+++ /dev/null
-/* -*-c-*-
- *
- * $Id: dsarand.c,v 1.4 2004/04/08 01:36:15 mdw Exp $
- *
- * Random number generator for DSA
- *
- * (c) 1999 Straylight/Edgeware
- */
-
-/*----- Licensing notice --------------------------------------------------*
- *
- * This file is part of Catacomb.
- *
- * Catacomb is free software; you can redistribute it and/or modify
- * it under the terms of the GNU Library General Public License as
- * published by the Free Software Foundation; either version 2 of the
- * License, or (at your option) any later version.
- *
- * Catacomb is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU Library General Public License for more details.
- *
- * You should have received a copy of the GNU Library General Public
- * License along with Catacomb; if not, write to the Free
- * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
- * MA 02111-1307, USA.
- */
-
-/*----- Header files ------------------------------------------------------*/
-
-#include <stdarg.h>
-#include <string.h>
-
-#include <mLib/alloc.h>
-#include <mLib/bits.h>
-#include <mLib/sub.h>
-
-#include "dsarand.h"
-#include "grand.h"
-#include "sha.h"
-
-/*----- Main code ---------------------------------------------------------*/
-
-/* --- @STEP@ --- *
- *
- * Arguments: @dsarand *d@ = pointer to context
- *
- * Use: Increments the buffer by one, interpreting it as a big-endian
- * integer. Carries outside the integer are discarded.
- */
-
-#define STEP(d) do { \
- dsarand *_d = (d); \
- octet *_p = _d->p; \
- octet *_q = _p + _d->sz; \
- unsigned _c = 1; \
- while (_c && _q > _p) { \
- _c += *--_q; \
- *_q = U8(_c); \
- _c >>= 8; \
- } \
-} while (0)
-
-/* --- @dsarand_init@ --- *
- *
- * Arguments: @dsarand *d@ = pointer to context
- * @const void *p@ = pointer to seed buffer
- * @size_t sz@ = size of the buffer
- *
- * Returns: ---
- *
- * Use: Initializes a DSA random number generator.
- */
-
-void dsarand_init(dsarand *d, const void *p, size_t sz)
-{
- d->p = xmalloc(sz);
- d->sz = sz;
- d->passes = 1;
- if (p)
- memcpy(d->p, p, sz);
-}
-
-/* --- @dsarand_reseed@ --- *
- *
- * Arguments: @dsarand *d@ = pointer to context
- * @const void *p@ = pointer to seed buffer
- * @size_t sz@ = size of the buffer
- *
- * Returns: ---
- *
- * Use: Initializes a DSA random number generator.
- */
-
-void dsarand_reseed(dsarand *d, const void *p, size_t sz)
-{
- xfree(d->p);
- d->p = xmalloc(sz);
- d->sz = sz;
- d->passes = 1;
- if (p)
- memcpy(d->p, p, sz);
-}
-
-/* --- @dsarand_destroy@ --- *
- *
- * Arguments: @dsarand *d@ = pointer to context
- *
- * Returns: ---
- *
- * Use: Disposes of a DSA random number generation context.
- */
-
-void dsarand_destroy(dsarand *d)
-{
- xfree(d->p);
-}
-
-/* --- @dsarand_fill@ --- *
- *
- * Arguments: @dsarand *d@ = pointer to context
- * @void *p@ = pointer to output buffer
- * @size_t sz@ = size of output buffer
- *
- * Returns: ---
- *
- * Use: Fills an output buffer with pseudorandom data.
- *
- * Let %$p$% be the numerical value of the input buffer, and let
- * %$b$% be the number of bytes required. Let
- * %$z = \lceil b / 20 \rceil$% be the number of SHA outputs
- * required. Then the output of pass %$n$% is
- *
- * %$P_n = \sum_{0 \le i < z} 2^{160i} SHA(p + nz + i)$%
- * %${} \bmod 2^{8b}$%
- *
- * and the actual result in the output buffer is the XOR of all
- * of the output passes.
- *
- * The DSA procedure for choosing @q@ involves two passes with
- * %$z = 1$%; the procedure for choosing @p@ involves one pass
- * with larger %$z$%. This generalization of the DSA generation
- * procedure is my own invention but it seems relatively sound.
- */
-
-void dsarand_fill(dsarand *d, void *p, size_t sz)
-{
- octet *q = p;
- unsigned n = d->passes;
-
- /* --- Write out the first pass --- *
- *
- * This can write directly to the output buffer, so it's done differently
- * from the latter passes.
- */
-
- {
- size_t o = sz;
-
- while (o) {
- sha_ctx h;
-
- /* --- Hash the input buffer --- */
-
- sha_init(&h);
- sha_hash(&h, d->p, d->sz);
-
- /* --- If enough space, extract the hash output directly --- */
-
- if (o >= SHA_HASHSZ) {
- o -= SHA_HASHSZ;
- sha_done(&h, q + o);
- }
-
- /* --- Otherwise take the hash result out of line and copy it --- */
-
- else {
- octet hash[SHA_HASHSZ];
- sha_done(&h, hash);
- memcpy(q, hash + (SHA_HASHSZ - o), o);
- o = 0;
- }
-
- /* --- Step the input buffer --- */
-
- STEP(d);
- }
-
- /* --- Another pass has been done --- */
-
- n--;
- }
-
- /* --- Write out subsequent passes --- *
- *
- * The hash output has to be done offline, so this is slightly easier.
- */
-
- while (n) {
- size_t o = sz;
-
- while (o) {
- sha_ctx h;
- octet hash[SHA_HASHSZ];
- size_t n;
- octet *pp, *qq;
-
- /* --- Hash the input buffer --- */
-
- sha_init(&h);
- sha_hash(&h, d->p, d->sz);
- sha_done(&h, hash);
-
- /* --- Work out how much output is wanted --- */
-
- n = SHA_HASHSZ;
- if (n > o)
- n = o;
- o -= n;
-
- /* --- XOR the data out --- */
-
- for (pp = hash + (SHA_HASHSZ - n), qq = q + o;
- pp < hash + SHA_HASHSZ; pp++, qq++)
- *qq ^= *pp;
-
- /* --- Step the input buffer --- */
-
- STEP(d);
- }
-
- /* --- Another pass is done --- */
-
- n--;
- }
-}
-
-/*----- Generic pseudorandom-number generator interface -------------------*/
-
-static const grand_ops gops;
-
-typedef struct gctx {
- grand r;
- dsarand d;
-} gctx;
-
-static void gdestroy(grand *r)
-{
- gctx *g = (gctx *)r;
- dsarand_destroy(&g->d);
- DESTROY(g);
-}
-
-static int gmisc(grand *r, unsigned op, ...)
-{
- gctx *g = (gctx *)r;
- va_list ap;
- int rc = 0;
- va_start(ap, op);
-
- switch (op) {
- case GRAND_CHECK:
- switch (va_arg(ap, unsigned)) {
- case GRAND_CHECK:
- case GRAND_SEEDBLOCK:
- case GRAND_SEEDRAND:
- case DSARAND_PASSES:
- case DSARAND_SEEDSZ:
- case DSARAND_GETSEED:
- rc = 1;
- break;
- default:
- rc = 0;
- break;
- }
- break;
- case GRAND_SEEDBLOCK: {
- const void *p = va_arg(ap, const void *);
- size_t sz = va_arg(ap, size_t);
- dsarand_reseed(&g->d, p, sz);
- } break;
- case GRAND_SEEDRAND: {
- grand *rr = va_arg(ap, grand *);
- rr->ops->fill(rr, g->d.p, g->d.sz);
- } break;
- case DSARAND_PASSES:
- g->d.passes = va_arg(ap, unsigned);
- break;
- case DSARAND_SEEDSZ:
- rc = g->d.sz;
- break;
- case DSARAND_GETSEED:
- memcpy(va_arg(ap, void *), g->d.p, g->d.sz);
- break;
- default:
- GRAND_BADOP;
- break;
- }
-
- va_end(ap);
- return (rc);
-}
-
-static void gfill(grand *r, void *p, size_t sz)
-{
- gctx *g = (gctx *)r;
- dsarand_fill(&g->d, p, sz);
-}
-
-static const grand_ops gops = {
- "dsarand",
- 0, 0,
- gmisc, gdestroy,
- grand_word, grand_byte, grand_word, grand_range, gfill
-};
-
-/* --- @dsarand_create@ --- *
- *
- * Arguments: @const void *p@ = pointer to seed buffer
- * @size_t sz@ = size of seed buffer
- *
- * Returns: Pointer to a generic generator.
- *
- * Use: Constructs a generic generator interface over a Catacomb
- * entropy pool generator.
- */
-
-grand *dsarand_create(const void *p, size_t sz)
-{
- gctx *g = CREATE(gctx);
- g->r.ops = &gops;
- dsarand_init(&g->d, p, sz);
- return (&g->r);
-}
-
-/*----- That's all, folks -------------------------------------------------*/
~mdw / catacomb / blobdiff