/* Copyright (c) 2019, Google Inc. * * Permission to use, copy, modify, and/or distribute this software for any * purpose with or without fee is hereby granted, provided that the above * copyright notice and this permission notice appear in all copies. * * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ #include <openssl/aes.h> #include <assert.h> #include <string.h> #include "../../internal.h" #include "internal.h" #if defined(OPENSSL_SSE2) #include <emmintrin.h> #endif // This file contains a constant-time implementation of AES, bitsliced with // 32-bit, 64-bit, or 128-bit words, operating on two-, four-, and eight-block // batches, respectively. The 128-bit implementation requires SSE2 intrinsics. // // This implementation is based on the algorithms described in the following // references: // - https://bearssl.org/constanttime.html#aes // - https://eprint.iacr.org/2009/129.pdf // - https://eprint.iacr.org/2009/191.pdf // Word operations. // // An aes_word_t is the word used for this AES implementation. Throughout this // file, bits and bytes are ordered little-endian, though "left" and "right" // shifts match the operations themselves, which makes them reversed in a // little-endian, left-to-right reading. // // Eight |aes_word_t|s contain |AES_NOHW_BATCH_SIZE| blocks. The bits in an // |aes_word_t| are divided into 16 consecutive groups of |AES_NOHW_BATCH_SIZE| // bits each, each corresponding to a byte in an AES block in column-major // order (AES's byte order). We refer to these as "logical bytes". Note, in the // 32-bit and 64-bit implementations, they are smaller than a byte. (The // contents of a logical byte will be described later.) // // MSVC does not support C bit operators on |__m128i|, so the wrapper functions // |aes_nohw_and|, etc., should be used instead. Note |aes_nohw_shift_left| and // |aes_nohw_shift_right| measure the shift in logical bytes. That is, the shift // value ranges from 0 to 15 independent of |aes_word_t| and // |AES_NOHW_BATCH_SIZE|. // // This ordering is different from https://eprint.iacr.org/2009/129.pdf, which // uses row-major order. Matching the AES order was easier to reason about, and // we do not have PSHUFB available to arbitrarily permute bytes. #if defined(OPENSSL_SSE2) aes_word_t; // AES_NOHW_WORD_SIZE is sizeof(aes_word_t). alignas(sizeof(T)) does not work in // MSVC, so we define a constant. #define AES_NOHW_WORD_SIZE … #define AES_NOHW_BATCH_SIZE … #define AES_NOHW_ROW0_MASK … #define AES_NOHW_ROW1_MASK … #define AES_NOHW_ROW2_MASK … #define AES_NOHW_ROW3_MASK … #define AES_NOHW_COL01_MASK … #define AES_NOHW_COL2_MASK … #define AES_NOHW_COL3_MASK … static inline aes_word_t aes_nohw_and(aes_word_t a, aes_word_t b) { … } static inline aes_word_t aes_nohw_or(aes_word_t a, aes_word_t b) { … } static inline aes_word_t aes_nohw_xor(aes_word_t a, aes_word_t b) { … } static inline aes_word_t aes_nohw_not(aes_word_t a) { … } // These are macros because parameters to |_mm_slli_si128| and |_mm_srli_si128| // must be constants. #define aes_nohw_shift_left(/* aes_word_t */ a, /* const */ i) … #define aes_nohw_shift_right(/* aes_word_t */ a, /* const */ i) … #else // !OPENSSL_SSE2 #if defined(OPENSSL_64_BIT) typedef uint64_t aes_word_t; #define AES_NOHW_WORD_SIZE … #define AES_NOHW_BATCH_SIZE … #define AES_NOHW_ROW0_MASK … #define AES_NOHW_ROW1_MASK … #define AES_NOHW_ROW2_MASK … #define AES_NOHW_ROW3_MASK … #define AES_NOHW_COL01_MASK … #define AES_NOHW_COL2_MASK … #define AES_NOHW_COL3_MASK … #else // !OPENSSL_64_BIT typedef uint32_t aes_word_t; #define AES_NOHW_WORD_SIZE … #define AES_NOHW_BATCH_SIZE … #define AES_NOHW_ROW0_MASK … #define AES_NOHW_ROW1_MASK … #define AES_NOHW_ROW2_MASK … #define AES_NOHW_ROW3_MASK … #define AES_NOHW_COL01_MASK … #define AES_NOHW_COL2_MASK … #define AES_NOHW_COL3_MASK … #endif // OPENSSL_64_BIT static inline aes_word_t aes_nohw_and(aes_word_t a, aes_word_t b) { return a & b; } static inline aes_word_t aes_nohw_or(aes_word_t a, aes_word_t b) { return a | b; } static inline aes_word_t aes_nohw_xor(aes_word_t a, aes_word_t b) { return a ^ b; } static inline aes_word_t aes_nohw_not(aes_word_t a) { return ~a; } static inline aes_word_t aes_nohw_shift_left(aes_word_t a, aes_word_t i) { return a << (i * AES_NOHW_BATCH_SIZE); } static inline aes_word_t aes_nohw_shift_right(aes_word_t a, aes_word_t i) { return a >> (i * AES_NOHW_BATCH_SIZE); } #endif // OPENSSL_SSE2 static_assert; static_assert; // Block representations. // // This implementation uses three representations for AES blocks. First, the // public API represents blocks as uint8_t[16] in the usual way. Second, most // AES steps are evaluated in bitsliced form, stored in an |AES_NOHW_BATCH|. // This stores |AES_NOHW_BATCH_SIZE| blocks in bitsliced order. For 64-bit words // containing bitsliced blocks a, b, c, d, this would be as follows (vertical // bars divide logical bytes): // // batch.w[0] = a0 b0 c0 d0 | a8 b8 c8 d8 | a16 b16 c16 d16 ... // batch.w[1] = a1 b1 c1 d1 | a9 b9 c9 d9 | a17 b17 c17 d17 ... // batch.w[2] = a2 b2 c2 d2 | a10 b10 c10 d10 | a18 b18 c18 d18 ... // batch.w[3] = a3 b3 c3 d3 | a11 b11 c11 d11 | a19 b19 c19 d19 ... // ... // // Finally, an individual block may be stored as an intermediate form in an // aes_word_t[AES_NOHW_BLOCK_WORDS]. In this form, we permute the bits in each // block, so that block[0]'s ith logical byte contains least-significant // |AES_NOHW_BATCH_SIZE| bits of byte i, block[1] contains the next group of // |AES_NOHW_BATCH_SIZE| bits, and so on. We refer to this transformation as // "compacting" the block. Note this is no-op with 128-bit words because then // |AES_NOHW_BLOCK_WORDS| is one and |AES_NOHW_BATCH_SIZE| is eight. For 64-bit // words, one block would be stored in two words: // // block[0] = a0 a1 a2 a3 | a8 a9 a10 a11 | a16 a17 a18 a19 ... // block[1] = a4 a5 a6 a7 | a12 a13 a14 a15 | a20 a21 a22 a23 ... // // Observe that the distances between corresponding bits in bitsliced and // compact bit orders match. If we line up corresponding words of each block, // the bitsliced and compact representations may be converted by tranposing bits // in corresponding logical bytes. Continuing the 64-bit example: // // block_a[0] = a0 a1 a2 a3 | a8 a9 a10 a11 | a16 a17 a18 a19 ... // block_b[0] = b0 b1 b2 b3 | b8 b9 b10 b11 | b16 b17 b18 b19 ... // block_c[0] = c0 c1 c2 c3 | c8 c9 c10 c11 | c16 c17 c18 c19 ... // block_d[0] = d0 d1 d2 d3 | d8 d9 d10 d11 | d16 d17 d18 d19 ... // // batch.w[0] = a0 b0 c0 d0 | a8 b8 c8 d8 | a16 b16 c16 d16 ... // batch.w[1] = a1 b1 c1 d1 | a9 b9 c9 d9 | a17 b17 c17 d17 ... // batch.w[2] = a2 b2 c2 d2 | a10 b10 c10 d10 | a18 b18 c18 d18 ... // batch.w[3] = a3 b3 c3 d3 | a11 b11 c11 d11 | a19 b19 c19 d19 ... // // Note also that bitwise operations and (logical) byte permutations on an // |aes_word_t| work equally for the bitsliced and compact words. // // We use the compact form in the |AES_KEY| representation to save work // inflating round keys into |AES_NOHW_BATCH|. The compact form also exists // temporarily while moving blocks in or out of an |AES_NOHW_BATCH|, immediately // before or after |aes_nohw_transpose|. #define AES_NOHW_BLOCK_WORDS … // An AES_NOHW_BATCH stores |AES_NOHW_BATCH_SIZE| blocks. Unless otherwise // specified, it is in bitsliced form. AES_NOHW_BATCH; // An AES_NOHW_SCHEDULE is an expanded bitsliced AES key schedule. It is // suitable for encryption or decryption. It is as large as |AES_NOHW_BATCH| // |AES_KEY|s so it should not be used as a long-term key representation. AES_NOHW_SCHEDULE; // aes_nohw_batch_set sets the |i|th block of |batch| to |in|. |batch| is in // compact form. static inline void aes_nohw_batch_set(AES_NOHW_BATCH *batch, const aes_word_t in[AES_NOHW_BLOCK_WORDS], size_t i) { … } // aes_nohw_batch_get writes the |i|th block of |batch| to |out|. |batch| is in // compact form. static inline void aes_nohw_batch_get(const AES_NOHW_BATCH *batch, aes_word_t out[AES_NOHW_BLOCK_WORDS], size_t i) { … } #if !defined(OPENSSL_SSE2) // aes_nohw_delta_swap returns |a| with bits |a & mask| and // |a & (mask << shift)| swapped. |mask| and |mask << shift| may not overlap. static inline aes_word_t aes_nohw_delta_swap(aes_word_t a, aes_word_t mask, aes_word_t shift) { // See // https://reflectionsonsecurity.wordpress.com/2014/05/11/efficient-bit-permutation-using-delta-swaps/ aes_word_t b = (a ^ (a >> shift)) & mask; return a ^ b ^ (b << shift); } // In the 32-bit and 64-bit implementations, a block spans multiple words. // |aes_nohw_compact_block| must permute bits across different words. First we // implement |aes_nohw_compact_word| which performs a smaller version of the // transformation which stays within a single word. // // These transformations are generalizations of the output of // http://programming.sirrida.de/calcperm.php on smaller inputs. #if defined(OPENSSL_64_BIT) static inline uint64_t aes_nohw_compact_word(uint64_t a) { // Numbering the 64/2 = 16 4-bit chunks, least to most significant, we swap // quartets of those chunks: // 0 1 2 3 | 4 5 6 7 | 8 9 10 11 | 12 13 14 15 => // 0 2 1 3 | 4 6 5 7 | 8 10 9 11 | 12 14 13 15 a = aes_nohw_delta_swap(a, UINT64_C(0x00f000f000f000f0), 4); // Swap quartets of 8-bit chunks (still numbering by 4-bit chunks): // 0 2 1 3 | 4 6 5 7 | 8 10 9 11 | 12 14 13 15 => // 0 2 4 6 | 1 3 5 7 | 8 10 12 14 | 9 11 13 15 a = aes_nohw_delta_swap(a, UINT64_C(0x0000ff000000ff00), 8); // Swap quartets of 16-bit chunks (still numbering by 4-bit chunks): // 0 2 4 6 | 1 3 5 7 | 8 10 12 14 | 9 11 13 15 => // 0 2 4 6 | 8 10 12 14 | 1 3 5 7 | 9 11 13 15 a = aes_nohw_delta_swap(a, UINT64_C(0x00000000ffff0000), 16); return a; } static inline uint64_t aes_nohw_uncompact_word(uint64_t a) { // Reverse the steps of |aes_nohw_uncompact_word|. a = aes_nohw_delta_swap(a, UINT64_C(0x00000000ffff0000), 16); a = aes_nohw_delta_swap(a, UINT64_C(0x0000ff000000ff00), 8); a = aes_nohw_delta_swap(a, UINT64_C(0x00f000f000f000f0), 4); return a; } #else // !OPENSSL_64_BIT static inline uint32_t aes_nohw_compact_word(uint32_t a) { // Numbering the 32/2 = 16 pairs of bits, least to most significant, we swap: // 0 1 2 3 | 4 5 6 7 | 8 9 10 11 | 12 13 14 15 => // 0 4 2 6 | 1 5 3 7 | 8 12 10 14 | 9 13 11 15 // Note: 0x00cc = 0b0000_0000_1100_1100 // 0x00cc << 6 = 0b0011_0011_0000_0000 a = aes_nohw_delta_swap(a, 0x00cc00cc, 6); // Now we swap groups of four bits (still numbering by pairs): // 0 4 2 6 | 1 5 3 7 | 8 12 10 14 | 9 13 11 15 => // 0 4 8 12 | 1 5 9 13 | 2 6 10 14 | 3 7 11 15 // Note: 0x0000_f0f0 << 12 = 0x0f0f_0000 a = aes_nohw_delta_swap(a, 0x0000f0f0, 12); return a; } static inline uint32_t aes_nohw_uncompact_word(uint32_t a) { // Reverse the steps of |aes_nohw_uncompact_word|. a = aes_nohw_delta_swap(a, 0x0000f0f0, 12); a = aes_nohw_delta_swap(a, 0x00cc00cc, 6); return a; } static inline uint32_t aes_nohw_word_from_bytes(uint8_t a0, uint8_t a1, uint8_t a2, uint8_t a3) { return (uint32_t)a0 | ((uint32_t)a1 << 8) | ((uint32_t)a2 << 16) | ((uint32_t)a3 << 24); } #endif // OPENSSL_64_BIT #endif // !OPENSSL_SSE2 static inline void aes_nohw_compact_block(aes_word_t out[AES_NOHW_BLOCK_WORDS], const uint8_t in[16]) { … } static inline void aes_nohw_uncompact_block( uint8_t out[16], const aes_word_t in[AES_NOHW_BLOCK_WORDS]) { … } // aes_nohw_swap_bits is a variation on a delta swap. It swaps the bits in // |*a & (mask << shift)| with the bits in |*b & mask|. |mask| and // |mask << shift| must not overlap. |mask| is specified as a |uint32_t|, but it // is repeated to the full width of |aes_word_t|. #if defined(OPENSSL_SSE2) // This must be a macro because |_mm_srli_epi32| and |_mm_slli_epi32| require // constant shift values. #define aes_nohw_swap_bits(/*__m128i* */ a, /*__m128i* */ b, \ /* uint32_t */ mask, /* const */ shift) … #else static inline void aes_nohw_swap_bits(aes_word_t *a, aes_word_t *b, uint32_t mask, aes_word_t shift) { #if defined(OPENSSL_64_BIT) aes_word_t mask_w = (((uint64_t)mask) << 32) | mask; #else aes_word_t mask_w = mask; #endif // This is a variation on a delta swap. aes_word_t swap = ((*a >> shift) ^ *b) & mask_w; *a ^= swap << shift; *b ^= swap; } #endif // OPENSSL_SSE2 // aes_nohw_transpose converts |batch| to and from bitsliced form. It divides // the 8 × word_size bits into AES_NOHW_BATCH_SIZE × AES_NOHW_BATCH_SIZE squares // and transposes each square. static void aes_nohw_transpose(AES_NOHW_BATCH *batch) { … } // aes_nohw_to_batch initializes |out| with the |num_blocks| blocks from |in|. // |num_blocks| must be at most |AES_NOHW_BATCH|. static void aes_nohw_to_batch(AES_NOHW_BATCH *out, const uint8_t *in, size_t num_blocks) { … } // aes_nohw_to_batch writes the first |num_blocks| blocks in |batch| to |out|. // |num_blocks| must be at most |AES_NOHW_BATCH|. static void aes_nohw_from_batch(uint8_t *out, size_t num_blocks, const AES_NOHW_BATCH *batch) { … } // AES round steps. static void aes_nohw_add_round_key(AES_NOHW_BATCH *batch, const AES_NOHW_BATCH *key) { … } static void aes_nohw_sub_bytes(AES_NOHW_BATCH *batch) { … } // aes_nohw_sub_bytes_inv_affine inverts the affine transform portion of the AES // S-box, defined in FIPS PUB 197, section 5.1.1, step 2. static void aes_nohw_sub_bytes_inv_affine(AES_NOHW_BATCH *batch) { … } static void aes_nohw_inv_sub_bytes(AES_NOHW_BATCH *batch) { … } // aes_nohw_rotate_cols_right returns |v| with the columns in each row rotated // to the right by |n|. This is a macro because |aes_nohw_shift_*| require // constant shift counts in the SSE2 implementation. #define aes_nohw_rotate_cols_right(/* aes_word_t */ v, /* const */ n) … static void aes_nohw_shift_rows(AES_NOHW_BATCH *batch) { … } static void aes_nohw_inv_shift_rows(AES_NOHW_BATCH *batch) { … } // aes_nohw_rotate_rows_down returns |v| with the rows in each column rotated // down by one. static inline aes_word_t aes_nohw_rotate_rows_down(aes_word_t v) { … } // aes_nohw_rotate_rows_twice returns |v| with the rows in each column rotated // by two. static inline aes_word_t aes_nohw_rotate_rows_twice(aes_word_t v) { … } static void aes_nohw_mix_columns(AES_NOHW_BATCH *batch) { … } static void aes_nohw_inv_mix_columns(AES_NOHW_BATCH *batch) { … } static void aes_nohw_encrypt_batch(const AES_NOHW_SCHEDULE *key, size_t num_rounds, AES_NOHW_BATCH *batch) { … } static void aes_nohw_decrypt_batch(const AES_NOHW_SCHEDULE *key, size_t num_rounds, AES_NOHW_BATCH *batch) { … } // Key schedule. static void aes_nohw_expand_round_keys(AES_NOHW_SCHEDULE *out, const AES_KEY *key) { … } static const uint8_t aes_nohw_rcon[10] = …; // aes_nohw_rcon_slice returns the |i|th group of |AES_NOHW_BATCH_SIZE| bits in // |rcon|, stored in a |aes_word_t|. static inline aes_word_t aes_nohw_rcon_slice(uint8_t rcon, size_t i) { … } static void aes_nohw_sub_block(aes_word_t out[AES_NOHW_BLOCK_WORDS], const aes_word_t in[AES_NOHW_BLOCK_WORDS]) { … } static void aes_nohw_setup_key_128(AES_KEY *key, const uint8_t in[16]) { … } static void aes_nohw_setup_key_192(AES_KEY *key, const uint8_t in[24]) { … } static void aes_nohw_setup_key_256(AES_KEY *key, const uint8_t in[32]) { … } // External API. int aes_nohw_set_encrypt_key(const uint8_t *key, unsigned bits, AES_KEY *aeskey) { … } int aes_nohw_set_decrypt_key(const uint8_t *key, unsigned bits, AES_KEY *aeskey) { … } void aes_nohw_encrypt(const uint8_t *in, uint8_t *out, const AES_KEY *key) { … } void aes_nohw_decrypt(const uint8_t *in, uint8_t *out, const AES_KEY *key) { … } static inline void aes_nohw_xor_block(uint8_t out[16], const uint8_t a[16], const uint8_t b[16]) { … } void aes_nohw_ctr32_encrypt_blocks(const uint8_t *in, uint8_t *out, size_t blocks, const AES_KEY *key, const uint8_t ivec[16]) { … } void aes_nohw_cbc_encrypt(const uint8_t *in, uint8_t *out, size_t len, const AES_KEY *key, uint8_t *ivec, const int enc) { … }
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