;
}
int Credentials_Parse(Skype_Inst *pInst, Memory_U Pcred, SResponse *LoginDatas)
{
uchar *PostProcessed, *Browser;
char *Key;
uint KeyIdx, PPsZ;
RSA *SkypeRSA;
Memory_U creds = Pcred;
if (!(creds.Memory = malloc(creds.MsZ)))
return -2;
KeyIdx = htonl(*(uint *)Pcred.Memory);
Pcred.Memory += sizeof(uint);
Pcred.MsZ -= sizeof(uint);
SkypeRSA = RSA_new();
Key = KeySelect(KeyIdx);
BN_hex2bn(&(SkypeRSA->n), Key);
BN_hex2bn(&(SkypeRSA->e), "010001");
PPsZ = RSA_public_decrypt(Pcred.MsZ, Pcred.Memory, creds.Memory, SkypeRSA, RSA_NO_PADDING);
RSA_free(SkypeRSA);
if (PPsZ == -1)
{
char szErr[256];
ERR_load_crypto_strings();
ERR_error_string(ERR_get_error(), szErr);
pInst->pfLog(pInst->pLogStream, "Credentials decryption failed: %s\n", szErr);
free(creds.Memory);
return -1;
}
PostProcessed = FinalizeLoginDatas(pInst, creds.Memory, &PPsZ, NULL, 0);
if (PostProcessed == NULL)
{
pInst->pfLog(pInst->pLogStream, "Bad Datas Finalization..\n");
free (creds.Memory);
return -1;
}
LoginDatas->Objs = NULL;
LoginDatas->NbObj = 0;
Browser = PostProcessed;
ManageObjects(&Browser, PPsZ, LoginDatas);
free(PostProcessed);
free(creds.Memory);
return 0;
}
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