diff options
Diffstat (limited to 'src/common/crypto_ed25519.c')
| -rw-r--r-- | src/common/crypto_ed25519.c | 50 |
1 files changed, 50 insertions, 0 deletions
diff --git a/src/common/crypto_ed25519.c b/src/common/crypto_ed25519.c index 188e18c710..6ebb2a78b9 100644 --- a/src/common/crypto_ed25519.c +++ b/src/common/crypto_ed25519.c @@ -28,6 +28,7 @@ #include "crypto_format.h" #include "torlog.h" #include "util.h" +#include "util_format.h" #include "ed25519/ref10/ed25519_ref10.h" #include "ed25519/donna/ed25519_donna_tor.h" @@ -57,6 +58,9 @@ typedef struct { int (*pubkey_from_curve25519_pubkey)(unsigned char *, const unsigned char *, int); + + int (*ed25519_scalarmult_with_group_order)(unsigned char *, + const unsigned char *); } ed25519_impl_t; /** The Ref10 Ed25519 implementation. This one is pure C and lightly @@ -77,6 +81,7 @@ static const ed25519_impl_t impl_ref10 = { ed25519_ref10_blind_public_key, ed25519_ref10_pubkey_from_curve25519_pubkey, + ed25519_ref10_scalarmult_with_group_order, }; /** The Ref10 Ed25519 implementation. This one is heavily optimized, but still @@ -97,6 +102,7 @@ static const ed25519_impl_t impl_donna = { ed25519_donna_blind_public_key, ed25519_donna_pubkey_from_curve25519_pubkey, + ed25519_donna_scalarmult_with_group_order, }; /** Which Ed25519 implementation are we using? NULL if we haven't decided @@ -754,3 +760,47 @@ ed25519_init(void) pick_ed25519_impl(); } +/* Return true if <b>point</b> is the identity element of the ed25519 group. */ +static int +ed25519_point_is_identity_element(const uint8_t *point) +{ + /* The identity element in ed25159 is the point with coordinates (0,1). */ + static const uint8_t ed25519_identity[32] = { + 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, + 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, + 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, + 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }; + tor_assert(sizeof(ed25519_identity) == ED25519_PUBKEY_LEN); + return tor_memeq(point, ed25519_identity, sizeof(ed25519_identity)); +} + +/** Validate <b>pubkey</b> to ensure that it has no torsion component. + * Return 0 if <b>pubkey</b> is valid, else return -1. */ +int +ed25519_validate_pubkey(const ed25519_public_key_t *pubkey) +{ + uint8_t result[32] = {9}; + + /* First check that we were not given the identity element */ + if (ed25519_point_is_identity_element(pubkey->pubkey)) { + log_warn(LD_CRYPTO, "ed25519 pubkey is the identity\n"); + return -1; + } + + /* For any point on the curve, doing l*point should give the identity element + * (where l is the group order). Do the computation and check that the + * identity element is returned. */ + if (get_ed_impl()->ed25519_scalarmult_with_group_order(result, + pubkey->pubkey) < 0) { + log_warn(LD_CRYPTO, "ed25519 group order scalarmult failed\n"); + return -1; + } + + if (!ed25519_point_is_identity_element(result)) { + log_warn(LD_CRYPTO, "ed25519 validation failed\n"); + return -1; + } + + return 0; +} + |