diff options
author | Don Dugger <n0ano@n0ano.com> | 2016-06-03 03:33:22 +0000 |
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committer | Gerrit Code Review <gerrit@172.30.200.206> | 2016-06-03 03:33:23 +0000 |
commit | da27230f80795d0028333713f036d44c53cb0e68 (patch) | |
tree | b3d379eaf000adf72b36cb01cdf4d79c3e3f064c /qemu/roms/ipxe/src/crypto/aes.c | |
parent | 0e68cb048bb8aadb14675f5d4286d8ab2fc35449 (diff) | |
parent | 437fd90c0250dee670290f9b714253671a990160 (diff) |
Merge "These changes are the raw update to qemu-2.6."
Diffstat (limited to 'qemu/roms/ipxe/src/crypto/aes.c')
-rw-r--r-- | qemu/roms/ipxe/src/crypto/aes.c | 808 |
1 files changed, 808 insertions, 0 deletions
diff --git a/qemu/roms/ipxe/src/crypto/aes.c b/qemu/roms/ipxe/src/crypto/aes.c new file mode 100644 index 000000000..b9e206bfb --- /dev/null +++ b/qemu/roms/ipxe/src/crypto/aes.c @@ -0,0 +1,808 @@ +/* + * 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 ); |