also support signing
[xonotic/d0_blind_id.git] / d0_blind_id.c
index 9bb650c..3abfb9d 100644 (file)
 
 // our SHA is SHA-256
 #define SHA_DIGESTSIZE 32
-const char *sha(const char *in, size_t len)
+const char *sha(const unsigned char *in, size_t len)
 {
        static char h[32];
-       d0_blind_id_util_sha256(h, in, len);
+       d0_blind_id_util_sha256(h, (const char *) in, len);
        return h;
 }
 
@@ -289,26 +289,33 @@ fail:
        return 0;
 }
 
-D0_WARN_UNUSED_RESULT D0_BOOL d0_longhash_destructive(d0_bignum_t *clobberme, char *outbuf, size_t outbuflen)
+D0_WARN_UNUSED_RESULT D0_BOOL d0_longhash_destructive(unsigned char *convbuf, size_t sz, unsigned char *outbuf, size_t outbuflen)
 {
-       d0_iobuf_t *out = NULL;
-       static unsigned char convbuf[1024];
-       size_t n, sz;
+       size_t n, i;
 
        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));
+               for(i = 0; i < sz; ++i)
+                       if(++convbuf[i])
+                               break; // stop until no carry
        }
-       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;
+}
+
+D0_WARN_UNUSED_RESULT D0_BOOL d0_longhash_bignum(const d0_bignum_t *in, unsigned char *outbuf, size_t outbuflen)
+{
+       static 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;
@@ -539,7 +546,7 @@ fail:
 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;
-       static unsigned char convbuf[2048], shabuf[2048];
+       static unsigned char shabuf[2048];
        size_t sz;
 
        // temps: temp0 rsa_blind_signature_camouflage^challenge, temp1 (4^s)*rsa_blind_signature_camouflage^challenge
@@ -556,7 +563,7 @@ D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_generate_private_id_request(d0_blind_i
        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_longhash_bignum(temp2, shabuf, sz));
        CHECK(d0_bignum_import_unsigned(temp2, shabuf, sz));
 
        // hash complete
@@ -722,7 +729,7 @@ fail:
        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, char *msg, size_t msglen, char *outbuf, size_t *outbuflen)
+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)
@@ -763,8 +770,8 @@ D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_authenticate_with_private_id_start(d0_
        CHECK_ASSIGN(ctx->t, d0_bignum_rand_range(ctx->t, zero, temp0));
        // can we SOMEHOW do this with just one mod_pow?
 
-       MPCHECK(d0_bignum_mod_pow(temp0, four, ctx->r, ctx->schnorr_G));
-       MPCHECK_ASSIGN(ctx->g_to_t, d0_bignum_mod_pow(ctx->g_to_t, four, ctx->t, ctx->schnorr_G));
+       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
@@ -840,7 +847,7 @@ D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_authenticate_with_private_id_challenge
                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_longhash_bignum(temp2, shabuf, sz));
                CHECK(d0_bignum_import_unsigned(temp2, shabuf, sz));
 
                // + 7 / 8 is too large, so let's mod it
@@ -999,7 +1006,7 @@ D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_authenticate_with_private_id_generate_
        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_longhash_bignum(temp2, shabuf, sz));
        CHECK(d0_bignum_import_unsigned(temp2, shabuf, sz));
 
        // + 7 / 8 is too large, so let's mod it
@@ -1011,6 +1018,162 @@ fail:
        return 0;
 }
 
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_sign_with_private_id_sign(d0_blind_id_t *ctx, D0_BOOL is_first, D0_BOOL send_modulus, const char *message, size_t msglen, char *outbuf, size_t *outbuflen)
+{
+       d0_iobuf_t *out = NULL;
+       static unsigned char convbuf[1024];
+       static unsigned char shabuf[1024];
+       d0_iobuf_t *conv = NULL;
+       size_t sz = 0;
+
+       if(is_first)
+       {
+               USING(schnorr_g_to_s); USING(schnorr_H_g_to_s_signature);
+       }
+       USING(schnorr_G);
+       USING(schnorr_s);
+       REPLACING(r);
+
+       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 SIGNATURE scheme
+       // generate random number r; x = g^r; send hash of H(m||r), remember r, forget x
+       CHECK(d0_dl_get_order(temp0, ctx->schnorr_G));
+       CHECK_ASSIGN(ctx->r, d0_bignum_rand_range(ctx->r, zero, temp0));
+       CHECK(d0_bignum_mod_pow(temp1, four, ctx->r, ctx->schnorr_G));
+
+       // hash it, hash it, everybody hash it
+       conv = d0_iobuf_open_write(convbuf, sizeof(convbuf));
+       CHECK(d0_iobuf_write_packet(conv, message, msglen));
+       CHECK(d0_iobuf_write_bignum(conv, temp1));
+       d0_iobuf_close(conv, &sz);
+       conv = NULL;
+       CHECK(d0_longhash_destructive(convbuf, sz, shabuf, (d0_bignum_size(temp0) + 7) / 8));
+       CHECK(d0_bignum_import_unsigned(temp2, shabuf, (d0_bignum_size(temp0) + 7) / 8));
+       CHECK(d0_iobuf_write_bignum(out, temp2));
+
+       // multiply with secret, sub k, modulo order
+       CHECK(d0_bignum_mod_mul(temp1, temp2, ctx->schnorr_s, temp0));
+       CHECK(d0_bignum_mod_sub(temp2, ctx->r, temp1, temp0));
+       CHECK(d0_iobuf_write_bignum(out, temp2));
+
+       // write the message itself
+       CHECK(d0_iobuf_write_packet(out, message, msglen));
+
+       return d0_iobuf_close(out, outbuflen);
+
+fail:
+       d0_iobuf_close(out, outbuflen);
+       return 0;
+}
+
+D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_sign_with_private_id_verify(d0_blind_id_t *ctx, D0_BOOL is_first, D0_BOOL recv_modulus, const char *inbuf, size_t inbuflen, char *msg, size_t *msglen, D0_BOOL *status)
+{
+       d0_iobuf_t *in = NULL;
+       d0_iobuf_t *conv = NULL;
+       static unsigned char convbuf[2048];
+       static unsigned char shabuf[2048];
+       size_t sz;
+
+       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);
+
+       in = d0_iobuf_open_read(inbuf, inbuflen);
+
+       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);
+
+               // check signature of key (t = k^d, so, t^challenge = k)
+               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!
+               CHECK(d0_bignum_mov(temp2, ctx->schnorr_g_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_bignum(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_H_g_to_s_signature));
+               }
+       }
+
+       CHECK(d0_dl_get_order(temp4, ctx->schnorr_G));
+       CHECK(d0_iobuf_read_bignum(in, temp0)); // e == H(m || g^r)
+       CHECK(d0_iobuf_read_bignum(in, temp1)); // x == (r - s*e) mod |G|
+       CHECK(d0_iobuf_read_packet(in, msg, msglen));
+
+       // VERIFY: g^x * (g^s)^-e = g^(x - s*e) = g^r
+
+       // verify schnorr ID scheme
+       // we need g^r = g^x (g^s)^e
+       CHECK(d0_bignum_mod_pow(temp2, four, temp1, ctx->schnorr_G));
+       CHECK(d0_bignum_mod_pow(temp1, ctx->schnorr_g_to_s, temp0, ctx->schnorr_G));
+       CHECK_ASSIGN(temp3, d0_bignum_mod_mul(temp3, temp1, temp2, ctx->schnorr_G)); // temp3 now is g^r
+
+       // hash it, hash it, everybody hash it
+       conv = d0_iobuf_open_write(convbuf, sizeof(convbuf));
+       CHECK(d0_iobuf_write_packet(conv, msg, *msglen));
+       CHECK(d0_iobuf_write_bignum(conv, temp3));
+       d0_iobuf_close(conv, &sz);
+       conv = NULL;
+       CHECK(d0_longhash_destructive(convbuf, sz, shabuf, (d0_bignum_size(temp4) + 7) / 8));
+       CHECK(d0_bignum_import_unsigned(temp1, shabuf, (d0_bignum_size(temp4) + 7) / 8));
+
+       // verify signature
+       CHECK(!d0_bignum_cmp(temp0, temp1));
+
+       if(status)
+               *status = !!d0_bignum_cmp(ctx->schnorr_H_g_to_s_signature, zero);
+
+       d0_iobuf_close(in, NULL);
+       return 1;
+
+fail:
+       d0_iobuf_close(in, NULL);
+       return 0;
+}
+
 D0_WARN_UNUSED_RESULT D0_BOOL d0_blind_id_fingerprint64_public_id(const d0_blind_id_t *ctx, char *outbuf, size_t *outbuflen)
 {
        d0_iobuf_t *out = NULL;
@@ -1052,7 +1215,7 @@ D0_BOOL d0_blind_id_sessionkey_public_id(const d0_blind_id_t *ctx, char *outbuf,
 
        // temps: temp0 result
        CHECK(d0_bignum_mod_pow(temp0, ctx->other_g_to_t, ctx->t, ctx->schnorr_G));
-       return d0_longhash_destructive(temp0, outbuf, *outbuflen);
+       return d0_longhash_bignum(temp0, (unsigned char *) outbuf, *outbuflen);
 
 fail:
        return 0;