gcm.h

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#ifndef _IPXE_GCM_H
#define _IPXE_GCM_H

/** @file
 *
 * Galois/Counter Mode (GCM)
 *
 */

FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
FILE_SECBOOT ( PERMITTED );

#include <stdint.h>
#include <ipxe/crypto.h>

/** A GCM counter */
struct gcm_counter {
        /** Initialisation vector */
        uint8_t iv[12];
        /** Counter value */
        uint32_t value;
} __attribute__ (( packed ));

/** A GCM length pair */
struct gcm_lengths {
        /** Additional data length */
        uint64_t add;
        /** Data length */
        uint64_t data;
} __attribute__ (( packed ));

/** A GCM block */
union gcm_block {
        /** Raw bytes */
        uint8_t byte[16];
        /** Raw words */
        uint16_t word[8];
        /** Raw dwords */
        uint32_t dword[4];
        /** Counter */
        struct gcm_counter ctr;
        /** Lengths */
        struct gcm_lengths len;
} __attribute__ (( packed ));

/** GCM context */
struct gcm_context {
        /** Accumulated hash (X) */
        union gcm_block hash;
        /** Accumulated lengths */
        union gcm_block len;
        /** Counter (Y) */
        union gcm_block ctr;
        /** Hash key (H) */
        union gcm_block key;
        /** Underlying block cipher */
        struct cipher_algorithm *raw_cipher;
        /** Underlying block cipher context */
        uint8_t raw_ctx[0];
};

extern void gcm_tag ( struct gcm_context *context, union gcm_block *tag );
extern int gcm_setkey ( struct gcm_context *context, const void *key,
                        size_t keylen, struct cipher_algorithm *raw_cipher );
extern void gcm_setiv ( struct gcm_context *context, const void *iv,
                        size_t ivlen );
extern void gcm_encrypt ( struct gcm_context *context, const void *src,
                          void *dst, size_t len );
extern void gcm_decrypt ( struct gcm_context *context, const void *src,
                          void *dst, size_t len );

/**
 * Create a GCM mode of behaviour of an existing cipher
 *
 * @v _cbc_name         Name for the new CBC cipher
 * @v _cbc_cipher       New cipher algorithm
 * @v _raw_cipher       Underlying cipher algorithm
 * @v _raw_context      Context structure for the underlying cipher
 * @v _blocksize        Cipher block size
 */
#define GCM_CIPHER( _gcm_name, _gcm_cipher, _raw_cipher, _raw_context,  \
                    _blocksize )                                        \
struct _gcm_name ## _context {                                          \
        /** GCM context */                                              \
        struct gcm_context gcm;                                         \
        /** Underlying block cipher context */                          \
        _raw_context raw;                                               \
};                                                                      \
static int _gcm_name ## _setkey ( void *ctx, const void *key,           \
                                  size_t keylen ) {                     \
        struct _gcm_name ## _context *context = ctx;                    \
        build_assert ( _blocksize == sizeof ( context->gcm.key ) );     \
        build_assert ( offsetof ( typeof ( *context ), gcm ) == 0 );    \
        build_assert ( offsetof ( typeof ( *context ), raw ) ==         \
                       offsetof ( typeof ( *context ), gcm.raw_ctx ) ); \
        return gcm_setkey ( &context->gcm, key, keylen, &_raw_cipher ); \
}                                                                       \
static void _gcm_name ## _setiv ( void *ctx, const void *iv,            \
                                  size_t ivlen ) {                      \
        struct _gcm_name ## _context *context = ctx;                    \
        gcm_setiv ( &context->gcm, iv, ivlen );                         \
}                                                                       \
static void _gcm_name ## _encrypt ( void *ctx, const void *src,         \
                                    void *dst, size_t len ) {           \
        struct _gcm_name ## _context *context = ctx;                    \
        gcm_encrypt ( &context->gcm, src, dst, len );                   \
}                                                                       \
static void _gcm_name ## _decrypt ( void *ctx, const void *src,         \
                                    void *dst, size_t len ) {           \
        struct _gcm_name ## _context *context = ctx;                    \
        gcm_decrypt ( &context->gcm, src, dst, len );                   \
}                                                                       \
static void _gcm_name ## _auth ( void *ctx, void *auth ) {              \
        struct _gcm_name ## _context *context = ctx;                    \
        union gcm_block *tag = auth;                                    \
        gcm_tag ( &context->gcm, tag );                                 \
}                                                                       \
struct cipher_algorithm _gcm_cipher = {                                 \
        .name           = #_gcm_name,                                   \
        .ctxsize        = sizeof ( struct _gcm_name ## _context ),      \
        .blocksize      = 1,                                            \
        .alignsize      = sizeof ( union gcm_block ),                   \
        .authsize       = sizeof ( union gcm_block ),                   \
        .setkey         = _gcm_name ## _setkey,                         \
        .setiv          = _gcm_name ## _setiv,                          \
        .encrypt        = _gcm_name ## _encrypt,                        \
        .decrypt        = _gcm_name ## _decrypt,                        \
        .auth           = _gcm_name ## _auth,                           \
};

#endif /* _IPXE_GCM_H */