aes_wrap.c File Reference

#include <stdlib.h>
#include <string.h>
#include <gpxe/crypto.h>
#include <gpxe/aes.h>

Go to the source code of this file.

Functions
	FILE_LICENCE (GPL2_OR_LATER)
int	aes_wrap (const void *kek, const void *src, void *dest, int nblk)
	Wrap a key or other data using AES Key Wrap (RFC 3394).
int	aes_unwrap (const void *kek, const void *src, void *dest, int nblk)
	Unwrap a key or other data using AES Key Wrap (RFC 3394).

---

Function Documentation

FILE_LICENCE

(

GPL2_OR_LATER

)

int aes_wrap	(	const void *	kek,
		const void *	src,
		void *	dest,
		int	nblk
	)

Wrap a key or other data using AES Key Wrap (RFC 3394).

Parameters:

	kek	Key Encryption Key, 16 bytes
	src	Data to encrypt
	nblk	Number of 8-byte blocks in data

Return values:

dest

Encrypted data (8 bytes longer than input)

The algorithm is implemented such that src and dest may point to the same buffer.

Definition at line 37 of file aes_wrap.c.

References aes_algorithm, AES_CTX_SIZE, cipher_encrypt, cipher_setkey(), free(), malloc(), memcpy, memmove(), memset(), and u8.

{
        u8 *A = dest;
        u8 B[16];
        u8 *R;
        int i, j;
        void *aes_ctx = malloc ( AES_CTX_SIZE );

        if ( ! aes_ctx )
                return -1;

        cipher_setkey ( &aes_algorithm, aes_ctx, kek, 16 );

        /* Set up */
        memset ( A, 0xA6, sizeof ( A ) );
        memmove ( dest + 8, src, nblk * 8 );

        /* Wrap */
        for ( j = 0; j < 6; j++ ) {
                R = dest + 8;
                for ( i = 1; i <= nblk; i++ ) {
                        memcpy ( B, A, 8 );
                        memcpy ( B + 8, R, 8 );
                        cipher_encrypt ( &aes_algorithm, aes_ctx, B, B, 16 );
                        memcpy ( A, B, 8 );
                        A[7] ^= ( nblk * j ) + i;
                        memcpy ( R, B + 8, 8 );
                        R += 8;
                }
        }

        free ( aes_ctx );
        return 0;
}

int aes_unwrap	(	const void *	kek,
		const void *	src,
		void *	dest,
		int	nblk
	)

Unwrap a key or other data using AES Key Wrap (RFC 3394).

Parameters:

	kek	Key Encryption Key, 16 bytes
	src	Data to decrypt
	nblk	Number of 8-byte blocks in plaintext key

Return values:

	dest	Decrypted data (8 bytes shorter than input)
	rc	Zero on success, nonzero on IV mismatch

The algorithm is implemented such that src and dest may point to the same buffer.

Definition at line 84 of file aes_wrap.c.

References aes_algorithm, AES_CTX_SIZE, cipher_decrypt, cipher_setkey(), free(), malloc(), memcpy, memmove(), and u8.

Referenced by ccmp_kie_decrypt().

{
        u8 A[8], B[16];
        u8 *R;
        int i, j;
        void *aes_ctx = malloc ( AES_CTX_SIZE );

        if ( ! aes_ctx )
                return -1;

        cipher_setkey ( &aes_algorithm, aes_ctx, kek, 16 );

        /* Set up */
        memcpy ( A, src, 8 );
        memmove ( dest, src + 8, nblk * 8 );

        /* Unwrap */
        for ( j = 5; j >= 0; j-- ) {
                R = dest + ( nblk - 1 ) * 8;
                for ( i = nblk; i >= 1; i-- ) {
                        memcpy ( B, A, 8 );
                        memcpy ( B + 8, R, 8 );
                        B[7] ^= ( nblk * j ) + i;
                        cipher_decrypt ( &aes_algorithm, aes_ctx, B, B, 16 );
                        memcpy ( A, B, 8 );
                        memcpy ( R, B + 8, 8 );
                        R -= 8;
                }
        }

        free ( aes_ctx );

        /* Check IV */
        for ( i = 0; i < 8; i++ ) {
                if ( A[i] != 0xA6 )
                        return -1;
        }

        return 0;
}