Random Byte Generation Example

Example 9–4 demonstrates how to find a slot with a mechanism that can generate random bytes. The example performs the following steps:

1. Initializes the cryptoki library.

2. Calls GetRandSlot() to find a slot with a mechanism that can generate random bytes.

   The task of finding a slot performs the following steps:

   1. Calling the function C_GetSlotList() to get a list of the available slots.

      C_GetSlotList() is called twice, as the PKCS #11 convention suggests. C_GetSlotList() is called the first time to get the number of slots for memory allocation. C_GetSlotList() is called the second time to retrieve the slots.

   2. Finding a slot that can generate random bytes.

      For each slot, the function obtains the token information by using GetTokenInfo() and checks for a match with the CKF_RNG flag set. When a slot that has the CKF_RNG flag set is found, the GetRandSlot() function returns.

3. Opens the session by using C_OpenSession().

4. Generates random bytes by using C_GenerateRandom().

5. Ends the session.

   The program uses C_CloseSession() to close the session and C_Finalize() to close the library.

The source code for the random number generation sample is shown in the following example.

The source code for this example is also available through the Sun download center. See http://www.sun.com/download/products.xml?id=41912db5.

Example 9–4 Generating Random Numbers Using PKCS #11 Functions

#include <stdio.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/types.h>
#include <security/cryptoki.h>
#include <security/pkcs11.h>

#define RANDSIZE 64

boolean_t GetRandSlot(CK_SLOT_ID_PTR pslot);

/* Example generates random bytes. */
void
main(int argc, char **argv)
{
	CK_RV   rv;
	CK_MECHANISM mech;
	CK_SESSION_HANDLE hSession;
	CK_SESSION_INFO sessInfo;
	CK_SLOT_ID slotID;
	CK_BYTE randBytes[RANDSIZE];

	boolean_t found_slot = B_FALSE;
	int error;
	int i;

	/* Initialize the CRYPTOKI library */
	rv = C_Initialize(NULL_PTR);

	if (rv != CKR_OK) {
		fprintf(stderr, "C_Initialize: Error = 0x%.8X\n", rv);
		exit(1);
	}

	found_slot = GetRandSlot(&slotID);

	if (!found_slot) {
		goto exit_program;
	}

	/* Open a session on the slot found */
	rv = C_OpenSession(slotID, CKF_SERIAL_SESSION, NULL_PTR, NULL_PTR,
	    &hSession);

	if (rv != CKR_OK) {
		fprintf(stderr, "C_OpenSession: rv = 0x%.8x\n", rv);
		error = 1;
		goto exit_program;
	}

	/* Generate random bytes */
	rv = C_GenerateRandom(hSession, randBytes, RANDSIZE);

	if (rv != CKR_OK) {
		fprintf(stderr, "C_GenerateRandom: rv = 0x%.8x\n", rv);
		error = 1;
		goto exit_session;
	}

	fprintf(stdout, "Random value: ");
	for (i = 0; i < RANDSIZE; i++) {
		fprintf(stdout, "%.2x", randBytes[i]);
	}

exit_session:
	(void) C_CloseSession(hSession);

exit_program:
	(void) C_Finalize(NULL_PTR);
	exit(error);

}

boolean_t
GetRandSlot(CK_SLOT_ID_PTR pslot)
{
	CK_SLOT_ID_PTR pSlotList;
	CK_SLOT_ID SlotID;
	CK_TOKEN_INFO tokenInfo;
	CK_ULONG ulSlotCount;
	CK_MECHANISM_TYPE_PTR pMechTypeList = NULL_PTR;
	CK_ULONG ulMechTypecount;
	boolean_t result = B_FALSE;
	int i = 0;

	CK_RV rv;

	/* Get slot list for memory allocation */
	rv = C_GetSlotList(0, NULL_PTR, &ulSlotCount);

	if ((rv == CKR_OK) && (ulSlotCount > 0)) {
		fprintf(stdout, "slotCount = %d\n", (int)ulSlotCount);
		pSlotList = malloc(ulSlotCount * sizeof (CK_SLOT_ID));

		if (pSlotList == NULL) {
			fprintf(stderr,
			    "System error: unable to allocate memory\n");
			return (result);
		}

		/* Get the slot list for processing */
		rv = C_GetSlotList(0, pSlotList, &ulSlotCount);
		if (rv != CKR_OK) {
			fprintf(stderr, "GetSlotList failed: unable to get "
			    "slot list.\n");
			free(pSlotList);
			return (result);
		}
	} else {
		fprintf(stderr, "GetSlotList failed: unable to get slot"
		    " count.\n");
		return (result);
	}

	/* Find a slot capable of doing random number generation */
	for (i = 0; i < ulSlotCount; i++) {
		SlotID = pSlotList[i];

		rv = C_GetTokenInfo(SlotID, &tokenInfo);

		if (rv != CKR_OK) {
			/* Check the next slot */
			continue;
		}

		if (tokenInfo.flags & CKF_RNG) {
			/* Found a random number generator */
			*pslot = SlotID;
			fprintf(stdout, "Slot # %d supports random number "
			    "generation!\n", SlotID);
			result = B_TRUE;
			break;
		}
	}

	if (pSlotList)
		free(pSlotList);

	return (result);

}