OpenSSL: SSL Client/Server Example

I'm experimenting a bit with the new iPhone 3.0 SDK, Core Data, Game Kit, Push Notification Service and so on...

I'm using C, so today a little Example of SSL Client/Server written in C using OpenSSL, I've written a small wrapper for SSL Socket, and here is How to use it.

/* SERVER CODE 
 * ==============================
 */
SFSocketGlobalInit();       /* Initialize SSL */

/* Alloc Socket, Initialize SSL and Listen */
SFSocket *socket = SFSocketAlloc();
SFSocketInit(socket, CA_FILE, DH_FILE, KEY_FILE, KEY_PASSWORD, NULL);
SFSocketListen(socket, INADDR_ANY, PORT);

do {
   SFSocket *clientSocket;
   char buffer[64];
   int rdSize;

   /* Accept Client Connection */
   if ((clientSocket = SFSocketAccept(socket)) == NULL)
       break;        

   /* Read Data from Client */
   if ((rdSize = SFSocketRead(clientSocket, buffer, 64 - 1)) > 0) {
       buffer[rdSize] = '\0';
       printf("Client: %s\n", buffer);
   }

   /* Write to Client */
   strcpy(buffer, "Hello Client!");
   SFSocketWrite(clientSocket, buffer, strlen(buffer));

   /* Disconnect Client */
   SFSocketRelease(clientSocket);        
} while (1);

/* Close and Release Socket Resources */
SFSocketRelease(socket);

Above you've the simplified server code (without error check!) and below you've the client code. The client try to connects to server, send an "Hello" message and the server reply with other greetings.

/* CLIENT CODE 
 * ==============================
 */
SFSocketGlobalInit();       /* Initialize SSL */

/* Alloc Socket, Initialize SSL */
SFSocket *socket = SFSocketAlloc();
SFSocketInit(socket, CA_FILE, NULL, KEY_FILE, KEY_PASSWORD, NULL);

/* Connect to Host */
SFSocketConnectToHost(socket, HOSTNAME, PORT);

/* Send Message to Server */
char buffer[64];
strcpy(buffer, "Hello from Client!");
SFSocketWrite(socket, buffer, strlen(buffer));

/* Read Message from Server */
if ((rdSize = SFSocketRead(socket, buffer, 64 - 1)) > 0) {
   buffer[rdSize] = '\0';
   printf("Server: %s\n", buffer);
}

/* Close and Release Socket Resources */
SFSocketRelease(socket);

Remember that you need to generate, at least, the Authority Certificate, Server Certificate and Clients Certificates. and here is How to do it.

- AUTHORITY Certificate:
 openssl genrsa -des3 -out ca.key 1024
 openssl req -new -x509 -key ca.key -out ca.crt

- SERVER Certificate
 openssl genrsa -des3 -out server.key 1024
 openssl req -new -key server.key -out server.csr
 openssl x509 -req -in server.csr -out server.crt -sha1 \
                   -CA ca.crt -CAkey ca.key -CAcreateserial 

- CLIENT Certificate
 openssl genrsa -des3 -out client.key 1024
 openssl req -new -key client.key -out client.csr
 openssl x509 -req -in client.csr -out client.crt -sha1 \
                   -CA ca.crt -CAkey ca.key -CAcreateserial

The Full Source Code is Available Here: SSL Client/Server Example Source Code.

OpenSSL: License Key with RSA

In the last days I've played a bit with C libraries like OpenSSL and SQLite. The first post after Site downtime is dedicated to OpenSSL.
how do can you create your own license system for your application? With OpenSSL and less than 10 lines of code, you can do it. Take a look at the code below.

...
unsigned char checkDigest[SHA_DIGEST_LENGTH];
unsigned char shaDigest[SHA_DIGEST_LENGTH];
const char *userKey = "Matteo License";
unsigned char *signature = NULL;
unsigned int signatureLength = 0;

/* Generate Your RSA Key Pair */
RSA *rsa = RSA_generate_key(512, RSA_F4, NULL, NULL);

/* Generate SHA1 of User Key */
SHA1(userKey, strlen(userKey), shaDigest);

/* Create License Key for the User Key */
signature = OPENSSL_malloc(RSA_size(rsa));
signatureLength = RSA_private_encrypt(SHA_DIGEST_LENGTH, shaDigest,
                                 signature, rsa, RSA_PKCS1_PADDING);

/* Check if User Signature is a valid License Key */
if (RSA_public_decrypt(signatureLength, signature, checkDigest,
                                rsa, RSA_PKCS1_PADDING) != SHA_DIGEST_LENGTH)
{
      /* Valid License Key */
} else {
      /* Invalid License Key */
}

free(signature);
RSA_free(rsa);
...

You need to store the RSA Public Key in your app and then give to each user a generated signature, and it's all.
Ok, this is a really base example (less than 10 lines of code) if you don't want reinvent a License Key system, take a look at AquaticPrime Framework (http://www.aquaticmac.com/).