ref: b540a22eb0c287398e21358d6b66c8e544001f77
dir: /sys/src/libsec/port/chacha.c/
/* Adapted from chacha-merged.c version 20080118 D. J. Bernstein Public domain. modified for use in Plan 9 and Inferno (no algorithmic changes), and including the changes to block number and nonce defined in RFC7539 */ #include "os.h" #include <libsec.h> enum{ Blockwords= ChachaBsize/sizeof(u32int) }; /* little-endian data order */ #define GET4(p) ((p)[0]|((p)[1]<<8)|((p)[2]<<16)|((p)[3]<<24)) #define PUT4(p,v) (p)[0]=(v);(p)[1]=(v)>>8;(p)[2]=(v)>>16;(p)[3]=(v)>>24 #define ROTATE(v,c) ((u32int)((v) << (c)) | ((v) >> (32 - (c)))) #define QUARTERROUND(ia,ib,ic,id) { \ u32int a, b, c, d, t; \ a = x[ia]; b = x[ib]; c = x[ic]; d = x[id]; \ a += b; t = d^a; d = ROTATE(t,16); \ c += d; t = b^c; b = ROTATE(t,12); \ a += b; t = d^a; d = ROTATE(t, 8); \ c += d; t = b^c; b = ROTATE(t, 7); \ x[ia] = a; x[ib] = b; x[ic] = c; x[id] = d; \ } #define ENCRYPT(s, x, y, d) {\ u32int v; \ uchar *sp, *dp; \ sp = (s); \ v = GET4(sp); \ v ^= (x)+(y); \ dp = (d); \ PUT4(dp, v); \ } static uchar sigma[16] = "expand 32-byte k"; static uchar tau[16] = "expand 16-byte k"; static void load(u32int *d, uchar *s, int nw) { int i; for(i = 0; i < nw; i++, s+=4) d[i] = GET4(s); } void setupChachastate(Chachastate *s, uchar *key, ulong keylen, uchar *iv, ulong ivlen, int rounds) { if(keylen != 256/8 && keylen != 128/8) sysfatal("invalid chacha key length"); if(ivlen != 96/8 && ivlen != 64/8) sysfatal("invalid chacha iv length"); if(rounds == 0) rounds = 20; s->rounds = rounds; if(keylen == 256/8) { /* recommended */ load(&s->input[0], sigma, 4); load(&s->input[4], key, 8); }else{ load(&s->input[0], tau, 4); load(&s->input[4], key, 4); load(&s->input[8], key, 4); } s->ivwords = ivlen/sizeof(u32int); s->input[12] = 0; s->input[13] = 0; if(iv == nil){ s->input[14] = 0; s->input[15] = 0; }else chacha_setiv(s, iv); } void chacha_setiv(Chachastate *s, uchar *iv) { load(&s->input[16 - s->ivwords], iv, s->ivwords); } void chacha_setblock(Chachastate *s, u64int blockno) { s->input[12] = blockno; if(s->ivwords == 2) s->input[13] = blockno>>32; } static void dorounds(u32int x[Blockwords], int rounds) { for(; rounds > 0; rounds -= 2) { QUARTERROUND(0, 4, 8,12) QUARTERROUND(1, 5, 9,13) QUARTERROUND(2, 6,10,14) QUARTERROUND(3, 7,11,15) QUARTERROUND(0, 5,10,15) QUARTERROUND(1, 6,11,12) QUARTERROUND(2, 7, 8,13) QUARTERROUND(3, 4, 9,14) } } static void encryptblock(Chachastate *s, uchar *src, uchar *dst) { u32int x[Blockwords]; int i; x[0] = s->input[0]; x[1] = s->input[1]; x[2] = s->input[2]; x[3] = s->input[3]; x[4] = s->input[4]; x[5] = s->input[5]; x[6] = s->input[6]; x[7] = s->input[7]; x[8] = s->input[8]; x[9] = s->input[9]; x[10] = s->input[10]; x[11] = s->input[11]; x[12] = s->input[12]; x[13] = s->input[13]; x[14] = s->input[14]; x[15] = s->input[15]; dorounds(x, s->rounds); for(i=0; i<nelem(x); i+=4){ ENCRYPT(src, x[i], s->input[i], dst); ENCRYPT(src+4, x[i+1], s->input[i+1], dst+4); ENCRYPT(src+8, x[i+2], s->input[i+2], dst+8); ENCRYPT(src+12, x[i+3], s->input[i+3], dst+12); src += 16; dst += 16; } if(++s->input[12] == 0 && s->ivwords == 2) s->input[13]++; } void chacha_encrypt2(uchar *src, uchar *dst, ulong bytes, Chachastate *s) { uchar tmp[ChachaBsize]; for(; bytes >= ChachaBsize; bytes -= ChachaBsize){ encryptblock(s, src, dst); src += ChachaBsize; dst += ChachaBsize; } if(bytes > 0){ memmove(tmp, src, bytes); encryptblock(s, tmp, tmp); memmove(dst, tmp, bytes); } } void chacha_encrypt(uchar *buf, ulong bytes, Chachastate *s) { chacha_encrypt2(buf, buf, bytes, s); }