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+/*
+ * Copyright (C) 2015 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ *
+ * You can also choose to distribute this program under the terms of
+ * the Unmodified Binary Distribution Licence (as given in the file
+ * COPYING.UBDL), provided that you have satisfied its requirements.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+/** @file
+ *
+ * AES algorithm
+ *
+ */
+
+#include <stdint.h>
+#include <string.h>
+#include <errno.h>
+#include <assert.h>
+#include <byteswap.h>
+#include <ipxe/rotate.h>
+#include <ipxe/crypto.h>
+#include <ipxe/ecb.h>
+#include <ipxe/cbc.h>
+#include <ipxe/aes.h>
+
+/** AES strides
+ *
+ * These are the strides (modulo 16) used to walk through the AES
+ * input state bytes in order of byte position after [Inv]ShiftRows.
+ */
+enum aes_stride {
+ /** Input stride for ShiftRows
+ *
+ * 0 4 8 c
+ * \ \ \
+ * 1 5 9 d
+ * \ \ \
+ * 2 6 a e
+ * \ \ \
+ * 3 7 b f
+ */
+ AES_STRIDE_SHIFTROWS = +5,
+ /** Input stride for InvShiftRows
+ *
+ * 0 4 8 c
+ * / / /
+ * 1 5 9 d
+ * / / /
+ * 2 6 a e
+ * / / /
+ * 3 7 b f
+ */
+ AES_STRIDE_INVSHIFTROWS = -3,
+};
+
+/** A single AES lookup table entry
+ *
+ * This represents the product (in the Galois field GF(2^8)) of an
+ * eight-byte vector multiplier with a single scalar multiplicand.
+ *
+ * The vector multipliers used for AES will be {1,1,1,3,2,1,1,3} for
+ * MixColumns and {1,9,13,11,14,9,13,11} for InvMixColumns. This
+ * allows for the result of multiplying any single column of the
+ * [Inv]MixColumns matrix by a scalar value to be obtained simply by
+ * extracting the relevant four-byte subset from the lookup table
+ * entry.
+ *
+ * For example, to find the result of multiplying the second column of
+ * the MixColumns matrix by the scalar value 0x80:
+ *
+ * MixColumns column[0]: { 2, 1, 1, 3 }
+ * MixColumns column[1]: { 3, 2, 1, 1 }
+ * MixColumns column[2]: { 1, 3, 2, 1 }
+ * MixColumns column[3]: { 1, 1, 3, 2 }
+ * Vector multiplier: { 1, 1, 1, 3, 2, 1, 1, 3 }
+ * Scalar multiplicand: 0x80
+ * Lookup table entry: { 0x80, 0x80, 0x80, 0x9b, 0x1b, 0x80, 0x80, 0x9b }
+ *
+ * The second column of the MixColumns matrix is {3,2,1,1}. The
+ * product of this column with the scalar value 0x80 can be obtained
+ * by extracting the relevant four-byte subset of the lookup table
+ * entry:
+ *
+ * MixColumns column[1]: { 3, 2, 1, 1 }
+ * Vector multiplier: { 1, 1, 1, 3, 2, 1, 1, 3 }
+ * Lookup table entry: { 0x80, 0x80, 0x80, 0x9b, 0x1b, 0x80, 0x80, 0x9b }
+ * Product: { 0x9b, 0x1b, 0x80, 0x80 }
+ *
+ * The column lookups require only seven bytes of the eight-byte
+ * entry: the remaining (first) byte is used to hold the scalar
+ * multiplicand itself (i.e. the first byte of the vector multiplier
+ * is always chosen to be 1).
+ */
+union aes_table_entry {
+ /** Viewed as an array of bytes */
+ uint8_t byte[8];
+} __attribute__ (( packed ));
+
+/** An AES lookup table
+ *
+ * This represents the products (in the Galois field GF(2^8)) of a
+ * constant eight-byte vector multiplier with all possible 256 scalar
+ * multiplicands.
+ *
+ * The entries are indexed by the AES [Inv]SubBytes S-box output
+ * values (denoted S(N)). This allows for the result of multiplying
+ * any single column of the [Inv]MixColumns matrix by S(N) to be
+ * obtained simply by extracting the relevant four-byte subset from
+ * the Nth table entry. For example:
+ *
+ * Input byte (N): 0x3a
+ * SubBytes output S(N): 0x80
+ * MixColumns column[1]: { 3, 2, 1, 1 }
+ * Vector multiplier: { 1, 1, 1, 3, 2, 1, 1, 3 }
+ * Table entry[0x3a]: { 0x80, 0x80, 0x80, 0x9b, 0x1b, 0x80, 0x80, 0x9b }
+ * Product: { 0x9b, 0x1b, 0x80, 0x80 }
+ *
+ * Since the first byte of the eight-byte vector multiplier is always
+ * chosen to be 1, the value of S(N) may be lookup up by extracting
+ * the first byte of the Nth table entry.
+ */
+struct aes_table {
+ /** Table entries, indexed by S(N) */
+ union aes_table_entry entry[256];
+} __attribute__ (( aligned ( 8 ) ));
+
+/** AES MixColumns lookup table */
+static struct aes_table aes_mixcolumns;
+
+/** AES InvMixColumns lookup table */
+static struct aes_table aes_invmixcolumns;
+
+/**
+ * Multiply [Inv]MixColumns matrix column by scalar multiplicand
+ *
+ * @v entry AES lookup table entry for scalar multiplicand
+ * @v column [Inv]MixColumns matrix column index
+ * @ret product Product of matrix column with scalar multiplicand
+ */
+static inline __attribute__ (( always_inline )) uint32_t
+aes_entry_column ( const union aes_table_entry *entry, unsigned int column ) {
+ const union {
+ uint8_t byte;
+ uint32_t column;
+ } __attribute__ (( may_alias )) *product;
+
+ /* Locate relevant four-byte subset */
+ product = container_of ( &entry->byte[ 4 - column ],
+ typeof ( *product ), byte );
+
+ /* Extract this four-byte subset */
+ return product->column;
+}
+
+/**
+ * Multiply [Inv]MixColumns matrix column by S-boxed input byte
+ *
+ * @v table AES lookup table
+ * @v stride AES row shift stride
+ * @v in AES input state
+ * @v offset Output byte offset (after [Inv]ShiftRows)
+ * @ret product Product of matrix column with S(input byte)
+ *
+ * Note that the specified offset is not the offset of the input byte;
+ * it is the offset of the output byte which corresponds to the input
+ * byte. This output byte offset is used to calculate both the input
+ * byte offset and to select the appropriate matric column.
+ *
+ * With a compile-time constant offset, this function will optimise
+ * down to a single "movzbl" (to extract the input byte) and will
+ * generate a single x86 memory reference expression which can then be
+ * used directly within a single "xorl" instruction.
+ */
+static inline __attribute__ (( always_inline )) uint32_t
+aes_column ( const struct aes_table *table, size_t stride,
+ const union aes_matrix *in, size_t offset ) {
+ const union aes_table_entry *entry;
+ unsigned int byte;
+
+ /* Extract input byte corresponding to this output byte offset
+ * (i.e. perform [Inv]ShiftRows).
+ */
+ byte = in->byte[ ( stride * offset ) & 0xf ];
+
+ /* Locate lookup table entry for this input byte (i.e. perform
+ * [Inv]SubBytes).
+ */
+ entry = &table->entry[byte];
+
+ /* Multiply appropriate matrix column by this input byte
+ * (i.e. perform [Inv]MixColumns).
+ */
+ return aes_entry_column ( entry, ( offset & 0x3 ) );
+}
+
+/**
+ * Calculate intermediate round output column
+ *
+ * @v table AES lookup table
+ * @v stride AES row shift stride
+ * @v in AES input state
+ * @v key AES round key
+ * @v column Column index
+ * @ret output Output column value
+ */
+static inline __attribute__ (( always_inline )) uint32_t
+aes_output ( const struct aes_table *table, size_t stride,
+ const union aes_matrix *in, const union aes_matrix *key,
+ unsigned int column ) {
+ size_t offset = ( column * 4 );
+
+ /* Perform [Inv]ShiftRows, [Inv]SubBytes, [Inv]MixColumns, and
+ * AddRoundKey for this column. The loop is unrolled to allow
+ * for the required compile-time constant optimisations.
+ */
+ return ( aes_column ( table, stride, in, ( offset + 0 ) ) ^
+ aes_column ( table, stride, in, ( offset + 1 ) ) ^
+ aes_column ( table, stride, in, ( offset + 2 ) ) ^
+ aes_column ( table, stride, in, ( offset + 3 ) ) ^
+ key->column[column] );
+}
+
+/**
+ * Perform a single intermediate round
+ *
+ * @v table AES lookup table
+ * @v stride AES row shift stride
+ * @v in AES input state
+ * @v out AES output state
+ * @v key AES round key
+ */
+static inline __attribute__ (( always_inline )) void
+aes_round ( const struct aes_table *table, size_t stride,
+ const union aes_matrix *in, union aes_matrix *out,
+ const union aes_matrix *key ) {
+
+ /* Perform [Inv]ShiftRows, [Inv]SubBytes, [Inv]MixColumns, and
+ * AddRoundKey for all columns. The loop is unrolled to allow
+ * for the required compile-time constant optimisations.
+ */
+ out->column[0] = aes_output ( table, stride, in, key, 0 );
+ out->column[1] = aes_output ( table, stride, in, key, 1 );
+ out->column[2] = aes_output ( table, stride, in, key, 2 );
+ out->column[3] = aes_output ( table, stride, in, key, 3 );
+}
+
+/**
+ * Perform encryption intermediate rounds
+ *
+ * @v in AES input state
+ * @v out AES output state
+ * @v key Round keys
+ * @v rounds Number of rounds (must be odd)
+ *
+ * This function is deliberately marked as non-inlinable to ensure
+ * maximal availability of registers for GCC's register allocator,
+ * which has a tendency to otherwise spill performance-critical
+ * registers to the stack.
+ */
+static __attribute__ (( noinline )) void
+aes_encrypt_rounds ( union aes_matrix *in, union aes_matrix *out,
+ const union aes_matrix *key, unsigned int rounds ) {
+ union aes_matrix *tmp;
+
+ /* Perform intermediate rounds */
+ do {
+ /* Perform one intermediate round */
+ aes_round ( &aes_mixcolumns, AES_STRIDE_SHIFTROWS,
+ in, out, key++ );
+
+ /* Swap input and output states for next round */
+ tmp = in;
+ in = out;
+ out = tmp;
+
+ } while ( --rounds );
+}
+
+/**
+ * Perform decryption intermediate rounds
+ *
+ * @v in AES input state
+ * @v out AES output state
+ * @v key Round keys
+ * @v rounds Number of rounds (must be odd)
+ *
+ * As with aes_encrypt_rounds(), this function is deliberately marked
+ * as non-inlinable.
+ *
+ * This function could potentially use the same binary code as is used
+ * for encryption. To compensate for the difference between ShiftRows
+ * and InvShiftRows, half of the input byte offsets would have to be
+ * modifiable at runtime (half by an offset of +4/-4, half by an
+ * offset of -4/+4 for ShiftRows/InvShiftRows). This can be
+ * accomplished in x86 assembly within the number of available
+ * registers, but GCC's register allocator struggles to do so,
+ * resulting in a significant performance decrease due to registers
+ * being spilled to the stack. We therefore use two separate but very
+ * similar binary functions based on the same C source.
+ */
+static __attribute__ (( noinline )) void
+aes_decrypt_rounds ( union aes_matrix *in, union aes_matrix *out,
+ const union aes_matrix *key, unsigned int rounds ) {
+ union aes_matrix *tmp;
+
+ /* Perform intermediate rounds */
+ do {
+ /* Perform one intermediate round */
+ aes_round ( &aes_invmixcolumns, AES_STRIDE_INVSHIFTROWS,
+ in, out, key++ );
+
+ /* Swap input and output states for next round */
+ tmp = in;
+ in = out;
+ out = tmp;
+
+ } while ( --rounds );
+}
+
+/**
+ * Perform standalone AddRoundKey
+ *
+ * @v state AES state
+ * @v key AES round key
+ */
+static inline __attribute__ (( always_inline )) void
+aes_addroundkey ( union aes_matrix *state, const union aes_matrix *key ) {
+
+ state->column[0] ^= key->column[0];
+ state->column[1] ^= key->column[1];
+ state->column[2] ^= key->column[2];
+ state->column[3] ^= key->column[3];
+}
+
+/**
+ * Perform final round
+ *
+ * @v table AES lookup table
+ * @v stride AES row shift stride
+ * @v in AES input state
+ * @v out AES output state
+ * @v key AES round key
+ */
+static void aes_final ( const struct aes_table *table, size_t stride,
+ const union aes_matrix *in, union aes_matrix *out,
+ const union aes_matrix *key ) {
+ const union aes_table_entry *entry;
+ unsigned int byte;
+ size_t out_offset;
+ size_t in_offset;
+
+ /* Perform [Inv]ShiftRows and [Inv]SubBytes */
+ for ( out_offset = 0, in_offset = 0 ; out_offset < 16 ;
+ out_offset++, in_offset = ( ( in_offset + stride ) & 0xf ) ) {
+
+ /* Extract input byte (i.e. perform [Inv]ShiftRows) */
+ byte = in->byte[in_offset];
+
+ /* Locate lookup table entry for this input byte
+ * (i.e. perform [Inv]SubBytes).
+ */
+ entry = &table->entry[byte];
+
+ /* Store output byte */
+ out->byte[out_offset] = entry->byte[0];
+ }
+
+ /* Perform AddRoundKey */
+ aes_addroundkey ( out, key );
+}
+
+/**
+ * Encrypt data
+ *
+ * @v ctx Context
+ * @v src Data to encrypt
+ * @v dst Buffer for encrypted data
+ * @v len Length of data
+ */
+static void aes_encrypt ( void *ctx, const void *src, void *dst, size_t len ) {
+ struct aes_context *aes = ctx;
+ union aes_matrix buffer[2];
+ union aes_matrix *in = &buffer[0];
+ union aes_matrix *out = &buffer[1];
+ unsigned int rounds = aes->rounds;
+
+ /* Sanity check */
+ assert ( len == sizeof ( *in ) );
+
+ /* Initialise input state */
+ memcpy ( in, src, sizeof ( *in ) );
+
+ /* Perform initial round (AddRoundKey) */
+ aes_addroundkey ( in, &aes->encrypt.key[0] );
+
+ /* Perform intermediate rounds (ShiftRows, SubBytes,
+ * MixColumns, AddRoundKey).
+ */
+ aes_encrypt_rounds ( in, out, &aes->encrypt.key[1], ( rounds - 2 ) );
+ in = out;
+
+ /* Perform final round (ShiftRows, SubBytes, AddRoundKey) */
+ out = dst;
+ aes_final ( &aes_mixcolumns, AES_STRIDE_SHIFTROWS, in, out,
+ &aes->encrypt.key[ rounds - 1 ] );
+}
+
+/**
+ * Decrypt data
+ *
+ * @v ctx Context
+ * @v src Data to decrypt
+ * @v dst Buffer for decrypted data
+ * @v len Length of data
+ */
+static void aes_decrypt ( void *ctx, const void *src, void *dst, size_t len ) {
+ struct aes_context *aes = ctx;
+ union aes_matrix buffer[2];
+ union aes_matrix *in = &buffer[0];
+ union aes_matrix *out = &buffer[1];
+ unsigned int rounds = aes->rounds;
+
+ /* Sanity check */
+ assert ( len == sizeof ( *in ) );
+
+ /* Initialise input state */
+ memcpy ( in, src, sizeof ( *in ) );
+
+ /* Perform initial round (AddRoundKey) */
+ aes_addroundkey ( in, &aes->decrypt.key[0] );
+
+ /* Perform intermediate rounds (InvShiftRows, InvSubBytes,
+ * InvMixColumns, AddRoundKey).
+ */
+ aes_decrypt_rounds ( in, out, &aes->decrypt.key[1], ( rounds - 2 ) );
+ in = out;
+
+ /* Perform final round (InvShiftRows, InvSubBytes, AddRoundKey) */
+ out = dst;
+ aes_final ( &aes_invmixcolumns, AES_STRIDE_INVSHIFTROWS, in, out,
+ &aes->decrypt.key[ rounds - 1 ] );
+}
+
+/**
+ * Multiply a polynomial by (x) modulo (x^8 + x^4 + x^3 + x^2 + 1) in GF(2^8)
+ *
+ * @v poly Polynomial to be multiplied
+ * @ret result Result
+ */
+static __attribute__ (( const )) unsigned int aes_double ( unsigned int poly ) {
+
+ /* Multiply polynomial by (x), placing the resulting x^8
+ * coefficient in the LSB (i.e. rotate byte left by one).
+ */
+ poly = rol8 ( poly, 1 );
+
+ /* If coefficient of x^8 (in LSB) is non-zero, then reduce by
+ * subtracting (x^8 + x^4 + x^3 + x^2 + 1) in GF(2^8).
+ */
+ if ( poly & 0x01 ) {
+ poly ^= 0x01; /* Subtract x^8 (currently in LSB) */
+ poly ^= 0x1b; /* Subtract (x^4 + x^3 + x^2 + 1) */
+ }
+
+ return poly;
+}
+
+/**
+ * Fill in MixColumns lookup table entry
+ *
+ * @v entry AES lookup table entry for scalar multiplicand
+ *
+ * The MixColumns lookup table vector multiplier is {1,1,1,3,2,1,1,3}.
+ */
+static void aes_mixcolumns_entry ( union aes_table_entry *entry ) {
+ unsigned int scalar_x_1;
+ unsigned int scalar_x;
+ unsigned int scalar;
+
+ /* Retrieve scalar multiplicand */
+ scalar = entry->byte[0];
+ entry->byte[1] = scalar;
+ entry->byte[2] = scalar;
+ entry->byte[5] = scalar;
+ entry->byte[6] = scalar;
+
+ /* Calculate scalar multiplied by (x) */
+ scalar_x = aes_double ( scalar );
+ entry->byte[4] = scalar_x;
+
+ /* Calculate scalar multiplied by (x + 1) */
+ scalar_x_1 = ( scalar_x ^ scalar );
+ entry->byte[3] = scalar_x_1;
+ entry->byte[7] = scalar_x_1;
+}
+
+/**
+ * Fill in InvMixColumns lookup table entry
+ *
+ * @v entry AES lookup table entry for scalar multiplicand
+ *
+ * The InvMixColumns lookup table vector multiplier is {1,9,13,11,14,9,13,11}.
+ */
+static void aes_invmixcolumns_entry ( union aes_table_entry *entry ) {
+ unsigned int scalar_x3_x2_x;
+ unsigned int scalar_x3_x2_1;
+ unsigned int scalar_x3_x2;
+ unsigned int scalar_x3_x_1;
+ unsigned int scalar_x3_1;
+ unsigned int scalar_x3;
+ unsigned int scalar_x2;
+ unsigned int scalar_x;
+ unsigned int scalar;
+
+ /* Retrieve scalar multiplicand */
+ scalar = entry->byte[0];
+
+ /* Calculate scalar multiplied by (x) */
+ scalar_x = aes_double ( scalar );
+
+ /* Calculate scalar multiplied by (x^2) */
+ scalar_x2 = aes_double ( scalar_x );
+
+ /* Calculate scalar multiplied by (x^3) */
+ scalar_x3 = aes_double ( scalar_x2 );
+
+ /* Calculate scalar multiplied by (x^3 + 1) */
+ scalar_x3_1 = ( scalar_x3 ^ scalar );
+ entry->byte[1] = scalar_x3_1;
+ entry->byte[5] = scalar_x3_1;
+
+ /* Calculate scalar multiplied by (x^3 + x + 1) */
+ scalar_x3_x_1 = ( scalar_x3_1 ^ scalar_x );
+ entry->byte[3] = scalar_x3_x_1;
+ entry->byte[7] = scalar_x3_x_1;
+
+ /* Calculate scalar multiplied by (x^3 + x^2) */
+ scalar_x3_x2 = ( scalar_x3 ^ scalar_x2 );
+
+ /* Calculate scalar multiplied by (x^3 + x^2 + 1) */
+ scalar_x3_x2_1 = ( scalar_x3_x2 ^ scalar );
+ entry->byte[2] = scalar_x3_x2_1;
+ entry->byte[6] = scalar_x3_x2_1;
+
+ /* Calculate scalar multiplied by (x^3 + x^2 + x) */
+ scalar_x3_x2_x = ( scalar_x3_x2 ^ scalar_x );
+ entry->byte[4] = scalar_x3_x2_x;
+}
+
+/**
+ * Generate AES lookup tables
+ *
+ */
+static void aes_generate ( void ) {
+ union aes_table_entry *entry;
+ union aes_table_entry *inventry;
+ unsigned int poly = 0x01;
+ unsigned int invpoly = 0x01;
+ unsigned int transformed;
+ unsigned int i;
+
+ /* Iterate over non-zero values of GF(2^8) using generator (x + 1) */
+ do {
+
+ /* Multiply polynomial by (x + 1) */
+ poly ^= aes_double ( poly );
+
+ /* Divide inverse polynomial by (x + 1). This code
+ * fragment is taken directly from the Wikipedia page
+ * on the Rijndael S-box. An explanation of why it
+ * works would be greatly appreciated.
+ */
+ invpoly ^= ( invpoly << 1 );
+ invpoly ^= ( invpoly << 2 );
+ invpoly ^= ( invpoly << 4 );
+ if ( invpoly & 0x80 )
+ invpoly ^= 0x09;
+ invpoly &= 0xff;
+
+ /* Apply affine transformation */
+ transformed = ( 0x63 ^ invpoly ^ rol8 ( invpoly, 1 ) ^
+ rol8 ( invpoly, 2 ) ^ rol8 ( invpoly, 3 ) ^
+ rol8 ( invpoly, 4 ) );
+
+ /* Populate S-box (within MixColumns lookup table) */
+ aes_mixcolumns.entry[poly].byte[0] = transformed;
+
+ } while ( poly != 0x01 );
+
+ /* Populate zeroth S-box entry (which has no inverse) */
+ aes_mixcolumns.entry[0].byte[0] = 0x63;
+
+ /* Fill in MixColumns and InvMixColumns lookup tables */
+ for ( i = 0 ; i < 256 ; i++ ) {
+
+ /* Fill in MixColumns lookup table entry */
+ entry = &aes_mixcolumns.entry[i];
+ aes_mixcolumns_entry ( entry );
+
+ /* Populate inverse S-box (within InvMixColumns lookup table) */
+ inventry = &aes_invmixcolumns.entry[ entry->byte[0] ];
+ inventry->byte[0] = i;
+
+ /* Fill in InvMixColumns lookup table entry */
+ aes_invmixcolumns_entry ( inventry );
+ }
+}
+
+/**
+ * Rotate key column
+ *
+ * @v column Key column
+ * @ret column Updated key column
+ */
+static inline __attribute__ (( always_inline )) uint32_t
+aes_key_rotate ( uint32_t column ) {
+
+ return ( ( __BYTE_ORDER == __LITTLE_ENDIAN ) ?
+ ror32 ( column, 8 ) : rol32 ( column, 8 ) );
+}
+
+/**
+ * Apply S-box to key column
+ *
+ * @v column Key column
+ * @ret column Updated key column
+ */
+static uint32_t aes_key_sbox ( uint32_t column ) {
+ unsigned int i;
+ uint8_t byte;
+
+ for ( i = 0 ; i < 4 ; i++ ) {
+ byte = ( column & 0xff );
+ byte = aes_mixcolumns.entry[byte].byte[0];
+ column = ( ( column & ~0xff ) | byte );
+ column = rol32 ( column, 8 );
+ }
+ return column;
+}
+
+/**
+ * Apply schedule round constant to key column
+ *
+ * @v column Key column
+ * @v rcon Round constant
+ * @ret column Updated key column
+ */
+static inline __attribute__ (( always_inline )) uint32_t
+aes_key_rcon ( uint32_t column, unsigned int rcon ) {
+
+ return ( ( __BYTE_ORDER == __LITTLE_ENDIAN ) ?
+ ( column ^ rcon ) : ( column ^ ( rcon << 24 ) ) );
+}
+
+/**
+ * Set key
+ *
+ * @v ctx Context
+ * @v key Key
+ * @v keylen Key length
+ * @ret rc Return status code
+ */
+static int aes_setkey ( void *ctx, const void *key, size_t keylen ) {
+ struct aes_context *aes = ctx;
+ union aes_matrix *enc;
+ union aes_matrix *dec;
+ union aes_matrix temp;
+ union aes_matrix zero;
+ unsigned int rcon = 0x01;
+ unsigned int rounds;
+ size_t offset = 0;
+ uint32_t *prev;
+ uint32_t *next;
+ uint32_t *end;
+ uint32_t tmp;
+
+ /* Generate lookup tables, if not already done */
+ if ( ! aes_mixcolumns.entry[0].byte[0] )
+ aes_generate();
+
+ /* Validate key length and calculate number of intermediate rounds */
+ switch ( keylen ) {
+ case ( 128 / 8 ) :
+ rounds = 11;
+ break;
+ case ( 192 / 8 ) :
+ rounds = 13;
+ break;
+ case ( 256 / 8 ) :
+ rounds = 15;
+ break;
+ default:
+ DBGC ( aes, "AES %p unsupported key length (%zd bits)\n",
+ aes, ( keylen * 8 ) );
+ return -EINVAL;
+ }
+ aes->rounds = rounds;
+ enc = aes->encrypt.key;
+ end = enc[rounds].column;
+
+ /* Copy raw key */
+ memcpy ( enc, key, keylen );
+ prev = enc->column;
+ next = ( ( ( void * ) prev ) + keylen );
+ tmp = next[-1];
+
+ /* Construct expanded key */
+ while ( next < end ) {
+
+ /* If this is the first column of an expanded key
+ * block, or the middle column of an AES-256 key
+ * block, then apply the S-box.
+ */
+ if ( ( offset == 0 ) || ( ( offset | keylen ) == 48 ) )
+ tmp = aes_key_sbox ( tmp );
+
+ /* If this is the first column of an expanded key
+ * block then rotate and apply the round constant.
+ */
+ if ( offset == 0 ) {
+ tmp = aes_key_rotate ( tmp );
+ tmp = aes_key_rcon ( tmp, rcon );
+ rcon = aes_double ( rcon );
+ }
+
+ /* XOR with previous key column */
+ tmp ^= *prev;
+
+ /* Store column */
+ *next = tmp;
+
+ /* Move to next column */
+ offset += sizeof ( *next );
+ if ( offset == keylen )
+ offset = 0;
+ next++;
+ prev++;
+ }
+ DBGC2 ( aes, "AES %p expanded %zd-bit key:\n", aes, ( keylen * 8 ) );
+ DBGC2_HDA ( aes, 0, &aes->encrypt, ( rounds * sizeof ( *enc ) ) );
+
+ /* Convert to decryption key */
+ memset ( &zero, 0, sizeof ( zero ) );
+ dec = &aes->decrypt.key[ rounds - 1 ];
+ memcpy ( dec--, enc++, sizeof ( *dec ) );
+ while ( dec > aes->decrypt.key ) {
+ /* Perform InvMixColumns (by reusing the encryption
+ * final-round code to perform ShiftRows+SubBytes and
+ * reusing the decryption intermediate-round code to
+ * perform InvShiftRows+InvSubBytes+InvMixColumns, all
+ * with a zero encryption key).
+ */
+ aes_final ( &aes_mixcolumns, AES_STRIDE_SHIFTROWS,
+ enc++, &temp, &zero );
+ aes_decrypt_rounds ( &temp, dec--, &zero, 1 );
+ }
+ memcpy ( dec--, enc++, sizeof ( *dec ) );
+ DBGC2 ( aes, "AES %p inverted %zd-bit key:\n", aes, ( keylen * 8 ) );
+ DBGC2_HDA ( aes, 0, &aes->decrypt, ( rounds * sizeof ( *dec ) ) );
+
+ return 0;
+}
+
+/**
+ * Set initialisation vector
+ *
+ * @v ctx Context
+ * @v iv Initialisation vector
+ */
+static void aes_setiv ( void *ctx __unused, const void *iv __unused ) {
+ /* Nothing to do */
+}
+
+/** Basic AES algorithm */
+struct cipher_algorithm aes_algorithm = {
+ .name = "aes",
+ .ctxsize = sizeof ( struct aes_context ),
+ .blocksize = AES_BLOCKSIZE,
+ .setkey = aes_setkey,
+ .setiv = aes_setiv,
+ .encrypt = aes_encrypt,
+ .decrypt = aes_decrypt,
+};
+
+/* AES in Electronic Codebook mode */
+ECB_CIPHER ( aes_ecb, aes_ecb_algorithm,
+ aes_algorithm, struct aes_context, AES_BLOCKSIZE );
+
+/* AES in Cipher Block Chaining mode */
+CBC_CIPHER ( aes_cbc, aes_cbc_algorithm,
+ aes_algorithm, struct aes_context, AES_BLOCKSIZE );
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-02 00:15:54 +0000