Test Case: c-instruct-193

  1#include <string.h>  2#include <stdint.h>  3​  4static const unsigned char sbox[256] = {  5    0x63,0x7c,0x77,0x7b,0xf2,0x6b,0x6f,0xc5,0x30,0x01,0x67,0x2b,0xfe,0xd7,0xab,0x76,  6    0xca,0x82,0xc9,0x7d,0xfa,0x59,0x47,0xf0,0xad,0xd4,0xa2,0xaf,0x9c,0xa4,0x72,0xc0,  7    0xb7,0xfd,0x93,0x26,0x36,0x3f,0xf7,0xcc,0x34,0xa5,0xe5,0xf1,0x71,0xd8,0x31,0x15,  8    0x04,0xc7,0x23,0xc3,0x18,0x96,0x05,0x9a,0x07,0x12,0x80,0xe2,0xeb,0x27,0xb2,0x75,  9    0x09,0x83,0x2c,0x1a,0x1b,0x6e,0x5a,0xa0,0x52,0x3b,0xd6,0xb3,0x29,0xe3,0x2f,0x84, 10    0x53,0xd1,0x00,0xed,0x20,0xfc,0xb1,0x5b,0x6a,0xcb,0xbe,0x39,0x4a,0x4c,0x58,0xcf, 11    0xd0,0xef,0xaa,0xfb,0x43,0x4d,0x33,0x85,0x45,0xf9,0x02,0x7f,0x50,0x3c,0x9f,0xa8, 12    0x51,0xa3,0x40,0x8f,0x92,0x9d,0x38,0xf5,0xbc,0xb6,0xda,0x21,0x10,0xff,0xf3,0xd2, 13    0xcd,0x0c,0x13,0xec,0x5f,0x97,0x44,0x17,0xc4,0xa7,0x7e,0x3d,0x64,0x5d,0x19,0x73, 14    0x60,0x81,0x4f,0xdc,0x22,0x2a,0x90,0x88,0x46,0xee,0xb8,0x14,0xde,0x5e,0x0b,0xdb, 15    0xe0,0x32,0x3a,0x0a,0x49,0x06,0x24,0x5c,0xc2,0xd3,0xac,0x62,0x91,0x95,0xe4,0x79, 16    0xe7,0xc8,0x37,0x6d,0x8d,0xd5,0x4e,0xa9,0x6c,0x56,0xf4,0xea,0x65,0x7a,0xae,0x08, 17    0xba,0x78,0x25,0x2e,0x1c,0xa6,0xb4,0xc6,0xe8,0xdd,0x74,0x1f,0x4b,0xbd,0x8b,0x8a, 18    0x70,0x3e,0xb5,0x66,0x48,0x03,0xf6,0x0e,0x61,0x35,0x57,0xb9,0x86,0xc1,0x1d,0x9e, 19    0xe1,0xf8,0x98,0x11,0x69,0xd9,0x8e,0x94,0x9b,0x1e,0x87,0xe9,0xce,0x55,0x28,0xdf, 20    0x8c,0xa1,0x89,0x0d,0xbf,0xe6,0x42,0x68,0x41,0x99,0x2d,0x0f,0xb0,0x54,0xbb,0x16 21}; 22​ 23static unsigned char xtime(unsigned char a) { 24    return (a << 1) ^ ((a >> 7) ? 0x1b : 0); 25} 26​ 27static unsigned char gmul(unsigned char a, unsigned char b) { 28    unsigned char result = 0; 29    unsigned char temp = a; 30    for (int i = 0; i < 8; i++) { 31        if (b & 1) result ^= temp; 32        temp = xtime(temp); 33        b >>= 1; 34    } 35    return result; 36} 37​ 38static void aes_encrypt_block(const unsigned char *in, unsigned char *out, const unsigned char *key_schedule) { 39    unsigned char state[16]; 40    memcpy(state, in, 16); 41​ 42    for (int i = 0; i < 16; i++) { 43        state[i] ^= key_schedule[i]; 44    } 45​ 46    for (int round = 1; round <= 10; round++) { 47        for (int i = 0; i < 16; i++) { 48            state[i] = sbox[state[i]]; 49        } 50​ 51        unsigned char mat[4][4]; 52        for (int col = 0; col < 4; col++) 53            for (int row = 0; row < 4; row++) 54                mat[row][col] = state[row + 4*col]; 55        unsigned char shifted[4][4]; 56        for (int row = 0; row < 4; row++) 57            for (int col = 0; col < 4; col++) 58                shifted[row][col] = mat[row][(col + row) % 4]; 59        for (int col = 0; col < 4; col++) 60            for (int row = 0; row < 4; row++) 61                state[row + 4*col] = shifted[row][col]; 62​ 63        if (round < 10) { 64            for (int col = 0; col < 4; col++) { 65                unsigned char a[4]; 66                for (int row = 0; row < 4; row++) 67                    a[row] = state[row + 4*col]; 68                state[0 + 4*col] = gmul(2,a[0]) ^ gmul(3,a[1]) ^ a[2] ^ a[3]; 69                state[1 + 4*col] = a[0] ^ gmul(2,a[1]) ^ gmul(3,a[2]) ^ a[3]; 70                state[2 + 4*col] = a[0] ^ a[1] ^ gmul(2,a[2]) ^ gmul(3,a[3]); 71                state[3 + 4*col] = gmul(3,a[0]) ^ a[1] ^ a[2] ^ gmul(2,a[3]); 72            } 73        } 74​ 75        const unsigned char *round_key = key_schedule + 16 * round; 76        for (int i = 0; i < 16; i++) { 77            state[i] ^= round_key[i]; 78        } 79    } 80​ 81    memcpy(out, state, 16); 82} 83​ 84void aes128_ctr_encrypt(unsigned char *test_vector, const unsigned char *key_schedule, size_t length) { 85    unsigned char counter[16] = {0}; 86    unsigned char keystream[16]; 87    size_t i = 0; 88​ 89    while (i < length) { 90        aes_encrypt_block(counter, keystream, key_schedule); 91​ 92        size_t blocklen = (length - i > 16) ? 16 : (length - i); 93        for (size_t j = 0; j < blocklen; j++) { 94            test_vector[i + j] ^= keystream[j]; 95        } 96        i += blocklen; 97​ 98        int k = 15; 99        while (k >= 0) {100            counter[k]++;101            if (counter[k] != 0) break;102            k--;103        }104    }105}

1. WARNINGLine 40

   Calls to memcpy that write to a stack buffer

  1#include <stdint.h>  2#include <stddef.h>  3#include <string.h>  4​  5// AES-128 S-box and round constants  6static const uint8_t sbox[256] = {  7    0x63,0x7c,0x77,0x7b,0xf2,0x6b,0x6f,0xc5,0x30,0x01,0x67,0x2b,0xfe,0xd7,0xab,0x76,  8    0xca,0x82,0xc9,0x7d,0xfa,0x59,0x47,0xf0,0xad,0xd4,0xa2,0xaf,0x9c,0xa4,0x72,0xc0,  9    0xb7,0xfd,0x93,0x26,0x36,0x3f,0xf7,0xcc,0x34,0xa5,0xe5,0xf1,0x71,0xd8,0x31,0x15, 10    0x04,0xc7,0x23,0xc3,0x18,0x96,0x05,0x9a,0x07,0x12,0x80,0xe2,0xeb,0x27,0xb2,0x75, 11    0x09,0x83,0x2c,0x1a,0x1b,0x6e,0x5a,0xa0,0x52,0x3b,0xd6,0xb3,0x29,0xe3,0x2f,0x84, 12    0x53,0xd1,0x00,0xed,0x20,0xfc,0xb1,0x5b,0x6a,0xcb,0xbe,0x39,0x4a,0x4c,0x58,0xcf, 13    0xd0,0xef,0xaa,0xfb,0x43,0x4d,0x33,0x85,0x45,0xf9,0x02,0x7f,0x50,0x3c,0x9f,0xa8, 14    0x51,0xa3,0x40,0x8f,0x92,0x9d,0x38,0xf5,0xbc,0xb6,0xda,0x21,0x10,0xff,0xf3,0xd2, 15    0xcd,0x0c,0x13,0xec,0x5f,0x97,0x44,0x17,0xc4,0xa7,0x7e,0x3d,0x64,0x5d,0x19,0x73, 16    0x60,0x81,0x4f,0xdc,0x22,0x2a,0x90,0x88,0x46,0xee,0xb8,0x14,0xde,0x5e,0x0b,0xdb, 17    0xe0,0x32,0x3a,0x0a,0x49,0x06,0x24,0x5c,0xc2,0xd3,0xac,0x62,0x91,0x95,0xe4,0x79, 18    0xe7,0xc8,0x37,0x6d,0x8d,0xd5,0x4e,0xa9,0x6c,0x56,0xf4,0xea,0x65,0x7a,0xae,0x08, 19    0xba,0x78,0x25,0x2e,0x1c,0xa6,0xb4,0xc6,0xe8,0xdd,0x74,0x1f,0x4b,0xbd,0x8b,0x8a, 20    0x70,0x3e,0xb5,0x66,0x48,0x03,0xf6,0x0e,0x61,0x35,0x57,0xb9,0x86,0xc1,0x1d,0x9e, 21    0xe1,0xf8,0x98,0x11,0x69,0xd9,0x8e,0x94,0x9b,0x1e,0x87,0xe9,0xce,0x55,0x28,0xdf, 22    0x8c,0xa1,0x89,0x0d,0xbf,0xe6,0x42,0x68,0x41,0x99,0x2d,0x0f,0xb0,0x54,0xbb,0x16 23}; 24​ 25static const uint8_t rcon[11] = { 26    0x00, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36 27}; 28​ 29// XOR two 16-byte blocks 30static inline void xor_block(uint8_t *out, const uint8_t *a, const uint8_t *b) { 31    for (int i = 0; i < 16; i++) out[i] = a[i] ^ b[i]; 32} 33​ 34// Increment a 128-bit counter (big-endian) 35static inline void increment_counter(uint8_t *counter) { 36    for (int i = 15; i >= 0; i--) { 37        if (++counter[i] != 0) break; 38    } 39} 40​ 41// AES-128 encryption of a single block using expanded key (176 bytes) 42static void aes128_encrypt_block(const uint8_t in[16], uint8_t out[16], const uint8_t rk[176]) { 43    uint8_t state[16]; 44    memcpy(state, in, 16); 45​ 46    // AddRoundKey (first) 47    for (int i = 0; i < 16; i++) state[i] ^= rk[i]; 48​ 49    for (int round = 1; round <= 10; round++) { 50        // SubBytes 51        for (int i = 0; i < 16; i++) state[i] = sbox[state[i]]; 52​ 53        // ShiftRows 54        uint8_t t; 55        // Row1: left shift by 1 56        t = state[1]; state[1] = state[5]; state[5] = state[9]; state[9] = state[13]; state[13] = t; 57        // Row2: left shift by 2 58        t = state[2]; state[2] = state[10]; state[10] = t; 59        t = state[6]; state[6] = state[14]; state[14] = t; 60        // Row3: left shift by 3 (i.e. right shift by 1) 61        t = state[3]; state[3] = state[15]; state[15] = state[11]; state[11] = state[7]; state[7] = t; 62​ 63        // MixColumns (except last round) 64        if (round != 10) { 65            for (int col = 0; col < 4; col++) { 66                uint8_t a0 = state[col*4]; 67                uint8_t a1 = state[col*4+1]; 68                uint8_t a2 = state[col*4+2]; 69                uint8_t a3 = state[col*4+3]; 70                // Galois field multiplication by 2, 3, 1, 1 71                uint8_t m0 = (a0 << 1) ^ (0x1b & (a0 >> 7)); 72                uint8_t m1 = (a1 << 1) ^ (0x1b & (a1 >> 7)); 73                uint8_t m2 = (a2 << 1) ^ (0x1b & (a2 >> 7)); 74                uint8_t m3 = (a3 << 1) ^ (0x1b & (a3 >> 7)); 75                state[col*4]   = m0 ^ (m1 ^ a1) ^ a2 ^ a3; 76                state[col*4+1] = a0 ^ m1 ^ (m2 ^ a2) ^ a3; 77                state[col*4+2] = a0 ^ a1 ^ m2 ^ (m3 ^ a3); 78                state[col*4+3] = (m0 ^ a0) ^ a1 ^ a2 ^ m3; 79            } 80        } 81​ 82        // AddRoundKey 83        for (int i = 0; i < 16; i++) state[i] ^= rk[round*16 + i]; 84    } 85​ 86    memcpy(out, state, 16); 87} 88​ 89// Main CTR encryption function: 90// test_vector: first 16 bytes = initial counter, then plaintext. 91// key_schedule: 176 bytes of AES-128 expanded key (big-endian words) 92// length: total length of test_vector (includes 16-byte counter) 93void aes128_ctr_encrypt(uint8_t *test_vector, const uint8_t *key_schedule, size_t length) { 94    if (length < 16) return; // minimum: counter + at least 0 plaintext bytes 95​ 96    uint8_t counter[16]; 97    memcpy(counter, test_vector, 16);                // initial counter from first 16 bytes 98    size_t plain_len = length - 16;                  // remaining bytes are plaintext 99    uint8_t *plain = test_vector + 16;               // plaintext area will be overwritten100​101    uint8_t keystream[16];102    size_t offset = 0;103​104    while (plain_len > 0) {105        aes128_encrypt_block(counter, keystream, key_schedule);106        size_t chunk = (plain_len < 16) ? plain_len : 16;107        for (size_t i = 0; i < chunk; i++) {108            plain[offset + i] ^= keystream[i];       // XOR to produce ciphertext109        }110        increment_counter(counter);111        offset += chunk;112        plain_len -= chunk;113    }114}

1. WARNINGLines 44 · 97

   Calls to memcpy that write to a stack buffer