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https://github.com/michaelrsweet/pdfio.git
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Update AES code with proper coding style/documentation for this project.
This commit is contained in:
Michael R Sweet
parent
4f123c2a01
commit
fceb5a807d
179
pdfio-aes.c
179
pdfio-aes.c
@ -1,7 +1,7 @@
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//
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// AES functions for PDFio.
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//
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// Copyright © 2021 by Michael R Sweet.
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// Copyright © 2021-2025 by Michael R Sweet.
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//
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// Licensed under Apache License v2.0. See the file "LICENSE" for more
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// information.
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@ -76,18 +76,18 @@ static const uint8_t Rcon[11] = // Round constants
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// Local functions...
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//
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static void AddRoundKey(size_t round, state_t *state, const uint8_t *RoundKey);
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static void SubBytes(state_t *state);
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static void ShiftRows(state_t *state);
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static void add_round_key(size_t round, state_t *state, const uint8_t *round_key);
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static void sub_bytes(state_t *state);
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static void shift_rows(state_t *state);
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static uint8_t xtime(uint8_t x);
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static void MixColumns(state_t *state);
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static uint8_t Multiply(uint8_t x, uint8_t y);
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static void InvMixColumns(state_t *state);
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static void InvSubBytes(state_t *state);
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static void InvShiftRows(state_t *state);
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static void Cipher(state_t *state, const _pdfio_aes_t *ctx);
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static void InvCipher(state_t *state, const _pdfio_aes_t *ctx);
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static void XorWithIv(uint8_t *buf, const uint8_t *Iv);
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static void mix_columns(state_t *state);
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static uint8_t multiply(uint8_t x, uint8_t y);
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static void inv_mix_columns(state_t *state);
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static void inv_sub_bytes(state_t *state);
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static void inv_shift_rows(state_t *state);
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static void cipher(state_t *state, const _pdfio_aes_t *ctx);
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static void inv_cipher(state_t *state, const _pdfio_aes_t *ctx);
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static void xor_with_iv(uint8_t *buf, const uint8_t *Iv);
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//
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@ -106,7 +106,6 @@ _pdfioCryptoAESInit(
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*rkptr, // Current round_key values
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*rkend, // End of round_key values
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tempa[4]; // Used for the column/row operations
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// size_t roundlen = keylen + 24; // Length of round_key
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size_t nwords = keylen / 4; // Number of 32-bit words in key
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@ -188,8 +187,8 @@ _pdfioCryptoAESDecrypt(
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while (len > 15)
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{
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memcpy(next_iv, outbuffer, 16);
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InvCipher((state_t *)outbuffer, ctx);
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XorWithIv(outbuffer, ctx->iv);
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inv_cipher((state_t *)outbuffer, ctx);
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xor_with_iv(outbuffer, ctx->iv);
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memcpy(ctx->iv, next_iv, 16);
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outbuffer += 16;
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len -= 16;
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@ -231,8 +230,8 @@ _pdfioCryptoAESEncrypt(
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while (len > 15)
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{
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XorWithIv(outbuffer, iv);
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Cipher((state_t*)outbuffer, ctx);
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xor_with_iv(outbuffer, iv);
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cipher((state_t*)outbuffer, ctx);
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iv = outbuffer;
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outbuffer += 16;
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len -= 16;
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@ -244,8 +243,8 @@ _pdfioCryptoAESEncrypt(
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// Pad the final buffer with (16 - len)...
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memset(outbuffer + len, 16 - len, 16 - len);
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XorWithIv(outbuffer, iv);
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Cipher((state_t*)outbuffer, ctx);
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xor_with_iv(outbuffer, iv);
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cipher((state_t*)outbuffer, ctx);
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iv = outbuffer;
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outbytes += 16;
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}
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@ -257,24 +256,32 @@ _pdfioCryptoAESEncrypt(
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}
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// This function adds the round key to state.
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//
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// 'add_round_key()' - Add the round key to state.
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//
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// The round key is added to the state by an XOR function.
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//
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static void
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AddRoundKey(size_t round, state_t *state, const uint8_t *RoundKey)
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add_round_key(size_t round, // I - Which round
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state_t *state, // I - Current state
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const uint8_t *round_key) // I - Key
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{
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unsigned i; // Looping var
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uint8_t *sptr = (*state)[0]; // Pointer into state
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for (RoundKey += round * 16, i = 16; i > 0; i --, sptr ++, RoundKey ++)
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*sptr ^= *RoundKey;
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for (round_key += round * 16, i = 16; i > 0; i --, sptr ++, round_key ++)
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*sptr ^= *round_key;
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}
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// The SubBytes Function Substitutes the values in the
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// state matrix with values in an S-box.
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//
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// 'sub_bytes()' - Substitute the values in the state matrix with values in an S-box.
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//
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static void
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SubBytes(state_t *state)
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sub_bytes(state_t *state) // I - Current state
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{
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unsigned i; // Looping var
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uint8_t *sptr = (*state)[0]; // Pointer into state
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@ -284,11 +291,16 @@ SubBytes(state_t *state)
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*sptr = sbox[*sptr];
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}
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// The ShiftRows() function shifts the rows in the state to the left.
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//
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// 'shift_rows()' - Shift the rows in the state to the left.
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//
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// Each row is shifted with different offset.
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// Offset = Row number. So the first row is not shifted.
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//
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static void
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ShiftRows(state_t *state)
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shift_rows(state_t *state) // I - Current state
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{
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uint8_t *sptr = (*state)[0]; // Pointer into state
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uint8_t temp; // Temporary value
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@ -319,21 +331,29 @@ ShiftRows(state_t *state)
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}
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static uint8_t
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xtime(uint8_t x)
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//
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// 'xtime()' - Compute the AES xtime function.
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//
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static uint8_t // O - xtime(x)
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xtime(uint8_t x) // I - Column value
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{
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return ((uint8_t)((x << 1) ^ ((x >> 7) * 0x1b)));
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}
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// MixColumns function mixes the columns of the state matrix
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//
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// 'mix_columns()' - Mix the columns of the state matrix.
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//
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static void
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MixColumns(state_t *state)
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mix_columns(state_t *state) // I - Current state
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{
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unsigned i; // Looping var
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uint8_t *sptr = (*state)[0]; // Pointer into state
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uint8_t Tmp, Tm, t; // Temporary values
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for (i = 4; i > 0; i --, sptr += 4)
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{
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t = sptr[0];
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@ -357,11 +377,15 @@ MixColumns(state_t *state)
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}
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// Multiply is used to multiply numbers in the field GF(2^8)
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//
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// 'multiply()' - Multiply numbers in the field GF(2^8)
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//
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// Note: The last call to xtime() is unneeded, but often ends up generating a smaller binary
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// The compiler seems to be able to vectorize the operation better this way.
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// See https://github.com/kokke/tiny-AES-c/pull/34
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static uint8_t Multiply(uint8_t x, uint8_t y)
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//
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static uint8_t multiply(uint8_t x, uint8_t y)
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{
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return (((y & 1) * x) ^
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((y>>1 & 1) * xtime(x)) ^
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@ -371,11 +395,15 @@ static uint8_t Multiply(uint8_t x, uint8_t y)
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}
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// MixColumns function mixes the columns of the state matrix.
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//
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// 'mix_columns()' - Mix the columns of the state matrix.
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//
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// The method used to multiply may be difficult to understand for the inexperienced.
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// Please use the references to gain more information.
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//
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static void
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InvMixColumns(state_t *state)
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inv_mix_columns(state_t *state) // I - Current state
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{
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unsigned i; // Looping var
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uint8_t *sptr = (*state)[0]; // Pointer into state
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@ -389,18 +417,20 @@ InvMixColumns(state_t *state)
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c = sptr[2];
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d = sptr[3];
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*sptr++ = Multiply(a, 0x0e) ^ Multiply(b, 0x0b) ^ Multiply(c, 0x0d) ^ Multiply(d, 0x09);
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*sptr++ = Multiply(a, 0x09) ^ Multiply(b, 0x0e) ^ Multiply(c, 0x0b) ^ Multiply(d, 0x0d);
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*sptr++ = Multiply(a, 0x0d) ^ Multiply(b, 0x09) ^ Multiply(c, 0x0e) ^ Multiply(d, 0x0b);
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*sptr++ = Multiply(a, 0x0b) ^ Multiply(b, 0x0d) ^ Multiply(c, 0x09) ^ Multiply(d, 0x0e);
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*sptr++ = multiply(a, 0x0e) ^ multiply(b, 0x0b) ^ multiply(c, 0x0d) ^ multiply(d, 0x09);
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*sptr++ = multiply(a, 0x09) ^ multiply(b, 0x0e) ^ multiply(c, 0x0b) ^ multiply(d, 0x0d);
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*sptr++ = multiply(a, 0x0d) ^ multiply(b, 0x09) ^ multiply(c, 0x0e) ^ multiply(d, 0x0b);
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*sptr++ = multiply(a, 0x0b) ^ multiply(b, 0x0d) ^ multiply(c, 0x09) ^ multiply(d, 0x0e);
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}
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}
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// The SubBytes Function Substitutes the values in the
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// state matrix with values in an S-box.
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//
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// 'sub_bytes()' - Substitute the values in the state matrix with values in an S-box.
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//
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static void
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InvSubBytes(state_t *state)
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inv_sub_bytes(state_t *state) // I - Current state
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{
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unsigned i; // Looping var
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uint8_t *sptr = (*state)[0]; // Pointer into state
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@ -411,8 +441,12 @@ InvSubBytes(state_t *state)
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}
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//
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// 'inv_shift_rows()' - Shift the rows in the state to the right.
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//
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static void
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InvShiftRows(state_t *state)
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inv_shift_rows(state_t *state) // I - Current state
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{
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uint8_t *sptr = (*state)[0]; // Pointer into state
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uint8_t temp; // Temporary value
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@ -443,40 +477,52 @@ InvShiftRows(state_t *state)
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}
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// Cipher is the main function that encrypts the PlainText.
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//
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// 'cipher()' - Encrypt the PlainText.
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//
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static void
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Cipher(state_t *state, const _pdfio_aes_t *ctx)
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cipher(state_t *state, // I - Current state
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const _pdfio_aes_t *ctx) // I - AES context
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{
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size_t round = 0;
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size_t round = 0; // Current round
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// Add the First round key to the state before starting the rounds.
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AddRoundKey(0, state, ctx->round_key);
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add_round_key(0, state, ctx->round_key);
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// There will be Nr rounds.
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// The first Nr-1 rounds are identical.
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// These Nr rounds are executed in the loop below.
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// Last one without MixColumns()
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// Last one without mix_columns()
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for (round = 1; round < ctx->round_size; round ++)
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{
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SubBytes(state);
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ShiftRows(state);
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MixColumns(state);
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AddRoundKey(round, state, ctx->round_key);
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sub_bytes(state);
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shift_rows(state);
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mix_columns(state);
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add_round_key(round, state, ctx->round_key);
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}
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// Add round key to last round
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SubBytes(state);
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ShiftRows(state);
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AddRoundKey(ctx->round_size, state, ctx->round_key);
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sub_bytes(state);
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shift_rows(state);
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add_round_key(ctx->round_size, state, ctx->round_key);
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}
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//
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// 'inv_cipher()' - Decrypt the CipherText.
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//
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static void
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InvCipher(state_t *state, const _pdfio_aes_t *ctx)
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inv_cipher(state_t *state, // I - Current state
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const _pdfio_aes_t *ctx) // I - AES context
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{
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size_t round;
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size_t round; // Current round
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// Add the First round key to the state before starting the rounds.
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AddRoundKey(ctx->round_size, state, ctx->round_key);
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add_round_key(ctx->round_size, state, ctx->round_key);
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// There will be Nr rounds.
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// The first Nr-1 rounds are identical.
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@ -484,20 +530,25 @@ InvCipher(state_t *state, const _pdfio_aes_t *ctx)
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// Last one without InvMixColumn()
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for (round = ctx->round_size - 1; ; round --)
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{
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InvShiftRows(state);
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InvSubBytes(state);
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AddRoundKey(round, state, ctx->round_key);
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inv_shift_rows(state);
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inv_sub_bytes(state);
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add_round_key(round, state, ctx->round_key);
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if (round == 0)
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break;
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InvMixColumns(state);
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inv_mix_columns(state);
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}
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}
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//
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// 'xor_with_iv()' - XOR a block with the initialization vector.
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//
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static void
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XorWithIv(uint8_t *buf, const uint8_t *Iv)
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xor_with_iv(uint8_t *buf, // I - Block
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const uint8_t *Iv) // I - Initialization vector
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{
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// 16-byte block...
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*buf++ ^= *Iv++;
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