aes.c

/* ==========================================================================
 * aes.c
 *
 * AES key schedule implementation for Interrogate
 *
 * Code by Sam Trenholme (http://www.samiam.org/rijndael.html) 
 *
 * Errors corrected and code modified for use in Interrogate by 
 * Carsten Maartmann-Moe <carmaa@gmail.com>
 * ==========================================================================
 */

#include <stdio.h>

#include "interrogate.h"

/* Log table using 0xe5 (229) as the generator */
unsigned char ltable[256] = {
    0x00, 0xff, 0xc8, 0x08, 0x91, 0x10, 0xd0, 0x36, 
    0x5a, 0x3e, 0xd8, 0x43, 0x99, 0x77, 0xfe, 0x18, 
    0x23, 0x20, 0x07, 0x70, 0xa1, 0x6c, 0x0c, 0x7f, 
    0x62, 0x8b, 0x40, 0x46, 0xc7, 0x4b, 0xe0, 0x0e, 
    0xeb, 0x16, 0xe8, 0xad, 0xcf, 0xcd, 0x39, 0x53, 
    0x6a, 0x27, 0x35, 0x93, 0xd4, 0x4e, 0x48, 0xc3, 
    0x2b, 0x79, 0x54, 0x28, 0x09, 0x78, 0x0f, 0x21, 
    0x90, 0x87, 0x14, 0x2a, 0xa9, 0x9c, 0xd6, 0x74, 
    0xb4, 0x7c, 0xde, 0xed, 0xb1, 0x86, 0x76, 0xa4, 
    0x98, 0xe2, 0x96, 0x8f, 0x02, 0x32, 0x1c, 0xc1, 
    0x33, 0xee, 0xef, 0x81, 0xfd, 0x30, 0x5c, 0x13, 
    0x9d, 0x29, 0x17, 0xc4, 0x11, 0x44, 0x8c, 0x80, 
    0xf3, 0x73, 0x42, 0x1e, 0x1d, 0xb5, 0xf0, 0x12, 
    0xd1, 0x5b, 0x41, 0xa2, 0xd7, 0x2c, 0xe9, 0xd5, 
    0x59, 0xcb, 0x50, 0xa8, 0xdc, 0xfc, 0xf2, 0x56, 
    0x72, 0xa6, 0x65, 0x2f, 0x9f, 0x9b, 0x3d, 0xba, 
    0x7d, 0xc2, 0x45, 0x82, 0xa7, 0x57, 0xb6, 0xa3, 
    0x7a, 0x75, 0x4f, 0xae, 0x3f, 0x37, 0x6d, 0x47, 
    0x61, 0xbe, 0xab, 0xd3, 0x5f, 0xb0, 0x58, 0xaf, 
    0xca, 0x5e, 0xfa, 0x85, 0xe4, 0x4d, 0x8a, 0x05, 
    0xfb, 0x60, 0xb7, 0x7b, 0xb8, 0x26, 0x4a, 0x67, 
    0xc6, 0x1a, 0xf8, 0x69, 0x25, 0xb3, 0xdb, 0xbd, 
    0x66, 0xdd, 0xf1, 0xd2, 0xdf, 0x03, 0x8d, 0x34, 
    0xd9, 0x92, 0x0d, 0x63, 0x55, 0xaa, 0x49, 0xec, 
    0xbc, 0x95, 0x3c, 0x84, 0x0b, 0xf5, 0xe6, 0xe7, 
    0xe5, 0xac, 0x7e, 0x6e, 0xb9, 0xf9, 0xda, 0x8e, 
    0x9a, 0xc9, 0x24, 0xe1, 0x0a, 0x15, 0x6b, 0x3a, 
    0xa0, 0x51, 0xf4, 0xea, 0xb2, 0x97, 0x9e, 0x5d, 
    0x22, 0x88, 0x94, 0xce, 0x19, 0x01, 0x71, 0x4c, 
    0xa5, 0xe3, 0xc5, 0x31, 0xbb, 0xcc, 0x1f, 0x2d, 
    0x3b, 0x52, 0x6f, 0xf6, 0x2e, 0x89, 0xf7, 0xc0, 
    0x68, 0x1b, 0x64, 0x04, 0x06, 0xbf, 0x83, 0x38 };

/* Anti-log table: */
unsigned char atable[256] = {
    0x01, 0xe5, 0x4c, 0xb5, 0xfb, 0x9f, 0xfc, 0x12, 
    0x03, 0x34, 0xd4, 0xc4, 0x16, 0xba, 0x1f, 0x36, 
    0x05, 0x5c, 0x67, 0x57, 0x3a, 0xd5, 0x21, 0x5a, 
    0x0f, 0xe4, 0xa9, 0xf9, 0x4e, 0x64, 0x63, 0xee, 
    0x11, 0x37, 0xe0, 0x10, 0xd2, 0xac, 0xa5, 0x29, 
    0x33, 0x59, 0x3b, 0x30, 0x6d, 0xef, 0xf4, 0x7b, 
    0x55, 0xeb, 0x4d, 0x50, 0xb7, 0x2a, 0x07, 0x8d, 
    0xff, 0x26, 0xd7, 0xf0, 0xc2, 0x7e, 0x09, 0x8c, 
    0x1a, 0x6a, 0x62, 0x0b, 0x5d, 0x82, 0x1b, 0x8f, 
    0x2e, 0xbe, 0xa6, 0x1d, 0xe7, 0x9d, 0x2d, 0x8a, 
    0x72, 0xd9, 0xf1, 0x27, 0x32, 0xbc, 0x77, 0x85, 
    0x96, 0x70, 0x08, 0x69, 0x56, 0xdf, 0x99, 0x94, 
    0xa1, 0x90, 0x18, 0xbb, 0xfa, 0x7a, 0xb0, 0xa7, 
    0xf8, 0xab, 0x28, 0xd6, 0x15, 0x8e, 0xcb, 0xf2, 
    0x13, 0xe6, 0x78, 0x61, 0x3f, 0x89, 0x46, 0x0d, 
    0x35, 0x31, 0x88, 0xa3, 0x41, 0x80, 0xca, 0x17, 
    0x5f, 0x53, 0x83, 0xfe, 0xc3, 0x9b, 0x45, 0x39, 
    0xe1, 0xf5, 0x9e, 0x19, 0x5e, 0xb6, 0xcf, 0x4b, 
    0x38, 0x04, 0xb9, 0x2b, 0xe2, 0xc1, 0x4a, 0xdd, 
    0x48, 0x0c, 0xd0, 0x7d, 0x3d, 0x58, 0xde, 0x7c, 
    0xd8, 0x14, 0x6b, 0x87, 0x47, 0xe8, 0x79, 0x84, 
    0x73, 0x3c, 0xbd, 0x92, 0xc9, 0x23, 0x8b, 0x97, 
    0x95, 0x44, 0xdc, 0xad, 0x40, 0x65, 0x86, 0xa2, 
    0xa4, 0xcc, 0x7f, 0xec, 0xc0, 0xaf, 0x91, 0xfd, 
    0xf7, 0x4f, 0x81, 0x2f, 0x5b, 0xea, 0xa8, 0x1c, 
    0x02, 0xd1, 0x98, 0x71, 0xed, 0x25, 0xe3, 0x24, 
    0x06, 0x68, 0xb3, 0x93, 0x2c, 0x6f, 0x3e, 0x6c, 
    0x0a, 0xb8, 0xce, 0xae, 0x74, 0xb1, 0x42, 0xb4, 
    0x1e, 0xd3, 0x49, 0xe9, 0x9c, 0xc8, 0xc6, 0xc7, 
    0x22, 0x6e, 0xdb, 0x20, 0xbf, 0x43, 0x51, 0x52, 
    0x66, 0xb2, 0x76, 0x60, 0xda, 0xc5, 0xf3, 0xf6, 
    0xaa, 0xcd, 0x9a, 0xa0, 0x75, 0x54, 0x0e, 0x01 };

/* Circular rotate */
void rotate(unsigned char *in) {
    unsigned char a,c;
    a = in[0];
    for(c=0;c<3;c++)
        in[c] = in[c + 1];
    in[3] = a;
    return;
}

/* Calculate the rcon used in key expansion */
unsigned char rcon(unsigned char in) {
    unsigned char c=1;
    if(in == 0)
        return 0;
    while(in != 1) {
        c = gmul(c,2);
        in--;
    }
    return c;
}

/* Galois field multiplication */
unsigned char gmul(unsigned char a, unsigned char b) {
    int s;
    int q;
    int z = 0;
    s = ltable[a] + ltable[b];
    s %= 255;
    /* Get the antilog */
    s = atable[s];
    /* Now, we have some fancy code that returns 0 if either
     a or b are zero; we write the code this way so that the
     code will (hopefully) run at a constant speed in order to
     minimize the risk of timing attacks */
    q = s;
    if(a == 0) {
        s = z;
    } else {
        s = q;
    }
    if(b == 0) {
        s = z;
    } else {
        q = z;
    }
    return s;
}

/* Inverse Galois field multiplication */
unsigned char gmul_inverse(unsigned char in) {
    /* 0 is self inverting */
    if(in == 0)
        return 0;
    else
        return atable[(255 - ltable[in])];
}

/* Calculate the s-box for a given number */
unsigned char sbox(unsigned char in) {
    unsigned char c, s, x;
    s = x = gmul_inverse(in);
    for(c = 0; c < 4; c++) {
        /* One bit circular rotate to the left */
        s = (s << 1) | (s >> 7);
        /* xor with x */
        x ^= s;
    }
    x ^= 99; /* 0x63 */
    return x;
}

/* This is the core key expansion, which, given a 4-byte value,
 * does some scrambling */
void schedule_core(unsigned char *in, unsigned char i) {
    unsigned char a;
    /* Rotate the input 8 bits to the left */
    rotate(in);
    /* Apply Rijndael's s-box on all 4 bytes */
    for(a = 0; a < 4; a++)
        in[a] = sbox(in[a]);
    /* On just the first byte, add 2^i to the byte */
    in[0] ^= rcon(i);
}

/* Key expansion function for 128-bit keys */
void expand_key(unsigned char *in) {
    unsigned char t[4];
    /* c is 16 because the first sub-key is the user-supplied key */
    unsigned char c = 16;
    unsigned char i = 1;
    unsigned char a;

    /* We need 11 sets of sixteen bytes each for 128-bit mode */
    while(c < 176) {
        /* Copy the temporary variable over from the last 4-byte
         * block */
        for(a = 0; a < 4; a++)
            t[a] = in[a + c - 4];
        /* Every four blocks (of four bytes),
         * do a complex calculation */
        if(c % 16 == 0) {
            schedule_core(t,i);
            i++;
        }
        for(a = 0; a < 4; a++) {
            in[c] = in[c - 16] ^ t[a];
            c++;
        }
    }
}

/* Key expansion function for 192-bit keys */
void expand_key_192(unsigned char *in) {
    unsigned char t[4];
    unsigned char c = 24;
    unsigned char i = 1;
    unsigned char a;
    while(c < 208) {
        /* Copy the temporary variable over */
        for(a = 0; a < 4; a++)
            t[a] = in[a + c - 4];
        /* Every six sets, do a complex calculation */
        if(c % 24 == 0) {
            schedule_core(t,i);
            i++;
        }
        for(a = 0; a < 4; a++) {
            in[c] = in[c - 24] ^ t[a];
            c++;
        }
    }
}

/* Key expansion function for 256-bit keys */
void expand_key_256(unsigned char *in) {
    unsigned char t[4];
    unsigned char c = 32;
    unsigned char i = 1;
    unsigned char a;
    while(c < 240) {
        /* Copy the temporary variable over */
        for(a = 0; a < 4; a++)
            t[a] = in[a + c - 4];
        /* Every eight sets, do a complex calculation */
        if(c % 32 == 0) {
            schedule_core(t,i);
            i++;
        }
        /* For 256-bit keys, we add an extra sbox to the
         * calculation */
        if(c % 32 == 16) {
            for(a = 0; a < 4; a++)
                t[a] = sbox(t[a]);
        }
        for(a = 0; a < 4; a++) {
            in[c] = in[c - 32] ^ t[a];
            c++;
        }
    }
}