#include <stdio.h>
#include <string.h>
#include "d0_bignum.h"
-#include "sha1.h"
+#include "sha2.h"
+
+// our SHA is SHA-256
+#define SHA_DIGESTSIZE 32
+const char *sha(const char *in, size_t len)
+{
+ static char h[32];
+ d0_blind_id_util_sha256(h, 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 :(
#define SCHNORR_BITS 20
// probability of cheat: 2^(-bits+1)
-#define SCHNORR_HASHSIZE 3
-// cannot be >= SHA_DIGEST_LENGTH
+#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
// public data (player ID public key, this is what the server gets to know)
d0_bignum_t *schnorr_4_to_s;
- d0_bignum_t *schnorr_4_to_s_signature; // 0 when signature is invalid
+ d0_bignum_t *schnorr_H_4_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
return 0;
}
+WARN_UNUSED_RESULT BOOL d0_longhash_destructive(d0_bignum_t *clobberme, char *outbuf, size_t outbuflen)
+{
+ d0_iobuf_t *out = NULL;
+ static unsigned char convbuf[1024];
+ size_t n, sz;
+
+ n = outbuflen;
+ while(n > SHA_DIGESTSIZE)
+ {
+ sz = (d0_bignum_size(clobberme) + 7) / 8;
+ CHECK(d0_bignum_export_unsigned(clobberme, convbuf, sizeof(convbuf)) >= 0);
+ memcpy(outbuf, sha(convbuf, sz), SHA_DIGESTSIZE);
+ outbuf += SHA_DIGESTSIZE;
+ n -= SHA_DIGESTSIZE;
+ CHECK(d0_bignum_add(clobberme, clobberme, one));
+ }
+ sz = (d0_bignum_size(clobberme) + 7) / 8;
+ CHECK(d0_bignum_export_unsigned(clobberme, convbuf, sizeof(convbuf)) >= 0);
+ memcpy(outbuf, sha(convbuf, sz), n);
+ 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->schnorr_G) d0_bignum_free(ctx->schnorr_G);
if(ctx->schnorr_s) d0_bignum_free(ctx->schnorr_s);
if(ctx->schnorr_4_to_s) d0_bignum_free(ctx->schnorr_4_to_s);
- if(ctx->schnorr_4_to_s_signature) d0_bignum_free(ctx->schnorr_4_to_s_signature);
+ if(ctx->schnorr_H_4_to_s_signature) d0_bignum_free(ctx->schnorr_H_4_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(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_4_to_s) CHECK_ASSIGN(ctx->schnorr_4_to_s, d0_bignum_mov(NULL, ctx->schnorr_G));
- if(src->schnorr_4_to_s_signature) CHECK_ASSIGN(ctx->schnorr_4_to_s_signature, d0_bignum_mov(NULL, src->schnorr_4_to_s_signature));
+ if(src->schnorr_4_to_s) CHECK_ASSIGN(ctx->schnorr_4_to_s, d0_bignum_mov(NULL, src->schnorr_4_to_s));
+ if(src->schnorr_H_4_to_s_signature) CHECK_ASSIGN(ctx->schnorr_H_4_to_s_signature, d0_bignum_mov(NULL, src->schnorr_H_4_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));
memcpy(ctx->msg, src->msg, sizeof(ctx->msg));
ctx->msglen = src->msglen;
memcpy(ctx->msghash, src->msghash, sizeof(ctx->msghash));
- return 0;
+ return 1;
fail:
d0_blind_id_clear(ctx);
- return 1;
+ return 0;
}
WARN_UNUSED_RESULT BOOL d0_blind_id_generate_private_key_fastreject(d0_blind_id_t *ctx, int k, d0_fastreject_function reject, void *pass)
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_4_to_s, d0_bignum_mod_pow(ctx->schnorr_4_to_s, four, ctx->schnorr_s, ctx->schnorr_G));
- CHECK_ASSIGN(ctx->schnorr_4_to_s_signature, d0_bignum_zero(ctx->schnorr_4_to_s_signature));
+ CHECK_ASSIGN(ctx->schnorr_H_4_to_s_signature, d0_bignum_zero(ctx->schnorr_H_4_to_s_signature));
return 1;
fail:
WARN_UNUSED_RESULT BOOL d0_blind_id_generate_private_id_request(d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
{
d0_iobuf_t *out = NULL;
+ static unsigned char convbuf[2048], shabuf[2048];
+ size_t sz;
// temps: temp0 rsa_blind_signature_camouflage^challenge, temp1 (4^s)*rsa_blind_signature_camouflage^challenge
USING(rsa_n); USING(rsa_e); USING(schnorr_4_to_s);
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));
- CHECK(d0_bignum_mod_mul(temp1, ctx->schnorr_4_to_s, temp0, ctx->rsa_n));
+
+ // we will actually sign HA(4^s) to prevent a malleability attack!
+ CHECK(d0_bignum_mov(temp2, ctx->schnorr_4_to_s));
+ 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(shabuf))
+ sz = sizeof(shabuf);
+ CHECK(d0_longhash_destructive(temp2, shabuf, sz));
+ CHECK(d0_bignum_import_unsigned(temp2, shabuf, sz));
+
+ // hash complete
+ CHECK(d0_bignum_mod_mul(temp1, temp2, temp0, ctx->rsa_n));
CHECK(d0_iobuf_write_bignum(out, temp1));
return d0_iobuf_close(out, outbuflen);
// temps: temp0 input, temp1 rsa_blind_signature_camouflage^-1
USING(rsa_blind_signature_camouflage); USING(rsa_n);
- REPLACING(schnorr_4_to_s_signature);
+ REPLACING(schnorr_H_4_to_s_signature);
in = d0_iobuf_open_read(inbuf, inbuflen);
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_4_to_s_signature, d0_bignum_mod_mul(ctx->schnorr_4_to_s_signature, temp0, temp1, ctx->rsa_n));
+ CHECK_ASSIGN(ctx->schnorr_H_4_to_s_signature, d0_bignum_mod_mul(ctx->schnorr_H_4_to_s_signature, temp0, temp1, ctx->rsa_n));
return d0_iobuf_close(in, NULL);
{
d0_iobuf_t *in = NULL;
- REPLACING(schnorr_s); REPLACING(schnorr_4_to_s); REPLACING(schnorr_4_to_s_signature);
+ REPLACING(schnorr_s); REPLACING(schnorr_4_to_s); REPLACING(schnorr_H_4_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_4_to_s, d0_iobuf_read_bignum(in, ctx->schnorr_4_to_s));
- CHECK_ASSIGN(ctx->schnorr_4_to_s_signature, d0_iobuf_read_bignum(in, ctx->schnorr_4_to_s_signature));
+ CHECK_ASSIGN(ctx->schnorr_H_4_to_s_signature, d0_iobuf_read_bignum(in, ctx->schnorr_H_4_to_s_signature));
return d0_iobuf_close(in, NULL);
{
d0_iobuf_t *in = NULL;
- REPLACING(schnorr_4_to_s); REPLACING(schnorr_4_to_s_signature);
+ REPLACING(schnorr_4_to_s); REPLACING(schnorr_H_4_to_s_signature);
in = d0_iobuf_open_read(inbuf, inbuflen);
CHECK_ASSIGN(ctx->schnorr_4_to_s, d0_iobuf_read_bignum(in, ctx->schnorr_4_to_s));
- CHECK_ASSIGN(ctx->schnorr_4_to_s_signature, d0_iobuf_read_bignum(in, ctx->schnorr_4_to_s_signature));
+ CHECK_ASSIGN(ctx->schnorr_H_4_to_s_signature, d0_iobuf_read_bignum(in, ctx->schnorr_H_4_to_s_signature));
return d0_iobuf_close(in, NULL);
{
d0_iobuf_t *out = NULL;
- USING(schnorr_s); USING(schnorr_4_to_s); USING(schnorr_4_to_s_signature);
+ USING(schnorr_s); USING(schnorr_4_to_s); USING(schnorr_H_4_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_4_to_s));
- CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s_signature));
+ CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_H_4_to_s_signature));
return d0_iobuf_close(out, outbuflen);
{
d0_iobuf_t *out = NULL;
- USING(schnorr_4_to_s); USING(schnorr_4_to_s_signature);
+ USING(schnorr_4_to_s); USING(schnorr_H_4_to_s_signature);
out = d0_iobuf_open_write(outbuf, *outbuflen);
CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s));
- CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s_signature));
+ CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_H_4_to_s_signature));
return d0_iobuf_close(out, outbuflen);
// temps: temp0 order, temp0 4^r
if(is_first)
{
- USING(schnorr_4_to_s); USING(schnorr_4_to_s_signature);
+ USING(schnorr_4_to_s); USING(schnorr_H_4_to_s_signature);
}
USING(schnorr_G);
REPLACING(r);
if(send_modulus)
CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_G));
CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s));
- CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_4_to_s_signature));
+ CHECK(d0_iobuf_write_bignum(out, ctx->schnorr_H_4_to_s_signature));
}
// start schnorr ID scheme
{
d0_iobuf_t *in = NULL;
d0_iobuf_t *out = NULL;
+ static unsigned char shabuf[2048];
+ size_t sz;
// temps: temp0 order, temp0 signature check
if(is_first)
{
- REPLACING(schnorr_4_to_s); REPLACING(schnorr_4_to_s_signature);
+ REPLACING(schnorr_4_to_s); REPLACING(schnorr_H_4_to_s_signature);
if(recv_modulus)
REPLACING(schnorr_G);
else
}
else
{
- USING(schnorr_4_to_s); USING(schnorr_4_to_s_signature);
+ USING(schnorr_4_to_s); USING(schnorr_H_4_to_s_signature);
USING(schnorr_G);
}
USING(rsa_e); USING(rsa_n);
CHECK(d0_bignum_cmp(ctx->schnorr_G, ctx->rsa_n) < 0);
}
CHECK_ASSIGN(ctx->schnorr_4_to_s, d0_iobuf_read_bignum(in, ctx->schnorr_4_to_s));
- CHECK(d0_bignum_cmp(ctx->schnorr_4_to_s, zero) > 0);
+ CHECK(d0_bignum_cmp(ctx->schnorr_4_to_s, zero) >= 0);
CHECK(d0_bignum_cmp(ctx->schnorr_4_to_s, ctx->schnorr_G) < 0);
- CHECK_ASSIGN(ctx->schnorr_4_to_s_signature, d0_iobuf_read_bignum(in, ctx->schnorr_4_to_s_signature));
- CHECK(d0_bignum_cmp(ctx->schnorr_4_to_s_signature, zero) >= 0);
- CHECK(d0_bignum_cmp(ctx->schnorr_4_to_s_signature, ctx->rsa_n) < 0);
+ CHECK_ASSIGN(ctx->schnorr_H_4_to_s_signature, d0_iobuf_read_bignum(in, ctx->schnorr_H_4_to_s_signature));
+ CHECK(d0_bignum_cmp(ctx->schnorr_H_4_to_s_signature, zero) >= 0);
+ CHECK(d0_bignum_cmp(ctx->schnorr_H_4_to_s_signature, ctx->rsa_n) < 0);
// check signature of key (t = k^d, so, t^challenge = k)
- CHECK(d0_bignum_mod_pow(temp0, ctx->schnorr_4_to_s_signature, ctx->rsa_e, ctx->rsa_n));
- if(d0_bignum_cmp(temp0, ctx->schnorr_4_to_s))
+ CHECK(d0_bignum_mod_pow(temp0, ctx->schnorr_H_4_to_s_signature, ctx->rsa_e, ctx->rsa_n));
+
+ // we will actually sign SHA(4^s) to prevent a malleability attack!
+ CHECK(d0_bignum_mov(temp2, ctx->schnorr_4_to_s));
+ 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(shabuf))
+ sz = sizeof(shabuf);
+ CHECK(d0_longhash_destructive(temp2, shabuf, sz));
+ CHECK(d0_bignum_import_unsigned(temp2, shabuf, sz));
+
+ // + 7 / 8 is too large, so let's mod it
+ CHECK(d0_bignum_divmod(NULL, temp1, temp2, ctx->rsa_n));
+
+ // hash complete
+ if(d0_bignum_cmp(temp0, temp1))
{
// accept the key anyway, but mark as failed signature! will later return 0 in status
- CHECK(d0_bignum_zero(ctx->schnorr_4_to_s_signature));
+ CHECK(d0_bignum_zero(ctx->schnorr_H_4_to_s_signature));
}
}
CHECK(d0_iobuf_write_bignum(out, temp0));
if(status)
- *status = !!d0_bignum_cmp(ctx->schnorr_4_to_s_signature, zero);
+ *status = !!d0_bignum_cmp(ctx->schnorr_H_4_to_s_signature, zero);
d0_iobuf_close(in, NULL);
return d0_iobuf_close(out, outbuflen);
}
if(status)
- *status = !!d0_bignum_cmp(ctx->schnorr_4_to_s_signature, zero);
+ *status = !!d0_bignum_cmp(ctx->schnorr_H_4_to_s_signature, zero);
if(ctx->msglen <= *msglen)
memcpy(msg, ctx->msg, ctx->msglen);
BOOL d0_blind_id_sessionkey_public_id(const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
{
- d0_iobuf_t *out = NULL;
- static unsigned char convbuf[1024];
- d0_iobuf_t *conv = NULL;
- size_t n, sz;
-
USING(r); USING(other_4_to_r); USING(schnorr_G);
- out = d0_iobuf_open_write(outbuf, *outbuflen);
- conv = d0_iobuf_open_write(convbuf, sizeof(convbuf));
-
// temps: temp0 result
CHECK(d0_bignum_mod_pow(temp0, ctx->other_4_to_r, ctx->r, ctx->schnorr_G));
- CHECK(d0_iobuf_write_bignum(conv, temp0));
- CHECK(d0_iobuf_close(conv, &sz));
- conv = NULL;
-
- n = *outbuflen;
- if(n > SHA_DIGESTSIZE)
- n = SHA_DIGESTSIZE;
- CHECK(d0_iobuf_write_raw(out, sha(convbuf, sz), n) == n);
-
- return d0_iobuf_close(out, outbuflen);
+ return d0_longhash_destructive(temp0, outbuf, *outbuflen);
fail:
- if(conv)
- d0_iobuf_close(conv, &sz);
- d0_iobuf_close(out, outbuflen);
return 0;
}
d0_blind_id_clear(a);
d0_free(a);
}
+
+void d0_blind_id_util_sha256(char *out, const char *in, size_t n)
+{
+ SHA256_CTX context;
+ SHA256_Init(&context);
+ SHA256_Update(&context, (const unsigned char *) in, n);
+ return SHA256_Final((unsigned char *) out, &context);
+}
projects / xonotic / d0_blind_id.git / blobdiff