I am trying to make a C++ class to make encrytion and decrytion simple
using the blowfish algorithm with openssl. Anyways, I have modelled my
program around
http://www.linuxgazette.com/issue87/misc/vinayak/sym_funcs.c.txt which is
a C program for reading and writing files, with encrytion using openssl.
Anyways, both programs seem to fail the same way on larger files (they
will pass on smaller files) and I can't seem to get EVP_DecryptFinal_ex to
work.
Here are my encrypt and decrypt functions with my defines as follows
IP_SIZE = 1024
OP_SIZE = 1032
int Encryption::encrypt(std::ifstream &istream, std::ofstream &ostream)
{
unsigned char outbuf[OP_SIZE];
int olen, tlen, n;
char inbuff[IP_SIZE];
EVP_CIPHER_CTX ctx;
EVP_CIPHER_CTX_init (&ctx);
EVP_EncryptInit_ex (&ctx, EVP_bf_cbc(), NULL, key, iv);
olen = 0;
tlen = 0;
for (int i = 0;;i++)
{
bzero(&inbuff, IP_SIZE);
if((n = istream.readsome(inbuff, IP_SIZE)) == -1)
{
std::cout << "read error\n";
break;
}
else if(n == 0)
break;
if(EVP_EncryptUpdate(&ctx, outbuf, &olen, (unsigned char*)inbuff, n)
!= 1)
{
std::cout << "error in encrypt update\n";
return 0;
}
std::cout << "before enc. fin. ||" << i << "||\n";
std::cout << "olen: " << olen << "\n";
//std::cout << "EVP_MAX_BLOCK_LENGTH: " << EVP_MAX_BLOCK_LENGTH << "\n";
if(EVP_EncryptFinal_ex(&ctx, outbuf + olen, &tlen) != 1)
{
std::cout << "error in encrypt final\n";
return 0;
}
else
{
std::cout << "Final success on: " << i << "\n";
std::cout << "tlen: " << tlen << "\n";
}
olen += tlen;
ostream.write((char*)outbuf, olen);
}
//EVP_CIPHER_CTX_cleanup (&ctx); not needed because of _ex's
return 1;
}
int Encryption::decrypt(std::ifstream &istream, std::ofstream &ostream)
{
unsigned char outbuf[IP_SIZE];
int olen, tlen, n;
char inbuff[OP_SIZE];
EVP_CIPHER_CTX ctx;
EVP_CIPHER_CTX_init (&ctx);
EVP_DecryptInit_ex (&ctx, EVP_bf_cbc (), NULL, key, iv);
tlen = 0;
std::cout << "OP_SIZE: " << OP_SIZE << "\n";
for (int i = 0;; i++)
{
bzero(&inbuff, OP_SIZE);
if((n = istream.readsome(inbuff, OP_SIZE)) == -1)
{
std::cout << "read error\n";
break;
}
else if(n == 0)
break;
if (EVP_DecryptUpdate(&ctx, outbuf, &olen, (unsigned char*)inbuff, n)
!= 1)
{
std::cout << "error in decrypt update\n";
return 0;
}
std::cout << "before dec. fin. ||" << i << "||\n";
std::cout << "inbuff size: " << n << "\n";
std::cout << "olen size: " << olen << "\n";
if (EVP_DecryptFinal_ex(&ctx, outbuf + olen, &tlen) != 1) //outbuf + olen
{
std::cout << "tlen: " << tlen << "\n";
std::cout << "error in decrypt final\n";
return 0;
}
else
{
//std::cout << "tlen: " << tlen << "\n";
}
olen += tlen;
ostream.write((char*)outbuf, olen);
}
//EVP_CIPHER_CTX_cleanup (&ctx); //not needed because of _ex's
return 1;
}
The output of my program during decryption is as follows
Key
166 234 103 213 202 55 168 35 155
193 103 2 98 36 200 0
------
Initialization vector
88 240 255 191 16 116 255 183
------
OP_SIZE: 1032
before dec. fin. ||0||
inbuff size: 1032
olen size: 1024
DecryptFinal Success: 0
tlen: 0
before dec. fin. ||1||
inbuff size: 1032
olen size: 1032
DecryptFinal Success: 1
tlen: 0
before dec. fin. ||2||
inbuff size: 1032
olen size: 1032
DecryptFinal Success: 2
tlen: 0
before dec. fin. ||3||
inbuff size: 1032
olen size: 1032
DecryptFinal Success: 3
tlen: 0
before dec. fin. ||4||
inbuff size: 1032
olen size: 1032
DecryptFinal Success: 4
tlen: 0
before dec. fin. ||5||
inbuff size: 1032
olen size: 1032
DecryptFinal Success: 5
tlen: 0
before dec. fin. ||6||
inbuff size: 1032
olen size: 1032
DecryptFinal Success: 6
tlen: 0
before dec. fin. ||7||
inbuff size: 968
olen size: 968
tlen: 0
error in decrypt final
Segmentation fault
I have spent too long (about 20 hours) trying to debug this, and I just
can't get it, I'd really appreciate it if anyone could help me or even
give me a little advice on where I am going wrong.
if anyone would like more information (like my whole class), let me know,
I didn't want to post it since it's about 3x this size of relatively
useless stuff for this problem.
Thanks in advance.
--
Matt
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