| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * Generalized version of KCDSA |
| 4 | * |
| 5 | * (c) 2004 Straylight/Edgeware |
| 6 | */ |
| 7 | |
| 8 | /*----- Licensing notice --------------------------------------------------* |
| 9 | * |
| 10 | * This file is part of Catacomb. |
| 11 | * |
| 12 | * Catacomb is free software; you can redistribute it and/or modify |
| 13 | * it under the terms of the GNU Library General Public License as |
| 14 | * published by the Free Software Foundation; either version 2 of the |
| 15 | * License, or (at your option) any later version. |
| 16 | * |
| 17 | * Catacomb is distributed in the hope that it will be useful, |
| 18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 20 | * GNU Library General Public License for more details. |
| 21 | * |
| 22 | * You should have received a copy of the GNU Library General Public |
| 23 | * License along with Catacomb; if not, write to the Free |
| 24 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
| 25 | * MA 02111-1307, USA. |
| 26 | */ |
| 27 | |
| 28 | /*----- Header files ------------------------------------------------------*/ |
| 29 | |
| 30 | #include "gkcdsa.h" |
| 31 | #include "group.h" |
| 32 | #include "ghash.h" |
| 33 | #include "mpbarrett.h" |
| 34 | #include "mprand.h" |
| 35 | |
| 36 | /*----- Main code ---------------------------------------------------------*/ |
| 37 | |
| 38 | /* --- @gkcdsa_beginhash@ --- * |
| 39 | * |
| 40 | * Arguments: @const gkcdsa *c@ = pointer to the context structure |
| 41 | * |
| 42 | * Returns: A hashing context for you to hash the message. |
| 43 | * |
| 44 | * Use: Initializes a hash function correctly for you to hash a |
| 45 | * message. Requires @h@, @g@ and @p@. |
| 46 | */ |
| 47 | |
| 48 | ghash *gkcdsa_beginhash(const gkcdsa *c) |
| 49 | { |
| 50 | ghash *h = GH_INIT(c->h); |
| 51 | mp *v = G_TOINT(c->g, MP_NEW, c->p); |
| 52 | size_t sz = c->h->bufsz; |
| 53 | void *p = xmalloc(sz); |
| 54 | if (/*ouch*/ !v) memset(p, 0, sz); |
| 55 | else mp_storeb(v, p, sz); |
| 56 | GH_HASH(h, p, sz); |
| 57 | mp_drop(v); xfree(p); |
| 58 | return (h); |
| 59 | } |
| 60 | |
| 61 | /* --- @gkcdsa_endhash@ --- * |
| 62 | * |
| 63 | * Arguments: @const gkcdsa *c@ = pointer to the context structure |
| 64 | * @ghash *h@ = the hashing context |
| 65 | * |
| 66 | * Returns: --- |
| 67 | * |
| 68 | * Use: Does any final thing that KCDSA wants to do when hashing a |
| 69 | * message. (Actually, there's nothing.) The hashing context |
| 70 | * isn't finalized. |
| 71 | */ |
| 72 | |
| 73 | void gkcdsa_endhash(const gkcdsa *c, ghash *h) { ; } |
| 74 | |
| 75 | /* --- @hashge@ --- * |
| 76 | * |
| 77 | * Arguments: @group *g@ = abstract group |
| 78 | * @const gchash *hc@ = hash class |
| 79 | * @ge *w@ = a group element |
| 80 | * |
| 81 | * Returns: A hash context, with the hash of @w@ in it. |
| 82 | */ |
| 83 | |
| 84 | static ghash *hashge(group *g, const gchash *hc, ge *w) |
| 85 | { |
| 86 | ghash *h; |
| 87 | size_t sz; |
| 88 | void *p; |
| 89 | buf b; |
| 90 | int rc; |
| 91 | |
| 92 | sz = hc->hashsz; |
| 93 | if (sz < g->noctets) |
| 94 | sz = g->noctets; |
| 95 | p = xmalloc(sz); |
| 96 | buf_init(&b, p, sz); |
| 97 | rc = G_TORAW(g, &b, w); |
| 98 | assert(rc == 0); |
| 99 | h = GH_INIT(hc); |
| 100 | GH_HASH(h, BBASE(&b), BLEN(&b)); |
| 101 | xfree(p); |
| 102 | return (h); |
| 103 | } |
| 104 | |
| 105 | /* --- @gkcdsa_sign@ --- * |
| 106 | * |
| 107 | * Arguments: @const gkcdsa *c@ = my context structure |
| 108 | * @gkcdsa_sig *s@ = where to put the signature (initialized) |
| 109 | * @const void *m@ = pointer to message hash |
| 110 | * @mp *k@ = random exponent for this message or null |
| 111 | * |
| 112 | * Returns: --- |
| 113 | * |
| 114 | * Use: Signs a message. Requires @g@, @u@, @h@, and @r@ if @k@ is |
| 115 | * null. This is a better idea than inventing @k@ yourself. |
| 116 | */ |
| 117 | |
| 118 | void gkcdsa_sign(const gkcdsa *c, gkcdsa_sig *s, const void *m, mp *k) |
| 119 | { |
| 120 | group *g = c->g; |
| 121 | mp *x, *y; |
| 122 | ge *z = G_CREATE(g); |
| 123 | size_t hsz = c->h->hashsz; |
| 124 | ghash *h; |
| 125 | |
| 126 | if (k) { MP_COPY(k); goto have_k; } |
| 127 | new_k: |
| 128 | k = mprand_range(k, g->r, c->r, 0); |
| 129 | have_k: |
| 130 | if (MP_ZEROP(k)) goto new_k; |
| 131 | G_EXP(g, z, g->g, k); |
| 132 | if (!s->r) s->r = xmalloc(hsz); |
| 133 | h = hashge(g, c->h, z); GH_DONE(h, s->r); |
| 134 | |
| 135 | x = mp_loadb(s->s, m, hsz); |
| 136 | y = mp_loadb(MP_NEW, s->r, hsz); |
| 137 | x = mp_xor(x, x, y); |
| 138 | mp_div(0, &x, x, g->r); |
| 139 | x = mp_sub(x, g->r, x); |
| 140 | x = mp_add(x, x, k); |
| 141 | if (MP_CMP(x, >=, g->r)) x = mp_sub(x, x, g->r); |
| 142 | x = mp_mul(x, x, c->u); mp_div(0, &x, x, g->r); |
| 143 | s->s = x; |
| 144 | mp_drop(k); mp_drop(y); GH_DESTROY(h); G_DESTROY(g, z); |
| 145 | } |
| 146 | |
| 147 | /* --- @gkcdsa_verify@ --- * |
| 148 | * |
| 149 | * Arguments: @const gkcdsa *c@ = my context structure |
| 150 | * @const gkcdsa_sig *s@ = the signature to verify |
| 151 | * @const void *m@ = pointer to message hash |
| 152 | * |
| 153 | * Returns: Zero if OK, negative on failure. |
| 154 | * |
| 155 | * Use: Checks a signature on a message, Requires @g@, @p@, @h@. |
| 156 | */ |
| 157 | |
| 158 | int gkcdsa_verify(const gkcdsa *c, const gkcdsa_sig *s, const void *m) |
| 159 | { |
| 160 | group *g = c->g; |
| 161 | size_t hsz = c->h->hashsz; |
| 162 | group_expfactor e[2]; |
| 163 | mp *x, *y; |
| 164 | ghash *h; |
| 165 | ge *z; |
| 166 | octet *p; |
| 167 | int rc = -1; |
| 168 | |
| 169 | if (MP_CMP(s->s, <, MP_ONE) || MP_CMP(s->s, >=, g->r)) |
| 170 | return (-1); |
| 171 | x = mp_loadb(MP_NEW, m, hsz); y = mp_loadb(MP_NEW, s->r, hsz); |
| 172 | x = mp_xor(x, x, y); mp_div(0, &x, x, g->r); |
| 173 | e[0].base = c->p; e[0].exp = s->s; |
| 174 | e[1].base = g->g; e[1].exp = x; |
| 175 | z = G_CREATE(g); G_MEXP(g, z, e, 2); |
| 176 | h = hashge(g, c->h, z); p = GH_DONE(h, 0); |
| 177 | if (memcmp(p, s->r, hsz) == 0) rc = 0; |
| 178 | mp_drop(x); mp_drop(y); G_DESTROY(g, z); GH_DESTROY(h); |
| 179 | return (rc); |
| 180 | } |
| 181 | |
| 182 | /*----- Test rig ----------------------------------------------------------*/ |
| 183 | |
| 184 | #ifdef TEST_RIG |
| 185 | |
| 186 | static group *getgroup(const char *p) { |
| 187 | group *g; qd_parse qd; |
| 188 | qd.p = p; qd.e = 0; g = group_parse(&qd); |
| 189 | if (g && !qd_eofp(&qd)) { G_DESTROYGROUP(g); g = 0; qd.e = "junk at eof"; } |
| 190 | if (!g) { fprintf(stderr, "bad group string `%.*s|%s': %s\n", qd.p - p, |
| 191 | p, qd.p, qd.e); exit(1); } |
| 192 | return (g); |
| 193 | } |
| 194 | |
| 195 | static ge *getge(group *g, const char *p) { |
| 196 | ge *x = G_CREATE(g); |
| 197 | if (group_readstring(g, x, p, 0)) { |
| 198 | fprintf(stderr, "bad group element `%s'\n", p); |
| 199 | exit(1); |
| 200 | } |
| 201 | return (x); |
| 202 | } |
| 203 | |
| 204 | static void showge(group *g, const char *p, ge *x) { |
| 205 | fprintf(stderr, "*** %s = ", p); group_writefile(g, x, stderr); |
| 206 | putc('\n', stderr); |
| 207 | } |
| 208 | |
| 209 | static void showmp(const char *p, mp *x, int r) { |
| 210 | fprintf(stderr, "*** %s = ", p); mp_writefile(x, stderr, r); |
| 211 | putc('\n', stderr); |
| 212 | } |
| 213 | |
| 214 | static int tsign(dstr *v) |
| 215 | { |
| 216 | gdsa c; |
| 217 | gkcdsa_sig s, ss = GKCDSA_SIG_INIT; |
| 218 | ghash *h; |
| 219 | mp *k; |
| 220 | dstr d = DSTR_INIT; |
| 221 | mp *x; |
| 222 | int ok = 1; |
| 223 | |
| 224 | c.g = getgroup(v[0].buf); c.h = ghash_byname(v[1].buf); |
| 225 | c.u = *(mp **)v[2].buf; k = *(mp **)v[4].buf; |
| 226 | s.r = (octet *)v[5].buf; s.s = *(mp **)v[6].buf; |
| 227 | DENSURE(&d, c.h->hashsz); d.len = c.h->hashsz; memset(d.buf, 0, d.len); |
| 228 | ss.r = (octet *)d.buf; |
| 229 | |
| 230 | x = mp_modinv(MP_NEW, c.u, c.g->r); |
| 231 | c.p = G_CREATE(c.g); G_EXP(c.g, c.p, c.g->g, x); |
| 232 | h = gkcdsa_beginhash(&c); |
| 233 | GH_HASH(h, v[3].buf, v[3].len); |
| 234 | gkcdsa_endhash(&c, h); |
| 235 | gkcdsa_sign(&c, &ss, GH_DONE(h, 0), k); |
| 236 | if (memcmp(s.r, ss.r, c.h->hashsz) || !MP_EQ(s.s, ss.s)) { |
| 237 | ok = 0; |
| 238 | fprintf(stderr, "*** sign failed!\n"); |
| 239 | fprintf(stderr, "*** group: %s\n", v[0].buf); |
| 240 | fprintf(stderr, "*** hash: %s\n", c.h->name); |
| 241 | showmp("private key", c.u, 16); |
| 242 | showge(c.g, "public key", c.p); |
| 243 | fprintf(stderr, "*** message: `%s'\n", v[3].buf); |
| 244 | fprintf(stderr, "*** computed r = "); |
| 245 | type_hex.dump(&d, stderr); putc('\n', stderr); |
| 246 | showmp("computed s", ss.s, 16); |
| 247 | fprintf(stderr, "*** computed r = "); |
| 248 | type_hex.dump(&v[5], stderr); putc('\n', stderr); |
| 249 | showmp("expected s", s.s, 16); |
| 250 | } |
| 251 | mp_drop(s.s); dstr_destroy(&d); mp_drop(ss.s); mp_drop(x); mp_drop(k); |
| 252 | mp_drop(c.u); G_DESTROY(c.g, c.p); G_DESTROYGROUP(c.g); GH_DESTROY(h); |
| 253 | assert(mparena_count(MPARENA_GLOBAL) == 0); |
| 254 | return (ok); |
| 255 | } |
| 256 | |
| 257 | static int tverify(dstr *v) |
| 258 | { |
| 259 | gkcdsa c; |
| 260 | gkcdsa_sig s; |
| 261 | ghash *h; |
| 262 | int rc, erc; |
| 263 | int ok = 1; |
| 264 | |
| 265 | c.g = getgroup(v[0].buf); c.h = ghash_byname(v[1].buf); |
| 266 | c.p = getge(c.g, v[2].buf); |
| 267 | s.r = (octet *)v[4].buf; s.s = *(mp **)v[5].buf; |
| 268 | erc = *(int *)v[6].buf; |
| 269 | |
| 270 | h = gkcdsa_beginhash(&c); |
| 271 | GH_HASH(h, v[3].buf, v[3].len); |
| 272 | gkcdsa_endhash(&c, h); |
| 273 | rc = gkcdsa_verify(&c, &s, GH_DONE(h, 0)); |
| 274 | if (!rc != !erc) { |
| 275 | ok = 0; |
| 276 | fprintf(stderr, "*** verify failed!\n"); |
| 277 | fprintf(stderr, "*** group: %s\n", v[0].buf); |
| 278 | fprintf(stderr, "*** hash: %s\n", c.h->name); |
| 279 | showge(c.g, "public key", c.p); |
| 280 | fprintf(stderr, "*** message: `%s'\n", v[3].buf); |
| 281 | fprintf(stderr, "*** sig r = "); |
| 282 | type_hex.dump(&v[4], stderr); putc('\n', stderr); |
| 283 | showmp("sig s", s.s, 16); |
| 284 | fprintf(stderr, "*** expected %s\n", !erc ? "pass" : "fail"); |
| 285 | } |
| 286 | mp_drop(s.s); G_DESTROY(c.g, c.p); G_DESTROYGROUP(c.g); |
| 287 | GH_DESTROY(h); |
| 288 | assert(mparena_count(MPARENA_GLOBAL) == 0); |
| 289 | return (ok); |
| 290 | } |
| 291 | |
| 292 | static const test_chunk tests[] = { |
| 293 | { "sign", tsign, { &type_string, &type_string, &type_mp, &type_string, |
| 294 | &type_mp, &type_hex, &type_mp } }, |
| 295 | { "verify", tverify, { &type_string, &type_string, &type_string, |
| 296 | &type_string, &type_hex, &type_mp, &type_int } }, |
| 297 | { 0 } |
| 298 | }; |
| 299 | |
| 300 | int main(int argc, char *argv[]) |
| 301 | { |
| 302 | sub_init(); |
| 303 | test_run(argc, argv, tests, SRCDIR "/t/gkcdsa"); |
| 304 | return (0); |
| 305 | } |
| 306 | |
| 307 | #endif |
| 308 | |
| 309 | /*----- That's all, folks -------------------------------------------------*/ |