OpenSSL Decryption - EVP_DecryptFinal_ex fails
I'm using this decryption function to get the plain text value of a cipher which was encrypted using EVP AES 265 GCM; I can see data in rawOut but ret = EVP_DecryptFinal_ex(ctx, rawOut, &len); returns 0; can you provide any insight as to why? I've also seen sources which do rawOut + len in the EVP_DecryptFinal_ex code, I'm not sure why this would be needed as it would move the pointer to the end of the buffer.
unsigned char* keyDecrypter(unsigned char* pszMasterKey)
{
ERR_load_crypto_strings();
int ret, len;
EVP_CIPHER_CTX* ctx;
unsigned char* rawOut = new unsigned char[48]; // ToDo Remove Hardcoded Value
Info info = m_header.processKeyInfo();
if (NULL == info.nonce)
return NULL;
if (!(ctx = EVP_CIPHER_CTX_new()))
return NULL;
if (!EVP_DecryptInit_ex(ctx, EVP_aes_256_gcm(), NULL, pszMasterKey, info.nonce))
return NULL;
if (!EVP_DecryptUpdate(ctx, NULL, &len, m_header.aad, m_header.aad_len))
return NULL;
if (!EVP_DecryptUpdate(ctx, rawOut, &len, m_header.encryptedValue, m_header.encryptedValueLen))
return NULL;
// Finalise the decryption. A positive return value indicates success,
// anything else is a failure - the plain text is not trustworthy.
ret = EVP_DecryptFinal_ex(ctx, rawOut, &len);
ERR_print_errors_fp(stderr);
EVP_CIPHER_CTX_free(ctx);
if (ret > 0)
{
return rawOut;
}
else
{
return NULL;
}
}
c++ c c++11 openssl public-key-encryption
asked Nov 20 at 13:29
Oliver Ciappara
448717
add a comment |
I'm using this decryption function to get the plain text value of a cipher which was encrypted using EVP AES 265 GCM; I can see data in rawOut but ret = EVP_DecryptFinal_ex(ctx, rawOut, &len); returns 0; can you provide any insight as to why? I've also seen sources which do rawOut + len in the EVP_DecryptFinal_ex code, I'm not sure why this would be needed as it would move the pointer to the end of the buffer.
unsigned char* keyDecrypter(unsigned char* pszMasterKey)
{
ERR_load_crypto_strings();
int ret, len;
EVP_CIPHER_CTX* ctx;
unsigned char* rawOut = new unsigned char[48]; // ToDo Remove Hardcoded Value
Info info = m_header.processKeyInfo();
if (NULL == info.nonce)
return NULL;
if (!(ctx = EVP_CIPHER_CTX_new()))
return NULL;
if (!EVP_DecryptInit_ex(ctx, EVP_aes_256_gcm(), NULL, pszMasterKey, info.nonce))
return NULL;
if (!EVP_DecryptUpdate(ctx, NULL, &len, m_header.aad, m_header.aad_len))
return NULL;
if (!EVP_DecryptUpdate(ctx, rawOut, &len, m_header.encryptedValue, m_header.encryptedValueLen))
return NULL;
// Finalise the decryption. A positive return value indicates success,
// anything else is a failure - the plain text is not trustworthy.
ret = EVP_DecryptFinal_ex(ctx, rawOut, &len);
ERR_print_errors_fp(stderr);
EVP_CIPHER_CTX_free(ctx);
if (ret > 0)
{
return rawOut;
}
else
{
return NULL;
}
}
c++ c c++11 openssl public-key-encryption
asked Nov 20 at 13:29
Oliver Ciappara
448717
add a comment |
I'm using this decryption function to get the plain text value of a cipher which was encrypted using EVP AES 265 GCM; I can see data in rawOut but ret = EVP_DecryptFinal_ex(ctx, rawOut, &len); returns 0; can you provide any insight as to why? I've also seen sources which do rawOut + len in the EVP_DecryptFinal_ex code, I'm not sure why this would be needed as it would move the pointer to the end of the buffer.
unsigned char* keyDecrypter(unsigned char* pszMasterKey)
{
ERR_load_crypto_strings();
int ret, len;
EVP_CIPHER_CTX* ctx;
unsigned char* rawOut = new unsigned char[48]; // ToDo Remove Hardcoded Value
Info info = m_header.processKeyInfo();
if (NULL == info.nonce)
return NULL;
if (!(ctx = EVP_CIPHER_CTX_new()))
return NULL;
if (!EVP_DecryptInit_ex(ctx, EVP_aes_256_gcm(), NULL, pszMasterKey, info.nonce))
return NULL;
if (!EVP_DecryptUpdate(ctx, NULL, &len, m_header.aad, m_header.aad_len))
return NULL;
if (!EVP_DecryptUpdate(ctx, rawOut, &len, m_header.encryptedValue, m_header.encryptedValueLen))
return NULL;
// Finalise the decryption. A positive return value indicates success,
// anything else is a failure - the plain text is not trustworthy.
ret = EVP_DecryptFinal_ex(ctx, rawOut, &len);
ERR_print_errors_fp(stderr);
EVP_CIPHER_CTX_free(ctx);
if (ret > 0)
{
return rawOut;
}
else
{
return NULL;
}
}
c++ c c++11 openssl public-key-encryption
asked Nov 20 at 13:29
Oliver Ciappara
448717
I'm using this decryption function to get the plain text value of a cipher which was encrypted using EVP AES 265 GCM; I can see data in rawOut but ret = EVP_DecryptFinal_ex(ctx, rawOut, &len); returns 0; can you provide any insight as to why? I've also seen sources which do rawOut + len in the EVP_DecryptFinal_ex code, I'm not sure why this would be needed as it would move the pointer to the end of the buffer.
unsigned char* keyDecrypter(unsigned char* pszMasterKey)
{
ERR_load_crypto_strings();
int ret, len;
EVP_CIPHER_CTX* ctx;
unsigned char* rawOut = new unsigned char[48]; // ToDo Remove Hardcoded Value
Info info = m_header.processKeyInfo();
if (NULL == info.nonce)
return NULL;
if (!(ctx = EVP_CIPHER_CTX_new()))
return NULL;
if (!EVP_DecryptInit_ex(ctx, EVP_aes_256_gcm(), NULL, pszMasterKey, info.nonce))
return NULL;
if (!EVP_DecryptUpdate(ctx, NULL, &len, m_header.aad, m_header.aad_len))
return NULL;
if (!EVP_DecryptUpdate(ctx, rawOut, &len, m_header.encryptedValue, m_header.encryptedValueLen))
return NULL;
// Finalise the decryption. A positive return value indicates success,
// anything else is a failure - the plain text is not trustworthy.
ret = EVP_DecryptFinal_ex(ctx, rawOut, &len);
ERR_print_errors_fp(stderr);
EVP_CIPHER_CTX_free(ctx);
if (ret > 0)
{
return rawOut;
}
else
{
return NULL;
}
}
c++ c c++11 openssl public-key-encryption
c++ c c++11 openssl public-key-encryption
asked Nov 20 at 13:29
Oliver Ciappara
448717
asked Nov 20 at 13:29
Oliver Ciappara
448717
edited Nov 20 at 13:47
asked Nov 20 at 13:29
Oliver Ciappara
448717
asked Nov 20 at 13:29
Oliver Ciappara
448717
asked Nov 20 at 13:29
Oliver Ciappara
448717
448717
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
You need to pass rawOut + len to EVP_DecryptFinal_ex. See in the example at the end of the documentation:
/* Buffer passed to EVP_EncryptFinal() must be after data just
* encrypted to avoid overwriting it.
*/
if(!EVP_EncryptFinal_ex(ctx, outbuf + outlen, &tmplen))
{
/* Error */
return 0;
}
outlen += tmplen;
Also note that rawOut must have enough room for (m_header.aad_len + cipher_block_size) bytes. You can get the block size with EVP_CIPHER_block_size().
answered Nov 20 at 14:25
sergiopm
1514
I have read the documentation and as I mentioned I'm unsure why the outbuf + outlen is needed, as for the cipher_block_size, thank you I've missed that I'll test that out. thanks for your answer
– Oliver Ciappara
Nov 20 at 14:44
So I've tried both suggestions and still not getting a positive value from the function. Thanks tho.
– Oliver Ciappara
Nov 20 at 15:07
add a comment |
Your Answer
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1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
You need to pass rawOut + len to EVP_DecryptFinal_ex. See in the example at the end of the documentation:
/* Buffer passed to EVP_EncryptFinal() must be after data just
* encrypted to avoid overwriting it.
*/
if(!EVP_EncryptFinal_ex(ctx, outbuf + outlen, &tmplen))
{
/* Error */
return 0;
}
outlen += tmplen;
Also note that rawOut must have enough room for (m_header.aad_len + cipher_block_size) bytes. You can get the block size with EVP_CIPHER_block_size().
answered Nov 20 at 14:25
sergiopm
1514
I have read the documentation and as I mentioned I'm unsure why the outbuf + outlen is needed, as for the cipher_block_size, thank you I've missed that I'll test that out. thanks for your answer
– Oliver Ciappara
Nov 20 at 14:44
So I've tried both suggestions and still not getting a positive value from the function. Thanks tho.
– Oliver Ciappara
Nov 20 at 15:07
add a comment |
You need to pass rawOut + len to EVP_DecryptFinal_ex. See in the example at the end of the documentation:
/* Buffer passed to EVP_EncryptFinal() must be after data just
* encrypted to avoid overwriting it.
*/
if(!EVP_EncryptFinal_ex(ctx, outbuf + outlen, &tmplen))
{
/* Error */
return 0;
}
outlen += tmplen;
Also note that rawOut must have enough room for (m_header.aad_len + cipher_block_size) bytes. You can get the block size with EVP_CIPHER_block_size().
answered Nov 20 at 14:25
sergiopm
1514
I have read the documentation and as I mentioned I'm unsure why the outbuf + outlen is needed, as for the cipher_block_size, thank you I've missed that I'll test that out. thanks for your answer
– Oliver Ciappara
Nov 20 at 14:44
So I've tried both suggestions and still not getting a positive value from the function. Thanks tho.
– Oliver Ciappara
Nov 20 at 15:07
add a comment |
You need to pass rawOut + len to EVP_DecryptFinal_ex. See in the example at the end of the documentation:
/* Buffer passed to EVP_EncryptFinal() must be after data just
* encrypted to avoid overwriting it.
*/
if(!EVP_EncryptFinal_ex(ctx, outbuf + outlen, &tmplen))
{
/* Error */
return 0;
}
outlen += tmplen;
Also note that rawOut must have enough room for (m_header.aad_len + cipher_block_size) bytes. You can get the block size with EVP_CIPHER_block_size().
answered Nov 20 at 14:25
sergiopm
1514
You need to pass rawOut + len to EVP_DecryptFinal_ex. See in the example at the end of the documentation:
/* Buffer passed to EVP_EncryptFinal() must be after data just
* encrypted to avoid overwriting it.
*/
if(!EVP_EncryptFinal_ex(ctx, outbuf + outlen, &tmplen))
{
/* Error */
return 0;
}
outlen += tmplen;
Also note that rawOut must have enough room for (m_header.aad_len + cipher_block_size) bytes. You can get the block size with EVP_CIPHER_block_size().
answered Nov 20 at 14:25
sergiopm
1514
answered Nov 20 at 14:25
sergiopm
1514
answered Nov 20 at 14:25
sergiopm
1514
answered Nov 20 at 14:25
sergiopm
1514
1514
I have read the documentation and as I mentioned I'm unsure why the outbuf + outlen is needed, as for the cipher_block_size, thank you I've missed that I'll test that out. thanks for your answer
– Oliver Ciappara
Nov 20 at 14:44
So I've tried both suggestions and still not getting a positive value from the function. Thanks tho.
– Oliver Ciappara
Nov 20 at 15:07
add a comment |
I have read the documentation and as I mentioned I'm unsure why the outbuf + outlen is needed, as for the cipher_block_size, thank you I've missed that I'll test that out. thanks for your answer
– Oliver Ciappara
Nov 20 at 14:44
So I've tried both suggestions and still not getting a positive value from the function. Thanks tho.
– Oliver Ciappara
Nov 20 at 15:07
I have read the documentation and as I mentioned I'm unsure why the outbuf + outlen is needed, as for the cipher_block_size, thank you I've missed that I'll test that out. thanks for your answer
– Oliver Ciappara
Nov 20 at 14:44
I have read the documentation and as I mentioned I'm unsure why the outbuf + outlen is needed, as for the cipher_block_size, thank you I've missed that I'll test that out. thanks for your answer
– Oliver Ciappara
Nov 20 at 14:44
So I've tried both suggestions and still not getting a positive value from the function. Thanks tho.
– Oliver Ciappara
Nov 20 at 15:07
So I've tried both suggestions and still not getting a positive value from the function. Thanks tho.
– Oliver Ciappara
Nov 20 at 15:07
add a comment |
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