Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Extract the secret key from a keypair #845

Merged
merged 3 commits into from
Jan 12, 2021
Merged

Extract the secret key from a keypair #845

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
fc96aa7
Add a function to extract the secretkey from a keypair
elichai Nov 5, 2020
36d9dc1
Add seckey extraction from keypair to the extrakeys tests
elichai Nov 5, 2020
33cb3c2
Add secret key extraction from keypair to constant time tests
elichai Dec 19, 2020
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
13 changes: 13 additions & 0 deletions include/secp256k1_extrakeys.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -165,6 +165,19 @@ SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_keypair_create(
const unsigned char *seckey
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);

/** Get the secret key from a keypair.
*
* Returns: 0 if the arguments are invalid. 1 otherwise.
* Args: ctx: pointer to a context object (cannot be NULL)
* Out: seckey: pointer to a 32-byte buffer for the secret key (cannot be NULL)
* In: keypair: pointer to a keypair (cannot be NULL)
*/
SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_keypair_sec(
const secp256k1_context* ctx,
unsigned char *seckey,
const secp256k1_keypair *keypair
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);

/** Get the public key from a keypair.
*
* Returns: 0 if the arguments are invalid. 1 otherwise.
Expand Down
10 changes: 10 additions & 0 deletions src/modules/extrakeys/main_impl.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -186,6 +186,16 @@ int secp256k1_keypair_create(const secp256k1_context* ctx, secp256k1_keypair *ke
return ret;
}

int secp256k1_keypair_sec(const secp256k1_context* ctx, unsigned char *seckey, const secp256k1_keypair *keypair) {
VERIFY_CHECK(ctx != NULL);
ARG_CHECK(seckey != NULL);
memset(seckey, 0, 32);
ARG_CHECK(keypair != NULL);

memcpy(seckey, &keypair->data[0], 32);
return 1;
}

int secp256k1_keypair_pub(const secp256k1_context* ctx, secp256k1_pubkey *pubkey, const secp256k1_keypair *keypair) {
VERIFY_CHECK(ctx != NULL);
ARG_CHECK(pubkey != NULL);
Expand Down
27 changes: 26 additions & 1 deletion src/modules/extrakeys/tests_impl.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -311,6 +311,7 @@ void test_xonly_pubkey_tweak_recursive(void) {

void test_keypair(void) {
unsigned char sk[32];
unsigned char sk_tmp[32];
unsigned char zeros96[96] = { 0 };
unsigned char overflows[32];
secp256k1_keypair keypair;
Expand Down Expand Up @@ -396,6 +397,28 @@ void test_keypair(void) {
CHECK(secp256k1_memcmp_var(&xonly_pk, &xonly_pk_tmp, sizeof(pk)) == 0);
CHECK(pk_parity == pk_parity_tmp);

/* Test keypair_seckey */
ecount = 0;
secp256k1_testrand256(sk);
CHECK(secp256k1_keypair_create(ctx, &keypair, sk) == 1);
CHECK(secp256k1_keypair_sec(none, sk_tmp, &keypair) == 1);
CHECK(secp256k1_keypair_sec(none, NULL, &keypair) == 0);
CHECK(ecount == 1);
CHECK(secp256k1_keypair_sec(none, sk_tmp, NULL) == 0);
CHECK(ecount == 2);
CHECK(secp256k1_memcmp_var(zeros96, sk_tmp, sizeof(sk_tmp)) == 0);

/* keypair returns the same seckey it got */
CHECK(secp256k1_keypair_create(sign, &keypair, sk) == 1);
CHECK(secp256k1_keypair_sec(none, sk_tmp, &keypair) == 1);
CHECK(secp256k1_memcmp_var(sk, sk_tmp, sizeof(sk_tmp)) == 0);


/* Using an invalid keypair is fine for keypair_seckey */
memset(&keypair, 0, sizeof(keypair));
CHECK(secp256k1_keypair_sec(none, sk_tmp, &keypair) == 1);
CHECK(secp256k1_memcmp_var(zeros96, sk_tmp, sizeof(sk_tmp)) == 0);

secp256k1_context_destroy(none);
secp256k1_context_destroy(sign);
secp256k1_context_destroy(verify);
Expand Down Expand Up @@ -484,6 +507,7 @@ void test_keypair_add(void) {
secp256k1_pubkey output_pk_xy;
secp256k1_pubkey output_pk_expected;
unsigned char pk32[32];
unsigned char sk32[32];
int pk_parity;

secp256k1_testrand256(tweak);
Expand All @@ -501,7 +525,8 @@ void test_keypair_add(void) {
CHECK(secp256k1_memcmp_var(&output_pk_xy, &output_pk_expected, sizeof(output_pk_xy)) == 0);

/* Check that the secret key in the keypair is tweaked correctly */
CHECK(secp256k1_ec_pubkey_create(ctx, &output_pk_expected, &keypair.data[0]) == 1);
CHECK(secp256k1_keypair_sec(none, sk32, &keypair) == 1);
CHECK(secp256k1_ec_pubkey_create(ctx, &output_pk_expected, sk32) == 1);
CHECK(secp256k1_memcmp_var(&output_pk_xy, &output_pk_expected, sizeof(output_pk_xy)) == 0);
}
secp256k1_context_destroy(none);
Expand Down
6 changes: 6 additions & 0 deletions src/valgrind_ctime_test.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -140,6 +140,12 @@ int main(void) {
ret = secp256k1_keypair_xonly_tweak_add(ctx, &keypair, msg);
VALGRIND_MAKE_MEM_DEFINED(&ret, sizeof(ret));
CHECK(ret == 1);

VALGRIND_MAKE_MEM_UNDEFINED(key, 32);
VALGRIND_MAKE_MEM_UNDEFINED(&keypair, sizeof(keypair));
ret = secp256k1_keypair_sec(ctx, key, &keypair);
VALGRIND_MAKE_MEM_DEFINED(&ret, sizeof(ret));
CHECK(ret == 1);
#endif

#ifdef ENABLE_MODULE_SCHNORRSIG
Expand Down