StringSource is using "new" operator. Should be deleting the memory or is it auto destroyed?
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Dwight Kulkarni
Apr 27, 2023, 1:30:58 PM4/27/23
to Crypto++ Users
Hello,
I note an example code sample for b64encode(..). I note that there are "new" calls inside the constructor(..).
The result is returned in the encoded string.
Do I need to do anything to delete the memory from the new calls ?
What happens to the memory in the variable "encoded", if the variable is passed up to another function and the StringSink is destroyed.
Should I make a copy of encoded and send it on to be safe ?
std::string b64encode(std::string str)
{
std::string encoded;
CryptoPP::StringSource(str, true,
new CryptoPP::Base64Encoder(
new CryptoPP::StringSink(encoded),
false
)
);
return encoded;
}
Jeffrey Walton
Apr 27, 2023, 1:35:43 PM4/27/23
to cryptop...@googlegroups.com
On Thu, Apr 27, 2023 at 1:31 PM Dwight Kulkarni <dwi...@realtime-7.com> wrote:
>
> I note an example code sample for b64encode(..). I note that there are "new" calls inside the constructor(..).
>
> The result is returned in the encoded string.
>
> Do I need to do anything to delete the memory from the new calls ?
>
> What happens to the memory in the variable "encoded", if the variable is passed up to another function and the StringSink is destroyed.
>
> Should I make a copy of encoded and send it on to be safe ?
https://www.cryptopp.com/wiki/Pipelining#Ownership
>
> I note an example code sample for b64encode(..). I note that there are "new" calls inside the constructor(..).
>
> The result is returned in the encoded string.
>
> Do I need to do anything to delete the memory from the new calls ?
>
> What happens to the memory in the variable "encoded", if the variable is passed up to another function and the StringSink is destroyed.
>
> Should I make a copy of encoded and send it on to be safe ?
Jeff
Dwight Kulkarni
Apr 27, 2023, 1:57:33 PM4/27/23
to Crypto++ Users
Hi Jeff,
Ok I think those RSA errors with memory are due to this pipelining, because the b64decode(..) b64encode(..) is called every where, and if I understand correctly, the string inside will be destroyed and I have to use the redirector. Can you confirm if you agree with this code change and my understanding of the problem ?
Previous Code:
std::string b64encode(std::string str)
{
std::string encoded;
CryptoPP::StringSource(str, true,
new CryptoPP::Base64Encoder(
new CryptoPP::StringSink(encoded),
false
)
);
return encoded; //encoded will be destroyed once StringSource(..) goes out of scope
}
New Code:
std::string b64encode(std::string str)
{
std::string encoded;
CryptoPP::Base64Encoder df(new CryptoPP::StringSink(encoded),false);
CryptoPP::StringSource(str, true, new Redirector(df) );
return encoded; //encoded won't be destroyed
}
based on this:
CCM< AES, TAG_SIZE >::Decryption d;
d.SetKeyWithIV( key, key.size(), iv, sizeof(iv) );
AuthenticatedDecryptionFilter df( d,
new StringSink( recovered )
); // AuthenticatedDecryptionFilter
// Cipher text includes the MAC tag
StringSource ss( cipher, true,
new Redirector( df )
); // StringSource
// If the object does not throw, here's the only
// opportunity to check the data's integrity
bool b = df.GetLastResult();
if( true == b ) {
cout << recovered << endl;
}
Jeffrey Walton
Apr 27, 2023, 2:10:38 PM4/27/23
to cryptop...@googlegroups.com
On Thu, Apr 27, 2023 at 1:57 PM Dwight Kulkarni <dwi...@realtime-7.com> wrote:
>
> Ok I think those RSA errors with memory are due to this pipelining, because the b64decode(..) b64encode(..) is called every where, and if I understand correctly, the string inside will be destroyed and I have to use the redirector. Can you confirm if you agree with this code change and my understanding of the problem ?
>
> Previous Code:
> std::string b64encode(std::string str)
> {
> using namespace CryptoPP;
>
> Ok I think those RSA errors with memory are due to this pipelining, because the b64decode(..) b64encode(..) is called every where, and if I understand correctly, the string inside will be destroyed and I have to use the redirector. Can you confirm if you agree with this code change and my understanding of the problem ?
>
> Previous Code:
> std::string b64encode(std::string str)
> {
>
> std::string encoded;
> StringSource(str, true,
> new Base64Encoder(
> new StringSink(encoded),
> false
> )
> );
> return encoded; //encoded will be destroyed once StringSource(..) goes out of scope
> }
This code is Ok.
> )
> );
> return encoded; //encoded will be destroyed once StringSource(..) goes out of scope
> }
The variable 'encoded' is not destroyed because it is a reference, and
not a pointer. 'encoded' is a stack variable. It will be destroyed
when the stack frame is cleaned up.
> New Code:
>
> std::string b64encode(std::string str)
> {
>
> std::string encoded;
> Base64Encoder df(new CryptoPP::StringSink(encoded),false);
> StringSource(str, true, new Redirector(df) );
> return encoded; //encoded won't be destroyed
> }
This code is Ok, too. This code is effectively the same as the first
> return encoded; //encoded won't be destroyed
> }
example. The Base64Encoder is now an automatic variable, and it will
be cleaned up when the destructor runs during stack cleanup.
The variable 'encoded' is not destroyed because it is a reference, and
not a pointer. 'encoded' is a stack variable. It will be destroyed
when the stack frame is cleaned up.
Your memory error lies elsewhere. Run Asan over your program.
Jeff
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