Merge pull request #30 from apoelstra/2018-09-audit-set-xquad

check the value of `ge_set_xquad` everywhere in -zkp modules

include/secp256k1_generator.h

@@ -13,15 +13,12 @@ extern "C" {
  *
  *  The exact representation of data inside is implementation defined and not
  *  guaranteed to be portable between different platforms or versions. It is
- *  however guaranteed to be 33 bytes in size, and can be safely copied/moved.
+ *  however guaranteed to be 64 bytes in size, and can be safely copied/moved.
- *  If you need to convert to a format suitable for storage or transmission, use
+ *  If you need to convert to a format suitable for storage, transmission, or
- *  the secp256k1_generator_serialize_*.
+ *  comparison, use secp256k1_generator_serialize and secp256k1_generator_parse.
- *
- *  Furthermore, it is guaranteed to identical points will have identical
- *  representation, so they can be memcmp'ed.
  */
 typedef struct {
-    unsigned char data[33];
+    unsigned char data[64];
 } secp256k1_generator;
 
 /** Parse a 33-byte generator byte sequence into a generator object.

include/secp256k1_rangeproof.h

@@ -14,15 +14,13 @@ extern "C" {
  *
  *  The exact representation of data inside is implementation defined and not
  *  guaranteed to be portable between different platforms or versions. It is
- *  however guaranteed to be 33 bytes in size, and can be safely copied/moved.
+ *  however guaranteed to be 64 bytes in size, and can be safely copied/moved.
- *  If you need to convert to a format suitable for storage or transmission, use
+ *  If you need to convert to a format suitable for storage, transmission, or
- *  secp256k1_pedersen_commitment_serialize and secp256k1_pedersen_commitment_parse.
+ *  comparison, use secp256k1_pedersen_commitment_serialize and
- *
+ *  secp256k1_pedersen_commitment_parse.
- *  Furthermore, it is guaranteed to identical signatures will have identical
- *  representation, so they can be memcmp'ed.
  */
 typedef struct {
-    unsigned char data[33];
+    unsigned char data[64];
 } secp256k1_pedersen_commitment;
 
 /**

src/modules/generator/main_impl.h

@@ -15,36 +15,55 @@
 #include "scalar.h"
 
 static void secp256k1_generator_load(secp256k1_ge* ge, const secp256k1_generator* gen) {
-    secp256k1_fe fe;
+    int succeed;
-    secp256k1_fe_set_b32(&fe, &gen->data[1]);
+    succeed = secp256k1_fe_set_b32(&ge->x, &gen->data[0]);
-    secp256k1_ge_set_xquad(ge, &fe);
+    VERIFY_CHECK(succeed != 0);
-    if (gen->data[0] & 1) {
+    succeed = secp256k1_fe_set_b32(&ge->y, &gen->data[32]);
-        secp256k1_ge_neg(ge, ge);
+    VERIFY_CHECK(succeed != 0);
-    }
+    ge->infinity = 0;
+    (void) succeed;
 }
 
-static void secp256k1_generator_save(secp256k1_generator* commit, secp256k1_ge* ge) {
+static void secp256k1_generator_save(secp256k1_generator *gen, secp256k1_ge* ge) {
-    secp256k1_fe_normalize(&ge->x);
+    VERIFY_CHECK(!secp256k1_ge_is_infinity(ge));
-    secp256k1_fe_get_b32(&commit->data[1], &ge->x);
+    secp256k1_fe_normalize_var(&ge->x);
-    commit->data[0] = 11 ^ secp256k1_fe_is_quad_var(&ge->y);
+    secp256k1_fe_normalize_var(&ge->y);
+    secp256k1_fe_get_b32(&gen->data[0], &ge->x);
+    secp256k1_fe_get_b32(&gen->data[32], &ge->y);
 }
 
 int secp256k1_generator_parse(const secp256k1_context* ctx, secp256k1_generator* gen, const unsigned char *input) {
+    secp256k1_fe x;
+    secp256k1_ge ge;
+
     VERIFY_CHECK(ctx != NULL);
     ARG_CHECK(gen != NULL);
     ARG_CHECK(input != NULL);
-    if ((input[0] & 0xFE) != 10) {
+
+    if ((input[0] & 0xFE) != 10 ||
+        !secp256k1_fe_set_b32(&x, &input[1]) ||
+        !secp256k1_ge_set_xquad(&ge, &x)) {
         return 0;
     }
-    memcpy(gen->data, input, sizeof(gen->data));
+    if (input[0] & 1) {
+        secp256k1_ge_neg(&ge, &ge);
+    }
+    secp256k1_generator_save(gen, &ge);
     return 1;
 }
 
 int secp256k1_generator_serialize(const secp256k1_context* ctx, unsigned char *output, const secp256k1_generator* gen) {
+    secp256k1_ge ge;
+
     VERIFY_CHECK(ctx != NULL);
     ARG_CHECK(output != NULL);
     ARG_CHECK(gen != NULL);
-    memcpy(output, gen->data, sizeof(gen->data));
+
+    secp256k1_generator_load(&ge, gen);
+
+    output[0] = 11 ^ secp256k1_fe_is_quad_var(&ge.y);
+    secp256k1_fe_normalize_var(&ge.x);
+    secp256k1_fe_get_b32(&output[1], &ge.x);
     return 1;
 }
 

src/modules/rangeproof/main_impl.h

@@ -16,13 +16,14 @@
 /** Alternative generator for secp256k1.
  *  This is the sha256 of 'g' after DER encoding (without compression),
  *  which happens to be a point on the curve.
- *  sage: G2 = EllipticCurve ([F (0), F (7)]).lift_x(int(hashlib.sha256('0479be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798483ada7726a3c4655da4fbfc0e1108a8fd17b448a68554199c47d08ffb10d4b8'.decode('hex')).hexdigest(),16))
+ *  sage: G2 = EllipticCurve ([F (0), F (7)]).lift_x(F(int(hashlib.sha256('0479be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798483ada7726a3c4655da4fbfc0e1108a8fd17b448a68554199c47d08ffb10d4b8'.decode('hex')).hexdigest(),16)))
- *  sage: '%x %x' % (11 - G2.xy()[1].is_square(), G2.xy()[0])
+ *  sage: '%x %x' % G2.xy()
  */
 static const secp256k1_generator secp256k1_generator_h_internal = {{
-    0x11,
     0x50, 0x92, 0x9b, 0x74, 0xc1, 0xa0, 0x49, 0x54, 0xb7, 0x8b, 0x4b, 0x60, 0x35, 0xe9, 0x7a, 0x5e,
-    0x07, 0x8a, 0x5a, 0x0f, 0x28, 0xec, 0x96, 0xd5, 0x47, 0xbf, 0xee, 0x9a, 0xce, 0x80, 0x3a, 0xc0
+    0x07, 0x8a, 0x5a, 0x0f, 0x28, 0xec, 0x96, 0xd5, 0x47, 0xbf, 0xee, 0x9a, 0xce, 0x80, 0x3a, 0xc0,
+    0x31, 0xd3, 0xc6, 0x86, 0x39, 0x73, 0x92, 0x6e, 0x04, 0x9e, 0x63, 0x7c, 0xb1, 0xb5, 0xf4, 0x0a,
+    0x36, 0xda, 0xc2, 0x8a, 0xf1, 0x76, 0x69, 0x68, 0xc3, 0x0c, 0x23, 0x13, 0xf3, 0xa3, 0x89, 0x04
 }};
 
 const secp256k1_generator *secp256k1_generator_h = &secp256k1_generator_h_internal;
@@ -43,22 +44,38 @@ static void secp256k1_pedersen_commitment_save(secp256k1_pedersen_commitment* co
 }
 
 int secp256k1_pedersen_commitment_parse(const secp256k1_context* ctx, secp256k1_pedersen_commitment* commit, const unsigned char *input) {
+    secp256k1_fe x;
+    secp256k1_ge ge;
+
     VERIFY_CHECK(ctx != NULL);
     ARG_CHECK(commit != NULL);
     ARG_CHECK(input != NULL);
     (void) ctx;
-    if ((input[0] & 0xFE) != 8) {
+
+    if ((input[0] & 0xFE) != 8 ||
+        !secp256k1_fe_set_b32(&x, &input[1]) ||
+        !secp256k1_ge_set_xquad(&ge, &x)) {
         return 0;
     }
-    memcpy(commit->data, input, sizeof(commit->data));
+    if (input[0] & 1) {
+        secp256k1_ge_neg(&ge, &ge);
+    }
+    secp256k1_pedersen_commitment_save(commit, &ge);
     return 1;
 }
 
 int secp256k1_pedersen_commitment_serialize(const secp256k1_context* ctx, unsigned char *output, const secp256k1_pedersen_commitment* commit) {
+    secp256k1_ge ge;
+
     VERIFY_CHECK(ctx != NULL);
     ARG_CHECK(output != NULL);
     ARG_CHECK(commit != NULL);
-    memcpy(output, commit->data, sizeof(commit->data));
+
+    secp256k1_pedersen_commitment_load(&ge, commit);
+
+    output[0] = 11 ^ secp256k1_fe_is_quad_var(&ge.y);
+    secp256k1_fe_normalize_var(&ge.x);
+    secp256k1_fe_get_b32(&output[1], &ge.x);
     return 1;
 }
 

src/modules/rangeproof/rangeproof_impl.h

@@ -609,8 +609,10 @@ SECP256K1_INLINE static int secp256k1_rangeproof_verify_impl(const secp256k1_ecm
     }
     for(i = 0; i < rings - 1; i++) {
         secp256k1_fe fe;
-        secp256k1_fe_set_b32(&fe, &proof[offset]);
+        if (!secp256k1_fe_set_b32(&fe, &proof[offset]) ||
-        secp256k1_ge_set_xquad(&c, &fe);
+            !secp256k1_ge_set_xquad(&c, &fe)) {
+            return 0;
+        }
         if (signs[i]) {
             secp256k1_ge_neg(&c, &c);
         }

src/modules/rangeproof/tests_impl.h

@@ -607,9 +607,75 @@ void test_multiple_generators(void) {
     }
 }
 
+void test_rangeproof_fixed_vectors(void) {
+    const unsigned char vector_1[] = {
+        0x62, 0x07, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x56, 0x02, 0x2a, 0x5c, 0x42, 0x0e, 0x1d,
+        0x51, 0xe1, 0xb7, 0xf3, 0x69, 0x04, 0xb5, 0xbb, 0x9b, 0x41, 0x66, 0x14, 0xf3, 0x64, 0x42, 0x26,
+        0xe3, 0xa7, 0x6a, 0x06, 0xbb, 0xa8, 0x5a, 0x49, 0x6f, 0x19, 0x76, 0xfb, 0xe5, 0x75, 0x77, 0x88,
+        0xab, 0xa9, 0x66, 0x44, 0x80, 0xea, 0x29, 0x95, 0x7f, 0xdf, 0x72, 0x4a, 0xaf, 0x02, 0xbe, 0xdd,
+        0x5d, 0x15, 0xd8, 0xae, 0xff, 0x74, 0xc9, 0x8c, 0x1a, 0x67, 0x0e, 0xb2, 0x57, 0x22, 0x99, 0xc3,
+        0x21, 0x46, 0x6f, 0x15, 0x58, 0x0e, 0xdb, 0xe6, 0x6e, 0xc4, 0x0d, 0xfe, 0x6f, 0x04, 0x6b, 0x0d,
+        0x18, 0x3d, 0x78, 0x40, 0x98, 0x56, 0x4e, 0xe4, 0x4a, 0x74, 0x90, 0xa7, 0xac, 0x9c, 0x16, 0xe0,
+        0x3e, 0x81, 0xaf, 0x0f, 0xe3, 0x4f, 0x34, 0x99, 0x52, 0xf7, 0xa7, 0xf6, 0xd3, 0x83, 0xa0, 0x17,
+        0x4b, 0x2d, 0xa7, 0xd4, 0xfd, 0xf7, 0x84, 0x45, 0xc4, 0x11, 0x71, 0x3d, 0x4a, 0x22, 0x34, 0x09,
+        0x9c, 0xa7, 0xe5, 0xc8, 0xba, 0x04, 0xbf, 0xfd, 0x25, 0x11, 0x7d, 0xa4, 0x43, 0x45, 0xc7, 0x62,
+        0x9e, 0x7b, 0x80, 0xf6, 0x09, 0xbb, 0x1b, 0x2e, 0xf3, 0xcd, 0x23, 0xe0, 0xed, 0x81, 0x43, 0x42,
+        0xbe, 0xc4, 0x9f, 0x58, 0x8a, 0x0d, 0x66, 0x79, 0x09, 0x70, 0x11, 0x68, 0x3d, 0x87, 0x38, 0x1c,
+        0x3c, 0x85, 0x52, 0x5b, 0x62, 0xf7, 0x3e, 0x7e, 0x87, 0xa2, 0x99, 0x24, 0xd0, 0x7d, 0x18, 0x63,
+        0x56, 0x48, 0xa4, 0x3a, 0xfe, 0x65, 0xfa, 0xa4, 0xd0, 0x67, 0xaa, 0x98, 0x65, 0x4d, 0xe4, 0x22,
+        0x75, 0x45, 0x52, 0xe8, 0x41, 0xc7, 0xed, 0x38, 0xeb, 0xf5, 0x02, 0x90, 0xc9, 0x45, 0xa3, 0xb0,
+        0x4d, 0x03, 0xd7, 0xab, 0x43, 0xe4, 0x21, 0xfc, 0x83, 0xd6, 0x12, 0x1d, 0x76, 0xb1, 0x3c, 0x67,
+        0x63, 0x1f, 0x52, 0x9d, 0xc3, 0x23, 0x5c, 0x4e, 0xa6, 0x8d, 0x01, 0x4a, 0xba, 0x9a, 0xf4, 0x16,
+        0x5b, 0x67, 0xc8, 0xe1, 0xd2, 0x42, 0x6d, 0xdf, 0xcd, 0x08, 0x6a, 0x73, 0x41, 0x6a, 0xc2, 0x84,
+        0xc6, 0x31, 0xbe, 0x57, 0xcb, 0x0e, 0xde, 0xbf, 0x71, 0xd5, 0x8a, 0xf7, 0x24, 0xb2, 0xa7, 0x89,
+        0x96, 0x62, 0x4f, 0xd9, 0xf7, 0xc3, 0xde, 0x4c, 0xab, 0x13, 0x72, 0xb4, 0xb3, 0x35, 0x04, 0x82,
+        0xa8, 0x75, 0x1d, 0xde, 0x46, 0xa8, 0x0d, 0xb8, 0x23, 0x44, 0x00, 0x44, 0xfa, 0x53, 0x6c, 0x2d,
+        0xce, 0xd3, 0xa6, 0x80, 0xa1, 0x20, 0xca, 0xd1, 0x63, 0xbb, 0xbe, 0x39, 0x5f, 0x9d, 0x27, 0x69,
+        0xb3, 0x33, 0x1f, 0xdb, 0xda, 0x67, 0x05, 0x37, 0xbe, 0x65, 0xe9, 0x7e, 0xa9, 0xc3, 0xff, 0x37,
+        0x8a, 0xb4, 0x2d, 0xfe, 0xf2, 0x16, 0x85, 0xc7, 0x0f, 0xd9, 0xbe, 0x14, 0xd1, 0x80, 0x14, 0x9f,
+        0x58, 0x56, 0x98, 0x41, 0xf6, 0x26, 0xf7, 0xa2, 0x71, 0x66, 0xb4, 0x7a, 0x9c, 0x12, 0x73, 0xd3,
+        0xdf, 0x77, 0x2b, 0x49, 0xe5, 0xca, 0x50, 0x57, 0x44, 0x6e, 0x3f, 0x58, 0x56, 0xbc, 0x21, 0x70,
+        0x4f, 0xc6, 0xaa, 0x12, 0xff, 0x7c, 0xa7, 0x3d, 0xed, 0x46, 0xc1, 0x40, 0xe6, 0x58, 0x09, 0x2a,
+        0xda, 0xb3, 0x76, 0xab, 0x44, 0xb5, 0x4e, 0xb3, 0x12, 0xe0, 0x26, 0x8a, 0x52, 0xac, 0x49, 0x1d,
+        0xe7, 0x06, 0x53, 0x3a, 0x01, 0x35, 0x21, 0x2e, 0x86, 0x48, 0xc5, 0x75, 0xc1, 0xa2, 0x7d, 0x22,
+        0x53, 0xf6, 0x3f, 0x41, 0xc5, 0xb3, 0x08, 0x7d, 0xa3, 0x67, 0xc0, 0xbb, 0xb6, 0x8d, 0xf0, 0xd3,
+        0x01, 0x72, 0xd3, 0x63, 0x82, 0x01, 0x1a, 0xe7, 0x1d, 0x22, 0xfa, 0x95, 0x33, 0xf6, 0xf2, 0xde,
+        0xa2, 0x53, 0x86, 0x55, 0x5a, 0xb4, 0x2e, 0x75, 0x75, 0xc6, 0xd5, 0x93, 0x9c, 0x57, 0xa9, 0x1f,
+        0xb9, 0x3e, 0xe8, 0x1c, 0xbf, 0xac, 0x1c, 0x54, 0x6f, 0xf5, 0xab, 0x41, 0xee, 0xb3, 0x0e, 0xd0,
+        0x76, 0xc4, 0x1a, 0x45, 0xcd, 0xf1, 0xd6, 0xcc, 0xb0, 0x83, 0x70, 0x73, 0xbc, 0x88, 0x74, 0xa0,
+        0x5b, 0xe7, 0x98, 0x10, 0x36, 0xbf, 0xec, 0x23, 0x1c, 0xc2, 0xb5, 0xba, 0x4b, 0x9d, 0x7f, 0x8c,
+        0x8a, 0xe2, 0xda, 0x18, 0xdd, 0xab, 0x27, 0x8a, 0x15, 0xeb, 0xb0, 0xd4, 0x3a, 0x8b, 0x77, 0x00,
+        0xc7, 0xbb, 0xcc, 0xfa, 0xba, 0xa4, 0x6a, 0x17, 0x5c, 0xf8, 0x51, 0x5d, 0x8d, 0x16, 0xcd, 0xa7,
+        0x0e, 0x71, 0x97, 0x98, 0x78, 0x5a, 0x41, 0xb3, 0xf0, 0x1f, 0x87, 0x2d, 0x65, 0xcd, 0x29, 0x49,
+        0xd2, 0x87, 0x2c, 0x91, 0xa9, 0x5f, 0xcc, 0xa9, 0xd8, 0xbb, 0x53, 0x18, 0xe7, 0xd6, 0xec, 0x65,
+        0xa6, 0x45, 0xf6, 0xce, 0xcf, 0x48, 0xf6, 0x1e, 0x3d, 0xd2, 0xcf, 0xcb, 0x3a, 0xcd, 0xbb, 0x92,
+        0x29, 0x24, 0x16, 0x7f, 0x8a, 0xa8, 0x5c, 0x0c, 0x45, 0x71, 0x33
+    };
+    const unsigned char commit_1[] = {
+        0x08,
+        0xf5, 0x1e, 0x0d, 0xc5, 0x86, 0x78, 0x51, 0xa9, 0x00, 0x00, 0xef, 0x4d, 0xe2, 0x94, 0x60, 0x89,
+        0x83, 0x04, 0xb4, 0x0e, 0x90, 0x10, 0x05, 0x1c, 0x7f, 0xd7, 0x33, 0x92, 0x1f, 0xe7, 0x74, 0x59
+    };
+    size_t min_value_1;
+    size_t max_value_1;
+    secp256k1_pedersen_commitment pc;
+
+    CHECK(secp256k1_pedersen_commitment_parse(ctx, &pc, commit_1));
+
+    CHECK(secp256k1_rangeproof_verify(
+        ctx,
+        &min_value_1, &max_value_1,
+        &pc,
+        vector_1, sizeof(vector_1),
+        NULL, 0,
+        secp256k1_generator_h
+    ));
+}
+
 void run_rangeproof_tests(void) {
     int i;
     test_api();
+    test_rangeproof_fixed_vectors();
     for (i = 0; i < 10*count; i++) {
         test_pedersen();
     }