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https://github.com/ipxe/ipxe
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[crypto] Add block cipher Galois/Counter mode of operation
Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown
@@ -38,6 +38,7 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
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#include <ipxe/crypto.h>
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#include <ipxe/ecb.h>
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#include <ipxe/cbc.h>
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#include <ipxe/gcm.h>
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#include <ipxe/aes.h>
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/** AES strides
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@@ -798,3 +799,7 @@ ECB_CIPHER ( aes_ecb, aes_ecb_algorithm,
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/* AES in Cipher Block Chaining mode */
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CBC_CIPHER ( aes_cbc, aes_cbc_algorithm,
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aes_algorithm, struct aes_context, AES_BLOCKSIZE );
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/* AES in Galois/Counter mode */
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GCM_CIPHER ( aes_gcm, aes_gcm_algorithm,
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aes_algorithm, struct aes_context, AES_BLOCKSIZE );
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531
src/crypto/gcm.c
Normal file
531
src/crypto/gcm.c
Normal file
@@ -0,0 +1,531 @@
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/*
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* Copyright (C) 2022 Michael Brown <mbrown@fensystems.co.uk>.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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* 02110-1301, USA.
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*
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* You can also choose to distribute this program under the terms of
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* the Unmodified Binary Distribution Licence (as given in the file
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* COPYING.UBDL), provided that you have satisfied its requirements.
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*/
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FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
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/** @file
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*
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* Galois/Counter Mode (GCM)
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*
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* The GCM algorithm is specified in
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*
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* https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-38d.pdf
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* https://csrc.nist.rip/groups/ST/toolkit/BCM/documents/proposedmodes/gcm/gcm-spec.pdf
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*
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*/
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#include <stdint.h>
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#include <string.h>
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#include <byteswap.h>
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#include <ipxe/crypto.h>
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#include <ipxe/gcm.h>
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/**
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* GCM field polynomial
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*
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* GCM treats 128-bit blocks as polynomials in GF(2^128) with the
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* field polynomial f(x) = 1 + x + x^2 + x^7 + x^128.
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*
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* In a somewhat bloody-minded interpretation of "big-endian", the
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* constant term (with degree zero) is arbitrarily placed in the
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* leftmost bit of the big-endian binary representation (i.e. the most
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* significant bit of byte 0), thereby failing to correspond to the
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* bit ordering in any CPU architecture in existence. This
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* necessitates some wholly gratuitous byte reversals when
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* constructing the multiplication tables, since all CPUs will treat
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* bit 0 as being the least significant bit within a byte.
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*
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* The field polynomial maps to the 128-bit constant
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* 0xe1000000000000000000000000000000 (with the x^128 term outside the
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* 128-bit range), and can therefore be treated as a single-byte
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* value.
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*/
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#define GCM_POLY 0xe1
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/**
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* Hash key for which multiplication tables are cached
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*
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* GCM operates much more efficiently with a cached multiplication
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* table, which costs 4kB per hash key. Since this exceeds the
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* available stack space, we place a single 4kB cache in .bss and
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* recalculate the cached values as required. In the common case of a
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* single HTTPS connection being used to download a (relatively) large
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* file, the same key will be used repeatedly for almost all GCM
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* operations, and so the overhead of recalculation is negligible.
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*/
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static const union gcm_block *gcm_cached_key;
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/**
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* Cached multiplication table (M0) for Shoup's method
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*
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* Each entry within this table represents the result of multiplying
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* the cached hash key by an arbitrary 8-bit polynomial.
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*/
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static union gcm_block gcm_cached_mult[256];
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/**
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* Cached reduction table (R) for Shoup's method
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*
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* Each entry within this table represents the result of multiplying
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* the fixed polynomial x^128 by an arbitrary 8-bit polynomial. Only
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* the leftmost 16 bits are stored, since all other bits within the
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* result will always be zero.
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*/
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static uint16_t gcm_cached_reduce[256];
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/**
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* Reverse bits in a byte
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*
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* @v byte Byte
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* @ret etyb Bit-reversed byte
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*/
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static inline __attribute__ (( always_inline )) uint8_t
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gcm_reverse ( const uint8_t byte ) {
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uint8_t etyb = etyb;
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uint8_t mask;
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for ( mask = 1 ; mask ; mask <<= 1 ) {
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etyb <<= 1;
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if ( byte & mask )
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etyb |= 1;
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}
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return etyb;
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}
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/**
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* Update GCM counter
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*
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* @v ctr Counter
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* @v delta Amount to add to counter
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*/
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static inline __attribute__ (( always_inline )) void
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gcm_count ( union gcm_block *ctr, uint32_t delta ) {
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uint32_t *value = &ctr->ctr.value;
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/* Update counter modulo 2^32 */
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*value = cpu_to_be32 ( be32_to_cpu ( *value ) + delta );
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}
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/**
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* XOR partial data block
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*
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* @v src1 Source buffer 1
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* @v src2 Source buffer 2
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* @v dst Destination buffer
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* @v len Length
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*/
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static inline void gcm_xor ( const void *src1, const void *src2, void *dst,
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size_t len ) {
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uint8_t *dst_bytes = dst;
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const uint8_t *src1_bytes = src1;
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const uint8_t *src2_bytes = src2;
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/* XOR one byte at a time */
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while ( len-- )
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*(dst_bytes++) = ( *(src1_bytes++) ^ *(src2_bytes++) );
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}
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/**
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* XOR whole data block in situ
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*
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* @v src Source block
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* @v dst Destination block
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*/
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static inline void gcm_xor_block ( const union gcm_block *src,
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union gcm_block *dst ) {
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/* XOR whole dwords */
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dst->dword[0] ^= src->dword[0];
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dst->dword[1] ^= src->dword[1];
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dst->dword[2] ^= src->dword[2];
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dst->dword[3] ^= src->dword[3];
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}
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/**
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* Multiply polynomial by (x)
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*
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* @v mult Multiplicand
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* @v res Result
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*/
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static void gcm_multiply_x ( const union gcm_block *mult,
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union gcm_block *res ) {
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unsigned int i;
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uint8_t byte;
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uint8_t carry;
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/* Multiply by (x) by shifting all bits rightward */
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for ( i = 0, carry = 0 ; i < sizeof ( res->byte ) ; i++ ) {
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byte = mult->byte[i];
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res->byte[i] = ( ( carry << 7 ) | ( byte >> 1 ) );
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carry = ( byte & 0x01 );
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}
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/* If result overflows, reduce modulo the field polynomial */
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if ( carry )
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res->byte[0] ^= GCM_POLY;
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}
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/**
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* Construct cached tables
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*
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* @v key Hash key
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* @v context Context
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*/
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static void gcm_cache ( const union gcm_block *key ) {
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union gcm_block *mult;
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uint16_t reduce;
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unsigned int this;
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unsigned int other;
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unsigned int i;
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/* Calculate M0[1..255] and R[1..255]
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*
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* The R[] values are independent of the key, but the overhead
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* of recalculating them here is negligible and saves on
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* overall code size since the calculations are related.
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*/
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for ( i = 1 ; i < 256 ; i++ ) {
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/* Reverse bit order to compensate for poor life choices */
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this = gcm_reverse ( i );
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/* Construct entries */
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mult = &gcm_cached_mult[this];
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if ( this & 0x80 ) {
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/* Odd number: entry[i] = entry[i - 1] + poly */
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other = ( this & 0x7f ); /* bit-reversed (i - 1) */
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gcm_xor ( key, &gcm_cached_mult[other], mult,
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sizeof ( *mult ) );
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reduce = gcm_cached_reduce[other];
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reduce ^= be16_to_cpu ( GCM_POLY << 8 );
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gcm_cached_reduce[this] = reduce;
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} else {
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/* Even number: entry[i] = entry[i/2] * (x) */
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other = ( this << 1 ); /* bit-reversed (i / 2) */
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gcm_multiply_x ( &gcm_cached_mult[other], mult );
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reduce = be16_to_cpu ( gcm_cached_reduce[other] );
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reduce >>= 1;
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gcm_cached_reduce[this] = cpu_to_be16 ( reduce );
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}
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}
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/* Record cached key */
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gcm_cached_key = key;
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}
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/**
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* Multiply polynomial by (x^8) in situ
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*
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* @v poly Multiplicand and result
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*/
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static void gcm_multiply_x_8 ( union gcm_block *poly ) {
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uint8_t *byte;
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uint8_t msb;
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/* Reduction table must already have been calculated */
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assert ( gcm_cached_key != NULL );
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/* Record most significant byte */
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byte = &poly->byte[ sizeof ( poly->byte ) - 1 ];
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msb = *byte;
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/* Multiply least significant bytes by shifting */
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for ( ; byte > &poly->byte[0] ; byte-- )
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*byte = *( byte - 1 );
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*byte = 0;
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/* Multiply most significant byte via reduction table */
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poly->word[0] ^= gcm_cached_reduce[msb];
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}
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/**
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* Multiply polynomial by hash key in situ
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*
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* @v key Hash key
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* @v poly Multiplicand and result
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*/
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static void gcm_multiply_key ( const union gcm_block *key,
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union gcm_block *poly ) {
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union gcm_block res;
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uint8_t *byte;
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/* Construct tables, if necessary */
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if ( gcm_cached_key != key )
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gcm_cache ( key );
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/* Multiply using Shoup's algorithm */
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byte = &poly->byte[ sizeof ( poly->byte ) - 1 ];
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memcpy ( &res, &gcm_cached_mult[ *byte ], sizeof ( res ) );
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for ( byte-- ; byte >= &poly->byte[0] ; byte-- ) {
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gcm_multiply_x_8 ( &res );
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gcm_xor_block ( &gcm_cached_mult[ *byte ], &res );
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}
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/* Overwrite result */
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memcpy ( poly, &res, sizeof ( *poly ) );
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}
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/**
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* Encrypt/decrypt/authenticate data
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*
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* @v context Context
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* @v src Input data, or NULL to process additional data
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* @v dst Output data, or NULL to process additional data
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* @v hash Hash input data
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* @v len Length of data
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*/
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static void gcm_process ( struct gcm_context *context, const void *src,
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void *dst, const void *hash, size_t len ) {
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union gcm_block tmp;
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uint64_t *total;
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size_t frag_len;
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unsigned int block;
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/* Sanity checks */
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assert ( hash != NULL );
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assert ( ( ( src == NULL ) && ( dst == NULL ) ) ||
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( ( hash == src ) || ( hash == dst ) ) );
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/* Calculate block number (for debugging) */
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block = ( ( ( context->len.len.add + 8 * sizeof ( tmp ) - 1 ) /
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( 8 * sizeof ( tmp ) ) ) +
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( ( context->len.len.data + 8 * sizeof ( tmp ) - 1 ) /
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( 8 * sizeof ( tmp ) ) ) + 1 );
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/* Update total length (in bits) */
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total = ( src ? &context->len.len.data : &context->len.len.add );
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*total += ( len * 8 );
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/* Process data */
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for ( ; len ; hash += frag_len, len -= frag_len, block++ ) {
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/* Calculate fragment length */
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frag_len = len;
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if ( frag_len > sizeof ( tmp ) )
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frag_len = sizeof ( tmp );
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/* Encrypt/decrypt block, if applicable */
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if ( dst ) {
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/* Increment counter */
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gcm_count ( &context->ctr, 1 );
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/* Encrypt counter */
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DBGC2 ( context, "GCM %p Y[%d]:\n", context, block );
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DBGC2_HDA ( context, 0, &context->ctr,
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sizeof ( context->ctr ) );
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cipher_encrypt ( context->raw_cipher, &context->raw_ctx,
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&context->ctr, &tmp, sizeof ( tmp ) );
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DBGC2 ( context, "GCM %p E(K,Y[%d]):\n",
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context, block );
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DBGC2_HDA ( context, 0, &tmp, sizeof ( tmp ) );
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/* Encrypt/decrypt data */
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gcm_xor ( src, &tmp, dst, frag_len );
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src += frag_len;
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dst += frag_len;
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}
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/* Update hash */
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gcm_xor ( hash, &context->hash, &context->hash, frag_len );
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gcm_multiply_key ( &context->key, &context->hash );
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DBGC2 ( context, "GCM %p X[%d]:\n", context, block );
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DBGC2_HDA ( context, 0, &context->hash,
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sizeof ( context->hash ) );
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}
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}
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/**
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* Construct hash
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*
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* @v context Context
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* @v hash Hash to fill in
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*/
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static void gcm_hash ( struct gcm_context *context, union gcm_block *hash ) {
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/* Construct big-endian lengths block */
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hash->len.add = cpu_to_be64 ( context->len.len.add );
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hash->len.data = cpu_to_be64 ( context->len.len.data );
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DBGC2 ( context, "GCM %p len(A)||len(C):\n", context );
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DBGC2_HDA ( context, 0, hash, sizeof ( *hash ) );
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/* Update hash */
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gcm_xor_block ( &context->hash, hash );
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gcm_multiply_key ( &context->key, hash );
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DBGC2 ( context, "GCM %p GHASH(H,A,C):\n", context );
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DBGC2_HDA ( context, 0, hash, sizeof ( *hash ) );
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}
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/**
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* Construct tag
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*
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* @v context Context
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* @v tag Tag
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*/
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void gcm_tag ( struct gcm_context *context, union gcm_block *tag ) {
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union gcm_block tmp;
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uint32_t offset;
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/* Construct hash */
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gcm_hash ( context, tag );
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/* Construct encrypted initial counter value */
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memcpy ( &tmp, &context->ctr, sizeof ( tmp ) );
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offset = ( ( -context->len.len.data ) / ( 8 * sizeof ( tmp ) ) );
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gcm_count ( &tmp, offset );
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cipher_encrypt ( context->raw_cipher, &context->raw_ctx, &tmp,
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&tmp, sizeof ( tmp ) );
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DBGC2 ( context, "GCM %p E(K,Y[0]):\n", context );
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DBGC2_HDA ( context, 0, &tmp, sizeof ( tmp ) );
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/* Construct tag */
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gcm_xor_block ( &tmp, tag );
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DBGC2 ( context, "GCM %p T:\n", context );
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DBGC2_HDA ( context, 0, tag, sizeof ( *tag ) );
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}
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/**
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* Set key
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*
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* @v context Context
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* @v key Key
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* @v keylen Key length
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* @v raw_cipher Underlying cipher
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* @ret rc Return status code
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*/
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int gcm_setkey ( struct gcm_context *context, const void *key, size_t keylen,
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struct cipher_algorithm *raw_cipher ) {
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int rc;
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/* Initialise GCM context */
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memset ( context, 0, sizeof ( *context ) );
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context->raw_cipher = raw_cipher;
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/* Set underlying block cipher key */
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if ( ( rc = cipher_setkey ( raw_cipher, context->raw_ctx, key,
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keylen ) ) != 0 )
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return rc;
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/* Construct GCM hash key */
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cipher_encrypt ( raw_cipher, context->raw_ctx, &context->ctr,
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&context->key, sizeof ( context->key ) );
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DBGC2 ( context, "GCM %p H:\n", context );
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DBGC2_HDA ( context, 0, &context->key, sizeof ( context->key ) );
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/* Reset counter */
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context->ctr.ctr.value = cpu_to_be32 ( 1 );
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/* Construct cached tables */
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gcm_cache ( &context->key );
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return 0;
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}
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/**
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* Set initialisation vector
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*
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* @v ctx Context
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* @v iv Initialisation vector
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* @v ivlen Initialisation vector length
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*/
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void gcm_setiv ( struct gcm_context *context, const void *iv, size_t ivlen ) {
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/* Reset counter */
|
||||
memset ( context->ctr.ctr.iv, 0, sizeof ( context->ctr.ctr.iv ) );
|
||||
context->ctr.ctr.value = cpu_to_be32 ( 1 );
|
||||
|
||||
/* Process initialisation vector */
|
||||
if ( ivlen == sizeof ( context->ctr.ctr.iv ) ) {
|
||||
|
||||
/* Initialisation vector is exactly 96 bits, use it as-is */
|
||||
memcpy ( context->ctr.ctr.iv, iv, ivlen );
|
||||
|
||||
} else {
|
||||
|
||||
/* Calculate hash over initialisation vector */
|
||||
gcm_process ( context, iv, NULL, iv, ivlen );
|
||||
gcm_hash ( context, &context->ctr );
|
||||
|
||||
/* Reset accumulated hash */
|
||||
memset ( &context->hash, 0, sizeof ( context->hash ) );
|
||||
|
||||
/* Reset data lengths */
|
||||
assert ( context->len.len.add == 0 );
|
||||
context->len.len.data = 0;
|
||||
}
|
||||
|
||||
DBGC2 ( context, "GCM %p Y[0]:\n", context );
|
||||
DBGC2_HDA ( context, 0, &context->ctr, sizeof ( context->ctr ) );
|
||||
}
|
||||
|
||||
/**
|
||||
* Encrypt data
|
||||
*
|
||||
* @v context Context
|
||||
* @v src Data to encrypt
|
||||
* @v dst Buffer for encrypted data, or NULL for additional data
|
||||
* @v len Length of data
|
||||
*/
|
||||
void gcm_encrypt ( struct gcm_context *context, const void *src, void *dst,
|
||||
size_t len ) {
|
||||
const void *hash;
|
||||
|
||||
/* Determine hash input */
|
||||
if ( dst ) {
|
||||
/* Encrypting: hash the encrypted data */
|
||||
hash = dst;
|
||||
} else {
|
||||
/* Authenticating: hash the input data */
|
||||
hash = src;
|
||||
src = NULL;
|
||||
}
|
||||
|
||||
/* Process data */
|
||||
gcm_process ( context, src, dst, hash, len );
|
||||
}
|
||||
|
||||
/**
|
||||
* Decrypt data
|
||||
*
|
||||
* @v context Context
|
||||
* @v src Data to decrypt
|
||||
* @v dst Buffer for decrypted data, or NULL for additional data
|
||||
* @v len Length of data
|
||||
*/
|
||||
void gcm_decrypt ( struct gcm_context *context, const void *src, void *dst,
|
||||
size_t len ) {
|
||||
const void *hash;
|
||||
|
||||
/* Determine hash input */
|
||||
hash = src;
|
||||
if ( ! dst ) {
|
||||
/* Authenticating: only hash */
|
||||
src = NULL;
|
||||
}
|
||||
|
||||
/* Process data */
|
||||
gcm_process ( context, src, dst, hash, len );
|
||||
}
|
||||
Reference in New Issue
Block a user