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d0_blind_id.c
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d0_blind_id.c
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/*
* FILE: d0_blind_id.c
* AUTHOR: Rudolf Polzer - [email protected]
*
* Copyright (c) 2010, Rudolf Polzer
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the copyright holder nor the names of contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTOR(S) ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTOR(S) BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* $Format:commit %H$
* $Id$
*/
#include "d0_blind_id.h"
#include <stdio.h>
#include <string.h>
#include "d0_bignum.h"
#include "sha2.h"
// old "positive" protocol, uses one extra mod_inv in verify stages
// #define D0_BLIND_ID_POSITIVE_PROTOCOL
// our SHA is SHA-256
#define SHA_DIGESTSIZE 32
const unsigned char *sha(unsigned char *h, const unsigned char *in, size_t len)
{
d0_blind_id_util_sha256((char *) h, (const char *) in, len);
return h;
}
// for zero knowledge, we need multiple instances of schnorr ID scheme... should normally be sequential
// parallel schnorr ID is not provably zero knowledge :(
// (evil verifier can know all questions in advance, so sequential is disadvantage for him)
// we'll just live with a 1:1048576 chance of cheating, and support reauthenticating
#define SCHNORR_BITS 20
// probability of cheat: 2^(-bits+1)
#define SCHNORR_HASHSIZE SHA_DIGESTSIZE
// cannot be >= SHA_DIGESTSIZE
// *8 must be >= SCHNORR_BITS
// no need to save bits here
#define MSGSIZE 640 // ought to be enough for anyone
struct d0_blind_id_s
{
// signing (Xonotic pub and priv key)
d0_bignum_t *rsa_n, *rsa_e, *rsa_d;
// public data (Schnorr ID)
d0_bignum_t *schnorr_G;
// private data (player ID private key)
d0_bignum_t *schnorr_s;
// public data (player ID public key, this is what the server gets to know)
d0_bignum_t *schnorr_g_to_s;
d0_bignum_t *schnorr_H_g_to_s_signature; // 0 when signature is invalid
// as hash function H, we get the SHA1 and reinterpret as bignum - yes, it always is < 160 bits
// temp data
d0_bignum_t *rsa_blind_signature_camouflage; // random number blind signature
d0_bignum_t *r; // random number for schnorr ID
d0_bignum_t *t; // for DH key exchange
d0_bignum_t *g_to_t; // for DH key exchange
d0_bignum_t *other_g_to_t; // for DH key exchange
d0_bignum_t *challenge; // challenge
char msghash[SCHNORR_HASHSIZE]; // init hash
char msg[MSGSIZE]; // message
size_t msglen; // message length
};
//#define CHECKDEBUG
#ifdef CHECKDEBUG
#define CHECK(x) do { if(!(x)) { fprintf(stderr, "CHECK FAILED (%s:%d): %s\n", __FILE__, __LINE__, #x); goto fail; } } while(0)
#define CHECK_ASSIGN(var, value) do { d0_bignum_t *val; val = value; if(!val) { fprintf(stderr, "CHECK FAILED (%s:%d): %s\n", __FILE__, __LINE__, #value); goto fail; } var = val; } while(0)
#else
#define CHECK(x) do { if(!(x)) goto fail; } while(0)
#define CHECK_ASSIGN(var, value) do { d0_bignum_t *val; val = value; if(!val) goto fail; var = val; } while(0)
#endif
#define USING(x) if(!(ctx->x)) return 0
#define REPLACING(x)
// safe to use
static d0_bignum_t *zero, *one, *four;
static d0_bignum_t *temp0, *temp1, *temp2, *temp3, *temp4;
static void *tempmutex = NULL; // hold this mutex when using temp0 to temp4
#define USINGTEMPS() int locked = 0
#define LOCKTEMPS() do { if(!locked) d0_lockmutex(tempmutex); locked = 1; } while(0)
#define UNLOCKTEMPS() do { if(locked) d0_unlockmutex(tempmutex); locked = 0; } while(0);
D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_INITIALIZE(void)
{
USINGTEMPS();
d0_initfuncs();
tempmutex = d0_createmutex();
LOCKTEMPS();
CHECK(d0_bignum_INITIALIZE());
CHECK_ASSIGN(zero, d0_bignum_int(zero, 0));
CHECK_ASSIGN(one, d0_bignum_int(one, 1));
CHECK_ASSIGN(four, d0_bignum_int(four, 4));
CHECK_ASSIGN(temp0, d0_bignum_int(temp0, 0));
CHECK_ASSIGN(temp1, d0_bignum_int(temp1, 0));
CHECK_ASSIGN(temp2, d0_bignum_int(temp2, 0));
CHECK_ASSIGN(temp3, d0_bignum_int(temp3, 0));
CHECK_ASSIGN(temp4, d0_bignum_int(temp4, 0));
UNLOCKTEMPS();
return 1;
fail:
UNLOCKTEMPS();
return 0;
}
void d0_blind_id_SHUTDOWN(void)
{
USINGTEMPS();
LOCKTEMPS();
d0_bignum_free(zero);
d0_bignum_free(one);
d0_bignum_free(four);
d0_bignum_free(temp0);
d0_bignum_free(temp1);
d0_bignum_free(temp2);
d0_bignum_free(temp3);
d0_bignum_free(temp4);
d0_bignum_SHUTDOWN();
UNLOCKTEMPS();
d0_destroymutex(tempmutex);
tempmutex = NULL;
}
// (G-1)/2
static d0_bignum_t *d0_dl_get_order(d0_bignum_t *o, const d0_bignum_t *G)
{
CHECK_ASSIGN(o, d0_bignum_sub(o, G, one));
CHECK(d0_bignum_shl(o, o, -1)); // order o = (G-1)/2
return o;
fail:
return NULL;
}
// 2o+1
d0_bignum_t *d0_dl_get_from_order(d0_bignum_t *G, const d0_bignum_t *o)
{
CHECK_ASSIGN(G, d0_bignum_shl(G, o, 1));
CHECK(d0_bignum_add(G, G, one));
return G;
fail:
return NULL;
}
// temps must NOT be locked when calling this
static D0_BOOL d0_dl_generate_key(size_t size, d0_bignum_t *G)
{
USINGTEMPS(); // using: temp0
if(size < 16)
size = 16;
for(;;)
{
LOCKTEMPS();
CHECK(d0_bignum_rand_bit_exact(temp0, size-1));
if(d0_bignum_isprime(temp0, 0) == 0)
continue;
CHECK(d0_dl_get_from_order(G, temp0));
if(d0_bignum_isprime(G, 10) == 0)
continue;
if(d0_bignum_isprime(temp0, 10) == 0) // finish the previous test
continue;
UNLOCKTEMPS();
break;
}
return 1;
fail:
UNLOCKTEMPS();
return 0;
}
// temps must NOT be locked when calling this
static D0_BOOL d0_rsa_generate_key(size_t size, d0_blind_id_t *ctx)
{
USINGTEMPS(); // uses temp1 to temp4
int fail = 0;
int gcdfail = 0;
int pb = (size + 1)/2;
int qb = size - pb;
if(pb < 8)
pb = 8;
if(qb < 8)
qb = 8;
// we use ctx->rsa_d for the first result so that we can unlock temps later
for (;;)
{
LOCKTEMPS();
CHECK(d0_bignum_rand_bit_exact(ctx->rsa_d, pb));
if(d0_bignum_isprime(ctx->rsa_d, 10) == 0)
{
UNLOCKTEMPS();
continue;
}
CHECK(d0_bignum_sub(temp2, ctx->rsa_d, one));
CHECK(d0_bignum_gcd(temp4, NULL, NULL, temp2, ctx->rsa_e));
if(!d0_bignum_cmp(temp4, one))
break;
if(++gcdfail == 16)
goto fail;
}
UNLOCKTEMPS();
gcdfail = 0;
for (;;)
{
LOCKTEMPS();
CHECK(d0_bignum_rand_bit_exact(temp1, qb));
if(!d0_bignum_cmp(temp1, ctx->rsa_d))
{
UNLOCKTEMPS();
if(++fail == 16)
goto fail;
continue;
}
fail = 0;
if(d0_bignum_isprime(temp1, 10) == 0)
{
UNLOCKTEMPS();
continue;
}
CHECK(d0_bignum_sub(temp3, temp1, one));
CHECK(d0_bignum_gcd(temp4, NULL, NULL, temp3, ctx->rsa_e));
if(!d0_bignum_cmp(temp4, one))
{
// we do NOT unlock, as we still need temp1 and temp3
break;
}
UNLOCKTEMPS();
if(++gcdfail == 16)
goto fail;
}
// ctx->rsa_n = ctx->rsa_d*temp1
CHECK(d0_bignum_mul(ctx->rsa_n, ctx->rsa_d, temp1));
// ctx->rsa_d = ctx->rsa_e^-1 mod (ctx->rsa_d-1)(temp1-1)
CHECK(d0_bignum_sub(temp2, ctx->rsa_d, one)); // we can't reuse the value from above because temps were unlocked
CHECK(d0_bignum_mul(temp1, temp2, temp3));
CHECK(d0_bignum_mod_inv(ctx->rsa_d, ctx->rsa_e, temp1));
UNLOCKTEMPS();
return 1;
fail:
UNLOCKTEMPS();
return 0;
}
// temps must NOT be locked when calling this
static D0_BOOL d0_rsa_generate_key_fastreject(size_t size, d0_fastreject_function reject, d0_blind_id_t *ctx, void *pass)
{
USINGTEMPS(); // uses temp1 to temp4
int fail = 0;
int gcdfail = 0;
int pb = (size + 1)/2;
int qb = size - pb;
if(pb < 8)
pb = 8;
if(qb < 8)
qb = 8;
// we use ctx->rsa_d for the first result so that we can unlock temps later
for (;;)
{
LOCKTEMPS();
CHECK(d0_bignum_rand_bit_exact(ctx->rsa_d, pb));
if(d0_bignum_isprime(ctx->rsa_d, 10) == 0)
{
UNLOCKTEMPS();
continue;
}
CHECK(d0_bignum_sub(temp2, ctx->rsa_d, one));
CHECK(d0_bignum_gcd(temp4, NULL, NULL, temp2, ctx->rsa_e));
if(!d0_bignum_cmp(temp4, one))
break;
if(++gcdfail == 16)
return 0;
}
UNLOCKTEMPS();
gcdfail = 0;
for (;;)
{
LOCKTEMPS();
CHECK(d0_bignum_rand_bit_exact(temp1, qb));
if(!d0_bignum_cmp(temp1, ctx->rsa_d))
{
UNLOCKTEMPS();
if(++fail == 16)
return 0;
continue;
}
fail = 0;
// n = ctx->rsa_d*temp1
CHECK(d0_bignum_mul(ctx->rsa_n, ctx->rsa_d, temp1));
if(reject(ctx, pass))
{
UNLOCKTEMPS();
continue;
}
if(d0_bignum_isprime(temp1, 10) == 0)
{
UNLOCKTEMPS();
continue;
}
CHECK(d0_bignum_sub(temp3, temp1, one));
CHECK(d0_bignum_gcd(temp4, NULL, NULL, temp3, ctx->rsa_e));
if(!d0_bignum_cmp(temp4, one))
{
// we do NOT unlock, as we still need temp3
break;
}
UNLOCKTEMPS();
if(++gcdfail == 16)
return 0;
}
// ctx->rsa_d = ctx->rsa_e^-1 mod (ctx->rsa_d-1)(temp1-1)
CHECK(d0_bignum_sub(temp2, ctx->rsa_d, one)); // we can't reuse the value from above because temps were unlocked
CHECK(d0_bignum_mul(temp1, temp2, temp3));
CHECK(d0_bignum_mod_inv(ctx->rsa_d, ctx->rsa_e, temp1));
UNLOCKTEMPS();
return 1;
fail:
UNLOCKTEMPS();
return 0;
}
D0_WARN_UNUSED_RESULT D0_BOOL d0_longhash_destructive(unsigned char *convbuf, size_t sz, unsigned char *outbuf, size_t outbuflen)
{
size_t n, i;
char shabuf[32];
n = outbuflen;
while(n > SHA_DIGESTSIZE)
{
memcpy(outbuf, sha(shabuf, convbuf, sz), SHA_DIGESTSIZE);
outbuf += SHA_DIGESTSIZE;
n -= SHA_DIGESTSIZE;
for(i = 0; i < sz; ++i)
if(++convbuf[i])
break; // stop until no carry
}
memcpy(outbuf, sha(shabuf, convbuf, sz), n);
return 1;
}
D0_WARN_UNUSED_RESULT D0_BOOL d0_longhash_bignum(const d0_bignum_t *in, unsigned char *outbuf, size_t outbuflen)
{
unsigned char convbuf[1024];
size_t sz;
CHECK(d0_bignum_export_unsigned(in, convbuf, sizeof(convbuf)) >= 0);
sz = (d0_bignum_size(in) + 7) / 8;
CHECK(d0_longhash_destructive(convbuf, sz, outbuf, outbuflen));
return 1;
fail:
return 0;
}
void d0_blind_id_clear(d0_blind_id_t *ctx)
{
if(ctx->rsa_n) d0_bignum_free(ctx->rsa_n);
if(ctx->rsa_e) d0_bignum_free(ctx->rsa_e);
if(ctx->rsa_d) d0_bignum_free(ctx->rsa_d);
if(ctx->schnorr_G) d0_bignum_free(ctx->schnorr_G);
if(ctx->schnorr_s) d0_bignum_free(ctx->schnorr_s);
if(ctx->schnorr_g_to_s) d0_bignum_free(ctx->schnorr_g_to_s);
if(ctx->schnorr_H_g_to_s_signature) d0_bignum_free(ctx->schnorr_H_g_to_s_signature);
if(ctx->rsa_blind_signature_camouflage) d0_bignum_free(ctx->rsa_blind_signature_camouflage);
if(ctx->r) d0_bignum_free(ctx->r);
if(ctx->challenge) d0_bignum_free(ctx->challenge);
if(ctx->t) d0_bignum_free(ctx->t);
if(ctx->g_to_t) d0_bignum_free(ctx->g_to_t);
if(ctx->other_g_to_t) d0_bignum_free(ctx->other_g_to_t);
memset(ctx, 0, sizeof(*ctx));
}
D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_copy(d0_blind_id_t *ctx, const d0_blind_id_t *src)
{
d0_blind_id_clear(ctx);
if(src->rsa_n) CHECK_ASSIGN(ctx->rsa_n, d0_bignum_mov(NULL, src->rsa_n));
if(src->rsa_e) CHECK_ASSIGN(ctx->rsa_e, d0_bignum_mov(NULL, src->rsa_e));
if(src->rsa_d) CHECK_ASSIGN(ctx->rsa_d, d0_bignum_mov(NULL, src->rsa_d));
if(src->schnorr_G) CHECK_ASSIGN(ctx->schnorr_G, d0_bignum_mov(NULL, src->schnorr_G));
if(src->schnorr_s) CHECK_ASSIGN(ctx->schnorr_s, d0_bignum_mov(NULL, src->schnorr_s));
if(src->schnorr_g_to_s) CHECK_ASSIGN(ctx->schnorr_g_to_s, d0_bignum_mov(NULL, src->schnorr_g_to_s));
if(src->schnorr_H_g_to_s_signature) CHECK_ASSIGN(ctx->schnorr_H_g_to_s_signature, d0_bignum_mov(NULL, src->schnorr_H_g_to_s_signature));
if(src->rsa_blind_signature_camouflage) CHECK_ASSIGN(ctx->rsa_blind_signature_camouflage, d0_bignum_mov(NULL, src->rsa_blind_signature_camouflage));
if(src->r) CHECK_ASSIGN(ctx->r, d0_bignum_mov(NULL, src->r));
if(src->challenge) CHECK_ASSIGN(ctx->challenge, d0_bignum_mov(NULL, src->challenge));
if(src->t) CHECK_ASSIGN(ctx->t, d0_bignum_mov(NULL, src->t));
if(src->g_to_t) CHECK_ASSIGN(ctx->g_to_t, d0_bignum_mov(NULL, src->g_to_t));
if(src->other_g_to_t) CHECK_ASSIGN(ctx->other_g_to_t, d0_bignum_mov(NULL, src->other_g_to_t));
memcpy(ctx->msg, src->msg, sizeof(ctx->msg));
ctx->msglen = src->msglen;
memcpy(ctx->msghash, src->msghash, sizeof(ctx->msghash));
return 1;
fail:
d0_blind_id_clear(ctx);
return 0;
}
D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_generate_private_key_fastreject(d0_blind_id_t *ctx, int k, d0_fastreject_function reject, void *pass)
{
REPLACING(rsa_e); REPLACING(rsa_d); REPLACING(rsa_n);
CHECK_ASSIGN(ctx->rsa_e, d0_bignum_int(ctx->rsa_e, 65537));
CHECK_ASSIGN(ctx->rsa_d, d0_bignum_zero(ctx->rsa_d));
CHECK_ASSIGN(ctx->rsa_n, d0_bignum_zero(ctx->rsa_n));
if(reject)
CHECK(d0_rsa_generate_key_fastreject(k+1, reject, ctx, pass)); // must fit G for sure
else
CHECK(d0_rsa_generate_key(k+1, ctx)); // must fit G for sure
return 1;
fail:
return 0;
}
D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_generate_private_key(d0_blind_id_t *ctx, int k)
{
return d0_blind_id_generate_private_key_fastreject(ctx, k, NULL, NULL);
}
D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_read_private_key(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
{
d0_iobuf_t *in = NULL;
REPLACING(rsa_n); REPLACING(rsa_e); REPLACING(rsa_d);
in = d0_iobuf_open_read(inbuf, inbuflen);
CHECK_ASSIGN(ctx->rsa_n, d0_iobuf_read_bignum(in, ctx->rsa_n));
CHECK_ASSIGN(ctx->rsa_e, d0_iobuf_read_bignum(in, ctx->rsa_e));
CHECK_ASSIGN(ctx->rsa_d, d0_iobuf_read_bignum(in, ctx->rsa_d));
return d0_iobuf_close(in, NULL);
fail:
d0_iobuf_close(in, NULL);
return 0;
}
D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_read_public_key(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
{
d0_iobuf_t *in = NULL;
REPLACING(rsa_n); REPLACING(rsa_e);
in = d0_iobuf_open_read(inbuf, inbuflen);
CHECK_ASSIGN(ctx->rsa_n, d0_iobuf_read_bignum(in, ctx->rsa_n));
CHECK_ASSIGN(ctx->rsa_e, d0_iobuf_read_bignum(in, ctx->rsa_e));
return d0_iobuf_close(in, NULL);
fail:
d0_iobuf_close(in, NULL);
return 0;
}
D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_write_private_key(const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
{
d0_iobuf_t *out = NULL;
USING(rsa_n); USING(rsa_e); USING(rsa_d);
out = d0_iobuf_open_write(outbuf, *outbuflen);
CHECK(d0_iobuf_write_bignum(out, ctx->rsa_n));
CHECK(d0_iobuf_write_bignum(out, ctx->rsa_e));
CHECK(d0_iobuf_write_bignum(out, ctx->rsa_d));
return d0_iobuf_close(out, outbuflen);
fail:
d0_iobuf_close(out, outbuflen);
return 0;
}
D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_write_public_key(const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
{
d0_iobuf_t *out = NULL;
USING(rsa_n); USING(rsa_e);
out = d0_iobuf_open_write(outbuf, *outbuflen);
CHECK(d0_iobuf_write_bignum(out, ctx->rsa_n));
CHECK(d0_iobuf_write_bignum(out, ctx->rsa_e));
return d0_iobuf_close(out, outbuflen);
fail:
if(!d0_iobuf_close(out, outbuflen))
return 0;
return 0;
}
D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_fingerprint64_public_key(const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
{
d0_iobuf_t *out = NULL;
unsigned char convbuf[2048];
d0_iobuf_t *conv = NULL;
size_t sz, n;
char shabuf[32];
USING(rsa_n); USING(rsa_e);
out = d0_iobuf_open_write(outbuf, *outbuflen);
conv = d0_iobuf_open_write(convbuf, sizeof(convbuf));
CHECK(d0_iobuf_write_bignum(conv, ctx->rsa_n));
CHECK(d0_iobuf_write_bignum(conv, ctx->rsa_e));
CHECK(d0_iobuf_close(conv, &sz));
conv = NULL;
n = (*outbuflen / 4) * 3;
if(n > SHA_DIGESTSIZE)
n = SHA_DIGESTSIZE;
CHECK(d0_iobuf_write_raw(out, sha(shabuf, convbuf, sz), n) == n);
CHECK(d0_iobuf_conv_base64_out(out));
return d0_iobuf_close(out, outbuflen);
fail:
if(conv)
d0_iobuf_close(conv, &sz);
d0_iobuf_close(out, outbuflen);
return 0;
}
D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_generate_private_id_modulus(d0_blind_id_t *ctx)
{
USING(rsa_n);
REPLACING(schnorr_G);
CHECK_ASSIGN(ctx->schnorr_G, d0_bignum_zero(ctx->schnorr_G));
CHECK(d0_dl_generate_key(d0_bignum_size(ctx->rsa_n)-1, ctx->schnorr_G));
return 1;
fail:
return 0;
}
D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_read_private_id_modulus(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
{
d0_iobuf_t *in = NULL;
REPLACING(schnorr_G);
in = d0_iobuf_open_read(inbuf, inbuflen);
CHECK_ASSIGN(ctx->schnorr_G, d0_iobuf_read_bignum(in, ctx->schnorr_G));
return d0_iobuf_close(in, NULL);
fail:
d0_iobuf_close(in, NULL);
return 0;
}
D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_write_private_id_modulus(const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
{
d0_iobuf_t *out = NULL;
USING(schnorr_G);
out = d0_iobuf_open_write(outbuf, *outbuflen);
CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_G));
return d0_iobuf_close(out, outbuflen);
fail:
d0_iobuf_close(out, outbuflen);
return 0;
}
D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_generate_private_id_start(d0_blind_id_t *ctx)
{
USINGTEMPS(); // temps: temp0 = order
USING(schnorr_G);
REPLACING(schnorr_s); REPLACING(schnorr_g_to_s);
LOCKTEMPS();
CHECK(d0_dl_get_order(temp0, ctx->schnorr_G));
CHECK_ASSIGN(ctx->schnorr_s, d0_bignum_rand_range(ctx->schnorr_s, zero, temp0));
CHECK_ASSIGN(ctx->schnorr_g_to_s, d0_bignum_mod_pow(ctx->schnorr_g_to_s, four, ctx->schnorr_s, ctx->schnorr_G));
CHECK_ASSIGN(ctx->schnorr_H_g_to_s_signature, d0_bignum_zero(ctx->schnorr_H_g_to_s_signature));
UNLOCKTEMPS();
return 1;
fail:
UNLOCKTEMPS();
return 0;
}
D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_generate_private_id_request(d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
{
d0_iobuf_t *out = NULL;
unsigned char hashbuf[2048];
size_t sz;
USINGTEMPS(); // temps: temp0 rsa_blind_signature_camouflage^challenge, temp1 (4^s)*rsa_blind_signature_camouflage^challenge
USING(rsa_n); USING(rsa_e); USING(schnorr_g_to_s);
REPLACING(rsa_blind_signature_camouflage);
out = d0_iobuf_open_write(outbuf, *outbuflen);
CHECK_ASSIGN(ctx->rsa_blind_signature_camouflage, d0_bignum_rand_bit_atmost(ctx->rsa_blind_signature_camouflage, d0_bignum_size(ctx->rsa_n)));
CHECK(d0_bignum_mod_pow(temp0, ctx->rsa_blind_signature_camouflage, ctx->rsa_e, ctx->rsa_n));
// we will actually sign HA(4^s) to prevent a malleability attack!
LOCKTEMPS();
sz = (d0_bignum_size(ctx->rsa_n) + 7) / 8; // this is too long, so we have to take the value % rsa_n when "decrypting"
if(sz > sizeof(hashbuf))
sz = sizeof(hashbuf);
CHECK(d0_longhash_bignum(ctx->schnorr_g_to_s, hashbuf, sz));
CHECK(d0_bignum_import_unsigned(temp2, hashbuf, sz));
// hash complete
CHECK(d0_bignum_mod_mul(temp1, temp2, temp0, ctx->rsa_n));
CHECK(d0_iobuf_write_bignum(out, temp1));
UNLOCKTEMPS();
return d0_iobuf_close(out, outbuflen);
fail:
UNLOCKTEMPS();
d0_iobuf_close(out, outbuflen);
return 0;
}
D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_answer_private_id_request(const d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen, char *outbuf, size_t *outbuflen)
{
d0_iobuf_t *in = NULL;
d0_iobuf_t *out = NULL;
USINGTEMPS(); // temps: temp0 input, temp1 temp0^d
USING(rsa_d); USING(rsa_n);
in = d0_iobuf_open_read(inbuf, inbuflen);
out = d0_iobuf_open_write(outbuf, *outbuflen);
LOCKTEMPS();
CHECK(d0_iobuf_read_bignum(in, temp0));
CHECK(d0_bignum_mod_pow(temp1, temp0, ctx->rsa_d, ctx->rsa_n));
CHECK(d0_iobuf_write_bignum(out, temp1));
UNLOCKTEMPS();
d0_iobuf_close(in, NULL);
return d0_iobuf_close(out, outbuflen);
fail:
UNLOCKTEMPS();
d0_iobuf_close(in, NULL);
d0_iobuf_close(out, outbuflen);
return 0;
}
D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_finish_private_id_request(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
{
d0_iobuf_t *in = NULL;
USINGTEMPS(); // temps: temp0 input, temp1 rsa_blind_signature_camouflage^-1
USING(rsa_blind_signature_camouflage); USING(rsa_n);
REPLACING(schnorr_H_g_to_s_signature);
in = d0_iobuf_open_read(inbuf, inbuflen);
LOCKTEMPS();
CHECK(d0_iobuf_read_bignum(in, temp0));
CHECK(d0_bignum_mod_inv(temp1, ctx->rsa_blind_signature_camouflage, ctx->rsa_n));
CHECK_ASSIGN(ctx->schnorr_H_g_to_s_signature, d0_bignum_mod_mul(ctx->schnorr_H_g_to_s_signature, temp0, temp1, ctx->rsa_n));
UNLOCKTEMPS();
return d0_iobuf_close(in, NULL);
fail:
UNLOCKTEMPS();
d0_iobuf_close(in, NULL);
return 0;
}
D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_read_private_id_request_camouflage(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
{
d0_iobuf_t *in = NULL;
REPLACING(rsa_blind_signature_camouflage);
in = d0_iobuf_open_read(inbuf, inbuflen);
CHECK_ASSIGN(ctx->rsa_blind_signature_camouflage, d0_iobuf_read_bignum(in, ctx->rsa_blind_signature_camouflage));
return d0_iobuf_close(in, NULL);
fail:
d0_iobuf_close(in, NULL);
return 0;
}
D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_write_private_id_request_camouflage(const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
{
d0_iobuf_t *out = NULL;
USING(rsa_blind_signature_camouflage);
out = d0_iobuf_open_write(outbuf, *outbuflen);
CHECK(d0_iobuf_write_bignum(out, ctx->rsa_blind_signature_camouflage));
return d0_iobuf_close(out, outbuflen);
fail:
d0_iobuf_close(out, outbuflen);
return 0;
}
D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_read_private_id(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
{
d0_iobuf_t *in = NULL;
REPLACING(schnorr_s); REPLACING(schnorr_g_to_s); REPLACING(schnorr_H_g_to_s_signature);
in = d0_iobuf_open_read(inbuf, inbuflen);
CHECK_ASSIGN(ctx->schnorr_s, d0_iobuf_read_bignum(in, ctx->schnorr_s));
CHECK_ASSIGN(ctx->schnorr_g_to_s, d0_iobuf_read_bignum(in, ctx->schnorr_g_to_s));
CHECK_ASSIGN(ctx->schnorr_H_g_to_s_signature, d0_iobuf_read_bignum(in, ctx->schnorr_H_g_to_s_signature));
return d0_iobuf_close(in, NULL);
fail:
d0_iobuf_close(in, NULL);
return 0;
}
D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_read_public_id(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen)
{
d0_iobuf_t *in = NULL;
REPLACING(schnorr_g_to_s); REPLACING(schnorr_H_g_to_s_signature);
in = d0_iobuf_open_read(inbuf, inbuflen);
CHECK_ASSIGN(ctx->schnorr_g_to_s, d0_iobuf_read_bignum(in, ctx->schnorr_g_to_s));
CHECK_ASSIGN(ctx->schnorr_H_g_to_s_signature, d0_iobuf_read_bignum(in, ctx->schnorr_H_g_to_s_signature));
return d0_iobuf_close(in, NULL);
fail:
d0_iobuf_close(in, NULL);
return 0;
}
D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_write_private_id(const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
{
d0_iobuf_t *out = NULL;
USING(schnorr_s); USING(schnorr_g_to_s); USING(schnorr_H_g_to_s_signature);
out = d0_iobuf_open_write(outbuf, *outbuflen);
CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_s));
CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_g_to_s));
CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_H_g_to_s_signature));
return d0_iobuf_close(out, outbuflen);
fail:
d0_iobuf_close(out, outbuflen);
return 0;
}
D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_write_public_id(const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
{
d0_iobuf_t *out = NULL;
USING(schnorr_g_to_s); USING(schnorr_H_g_to_s_signature);
out = d0_iobuf_open_write(outbuf, *outbuflen);
CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_g_to_s));
CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_H_g_to_s_signature));
return d0_iobuf_close(out, outbuflen);
fail:
d0_iobuf_close(out, outbuflen);
return 0;
}
D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_authenticate_with_private_id_start(d0_blind_id_t *ctx, D0_BOOL is_first, D0_BOOL send_modulus, const char *msg, size_t msglen, char *outbuf, size_t *outbuflen)
// start =
// first run: send 4^s, 4^s signature
// 1. get random r, send HASH(4^r)
{
d0_iobuf_t *out = NULL;
unsigned char convbuf[1024];
d0_iobuf_t *conv = NULL;
size_t sz = 0;
D0_BOOL failed = 0;
char shabuf[32];
USINGTEMPS(); // temps: temp0 order, temp0 4^r
if(is_first)
{
USING(schnorr_g_to_s); USING(schnorr_H_g_to_s_signature);
}
USING(schnorr_G);
REPLACING(r); REPLACING(t); REPLACING(g_to_t);
out = d0_iobuf_open_write(outbuf, *outbuflen);
if(is_first)
{
// send ID
if(send_modulus)
CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_G));
CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_g_to_s));
CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_H_g_to_s_signature));
}
// start schnorr ID scheme
// generate random number r; x = g^r; send hash of x, remember r, forget x
LOCKTEMPS();
CHECK(d0_dl_get_order(temp0, ctx->schnorr_G));
#ifdef RNG_XKCD
CHECK_ASSIGN(ctx->r, d0_bignum_int(ctx->r, 4)); // decided by fair dice roll
#else
CHECK_ASSIGN(ctx->r, d0_bignum_rand_range(ctx->r, zero, temp0));
#endif
// initialize Signed Diffie Hellmann
// we already have the group order in temp1
#ifdef RNG_XKCD
CHECK_ASSIGN(ctx->t, d0_bignum_int(ctx->t, 4)); // decided by fair dice roll
#else
CHECK_ASSIGN(ctx->t, d0_bignum_rand_range(ctx->t, zero, temp0));
#endif
// can we SOMEHOW do this with just one mod_pow?
CHECK(d0_bignum_mod_pow(temp0, four, ctx->r, ctx->schnorr_G));
CHECK_ASSIGN(ctx->g_to_t, d0_bignum_mod_pow(ctx->g_to_t, four, ctx->t, ctx->schnorr_G));
CHECK(!failed);
// hash it, hash it, everybody hash it
conv = d0_iobuf_open_write(convbuf, sizeof(convbuf));
CHECK(d0_iobuf_write_bignum(conv, temp0));
CHECK(d0_iobuf_write_bignum(conv, ctx->g_to_t));
CHECK(d0_iobuf_write_packet(conv, msg, msglen));
CHECK(d0_iobuf_write_bignum(conv, temp0));
UNLOCKTEMPS();
CHECK(d0_iobuf_write_bignum(conv, ctx->g_to_t));
d0_iobuf_close(conv, &sz);
conv = NULL;
CHECK(d0_iobuf_write_raw(out, sha(shabuf, convbuf, sz), SCHNORR_HASHSIZE) == SCHNORR_HASHSIZE);
CHECK(d0_iobuf_write_packet(out, msg, msglen));
return d0_iobuf_close(out, outbuflen);
fail:
UNLOCKTEMPS();
d0_iobuf_close(out, outbuflen);
return 0;
}
D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_authenticate_with_private_id_challenge(d0_blind_id_t *ctx, D0_BOOL is_first, D0_BOOL recv_modulus, const char *inbuf, size_t inbuflen, char *outbuf, size_t *outbuflen, D0_BOOL *status)
// first run: get 4^s, 4^s signature
// 1. check sig
// 2. save HASH(4^r)
// 3. send challenge challenge of SCHNORR_BITS
{
d0_iobuf_t *in = NULL;
d0_iobuf_t *out = NULL;
unsigned char hashbuf[2048];
size_t sz;
USINGTEMPS(); // temps: temp0 order, temp0 signature check
if(is_first)
{
REPLACING(schnorr_g_to_s); REPLACING(schnorr_H_g_to_s_signature);
if(recv_modulus)
REPLACING(schnorr_G);
else
USING(schnorr_G);
}
else
{
USING(schnorr_g_to_s); USING(schnorr_H_g_to_s_signature);
USING(schnorr_G);
}
USING(rsa_e); USING(rsa_n);
REPLACING(challenge); REPLACING(msg); REPLACING(msglen); REPLACING(msghash); REPLACING(r); REPLACING(t);
in = d0_iobuf_open_read(inbuf, inbuflen);
out = d0_iobuf_open_write(outbuf, *outbuflen);
if(is_first)
{
if(recv_modulus)
{
CHECK_ASSIGN(ctx->schnorr_G, d0_iobuf_read_bignum(in, ctx->schnorr_G));
CHECK(d0_bignum_cmp(ctx->schnorr_G, zero) > 0);
CHECK(d0_bignum_cmp(ctx->schnorr_G, ctx->rsa_n) < 0);
}
CHECK_ASSIGN(ctx->schnorr_g_to_s, d0_iobuf_read_bignum(in, ctx->schnorr_g_to_s));
CHECK(d0_bignum_cmp(ctx->schnorr_g_to_s, zero) >= 0);
CHECK(d0_bignum_cmp(ctx->schnorr_g_to_s, ctx->schnorr_G) < 0);
CHECK_ASSIGN(ctx->schnorr_H_g_to_s_signature, d0_iobuf_read_bignum(in, ctx->schnorr_H_g_to_s_signature));
CHECK(d0_bignum_cmp(ctx->schnorr_H_g_to_s_signature, zero) >= 0);
CHECK(d0_bignum_cmp(ctx->schnorr_H_g_to_s_signature, ctx->rsa_n) < 0);
if(d0_bignum_cmp(ctx->schnorr_H_g_to_s_signature, zero))
{
// check signature of key (t = k^d, so, t^challenge = k)
LOCKTEMPS();
CHECK(d0_bignum_mod_pow(temp0, ctx->schnorr_H_g_to_s_signature, ctx->rsa_e, ctx->rsa_n));
// we will actually sign SHA(4^s) to prevent a malleability attack!
sz = (d0_bignum_size(ctx->rsa_n) + 7) / 8; // this is too long, so we have to take the value % rsa_n when "decrypting"
if(sz > sizeof(hashbuf))
sz = sizeof(hashbuf);
CHECK(d0_longhash_bignum(ctx->schnorr_g_to_s, hashbuf, sz));
CHECK(d0_bignum_import_unsigned(temp2, hashbuf, sz));
// + 7 / 8 is too large, so let's mod it
CHECK(d0_bignum_divmod(NULL, temp1, temp2, ctx->rsa_n));
// hash complete
CHECK(d0_bignum_cmp(temp0, temp1) == 0);
}
}
CHECK(d0_iobuf_read_raw(in, ctx->msghash, SCHNORR_HASHSIZE));
ctx->msglen = MSGSIZE;
CHECK(d0_iobuf_read_packet(in, ctx->msg, &ctx->msglen));
// send challenge
#ifdef RNG_XKCD
CHECK_ASSIGN(ctx->challenge, d0_bignum_int(ctx->challenge, 4)); // decided by fair dice roll
#else
CHECK_ASSIGN(ctx->challenge, d0_bignum_rand_bit_atmost(ctx->challenge, SCHNORR_BITS));
#endif
CHECK(d0_iobuf_write_bignum(out, ctx->challenge));
// Diffie Hellmann send
LOCKTEMPS();
CHECK(d0_dl_get_order(temp0, ctx->schnorr_G));
#ifdef RNG_XKCD
CHECK_ASSIGN(ctx->t, d0_bignum_int(ctx->t, 4)); // decided by fair dice roll
#else
CHECK_ASSIGN(ctx->t, d0_bignum_rand_range(ctx->t, zero, temp0));
#endif
CHECK(d0_bignum_mod_pow(temp0, four, ctx->t, ctx->schnorr_G));
CHECK(d0_iobuf_write_bignum(out, temp0));
UNLOCKTEMPS();
if(status)
*status = !!d0_bignum_cmp(ctx->schnorr_H_g_to_s_signature, zero);
d0_iobuf_close(in, NULL);
return d0_iobuf_close(out, outbuflen);
fail:
UNLOCKTEMPS();
d0_iobuf_close(in, NULL);
d0_iobuf_close(out, outbuflen);
return 0;
}
D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_authenticate_with_private_id_response(d0_blind_id_t *ctx, const char *inbuf, size_t inbuflen, char *outbuf, size_t *outbuflen)
// 1. read challenge challenge of SCHNORR_BITS
// 2. reply with r + s * challenge mod order
{
d0_iobuf_t *in = NULL;