105 lines
1.4 KiB
C
105 lines
1.4 KiB
C
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#include "os.h"
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#include <libsec.h>
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void
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setupRC4state(RC4state *key, uint8_t *start, int n)
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{
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int t;
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int index2;
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uint8_t *state;
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uint8_t *p, *e, *sp, *se;
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state = key->state;
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se = &state[256];
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for(sp = state; sp < se; sp++)
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*sp = sp - state;
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key->x = 0;
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key->y = 0;
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index2 = 0;
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e = start + n;
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p = start;
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for(sp = state; sp < se; sp++)
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{
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t = *sp;
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index2 = (*p + t + index2) & 255;
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*sp = state[index2];
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state[index2] = t;
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if(++p >= e)
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p = start;
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}
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}
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void
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rc4(RC4state *key, uint8_t *p, int len)
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{
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int tx, ty;
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int x, y;
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uint8_t *state;
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uint8_t *e;
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x = key->x;
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y = key->y;
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state = &key->state[0];
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for(e = p + len; p < e; p++)
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{
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x = (x+1)&255;
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tx = state[x];
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y = (y+tx)&255;
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ty = state[y];
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state[x] = ty;
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state[y] = tx;
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*p ^= state[(tx+ty)&255];
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}
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key->x = x;
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key->y = y;
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}
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void
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rc4skip(RC4state *key, int len)
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{
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int tx, ty;
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int x, y;
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uint8_t *state;
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int i;
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x = key->x;
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y = key->y;
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state = &key->state[0];
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for(i=0; i<len; i++)
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{
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x = (x+1)&255;
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tx = state[x];
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y = (y+tx)&255;
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ty = state[y];
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state[x] = ty;
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state[y] = tx;
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}
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key->x = x;
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key->y = y;
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}
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void
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rc4back(RC4state *key, int len)
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{
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int tx, ty;
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int x, y;
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uint8_t *state;
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int i;
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x = key->x;
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y = key->y;
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state = &key->state[0];
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for(i=0; i<len; i++)
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{
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ty = state[x];
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tx = state[y];
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state[y] = ty;
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state[x] = tx;
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y = (y-tx)&255;
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x = (x-1)&255;
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}
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key->x = x;
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key->y = y;
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}
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