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irbull/OpenSSLExample.cpp

Created August 11, 2016 18:32
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Code signing and verification with OpenSSL
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OpenSSLExample.cpp
#include <iostream>
#include <openssl/aes.h>
#include <openssl/evp.h>
#include <openssl/rsa.h>
#include <openssl/pem.h>
#include <openssl/ssl.h>
#include <openssl/bio.h>
#include <openssl/err.h>
#include <assert.h>
std::string privateKey ="-----BEGIN RSA PRIVATE KEY-----\n"\
"MIIEowIBAAKCAQEAy8Dbv8prpJ/0kKhlGeJYozo2t60EG8L0561g13R29LvMR5hy\n"\
"vGZlGJpmn65+A4xHXInJYiPuKzrKUnApeLZ+vw1HocOAZtWK0z3r26uA8kQYOKX9\n"\
"Qt/DbCdvsF9wF8gRK0ptx9M6R13NvBxvVQApfc9jB9nTzphOgM4JiEYvlV8FLhg9\n"\
"yZovMYd6Wwf3aoXK891VQxTr/kQYoq1Yp+68i6T4nNq7NWC+UNVjQHxNQMQMzU6l\n"\
"WCX8zyg3yH88OAQkUXIXKfQ+NkvYQ1cxaMoVPpY72+eVthKzpMeyHkBn7ciumk5q\n"\
"gLTEJAfWZpe4f4eFZj/Rc8Y8Jj2IS5kVPjUywQIDAQABAoIBADhg1u1Mv1hAAlX8\n"\
"omz1Gn2f4AAW2aos2cM5UDCNw1SYmj+9SRIkaxjRsE/C4o9sw1oxrg1/z6kajV0e\n"\
"N/t008FdlVKHXAIYWF93JMoVvIpMmT8jft6AN/y3NMpivgt2inmmEJZYNioFJKZG\n"\
"X+/vKYvsVISZm2fw8NfnKvAQK55yu+GRWBZGOeS9K+LbYvOwcrjKhHz66m4bedKd\n"\
"gVAix6NE5iwmjNXktSQlJMCjbtdNXg/xo1/G4kG2p/MO1HLcKfe1N5FgBiXj3Qjl\n"\
"vgvjJZkh1as2KTgaPOBqZaP03738VnYg23ISyvfT/teArVGtxrmFP7939EvJFKpF\n"\
"1wTxuDkCgYEA7t0DR37zt+dEJy+5vm7zSmN97VenwQJFWMiulkHGa0yU3lLasxxu\n"\
"m0oUtndIjenIvSx6t3Y+agK2F3EPbb0AZ5wZ1p1IXs4vktgeQwSSBdqcM8LZFDvZ\n"\
"uPboQnJoRdIkd62XnP5ekIEIBAfOp8v2wFpSfE7nNH2u4CpAXNSF9HsCgYEA2l8D\n"\
"JrDE5m9Kkn+J4l+AdGfeBL1igPF3DnuPoV67BpgiaAgI4h25UJzXiDKKoa706S0D\n"\
"4XB74zOLX11MaGPMIdhlG+SgeQfNoC5lE4ZWXNyESJH1SVgRGT9nBC2vtL6bxCVV\n"\
"WBkTeC5D6c/QXcai6yw6OYyNNdp0uznKURe1xvMCgYBVYYcEjWqMuAvyferFGV+5\n"\
"nWqr5gM+yJMFM2bEqupD/HHSLoeiMm2O8KIKvwSeRYzNohKTdZ7FwgZYxr8fGMoG\n"\
"PxQ1VK9DxCvZL4tRpVaU5Rmknud9hg9DQG6xIbgIDR+f79sb8QjYWmcFGc1SyWOA\n"\
"SkjlykZ2yt4xnqi3BfiD9QKBgGqLgRYXmXp1QoVIBRaWUi55nzHg1XbkWZqPXvz1\n"\
"I3uMLv1jLjJlHk3euKqTPmC05HoApKwSHeA0/gOBmg404xyAYJTDcCidTg6hlF96\n"\
"ZBja3xApZuxqM62F6dV4FQqzFX0WWhWp5n301N33r0qR6FumMKJzmVJ1TA8tmzEF\n"\
"yINRAoGBAJqioYs8rK6eXzA8ywYLjqTLu/yQSLBn/4ta36K8DyCoLNlNxSuox+A5\n"\
"w6z2vEfRVQDq4Hm4vBzjdi3QfYLNkTiTqLcvgWZ+eX44ogXtdTDO7c+GeMKWz4XX\n"\
"uJSUVL5+CVjKLjZEJ6Qc2WZLl94xSwL71E41H4YciVnSCQxVc4Jw\n"\
"-----END RSA PRIVATE KEY-----\n\0";
std::string publicKey ="-----BEGIN PUBLIC KEY-----\n"\
"MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAy8Dbv8prpJ/0kKhlGeJY\n"\
"ozo2t60EG8L0561g13R29LvMR5hyvGZlGJpmn65+A4xHXInJYiPuKzrKUnApeLZ+\n"\
"vw1HocOAZtWK0z3r26uA8kQYOKX9Qt/DbCdvsF9wF8gRK0ptx9M6R13NvBxvVQAp\n"\
"fc9jB9nTzphOgM4JiEYvlV8FLhg9yZovMYd6Wwf3aoXK891VQxTr/kQYoq1Yp+68\n"\
"i6T4nNq7NWC+UNVjQHxNQMQMzU6lWCX8zyg3yH88OAQkUXIXKfQ+NkvYQ1cxaMoV\n"\
"PpY72+eVthKzpMeyHkBn7ciumk5qgLTEJAfWZpe4f4eFZj/Rc8Y8Jj2IS5kVPjUy\n"\
"wQIDAQAB\n"\
"-----END PUBLIC KEY-----\n";
RSA* createPrivateRSA(std::string key) {
RSA *rsa = NULL;
const char* c_string = key.c_str();
BIO * keybio = BIO_new_mem_buf((void*)c_string, -1);
if (keybio==NULL) {
return 0;
}
rsa = PEM_read_bio_RSAPrivateKey(keybio, &rsa,NULL, NULL);
return rsa;
}
RSA* createPublicRSA(std::string key) {
RSA *rsa = NULL;
BIO *keybio;
const char* c_string = key.c_str();
keybio = BIO_new_mem_buf((void*)c_string, -1);
if (keybio==NULL) {
return 0;
}
rsa = PEM_read_bio_RSA_PUBKEY(keybio, &rsa,NULL, NULL);
return rsa;
}
bool RSASign( RSA* rsa,
const unsigned char* Msg,
size_t MsgLen,
unsigned char** EncMsg,
size_t* MsgLenEnc) {
EVP_MD_CTX* m_RSASignCtx = EVP_MD_CTX_create();
EVP_PKEY* priKey = EVP_PKEY_new();
EVP_PKEY_assign_RSA(priKey, rsa);
if (EVP_DigestSignInit(m_RSASignCtx,NULL, EVP_sha256(), NULL,priKey)<=0) {
return false;
}
if (EVP_DigestSignUpdate(m_RSASignCtx, Msg, MsgLen) <= 0) {
return false;
}
if (EVP_DigestSignFinal(m_RSASignCtx, NULL, MsgLenEnc) <=0) {
return false;
}
*EncMsg = (unsigned char*)malloc(*MsgLenEnc);
if (EVP_DigestSignFinal(m_RSASignCtx, *EncMsg, MsgLenEnc) <= 0) {
return false;
}
EVP_MD_CTX_cleanup(m_RSASignCtx);
return true;
}
bool RSAVerifySignature( RSA* rsa,
unsigned char* MsgHash,
size_t MsgHashLen,
const char* Msg,
size_t MsgLen,
bool* Authentic) {
*Authentic = false;
EVP_PKEY* pubKey = EVP_PKEY_new();
EVP_PKEY_assign_RSA(pubKey, rsa);
EVP_MD_CTX* m_RSAVerifyCtx = EVP_MD_CTX_create();
if (EVP_DigestVerifyInit(m_RSAVerifyCtx,NULL, EVP_sha256(),NULL,pubKey)<=0) {
return false;
}
if (EVP_DigestVerifyUpdate(m_RSAVerifyCtx, Msg, MsgLen) <= 0) {
return false;
}
int AuthStatus = EVP_DigestVerifyFinal(m_RSAVerifyCtx, MsgHash, MsgHashLen);
if (AuthStatus==1) {
*Authentic = true;
EVP_MD_CTX_cleanup(m_RSAVerifyCtx);
return true;
} else if(AuthStatus==0){
*Authentic = false;
EVP_MD_CTX_cleanup(m_RSAVerifyCtx);
return true;
} else{
*Authentic = false;
EVP_MD_CTX_cleanup(m_RSAVerifyCtx);
return false;
}
}
void Base64Encode( const unsigned char* buffer,
size_t length,
char** base64Text) {
BIO *bio, *b64;
BUF_MEM *bufferPtr;
b64 = BIO_new(BIO_f_base64());
bio = BIO_new(BIO_s_mem());
bio = BIO_push(b64, bio);
BIO_write(bio, buffer, length);
BIO_flush(bio);
BIO_get_mem_ptr(bio, &bufferPtr);
BIO_set_close(bio, BIO_NOCLOSE);
BIO_free_all(bio);
*base64Text=(*bufferPtr).data;
}
size_t calcDecodeLength(const char* b64input) {
size_t len = strlen(b64input), padding = 0;
if (b64input[len-1] == '=' && b64input[len-2] == '=') //last two chars are =
padding = 2;
else if (b64input[len-1] == '=') //last char is =
padding = 1;
return (len*3)/4 - padding;
}
void Base64Decode(const char* b64message, unsigned char** buffer, size_t* length) {
BIO *bio, *b64;
int decodeLen = calcDecodeLength(b64message);
*buffer = (unsigned char*)malloc(decodeLen + 1);
(*buffer)[decodeLen] = '\0';
bio = BIO_new_mem_buf(b64message, -1);
b64 = BIO_new(BIO_f_base64());
bio = BIO_push(b64, bio);
*length = BIO_read(bio, *buffer, strlen(b64message));
BIO_free_all(bio);
}
char* signMessage(std::string privateKey, std::string plainText) {
RSA* privateRSA = createPrivateRSA(privateKey);
unsigned char* encMessage;
char* base64Text;
size_t encMessageLength;
RSASign(privateRSA, (unsigned char*) plainText.c_str(), plainText.length(), &encMessage, &encMessageLength);
Base64Encode(encMessage, encMessageLength, &base64Text);
free(encMessage);
return base64Text;
}
bool verifySignature(std::string publicKey, std::string plainText, char* signatureBase64) {
RSA* publicRSA = createPublicRSA(publicKey);
unsigned char* encMessage;
size_t encMessageLength;
bool authentic;
Base64Decode(signatureBase64, &encMessage, &encMessageLength);
bool result = RSAVerifySignature(publicRSA, encMessage, encMessageLength, plainText.c_str(), plainText.length(), &authentic);
return result & authentic;
}
int main() {
std::string plainText = "My secret message.\n";
char* signature = signMessage(privateKey, plainText);
bool authentic = verifySignature(publicKey, "My secret message.\n", signature);
if ( authentic ) {
std::cout << "Authentic" << std::endl;
} else {
std::cout << "Not Authentic" << std::endl;
}
}
@rpolasek-sde
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rpolasek-sde commented Feb 15, 2023 •
edited
Loading

there are still memory leaks. one of them can be solved by adding free(signature); as a last line in the main() and then there is 1 memory leak remaining which i haven't found yet:

==28980== HEAP SUMMARY:
==28980==     in use at exit: 32 bytes in 1 blocks
==28980==   total heap usage: 11,284 allocs, 11,283 frees, 1,362,954 bytes allocated
==28980==
==28980== 32 bytes in 1 blocks are definitely lost in loss record 1 of 1
==28980==    at 0x4848899: malloc (in /usr/libexec/valgrind/vgpreload_memcheck-amd64-linux.so)
==28980==    by 0x4A2B41D: CRYPTO_zalloc (in /usr/lib/x86_64-linux-gnu/libcrypto.so.3)
==28980==    by 0x496AD13: BUF_MEM_new (in /usr/lib/x86_64-linux-gnu/libcrypto.so.3)
==28980==    by 0x496AD6C: BUF_MEM_new_ex (in /usr/lib/x86_64-linux-gnu/libcrypto.so.3)
==28980==    by 0x4958E99: ??? (in /usr/lib/x86_64-linux-gnu/libcrypto.so.3)
==28980==    by 0x494FA13: BIO_new_ex (in /usr/lib/x86_64-linux-gnu/libcrypto.so.3)
==28980==    by 0x10AC23: Base64Encode(unsigned char const*, unsigned long, char**) (openssl_example_new.cc:165)
==28980==    by 0x10AEF5: signMessage(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >) (openssl_example_new.cc:211)
==28980==    by 0x10B0DA: main (openssl_example_new.cc:232)
==28980==
==28980== LEAK SUMMARY:
==28980==    definitely lost: 32 bytes in 1 blocks
==28980==    indirectly lost: 0 bytes in 0 blocks
==28980==      possibly lost: 0 bytes in 0 blocks
==28980==    still reachable: 0 bytes in 0 blocks
==28980==         suppressed: 0 bytes in 0 blocks
==28980==
==28980== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)

btw. how could we replace 3 deprecated functions?

/home/xyz/abc/cc/openssl/openssl_example_new.cc:59:37: warning: ‘RSA* PEM_read_bio_RSAPrivateKey(BIO*, RSA**, int (*)(char*, int, int, void*), void*)’ is deprecated: Since OpenSSL 3.0 [-Wdeprecated-declarations]
   59 |     rsa = PEM_read_bio_RSAPrivateKey(keybio, &rsa, nullptr, nullptr);
      |           ~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /home/xyz/abc/cc/openssl/openssl_example_new.cc:7:
/usr/include/openssl/pem.h:447:1: note: declared here
  447 | DECLARE_PEM_rw_cb_attr(OSSL_DEPRECATEDIN_3_0, RSAPrivateKey, RSA)
      | ^~~~~~~~~~~~~~~~~~~~~~
/home/xyz/abc/cc/openssl/openssl_example_new.cc: In function ‘RSA* createPublicRSA(std::string)’:
/home/xzy/abc/cc/openssl/openssl_example_new.cc:87:34: warning: ‘RSA* PEM_read_bio_RSA_PUBKEY(BIO*, RSA**, int (*)(char*, int, int, void*), void*)’ is deprecated: Since OpenSSL 3.0 [-Wdeprecated-declarations]
   87 |     rsa = PEM_read_bio_RSA_PUBKEY(keybio, &rsa,nullptr, nullptr);
      |           ~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/openssl/pem.h:449:1: note: declared here
  449 | DECLARE_PEM_rw_attr(OSSL_DEPRECATEDIN_3_0, RSA_PUBKEY, RSA)
      | ^~~~~~~~~~~~~~~~~~~
[100%] Linking CXX executable openssl_example_new
[100%] Built target openssl_example_new
Authentic

@rpolasek-sde
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i've just found last memory leaks. you can fix it by adding free(bufferPtr); as a last line in the Base64Encode() but that's not much nice code at all...

@frankz61
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It really helped me. i think the part of base64 code can`t peer to current standard. use some other popular base64 open source library can make it more compatible.

@PiaoL
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PiaoL commented Apr 22, 2024

It really helped me, i'm using Objective-C

@ahuigo
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ahuigo commented May 23, 2024

for openssl>=1.1.0 use EVP_MD_CTX_free instead of EVP_MD_CTX_cleanup. It works for me on my linux.

#include <iostream>
#include <openssl/aes.h>
#include <openssl/evp.h>
#include <openssl/rsa.h>
#include <openssl/pem.h>
#include <openssl/ssl.h>
#include <openssl/bio.h>
#include <openssl/err.h>
#include <assert.h>
#include <cstring>

/**
g++  b.cpp -o main -lcryptopp -lssl -lcrypto  2>&1  && ./main
*/

std::string privateKey ="-----BEGIN RSA PRIVATE KEY-----\n"\
"MIIEowIBAAKCAQEAy8Dbv8prpJ/0kKhlGeJYozo2t60EG8L0561g13R29LvMR5hy\n"\
"vGZlGJpmn65+A4xHXInJYiPuKzrKUnApeLZ+vw1HocOAZtWK0z3r26uA8kQYOKX9\n"\
"Qt/DbCdvsF9wF8gRK0ptx9M6R13NvBxvVQApfc9jB9nTzphOgM4JiEYvlV8FLhg9\n"\
"yZovMYd6Wwf3aoXK891VQxTr/kQYoq1Yp+68i6T4nNq7NWC+UNVjQHxNQMQMzU6l\n"\
"WCX8zyg3yH88OAQkUXIXKfQ+NkvYQ1cxaMoVPpY72+eVthKzpMeyHkBn7ciumk5q\n"\
"gLTEJAfWZpe4f4eFZj/Rc8Y8Jj2IS5kVPjUywQIDAQABAoIBADhg1u1Mv1hAAlX8\n"\
"omz1Gn2f4AAW2aos2cM5UDCNw1SYmj+9SRIkaxjRsE/C4o9sw1oxrg1/z6kajV0e\n"\
"N/t008FdlVKHXAIYWF93JMoVvIpMmT8jft6AN/y3NMpivgt2inmmEJZYNioFJKZG\n"\
"X+/vKYvsVISZm2fw8NfnKvAQK55yu+GRWBZGOeS9K+LbYvOwcrjKhHz66m4bedKd\n"\
"gVAix6NE5iwmjNXktSQlJMCjbtdNXg/xo1/G4kG2p/MO1HLcKfe1N5FgBiXj3Qjl\n"\
"vgvjJZkh1as2KTgaPOBqZaP03738VnYg23ISyvfT/teArVGtxrmFP7939EvJFKpF\n"\
"1wTxuDkCgYEA7t0DR37zt+dEJy+5vm7zSmN97VenwQJFWMiulkHGa0yU3lLasxxu\n"\
"m0oUtndIjenIvSx6t3Y+agK2F3EPbb0AZ5wZ1p1IXs4vktgeQwSSBdqcM8LZFDvZ\n"\
"uPboQnJoRdIkd62XnP5ekIEIBAfOp8v2wFpSfE7nNH2u4CpAXNSF9HsCgYEA2l8D\n"\
"JrDE5m9Kkn+J4l+AdGfeBL1igPF3DnuPoV67BpgiaAgI4h25UJzXiDKKoa706S0D\n"\
"4XB74zOLX11MaGPMIdhlG+SgeQfNoC5lE4ZWXNyESJH1SVgRGT9nBC2vtL6bxCVV\n"\
"WBkTeC5D6c/QXcai6yw6OYyNNdp0uznKURe1xvMCgYBVYYcEjWqMuAvyferFGV+5\n"\
"nWqr5gM+yJMFM2bEqupD/HHSLoeiMm2O8KIKvwSeRYzNohKTdZ7FwgZYxr8fGMoG\n"\
"PxQ1VK9DxCvZL4tRpVaU5Rmknud9hg9DQG6xIbgIDR+f79sb8QjYWmcFGc1SyWOA\n"\
"SkjlykZ2yt4xnqi3BfiD9QKBgGqLgRYXmXp1QoVIBRaWUi55nzHg1XbkWZqPXvz1\n"\
"I3uMLv1jLjJlHk3euKqTPmC05HoApKwSHeA0/gOBmg404xyAYJTDcCidTg6hlF96\n"\
"ZBja3xApZuxqM62F6dV4FQqzFX0WWhWp5n301N33r0qR6FumMKJzmVJ1TA8tmzEF\n"\
"yINRAoGBAJqioYs8rK6eXzA8ywYLjqTLu/yQSLBn/4ta36K8DyCoLNlNxSuox+A5\n"\
"w6z2vEfRVQDq4Hm4vBzjdi3QfYLNkTiTqLcvgWZ+eX44ogXtdTDO7c+GeMKWz4XX\n"\
"uJSUVL5+CVjKLjZEJ6Qc2WZLl94xSwL71E41H4YciVnSCQxVc4Jw\n"\
"-----END RSA PRIVATE KEY-----\n\0";

std::string publicKey ="-----BEGIN PUBLIC KEY-----\n"\
"MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAy8Dbv8prpJ/0kKhlGeJY\n"\
"ozo2t60EG8L0561g13R29LvMR5hyvGZlGJpmn65+A4xHXInJYiPuKzrKUnApeLZ+\n"\
"vw1HocOAZtWK0z3r26uA8kQYOKX9Qt/DbCdvsF9wF8gRK0ptx9M6R13NvBxvVQAp\n"\
"fc9jB9nTzphOgM4JiEYvlV8FLhg9yZovMYd6Wwf3aoXK891VQxTr/kQYoq1Yp+68\n"\
"i6T4nNq7NWC+UNVjQHxNQMQMzU6lWCX8zyg3yH88OAQkUXIXKfQ+NkvYQ1cxaMoV\n"\
"PpY72+eVthKzpMeyHkBn7ciumk5qgLTEJAfWZpe4f4eFZj/Rc8Y8Jj2IS5kVPjUy\n"\
"wQIDAQAB\n"\
"-----END PUBLIC KEY-----\n";

RSA* createPrivateRSA(std::string key) {
  RSA *rsa = NULL;
  const char* c_string = key.c_str();
  BIO * keybio = BIO_new_mem_buf((void*)c_string, -1);
  if (keybio==NULL) {
      return 0;
  }
  rsa = PEM_read_bio_RSAPrivateKey(keybio, &rsa,NULL, NULL);
  return rsa;
}

RSA* createPublicRSA(std::string key) {
  RSA *rsa = NULL;
  BIO *keybio;
  const char* c_string = key.c_str();
  keybio = BIO_new_mem_buf((void*)c_string, -1);
  if (keybio==NULL) {
      return 0;
  }
  rsa = PEM_read_bio_RSA_PUBKEY(keybio, &rsa,NULL, NULL);
  return rsa;
}

bool RSASign( RSA* rsa,
              const unsigned char* Msg,
              size_t MsgLen,
              unsigned char** EncMsg,
              size_t* MsgLenEnc) {
  EVP_MD_CTX* m_RSASignCtx = EVP_MD_CTX_create();
  EVP_PKEY* priKey  = EVP_PKEY_new();
  EVP_PKEY_assign_RSA(priKey, rsa);
  if (EVP_DigestSignInit(m_RSASignCtx,NULL, EVP_sha256(), NULL,priKey)<=0) {
      return false;
  }
  if (EVP_DigestSignUpdate(m_RSASignCtx, Msg, MsgLen) <= 0) {
      return false;
  }
  if (EVP_DigestSignFinal(m_RSASignCtx, NULL, MsgLenEnc) <=0) {
      return false;
  }
  *EncMsg = (unsigned char*)malloc(*MsgLenEnc);
  if (EVP_DigestSignFinal(m_RSASignCtx, *EncMsg, MsgLenEnc) <= 0) {
      return false;
  }
//   EVP_MD_CTX_free(m_RSASignCtx);
  EVP_MD_CTX_free(m_RSASignCtx);
  return true;
}

bool RSAVerifySignature( RSA* rsa,
                         unsigned char* MsgHash,
                         size_t MsgHashLen,
                         const char* Msg,
                         size_t MsgLen,
                         bool* Authentic) {
  *Authentic = false;
  EVP_PKEY* pubKey  = EVP_PKEY_new();
  EVP_PKEY_assign_RSA(pubKey, rsa);
  EVP_MD_CTX* m_RSAVerifyCtx = EVP_MD_CTX_create();

  if (EVP_DigestVerifyInit(m_RSAVerifyCtx,NULL, EVP_sha256(),NULL,pubKey)<=0) {
    return false;
  }
  if (EVP_DigestVerifyUpdate(m_RSAVerifyCtx, Msg, MsgLen) <= 0) {
    return false;
  }
  int AuthStatus = EVP_DigestVerifyFinal(m_RSAVerifyCtx, MsgHash, MsgHashLen);
  if (AuthStatus==1) {
    *Authentic = true;
    EVP_MD_CTX_free(m_RSAVerifyCtx);
    return true;
  } else if(AuthStatus==0){
    *Authentic = false;
    EVP_MD_CTX_free(m_RSAVerifyCtx);
    return true;
  } else{
    *Authentic = false;
    EVP_MD_CTX_free(m_RSAVerifyCtx);
    return false;
  }
}

void Base64Encode( const unsigned char* buffer,
                   size_t length,
                   char** base64Text) {
  BIO *bio, *b64;
  BUF_MEM *bufferPtr;

  b64 = BIO_new(BIO_f_base64());
  bio = BIO_new(BIO_s_mem());
  bio = BIO_push(b64, bio);

  BIO_write(bio, buffer, length);
  BIO_flush(bio);
  BIO_get_mem_ptr(bio, &bufferPtr);
  BIO_set_close(bio, BIO_NOCLOSE);
  BIO_free_all(bio);

  *base64Text=(*bufferPtr).data;
}

size_t calcDecodeLength(const char* b64input) {
  size_t len = strlen(b64input), padding = 0;

  if (b64input[len-1] == '=' && b64input[len-2] == '=') //last two chars are =
    padding = 2;
  else if (b64input[len-1] == '=') //last char is =
    padding = 1;
  return (len*3)/4 - padding;
}

void Base64Decode(const char* b64message, unsigned char** buffer, size_t* length) {
  BIO *bio, *b64;

  int decodeLen = calcDecodeLength(b64message);
  *buffer = (unsigned char*)malloc(decodeLen + 1);
  (*buffer)[decodeLen] = '\0';

  bio = BIO_new_mem_buf(b64message, -1);
  b64 = BIO_new(BIO_f_base64());
  bio = BIO_push(b64, bio);

  *length = BIO_read(bio, *buffer, strlen(b64message));
  BIO_free_all(bio);
}

char* signMessage(std::string privateKey, std::string plainText) {
  RSA* privateRSA = createPrivateRSA(privateKey); 
  unsigned char* encMessage;
  char* base64Text;
  size_t encMessageLength;
  RSASign(privateRSA, (unsigned char*) plainText.c_str(), plainText.length(), &encMessage, &encMessageLength);
  Base64Encode(encMessage, encMessageLength, &base64Text);
  free(encMessage);
  return base64Text;
}

bool verifySignature(std::string publicKey, std::string plainText, char* signatureBase64) {
  RSA* publicRSA = createPublicRSA(publicKey);
  unsigned char* encMessage;
  size_t encMessageLength;
  bool authentic;
  Base64Decode(signatureBase64, &encMessage, &encMessageLength);
  bool result = RSAVerifySignature(publicRSA, encMessage, encMessageLength, plainText.c_str(), plainText.length(), &authentic);
  return result & authentic;
}

int main() {
  std::string plainText = "My secret message.\n";
  char* signature = signMessage(privateKey, plainText);
  bool authentic = verifySignature(publicKey, "My secret message.\n", signature);
  if ( authentic ) {
    std::cout << "Authentic" << std::endl;
  } else {
    std::cout << "Not Authentic" << std::endl;
  }
}

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