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4366618a2

Denys Vlasenko

2026-10-04

SUCCESS Duration: 438s

Subject

tls_aes: use bytes for AES state

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Architecture & Compiler Flags

Architecture: x86_64-linux-gnu Compiler: gcc (Ubuntu 11.4.0-1ubuntu1~22.04.3) 11.4.0

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Commit Diff GitHub →

networking/tls_aes.c +25 -18

networking/tls_aes.c+25 -18

@@ -127,9 +127,9 @@ static uint32_t Subword(uint32_t x)
	// The round keys are used in each round to decrypt the states.
	static int KeyExpansion(uint32_t RoundKey, const void key, unsigned key_len)
	{
-	// The round constant word array, Rcon[i], contains the values given by
-	// x to th e power (i-1) being powers of x (x is denoted as {02}) in the field GF(2^8).
-	// Note that i starts at 2, not 0.
+	// Rcon[i] is x^i in GF(2^8), where x^i is represented by (1<<i).
+	// AES uses reduction polynomial x^8 + x^4 + x^3 + x + 1,
+	// thus x^8 = x^4 + x^3 + x + 1, represented as 00011011 (0x1b).
	static const uint8_t Rcon[] ALIGN1 = {
	0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36
	//..... 0x6c, 0xd8, 0xab, 0x4d, 0x9a, 0x2f, 0x5e, 0xbc, 0x63, 0xc6,...
@@ -169,14 +169,21 @@ static int KeyExpansion(uint32_t RoundKey, const void key, unsigned key_len)
	if (j == words_key) {
	j = 0;
	k++;
+	//TODO: we can eliminate k and Rcon[] and just generate Rcon[k]?
+	//instead of k++, do: Rcon = (Rcon << 1) & ^ ((Rcon & 0x80) ? 0x1b : 0)
	}
	}
	return rounds;
	}

+	// The code might be smaller on some arch if astate[16] arrays'
+	// elements are wider (e.g. 32-bit words rather than bytes).
+	// If so, make this typedef conditional for such arch:
+	typedef uint8_t state_t;
+
	// This function adds the round key to state.
	// The round key is added to the state by an XOR function.
-	static void AddRoundKey(unsigned astate[16], const uint32_t *RoundKeys)
+	static void AddRoundKey(state_t astate[16], const uint32_t *RoundKeys)
	{
	int i;

@@ -191,7 +198,7 @@ static void AddRoundKey(unsigned astate[16], const uint32_t *RoundKeys)

	// The SubBytes Function Substitutes the values in the
	// state matrix with values in an S-box.
-	static void SubBytes(unsigned astate[16])
+	static void SubBytes(state_t astate[16])
	{
	int i;

@@ -208,7 +215,7 @@ static void SubBytes(unsigned astate[16])
	// The ShiftRows() function shifts the rows in the state to the left.
	// Each row is shifted with different offset.
	// Offset = Row number. So the first row is not shifted.
-	static void ShiftRows(unsigned astate[16])
+	static void ShiftRows(state_t astate[16])
	{
	unsigned v;

@@ -232,7 +239,7 @@ static void ShiftRows(unsigned astate[16])
	}

	// MixColumns function mixes the columns of the state matrix
-	static void MixColumns(unsigned astate[16])
+	static void MixColumns(state_t astate[16])
	{
	int i;

@@ -257,7 +264,7 @@ static void MixColumns(unsigned astate[16])

	// The SubBytes Function Substitutes the values in the
	// state matrix with values in an S-box.
-	static void InvSubBytes(unsigned astate[16])
+	static void InvSubBytes(state_t astate[16])
	{
	int i;

@@ -265,7 +272,7 @@ static void InvSubBytes(unsigned astate[16])
	astate[i] = rsbox[astate[i]];
	}

-	static void InvShiftRows(unsigned astate[16])
+	static void InvShiftRows(state_t astate[16])
	{
	unsigned v;

@@ -299,7 +306,7 @@ static ALWAYS_INLINE unsigned Multiply(unsigned x)
	// MixColumns function mixes the columns of the state matrix.
	// The method used to multiply may be difficult to understand for the inexperienced.
	// Please use the references to gain more information.
-	static void InvMixColumns(unsigned astate[16])
+	static void InvMixColumns(state_t astate[16])
	{
	int i;

@@ -326,7 +333,7 @@ static void InvMixColumns(unsigned astate[16])
	}
	}

-	static void aes_encrypt_1(struct tls_aes *aes, unsigned astate[16])
+	static void aes_encrypt_1(struct tls_aes *aes, state_t astate[16])
	{
	unsigned rounds = aes->rounds;
	const uint32_t *RoundKey = aes->key;
@@ -350,7 +357,7 @@ void FAST_FUNC aes_setkey(struct tls_aes aes, const void key, unsigned key_len

	void FAST_FUNC aes_encrypt_one_block(struct tls_aes aes, const void data, void *dst)
	{
-	unsigned astate[16];
+	state_t astate[16];
	unsigned i;

	const uint8_t *pt = data;
@@ -373,12 +380,12 @@ void FAST_FUNC aes_cbc_encrypt(struct tls_aes aes, void iv, const void *data,
	memcpy(iv2, iv, 16);
	while (len > 0) {
	{
-	/* almost aes_encrypt_one_block(rounds, RoundKey, pt, ct);
+	/* almost aes_encrypt_one_block(aes, pt, ct);
	* but xor'ing of IV with plaintext[] is combined
	* with plaintext[] -> astate[]
	*/
	int i;
-	unsigned astate[16];
+	state_t astate[16];
	for (i = 0; i < 16; i++)
	astate[i] = pt[i] ^ iv2[i];
	aes_encrypt_1(aes, astate);
@@ -391,7 +398,7 @@ void FAST_FUNC aes_cbc_encrypt(struct tls_aes aes, void iv, const void *data,
	}
	}

-	static void aes_decrypt_1(struct tls_aes *aes, unsigned astate[16])
+	static void aes_decrypt_1(struct tls_aes *aes, state_t astate[16])
	{
	unsigned rounds = aes->rounds;
	const uint32_t *RoundKey = aes->key;
@@ -414,7 +421,7 @@ static void aes_decrypt_one_block(struct tls_aes aes, const void data, void *d
	{
	unsigned rounds = aes->rounds;
	const uint32_t *RoundKey = aes->key;
-	unsigned astate[16];
+	state_t astate[16];
	unsigned i;

	const uint8_t *ct = data;
@@ -442,11 +449,11 @@ void FAST_FUNC aes_cbc_decrypt(struct tls_aes aes, void iv, const void *data,
	while (len) {
	ivnext = (ivbuf==iv2) ? iv3 : iv2;
	{
-	/* almost aes_decrypt_one_block(rounds, RoundKey, ct, pt)
+	/* almost aes_decrypt_one_block(aes, ct, pt)
	* but xor'ing of ivbuf is combined with astate[] -> plaintext[]
	*/
	int i;
-	unsigned astate[16];
+	state_t astate[16];
	for (i = 0; i < 16; i++)
	ivnext[i] = astate[i] = ct[i];
	aes_decrypt_1(aes, astate);