From 76e48178c80aee6f759786c7632274d5deb643e7 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Thomas=20G=C3=B6ttgens?= Date: Tue, 26 Apr 2022 17:50:50 +0200 Subject: [PATCH] use a tiny software AES lib if user needs AES-256 --- src/nrf52/NRF52CryptoEngine.cpp | 16 ++- src/nrf52/aes-256/tiny-aes.cpp | 239 ++++++++++++++++++++++++++++++++ src/nrf52/aes-256/tiny-aes.h | 23 +++ 3 files changed, 275 insertions(+), 3 deletions(-) create mode 100644 src/nrf52/aes-256/tiny-aes.cpp create mode 100644 src/nrf52/aes-256/tiny-aes.h diff --git a/src/nrf52/NRF52CryptoEngine.cpp b/src/nrf52/NRF52CryptoEngine.cpp index 49f85a85..b508ed55 100644 --- a/src/nrf52/NRF52CryptoEngine.cpp +++ b/src/nrf52/NRF52CryptoEngine.cpp @@ -1,7 +1,7 @@ #include "configuration.h" #include "CryptoEngine.h" #include - +#include "aes-256/tiny-aes.h" class NRF52CryptoEngine : public CryptoEngine { public: @@ -18,7 +18,12 @@ class NRF52CryptoEngine : public CryptoEngine { // DEBUG_MSG("NRF52 encrypt!\n"); - if (key.length > 0) { + if (key.length > 16) { + AES_ctx ctx; + initNonce(fromNode, packetId); + AES_init_ctx_iv(&ctx, key.bytes, nonce); + AES_CTR_xcrypt_buffer(&ctx, bytes, numBytes); + } else if (key.length > 0) { nRFCrypto.begin(); nRFCrypto_AES ctx; uint8_t myLen = ctx.blockLen(numBytes); @@ -36,7 +41,12 @@ class NRF52CryptoEngine : public CryptoEngine { // DEBUG_MSG("NRF52 decrypt!\n"); - if (key.length > 0) { + if (key.length > 16) { + AES_ctx ctx; + initNonce(fromNode, packetId); + AES_init_ctx_iv(&ctx, key.bytes, nonce); + AES_CTR_xcrypt_buffer(&ctx, bytes, numBytes); + } else if (key.length > 0) { nRFCrypto.begin(); nRFCrypto_AES ctx; uint8_t myLen = ctx.blockLen(numBytes); diff --git a/src/nrf52/aes-256/tiny-aes.cpp b/src/nrf52/aes-256/tiny-aes.cpp new file mode 100644 index 00000000..48435ce7 --- /dev/null +++ b/src/nrf52/aes-256/tiny-aes.cpp @@ -0,0 +1,239 @@ +/* +AES-256 Software Implementation + +based on https://github.com/kokke/tiny-AES-C/ which is in public domain + +NOTE: String length must be evenly divisible by 16byte (str_len % 16 == 0) + You should pad the end of the string with zeros if this is not the case. + For AES192/256 the key size is proportionally larger. +*/ + +#include +#include "tiny-aes.h" + +#define Nb 4 +#define Nk 8 +#define Nr 14 + +typedef uint8_t state_t[4][4]; + +static const uint8_t sbox[256] = { + //0 1 2 3 4 5 6 7 8 9 A B C D E F + 0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76, + 0xca, 0x82, 0xc9, 0x7d, 0xfa, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0, + 0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15, + 0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75, + 0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84, + 0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf, + 0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8, + 0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2, + 0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73, + 0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb, + 0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79, + 0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08, + 0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a, + 0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e, + 0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf, + 0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16 }; + +static const uint8_t Rcon[11] = { + 0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36 }; + +#define getSBoxValue(num) (sbox[(num)]) + +static void KeyExpansion(uint8_t* RoundKey, const uint8_t* Key) +{ + unsigned i, j, k; + uint8_t tempa[4]; + + for (i = 0; i < Nk; ++i) + { + RoundKey[(i * 4) + 0] = Key[(i * 4) + 0]; + RoundKey[(i * 4) + 1] = Key[(i * 4) + 1]; + RoundKey[(i * 4) + 2] = Key[(i * 4) + 2]; + RoundKey[(i * 4) + 3] = Key[(i * 4) + 3]; + } + + for (i = Nk; i < Nb * (Nr + 1); ++i) + { + { + k = (i - 1) * 4; + tempa[0]=RoundKey[k + 0]; + tempa[1]=RoundKey[k + 1]; + tempa[2]=RoundKey[k + 2]; + tempa[3]=RoundKey[k + 3]; + + } + + if (i % Nk == 0) + { + const uint8_t u8tmp = tempa[0]; + tempa[0] = tempa[1]; + tempa[1] = tempa[2]; + tempa[2] = tempa[3]; + tempa[3] = u8tmp; + + tempa[0] = getSBoxValue(tempa[0]); + tempa[1] = getSBoxValue(tempa[1]); + tempa[2] = getSBoxValue(tempa[2]); + tempa[3] = getSBoxValue(tempa[3]); + + tempa[0] = tempa[0] ^ Rcon[i/Nk]; + } + + if (i % Nk == 4) + { + tempa[0] = getSBoxValue(tempa[0]); + tempa[1] = getSBoxValue(tempa[1]); + tempa[2] = getSBoxValue(tempa[2]); + tempa[3] = getSBoxValue(tempa[3]); + } + + j = i * 4; k=(i - Nk) * 4; + RoundKey[j + 0] = RoundKey[k + 0] ^ tempa[0]; + RoundKey[j + 1] = RoundKey[k + 1] ^ tempa[1]; + RoundKey[j + 2] = RoundKey[k + 2] ^ tempa[2]; + RoundKey[j + 3] = RoundKey[k + 3] ^ tempa[3]; + } +} + +void AES_init_ctx(struct AES_ctx* ctx, const uint8_t* key) +{ + KeyExpansion(ctx->RoundKey, key); +} +void AES_init_ctx_iv(struct AES_ctx* ctx, const uint8_t* key, const uint8_t* iv) +{ + KeyExpansion(ctx->RoundKey, key); + memcpy (ctx->Iv, iv, AES_BLOCKLEN); +} +void AES_ctx_set_iv(struct AES_ctx* ctx, const uint8_t* iv) +{ + memcpy (ctx->Iv, iv, AES_BLOCKLEN); +} + +static void AddRoundKey(uint8_t round, state_t* state, const uint8_t* RoundKey) +{ + uint8_t i,j; + for (i = 0; i < 4; ++i) + { + for (j = 0; j < 4; ++j) + { + (*state)[i][j] ^= RoundKey[(round * Nb * 4) + (i * Nb) + j]; + } + } +} + +static void SubBytes(state_t* state) +{ + uint8_t i, j; + for (i = 0; i < 4; ++i) + { + for (j = 0; j < 4; ++j) + { + (*state)[j][i] = getSBoxValue((*state)[j][i]); + } + } +} + +static void ShiftRows(state_t* state) +{ + uint8_t temp; + + temp = (*state)[0][1]; + (*state)[0][1] = (*state)[1][1]; + (*state)[1][1] = (*state)[2][1]; + (*state)[2][1] = (*state)[3][1]; + (*state)[3][1] = temp; + + temp = (*state)[0][2]; + (*state)[0][2] = (*state)[2][2]; + (*state)[2][2] = temp; + + temp = (*state)[1][2]; + (*state)[1][2] = (*state)[3][2]; + (*state)[3][2] = temp; + + temp = (*state)[0][3]; + (*state)[0][3] = (*state)[3][3]; + (*state)[3][3] = (*state)[2][3]; + (*state)[2][3] = (*state)[1][3]; + (*state)[1][3] = temp; +} + +static uint8_t xtime(uint8_t x) +{ + return ((x<<1) ^ (((x>>7) & 1) * 0x1b)); +} + +static void MixColumns(state_t* state) +{ + uint8_t i; + uint8_t Tmp, Tm, t; + for (i = 0; i < 4; ++i) + { + t = (*state)[i][0]; + Tmp = (*state)[i][0] ^ (*state)[i][1] ^ (*state)[i][2] ^ (*state)[i][3] ; + Tm = (*state)[i][0] ^ (*state)[i][1] ; Tm = xtime(Tm); (*state)[i][0] ^= Tm ^ Tmp ; + Tm = (*state)[i][1] ^ (*state)[i][2] ; Tm = xtime(Tm); (*state)[i][1] ^= Tm ^ Tmp ; + Tm = (*state)[i][2] ^ (*state)[i][3] ; Tm = xtime(Tm); (*state)[i][2] ^= Tm ^ Tmp ; + Tm = (*state)[i][3] ^ t ; Tm = xtime(Tm); (*state)[i][3] ^= Tm ^ Tmp ; + } +} + +#define Multiply(x, y) \ + ( ((y & 1) * x) ^ \ + ((y>>1 & 1) * xtime(x)) ^ \ + ((y>>2 & 1) * xtime(xtime(x))) ^ \ + ((y>>3 & 1) * xtime(xtime(xtime(x)))) ^ \ + ((y>>4 & 1) * xtime(xtime(xtime(xtime(x)))))) \ + + +static void Cipher(state_t* state, const uint8_t* RoundKey) +{ + uint8_t round = 0; + + AddRoundKey(0, state, RoundKey); + + for (round = 1; ; ++round) + { + SubBytes(state); + ShiftRows(state); + if (round == Nr) { + break; + } + MixColumns(state); + AddRoundKey(round, state, RoundKey); + } + AddRoundKey(Nr, state, RoundKey); +} + +void AES_CTR_xcrypt_buffer(struct AES_ctx* ctx, uint8_t* buf, size_t length) +{ + uint8_t buffer[AES_BLOCKLEN]; + + size_t i; + int bi; + for (i = 0, bi = AES_BLOCKLEN; i < length; ++i, ++bi) + { + if (bi == AES_BLOCKLEN) + { + + memcpy(buffer, ctx->Iv, AES_BLOCKLEN); + Cipher((state_t*)buffer,ctx->RoundKey); + + for (bi = (AES_BLOCKLEN - 1); bi >= 0; --bi) + { + if (ctx->Iv[bi] == 255) + { + ctx->Iv[bi] = 0; + continue; + } + ctx->Iv[bi] += 1; + break; + } + bi = 0; + } + + buf[i] = (buf[i] ^ buffer[bi]); + } +} diff --git a/src/nrf52/aes-256/tiny-aes.h b/src/nrf52/aes-256/tiny-aes.h new file mode 100644 index 00000000..eded2c77 --- /dev/null +++ b/src/nrf52/aes-256/tiny-aes.h @@ -0,0 +1,23 @@ +#ifndef _TINY_AES_H_ +#define _TINY_AES_H_ + +#include +#include + +#define AES_BLOCKLEN 16 // Block length in bytes - AES is 128b block only +// #define AES_KEYLEN 32 +#define AES_keyExpSize 240 + +struct AES_ctx +{ + uint8_t RoundKey[AES_keyExpSize]; + uint8_t Iv[AES_BLOCKLEN]; +}; + +void AES_init_ctx(struct AES_ctx* ctx, const uint8_t* key); +void AES_init_ctx_iv(struct AES_ctx* ctx, const uint8_t* key, const uint8_t* iv); +void AES_ctx_set_iv(struct AES_ctx* ctx, const uint8_t* iv); + +void AES_CTR_xcrypt_buffer(struct AES_ctx* ctx, uint8_t* buf, size_t length); + +#endif // _TINY_AES_H_