m_sasl_dh-aes: Add module

modules/extra/m_sasl_dh-aes.cpp

@@ -0,0 +1,183 @@
+/* RequiredLibraries: ssl,crypto */
+
+#include "module.h"
+#include "modules/sasl.h"
+
+#include <openssl/bn.h>
+#include <openssl/dh.h>
+#include <openssl/aes.h>
+
+using namespace SASL;
+
+class DHAES : public Mechanism
+{
+	void Err(Session* sess, BIGNUM* key = NULL)
+	{
+		if (key)
+			BN_free(key);
+
+		sasl->Fail(sess);
+		return delete sess;
+	}
+
+ public:
+	struct Session : SASL::Session
+	{
+		DH* dh;
+		Session(Mechanism *m, const Anope::string &u, DH* dh_params) : SASL::Session(m, u)
+		{
+			if (!(dh = DH_new()))
+				return;
+
+			dh->g = BN_dup(dh_params->g);
+			dh->p = BN_dup(dh_params->p);
+
+			if (!DH_generate_key(dh))
+			{
+				DH_free(dh);
+				dh = NULL;
+			}
+		}
+
+		~Session()
+		{
+			if (dh)
+				DH_free(dh);
+		}
+	};
+
+	DH* dh_params;
+	const size_t keysize;
+	SASL::Session* CreateSession(const Anope::string &uid) anope_override
+	{
+		return new Session(this, uid, dh_params);
+	}
+
+	DHAES(Module *o) : Mechanism(o, "DH-AES"), keysize(256 / 8)
+	{
+		if (!(dh_params = DH_new()))
+			throw ModuleException("DH_new() failed!");
+
+		if (!DH_generate_parameters_ex(dh_params, keysize * 8, 5, NULL))
+		{
+			DH_free(dh_params);
+			throw ModuleException("Could not generate DH-params");
+		}
+	}
+
+	~DHAES()
+	{
+		DH_free(dh_params);
+	}
+
+	void ProcessMessage(SASL::Session *session, const SASL::Message &m) anope_override
+	{
+		Session *sess = anope_dynamic_static_cast<Session *>(session);
+
+		if (!sess->dh)
+		{
+			sasl->SendMessage(sess, "D", "A");
+			delete sess;
+			return;
+		}
+
+		if (m.type == "S")
+		{
+			// Format: [ss]<p>[ss]<g>[ss]<pub_key>
+			// Where ss is a unsigned short with the size of the key
+			const BIGNUM* dhval[] = { sess->dh->p, sess->dh->g, sess->dh->pub_key };
+
+			// Find the size of our buffer - initialized at 6 because of string size data
+			size_t size = 6;
+			for (size_t i = 0; i < 3; i++)
+				size += BN_num_bytes(dhval[i]);
+
+			// Fill in the DH data
+			std::vector<unsigned char> buffer(size);
+			for (size_t i = 0, pos = 0; i < 3; i++)
+			{
+				*reinterpret_cast<uint16_t*>(&buffer[pos]) = htons(BN_num_bytes(dhval[i]));
+				pos += 2;
+				BN_bn2bin(dhval[i], &buffer[pos]);
+				pos += BN_num_bytes(dhval[i]);
+			}
+
+			Anope::string encoded;
+			Anope::B64Encode(Anope::string(buffer.begin(), buffer.end()), encoded);
+			sasl->SendMessage(sess, "C", encoded);
+		}
+		else if (m.type == "C")
+		{
+			// Make sure we have some data - actual size check is done later
+			if (m.data.length() < 10)
+				return Err(sess);
+
+			// Format: [ss]<key>[ss]<iv>[ss]<encrypted>
+			// <encrypted> = <username>\0<password>\0
+
+			Anope::string decoded;
+			Anope::B64Decode(m.data, decoded);
+
+			// Make sure we have an IV and at least one encrypted block
+			if ((decoded.length() < keysize + 2 + (AES_BLOCK_SIZE * 2)) || ((decoded.length() - keysize - 2) % AES_BLOCK_SIZE))
+				return Err(sess);
+
+			const unsigned char* data = reinterpret_cast<const unsigned char*>(decoded.data());
+
+			// Control the size of the key
+			if (ntohs(*reinterpret_cast<const uint16_t*>(&data[0])) != keysize)
+				return Err(sess);
+
+			// Convert pubkey from binary
+			size_t pos = 2;
+			BIGNUM* pubkey = BN_bin2bn(&data[pos], keysize, NULL);
+			if (!pubkey)
+				return Err(sess);
+
+			// Find shared key
+			std::vector<unsigned char> secretkey(keysize);
+			if (DH_compute_key(&secretkey[0], pubkey, sess->dh) != static_cast<int>(keysize))
+				return Err(sess, pubkey);
+
+			// Set decryption key
+			AES_KEY AESKey;
+			AES_set_decrypt_key(&secretkey[0], keysize * 8, &AESKey);
+
+			// Fetch IV
+			pos += keysize;
+			std::vector<unsigned char> IV(data + pos, data + pos + AES_BLOCK_SIZE);
+
+			// Find encrypted blocks, and decrypt
+			pos += AES_BLOCK_SIZE;
+			size_t size = decoded.length() - pos;
+			std::vector<char> decrypted(size + 2, 0);
+			AES_cbc_encrypt(&data[pos], reinterpret_cast<unsigned char*>(&decrypted[0]), size, &AESKey, &IV[0], AES_DECRYPT);
+
+			std::string username = &decrypted[0];
+			std::string password = &decrypted[username.length() + 1];
+
+			if (username.empty() || password.empty())
+				return Err(sess, pubkey);
+
+			SASL::IdentifyRequest* req = new SASL::IdentifyRequest(this->owner, m.source, username, password);
+			FOREACH_MOD(OnCheckAuthentication, (NULL, req));
+			req->Dispatch();
+
+			BN_free(pubkey);
+		}
+	}
+};
+
+
+class ModuleSASLDHAES : public Module
+{
+	DHAES dhaes;
+
+ public:
+	ModuleSASLDHAES(const Anope::string &modname, const Anope::string &creator) : Module(modname, creator, VENDOR | EXTRA),
+		dhaes(this)
+	{
+	}
+};
+
+MODULE_INIT(ModuleSASLDHAES)