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authorlloyd <[email protected]>2011-04-08 14:57:49 +0000
committerlloyd <[email protected]>2011-04-08 14:57:49 +0000
commitfc62f7f284387a180e42402e8706965a666efba7 (patch)
tree9abe74c670993c111bd3a5bf5fb568767f9e75be /doc/examples/rsa_dec.cpp
parent438f3eb73e494fcab82b239452d712bec06f48c9 (diff)
More pubkey doc updates
Diffstat (limited to 'doc/examples/rsa_dec.cpp')
-rw-r--r--doc/examples/rsa_dec.cpp129
1 files changed, 129 insertions, 0 deletions
diff --git a/doc/examples/rsa_dec.cpp b/doc/examples/rsa_dec.cpp
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+/*
+* (C) 2002-2010 Jack Lloyd
+*
+* Distributed under the terms of the Botan license
+*/
+
+/*
+Decrypt an encrypted RSA private key. Then use that key to decrypt a
+message. This program can decrypt messages generated by rsa_enc, and uses the
+same key format as that generated by rsa_kgen.
+*/
+
+#include <iostream>
+#include <fstream>
+#include <string>
+#include <memory>
+
+#include <botan/botan.h>
+#include <botan/pubkey.h>
+#include <botan/rsa.h>
+using namespace Botan;
+
+SecureVector<byte> b64_decode(const std::string&);
+SymmetricKey derive_key(const std::string&, const SymmetricKey&, u32bit);
+
+const std::string SUFFIX = ".enc";
+
+int main(int argc, char* argv[])
+ {
+ if(argc != 4)
+ {
+ std::cout << "Usage: " << argv[0] << " keyfile messagefile passphrase"
+ << std::endl;
+ return 1;
+ }
+
+ Botan::LibraryInitializer init;
+
+ try
+ {
+ AutoSeeded_RNG rng;
+
+ std::auto_ptr<PKCS8_PrivateKey> key(
+ PKCS8::load_key(argv[1], rng, argv[3]));
+
+ RSA_PrivateKey* rsakey = dynamic_cast<RSA_PrivateKey*>(key.get());
+ if(!rsakey)
+ {
+ std::cout << "The loaded key is not a RSA key!\n";
+ return 1;
+ }
+
+ std::ifstream message(argv[2]);
+ if(!message)
+ {
+ std::cout << "Couldn't read the message file." << std::endl;
+ return 1;
+ }
+
+ std::string outfile(argv[2]);
+ outfile = outfile.replace(outfile.find(SUFFIX), SUFFIX.length(), "");
+
+ std::ofstream plaintext(outfile.c_str(), std::ios::binary);
+ if(!plaintext)
+ {
+ std::cout << "Couldn't write the plaintext to "
+ << outfile << std::endl;
+ return 1;
+ }
+
+ std::string enc_masterkey_str;
+ std::getline(message, enc_masterkey_str);
+ std::string mac_str;
+ std::getline(message, mac_str);
+
+ SecureVector<byte> enc_masterkey = b64_decode(enc_masterkey_str);
+
+ PK_Decryptor_EME decryptor(*rsakey, "EME1(SHA-1)");
+
+ SecureVector<byte> masterkey = decryptor.decrypt(enc_masterkey);
+
+ SymmetricKey cast_key = derive_key("CAST", masterkey, 16);
+ InitializationVector iv = derive_key("IV", masterkey, 8);
+ SymmetricKey mac_key = derive_key("MAC", masterkey, 16);
+
+ Pipe pipe(new Base64_Decoder,
+ get_cipher("CAST-128/CBC/PKCS7", cast_key, iv, DECRYPTION),
+ new Fork(
+ 0,
+ new Chain(
+ new MAC_Filter("HMAC(SHA-1)", mac_key, 12),
+ new Base64_Encoder
+ )
+ )
+ );
+
+ pipe.start_msg();
+ message >> pipe;
+ pipe.end_msg();
+
+ std::string our_mac = pipe.read_all_as_string(1);
+
+ if(our_mac != mac_str)
+ std::cout << "WARNING: MAC in message failed to verify\n";
+
+ plaintext << pipe.read_all_as_string(0);
+ }
+ catch(std::exception& e)
+ {
+ std::cout << "Exception caught: " << e.what() << std::endl;
+ return 1;
+ }
+ return 0;
+ }
+
+SecureVector<byte> b64_decode(const std::string& in)
+ {
+ Pipe pipe(new Base64_Decoder);
+ pipe.process_msg(in);
+ return pipe.read_all();
+ }
+
+SymmetricKey derive_key(const std::string& param,
+ const SymmetricKey& masterkey,
+ u32bit outputlength)
+ {
+ std::auto_ptr<KDF> kdf(get_kdf("KDF2(SHA-1)"));
+ return kdf->derive_key(outputlength, masterkey.bits_of(), param);
+ }