Merge pull request bitcoin#347

8e48787 Change secp256k1_ec_pubkey_combine's count argument to size_t. (Gregory Maxwell)
c69dea0 Clear output in more cases for pubkey_combine, adds tests. (Gregory Maxwell)
269d422 Comment copyediting. (Gregory Maxwell)

include/secp256k1.h

@@ -229,7 +229,7 @@ SECP256K1_API void secp256k1_context_set_illegal_callback(
  *  crashing.
  *
  *  Args: ctx:  an existing context object (cannot be NULL)
- *  In:   fun:  a pointer to a function to call when an interal error occurs,
+ *  In:   fun:  a pointer to a function to call when an internal error occurs,
  *              taking a message and an opaque pointer (NULL restores a default
  *              handler that calls abort).
  *        data: the opaque pointer to pass to fun above.
@@ -562,18 +562,16 @@ SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_context_randomize(
  *  Returns: 1: the sum of the public keys is valid.
  *           0: the sum of the public keys is not valid.
  *  Args:   ctx:        pointer to a context object
- *  Out:    out:        pointer to pubkey for placing the resulting public key
+ *  Out:    out:        pointer to a public key object for placing the resulting public key
  *                      (cannot be NULL)
  *  In:     ins:        pointer to array of pointers to public keys (cannot be NULL)
  *          n:          the number of public keys to add together (must be at least 1)
- *  Use secp256k1_ec_pubkey_compress and secp256k1_ec_pubkey_decompress if the
- *  uncompressed format is needed.
  */
 SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_combine(
     const secp256k1_context* ctx,
     secp256k1_pubkey *out,
     const secp256k1_pubkey * const * ins,
-    int n
+    size_t n
 ) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
 
 # ifdef __cplusplus

include/secp256k1_recovery.h

@@ -92,7 +92,7 @@ SECP256K1_API int secp256k1_ecdsa_sign_recoverable(
  *  Returns: 1: public key successfully recovered (which guarantees a correct signature).
  *           0: otherwise.
  *  Args:    ctx:        pointer to a context object, initialized for verification (cannot be NULL)
- *  Out:     pubkey:     pointer to the recoved public key (cannot be NULL)
+ *  Out:     pubkey:     pointer to the recovered public key (cannot be NULL)
  *  In:      sig:        pointer to initialized signature that supports pubkey recovery (cannot be NULL)
  *           msg32:      the 32-byte message hash assumed to be signed (cannot be NULL)
  */

include/secp256k1_schnorr.h

@@ -99,7 +99,7 @@ SECP256K1_API int secp256k1_schnorr_generate_nonce_pair(
 /** Produce a partial Schnorr signature, which can be combined using
  *  secp256k1_schnorr_partial_combine, to end up with a full signature that is
  *  verifiable using secp256k1_schnorr_verify.
- *  Returns: 1: signature created succesfully.
+ *  Returns: 1: signature created successfully.
  *           0: no valid signature exists with this combination of keys, nonces
  *              and message (chance around 1 in 2^128)
  *          -1: invalid private key, nonce, or public nonces.
@@ -148,7 +148,7 @@ SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_schnorr_partial_sign(
 ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4) SECP256K1_ARG_NONNULL(5) SECP256K1_ARG_NONNULL(6);
 
 /** Combine multiple Schnorr partial signatures.
- * Returns: 1: the passed signatures were succesfully combined.
+ * Returns: 1: the passed signatures were successfully combined.
  *          0: the resulting signature is not valid (chance of 1 in 2^256)
  *         -1: some inputs were invalid, or the signatures were not created
  *             using the same set of nonces
@@ -163,7 +163,7 @@ SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_schnorr_partial_combine
   const secp256k1_context* ctx,
   unsigned char *sig64,
   const unsigned char * const * sig64sin,
-  int n
+  size_t n
 ) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
 
 # ifdef __cplusplus

src/ecdsa_impl.h

@@ -75,8 +75,9 @@ static int secp256k1_der_read_len(const unsigned char **sigp, const unsigned cha
         return -1;
     }
     if ((size_t)lenleft > sizeof(size_t)) {
-        /* The resulthing length would exceed the range of a size_t, so
-           certainly longer than the passed array size. */
+        /* The resulting length would exceed the range of a size_t, so
+         * certainly longer than the passed array size.
+         */
         return -1;
     }
     while (lenleft > 0) {
@@ -267,13 +268,17 @@ static int secp256k1_ecdsa_sig_sign(const secp256k1_ecmult_gen_context *ctx, sec
     secp256k1_fe_get_b32(b, &r.x);
     secp256k1_scalar_set_b32(sigr, b, &overflow);
     if (secp256k1_scalar_is_zero(sigr)) {
-        /* P.x = order is on the curve, so technically sig->r could end up zero, which would be an invalid signature. */
-        /* This branch is cryptographically unreachable as hitting it requires finding the discrete log of P.x = N. */
+        /* P.x = order is on the curve, so technically sig->r could end up zero, which would be an invalid signature.
+         * This branch is cryptographically unreachable as hitting it requires finding the discrete log of P.x = N.
+         */
         secp256k1_gej_clear(&rp);
         secp256k1_ge_clear(&r);
         return 0;
     }
     if (recid) {
+        /* The overflow condition is cryptographically unreachable as hitting it requires finding the discrete log
+         * of some P where P.x >= order, and only 1 in about 2^127 points meet this criteria.
+         */
         *recid = (overflow ? 2 : 0) | (secp256k1_fe_is_odd(&r.y) ? 1 : 0);
     }
     secp256k1_scalar_mul(&n, sigr, seckey);

src/field.h

@@ -10,7 +10,7 @@
 /** Field element module.
  *
  *  Field elements can be represented in several ways, but code accessing
- *  it (and implementations) need to take certain properaties into account:
+ *  it (and implementations) need to take certain properties into account:
  *  - Each field element can be normalized or not.
  *  - Each field element has a magnitude, which represents how far away
  *    its representation is away from normalization. Normalized elements

src/modules/schnorr/main_impl.h

@@ -154,7 +154,7 @@ int secp256k1_schnorr_partial_sign(const secp256k1_context* ctx, unsigned char *
     return secp256k1_schnorr_sig_sign(&ctx->ecmult_gen_ctx, sig64, &sec, &non, &pubnon, secp256k1_schnorr_msghash_sha256, msg32);
 }
 
-int secp256k1_schnorr_partial_combine(const secp256k1_context* ctx, unsigned char *sig64, const unsigned char * const *sig64sin, int n) {
+int secp256k1_schnorr_partial_combine(const secp256k1_context* ctx, unsigned char *sig64, const unsigned char * const *sig64sin, size_t n) {
     ARG_CHECK(sig64 != NULL);
     ARG_CHECK(n >= 1);
     ARG_CHECK(sig64sin != NULL);

src/modules/schnorr/schnorr.h

@@ -15,6 +15,6 @@ typedef void (*secp256k1_schnorr_msghash)(unsigned char *h32, const unsigned cha
 static int secp256k1_schnorr_sig_sign(const secp256k1_ecmult_gen_context* ctx, unsigned char *sig64, const secp256k1_scalar *key, const secp256k1_scalar *nonce, const secp256k1_ge *pubnonce, secp256k1_schnorr_msghash hash, const unsigned char *msg32);
 static int secp256k1_schnorr_sig_verify(const secp256k1_ecmult_context* ctx, const unsigned char *sig64, const secp256k1_ge *pubkey, secp256k1_schnorr_msghash hash, const unsigned char *msg32);
 static int secp256k1_schnorr_sig_recover(const secp256k1_ecmult_context* ctx, const unsigned char *sig64, secp256k1_ge *pubkey, secp256k1_schnorr_msghash hash, const unsigned char *msg32);
-static int secp256k1_schnorr_sig_combine(unsigned char *sig64, int n, const unsigned char * const *sig64ins);
+static int secp256k1_schnorr_sig_combine(unsigned char *sig64, size_t n, const unsigned char * const *sig64ins);
 
 #endif

src/modules/schnorr/schnorr_impl.h

@@ -178,9 +178,9 @@ static int secp256k1_schnorr_sig_recover(const secp256k1_ecmult_context* ctx, co
     return 1;
 }
 
-static int secp256k1_schnorr_sig_combine(unsigned char *sig64, int n, const unsigned char * const *sig64ins) {
+static int secp256k1_schnorr_sig_combine(unsigned char *sig64, size_t n, const unsigned char * const *sig64ins) {
     secp256k1_scalar s = SECP256K1_SCALAR_CONST(0, 0, 0, 0, 0, 0, 0, 0);
-    int i;
+    size_t i;
     for (i = 0; i < n; i++) {
         secp256k1_scalar si;
         int overflow;

src/secp256k1.c

@@ -530,12 +530,13 @@ int secp256k1_context_randomize(secp256k1_context* ctx, const unsigned char *see
     return 1;
 }
 
-int secp256k1_ec_pubkey_combine(const secp256k1_context* ctx, secp256k1_pubkey *pubnonce, const secp256k1_pubkey * const *pubnonces, int n) {
-    int i;
+int secp256k1_ec_pubkey_combine(const secp256k1_context* ctx, secp256k1_pubkey *pubnonce, const secp256k1_pubkey * const *pubnonces, size_t n) {
+    size_t i;
     secp256k1_gej Qj;
     secp256k1_ge Q;
 
     ARG_CHECK(pubnonce != NULL);
+    memset(pubnonce, 0, sizeof(*pubnonce));
     ARG_CHECK(n >= 1);
     ARG_CHECK(pubnonces != NULL);
 
@@ -546,7 +547,6 @@ int secp256k1_ec_pubkey_combine(const secp256k1_context* ctx, secp256k1_pubkey *
         secp256k1_gej_add_ge(&Qj, &Qj, &Q);
     }
     if (secp256k1_gej_is_infinity(&Qj)) {
-        memset(pubnonce, 0, sizeof(*pubnonce));
         return 0;
     }
     secp256k1_ge_set_gej(&Q, &Qj);

src/tests.c

@@ -594,7 +594,7 @@ void scalar_test(void) {
     }
 
     {
-        /* Test that multipying the scalars is equal to multiplying their numbers modulo the order. */
+        /* Test that multiplying the scalars is equal to multiplying their numbers modulo the order. */
         secp256k1_scalar r;
         secp256k1_num r2num;
         secp256k1_num rnum;
@@ -840,7 +840,7 @@ void run_scalar_tests(void) {
 
     {
         /* Static test vectors.
-         * These were reduced from ~10^12 random vectors based on comparision-decision
+         * These were reduced from ~10^12 random vectors based on comparison-decision
          *  and edge-case coverage on 32-bit and 64-bit implementations.
          * The responses were generated with Sage 5.9.
          */
@@ -1737,7 +1737,7 @@ void test_ge(void) {
     /* Points: (infinity, p1, p1, -p1, -p1, p2, p2, -p2, -p2, p3, p3, -p3, -p3, p4, p4, -p4, -p4).
      * The second in each pair of identical points uses a random Z coordinate in the Jacobian form.
      * All magnitudes are randomized.
-     * All 17*17 combinations of points are added to eachother, using all applicable methods.
+     * All 17*17 combinations of points are added to each other, using all applicable methods.
      *
      * When the endomorphism code is compiled in, p5 = lambda*p1 and p6 = lambda^2*p1 are added as well.
      */
@@ -2420,7 +2420,7 @@ void run_ecmult_constants(void) {
 }
 
 void test_ecmult_gen_blind(void) {
-    /* Test ecmult_gen() blinding and confirm that the blinding changes, the affline points match, and the z's don't match. */
+    /* Test ecmult_gen() blinding and confirm that the blinding changes, the affine points match, and the z's don't match. */
     secp256k1_scalar key;
     secp256k1_scalar b;
     unsigned char seed32[32];
@@ -2902,10 +2902,14 @@ void run_eckey_edge_case_test(void) {
         0xbf, 0xd2, 0x5e, 0x8c, 0xd0, 0x36, 0x41, 0x41
     };
     const unsigned char zeros[sizeof(secp256k1_pubkey)] = {0x00};
-    unsigned char ctmp[32];
-    unsigned char ctmp2[32];
+    unsigned char ctmp[33];
+    unsigned char ctmp2[33];
     secp256k1_pubkey pubkey;
     secp256k1_pubkey pubkey2;
+    secp256k1_pubkey pubkey_one;
+    secp256k1_pubkey pubkey_negone;
+    const secp256k1_pubkey *pubkeys[3];
+    size_t len;
     int32_t ecount;
     /* Group order is too large, reject. */
     CHECK(secp256k1_ec_seckey_verify(ctx, orderc) == 0);
@@ -2937,6 +2941,7 @@ void run_eckey_edge_case_test(void) {
     CHECK(secp256k1_ec_pubkey_create(ctx, &pubkey, ctmp) == 1);
     VG_CHECK(&pubkey, sizeof(pubkey));
     CHECK(memcmp(&pubkey, zeros, sizeof(secp256k1_pubkey)) > 0);
+    pubkey_one = pubkey;
     /* Group order + 1 is too large, reject. */
     memcpy(ctmp, orderc, 32);
     ctmp[31] = 0x42;
@@ -2954,6 +2959,7 @@ void run_eckey_edge_case_test(void) {
     CHECK(secp256k1_ec_pubkey_create(ctx, &pubkey, ctmp) == 1);
     VG_CHECK(&pubkey, sizeof(pubkey));
     CHECK(memcmp(&pubkey, zeros, sizeof(secp256k1_pubkey)) > 0);
+    pubkey_negone = pubkey;
     /* Tweak of zero leaves the value changed. */
     memset(ctmp2, 0, 32);
     CHECK(secp256k1_ec_privkey_tweak_add(ctx, ctmp, ctmp2) == 1);
@@ -3060,6 +3066,67 @@ void run_eckey_edge_case_test(void) {
     CHECK(secp256k1_ec_pubkey_create(ctx, &pubkey, NULL) == 0);
     CHECK(ecount == 2);
     CHECK(memcmp(&pubkey, zeros, sizeof(secp256k1_pubkey)) == 0);
+    /* secp256k1_ec_pubkey_combine tests. */
+    ecount = 0;
+    pubkeys[0] = &pubkey_one;
+    VG_UNDEF(&pubkeys[0], sizeof(secp256k1_pubkey *));
+    VG_UNDEF(&pubkeys[1], sizeof(secp256k1_pubkey *));
+    VG_UNDEF(&pubkeys[2], sizeof(secp256k1_pubkey *));
+    memset(&pubkey, 255, sizeof(secp256k1_pubkey));
+    VG_UNDEF(&pubkey, sizeof(secp256k1_pubkey));
+    CHECK(secp256k1_ec_pubkey_combine(ctx, &pubkey, pubkeys, 0) == 0);
+    VG_CHECK(&pubkey, sizeof(secp256k1_pubkey));
+    CHECK(memcmp(&pubkey, zeros, sizeof(secp256k1_pubkey)) == 0);
+    CHECK(ecount == 1);
+    CHECK(secp256k1_ec_pubkey_combine(ctx, NULL, pubkeys, 1) == 0);
+    CHECK(memcmp(&pubkey, zeros, sizeof(secp256k1_pubkey)) == 0);
+    CHECK(ecount == 2);
+    memset(&pubkey, 255, sizeof(secp256k1_pubkey));
+    VG_UNDEF(&pubkey, sizeof(secp256k1_pubkey));
+    CHECK(secp256k1_ec_pubkey_combine(ctx, &pubkey, NULL, 1) == 0);
+    VG_CHECK(&pubkey, sizeof(secp256k1_pubkey));
+    CHECK(memcmp(&pubkey, zeros, sizeof(secp256k1_pubkey)) == 0);
+    CHECK(ecount == 3);
+    pubkeys[0] = &pubkey_negone;
+    memset(&pubkey, 255, sizeof(secp256k1_pubkey));
+    VG_UNDEF(&pubkey, sizeof(secp256k1_pubkey));
+    CHECK(secp256k1_ec_pubkey_combine(ctx, &pubkey, pubkeys, 1) == 1);
+    VG_CHECK(&pubkey, sizeof(secp256k1_pubkey));
+    CHECK(memcmp(&pubkey, zeros, sizeof(secp256k1_pubkey)) > 0);
+    CHECK(ecount == 3);
+    len = 33;
+    CHECK(secp256k1_ec_pubkey_serialize(ctx, ctmp, &len, &pubkey, SECP256K1_EC_COMPRESSED) == 1);
+    CHECK(secp256k1_ec_pubkey_serialize(ctx, ctmp2, &len, &pubkey_negone, SECP256K1_EC_COMPRESSED) == 1);
+    CHECK(memcmp(ctmp, ctmp2, 33) == 0);
+    /* Result is infinity. */
+    pubkeys[0] = &pubkey_one;
+    pubkeys[1] = &pubkey_negone;
+    memset(&pubkey, 255, sizeof(secp256k1_pubkey));
+    VG_UNDEF(&pubkey, sizeof(secp256k1_pubkey));
+    CHECK(secp256k1_ec_pubkey_combine(ctx, &pubkey, pubkeys, 2) == 0);
+    VG_CHECK(&pubkey, sizeof(secp256k1_pubkey));
+    CHECK(memcmp(&pubkey, zeros, sizeof(secp256k1_pubkey)) == 0);
+    CHECK(ecount == 3);
+    /* Passes through infinity but comes out one. */
+    pubkeys[2] = &pubkey_one;
+    memset(&pubkey, 255, sizeof(secp256k1_pubkey));
+    VG_UNDEF(&pubkey, sizeof(secp256k1_pubkey));
+    CHECK(secp256k1_ec_pubkey_combine(ctx, &pubkey, pubkeys, 3) == 1);
+    VG_CHECK(&pubkey, sizeof(secp256k1_pubkey));
+    CHECK(memcmp(&pubkey, zeros, sizeof(secp256k1_pubkey)) > 0);
+    CHECK(ecount == 3);
+    len = 33;
+    CHECK(secp256k1_ec_pubkey_serialize(ctx, ctmp, &len, &pubkey, SECP256K1_EC_COMPRESSED) == 1);
+    CHECK(secp256k1_ec_pubkey_serialize(ctx, ctmp2, &len, &pubkey_one, SECP256K1_EC_COMPRESSED) == 1);
+    CHECK(memcmp(ctmp, ctmp2, 33) == 0);
+    /* Adds to two. */
+    pubkeys[1] = &pubkey_one;
+    memset(&pubkey, 255, sizeof(secp256k1_pubkey));
+    VG_UNDEF(&pubkey, sizeof(secp256k1_pubkey));
+    CHECK(secp256k1_ec_pubkey_combine(ctx, &pubkey, pubkeys, 2) == 1);
+    VG_CHECK(&pubkey, sizeof(secp256k1_pubkey));
+    CHECK(memcmp(&pubkey, zeros, sizeof(secp256k1_pubkey)) > 0);
+    CHECK(ecount == 3);
     secp256k1_context_set_illegal_callback(ctx, NULL, NULL);
 }
 
@@ -3139,7 +3206,7 @@ static int nonce_function_test_retry(unsigned char *nonce32, const unsigned char
        }
        return 1;
    }
-   /* Retry rate of 6979 is negligible esp. as we only call this in determinstic tests. */
+   /* Retry rate of 6979 is negligible esp. as we only call this in deterministic tests. */
    /* If someone does fine a case where it retries for secp256k1, we'd like to know. */
    if (counter > 5) {
        return 0;
@@ -3933,6 +4000,9 @@ void test_ecdsa_edge_cases(void) {
         CHECK(ecount == 5);
         CHECK(secp256k1_ecdsa_signature_parse_compact(ctx, &sig, signature) == 1);
         CHECK(ecount == 5);
+        memset(signature, 255, 64);
+        CHECK(secp256k1_ecdsa_signature_parse_compact(ctx, &sig, signature) == 0);
+        CHECK(ecount == 5);
         secp256k1_context_set_illegal_callback(ctx, NULL, NULL);
     }
 
@@ -3966,7 +4036,7 @@ void test_ecdsa_edge_cases(void) {
         CHECK(secp256k1_ecdsa_sign(ctx, &sig2, msg, key, nonce_function_rfc6979, extra) == 1);
         CHECK(!is_empty_signature(&sig2));
         CHECK(memcmp(&sig, &sig2, sizeof(sig)) == 0);
-        /* The default nonce function is determinstic. */
+        /* The default nonce function is deterministic. */
         CHECK(secp256k1_ecdsa_sign(ctx, &sig2, msg, key, NULL, extra) == 1);
         CHECK(!is_empty_signature(&sig2));
         CHECK(memcmp(&sig, &sig2, sizeof(sig)) == 0);
@@ -3998,7 +4068,7 @@ void test_ecdsa_edge_cases(void) {
     }
 
     {
-        /* Check that optional nonce arguments do not have equivilent effect. */
+        /* Check that optional nonce arguments do not have equivalent effect. */
         const unsigned char zeros[32] = {0};
         unsigned char nonce[32];
         unsigned char nonce2[32];