Message Digest Example

This example uses PKCS #11 functions to create a digest from an input file. The example performs the following steps:

1. Specifies the digest mechanism.

   In this example, the CKM_MD5 digest mechanism is used.

2. Finds a slot that is capable of the specified digest algorithm.

   This example uses the Sun convenience function SUNW_C_GetMechSession(). SUNW_C_GetMechSession() opens the cryptoki library, which holds all the PKCS #11 functions that are used in the Oracle Solaris cryptographic framework. SUNW_C_GetMechSession() then finds the slot with the desired mechanism. The session is then started. Effectively, this convenience function replaces the C_Initialize() call, the C_OpenSession() call, and any code needed to find a slot that supports the specified mechanism.

3. Obtains cryptoki information.

   This part is not actually needed to create the message digest, but is included to demonstrate use of the C_GetInfo() function. This example gets the manufacturer ID. The other information options retrieve version and library data.

4. Conducts a digest operation with the slot.

   The message digest is created in this task through these steps:

   1. Opening the input file.

   2. Initializing the digest operation by calling C_DigestInit().

   3. Processing the data a piece at a time with C_DigestUpdate().

   4. Ending the digest process by using C_DigestFinal() to get the complete digest.

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 message digest example 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 9–1 Creating a Message Digest 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 BUFFERSIZ    8192
#define MAXDIGEST    64

/* Calculate the digest of a user supplied file. */
void
main(int argc, char **argv)
{
	CK_BYTE digest[MAXDIGEST];
	CK_INFO info;
	CK_MECHANISM mechanism;
	CK_SESSION_HANDLE hSession;
	CK_SESSION_INFO Info;
	CK_ULONG ulDatalen = BUFFERSIZ;
	CK_ULONG ulDigestLen = MAXDIGEST;
	CK_RV rv;
	CK_SLOT_ID SlotID;

	int i, bytes_read = 0;
	char inbuf[BUFFERSIZ];
	FILE *fs;
	int error = 0;

	/* Specify the CKM_MD5 digest mechanism as the target */
	mechanism.mechanism = CKM_MD5;
	mechanism.pParameter = NULL_PTR;
	mechanism.ulParameterLen = 0;

	/* Use SUNW convenience function to initialize the cryptoki
	 * library, and open a session with a slot that supports
	 * the mechanism we plan on using. */
	rv = SUNW_C_GetMechSession(mechanism.mechanism, &hSession);
	if (rv != CKR_OK) {
		fprintf(stderr, "SUNW_C_GetMechSession: rv = 0x%.8X\n", rv);
		exit(1);
	}

	/* Get cryptoki information, the manufacturer ID */
	rv = C_GetInfo(&info);
	if (rv != CKR_OK) {
		fprintf(stderr, "WARNING: C_GetInfo: rv = 0x%.8X\n", rv);
	}
	fprintf(stdout, "Manufacturer ID = %s\n", info.manufacturerID);

	/* Open the input file */
	if ((fs = fopen(argv[1], "r")) == NULL) {
		perror("fopen");
		fprintf(stderr, "\n\tusage: %s filename>\n", argv[0]);
		error = 1;
		goto exit_session;
	}

	/* Initialize the digest session */
	if ((rv = C_DigestInit(hSession, &mechanism)) != CKR_OK) {
		fprintf(stderr, "C_DigestInit: rv = 0x%.8X\n", rv);
		error = 1;
		goto exit_digest;
	}

	/* Read in the data and create digest of this portion */
	while (!feof(fs) && (ulDatalen = fread(inbuf, 1, BUFFERSIZ, fs)) > 0) {
		if ((rv = C_DigestUpdate(hSession, (CK_BYTE_PTR)inbuf,
				    ulDatalen)) != CKR_OK) {
			fprintf(stderr, "C_DigestUpdate: rv = 0x%.8X\n", rv);
			error = 1;
			goto exit_digest;
		}
		bytes_read += ulDatalen;
	}
	fprintf(stdout, "%d bytes read and digested!!!\n\n", bytes_read);

	/* Get complete digest */
	ulDigestLen = sizeof (digest);
	if ((rv = C_DigestFinal(hSession, (CK_BYTE_PTR)digest,
			    &ulDigestLen)) != CKR_OK) {
		fprintf(stderr, "C_DigestFinal: rv = 0x%.8X\n", rv);
		error = 1;
		goto exit_digest;
	}

	/* Print the results */
	fprintf(stdout, "The value of the digest is: ");
	for (i = 0; i < ulDigestLen; i++) {
		fprintf(stdout, "%.2x", digest[i]);
	}
	fprintf(stdout, "\nDone!!!\n");

exit_digest:
	fclose(fs);

exit_session:
	(void) C_CloseSession(hSession);

exit_program:
	(void) C_Finalize(NULL_PTR);

	exit(error);

}