diff options
Diffstat (limited to 'src/common/crypto_curve25519.c')
| -rw-r--r-- | src/common/crypto_curve25519.c | 119 |
1 files changed, 116 insertions, 3 deletions
diff --git a/src/common/crypto_curve25519.c b/src/common/crypto_curve25519.c index 5bb14b0d95..80b0d88952 100644 --- a/src/common/crypto_curve25519.c +++ b/src/common/crypto_curve25519.c @@ -14,6 +14,8 @@ #include "util.h" #include "torlog.h" +#include "ed25519/donna/ed25519_donna_tor.h" + /* ============================== Part 1: wrap a suitable curve25519 implementation as curve25519_impl ============================== */ @@ -30,6 +32,10 @@ int curve25519_donna(uint8_t *mypublic, #endif #endif +static void pick_curve25519_basepoint_impl(void); + +static int curve25519_use_ed = -1; + STATIC int curve25519_impl(uint8_t *output, const uint8_t *secret, const uint8_t *basepoint) @@ -50,6 +56,34 @@ curve25519_impl(uint8_t *output, const uint8_t *secret, return r; } +STATIC int +curve25519_basepoint_impl(uint8_t *output, const uint8_t *secret) +{ + int r = 0; + if (PREDICT_UNLIKELY(curve25519_use_ed == -1)) { + pick_curve25519_basepoint_impl(); + } + + /* TODO: Someone should benchmark curved25519_scalarmult_basepoint versus + * an optimized NaCl build to see which should be used when compiled with + * NaCl available. I suspected that the ed25519 optimization always wins. + */ + if (PREDICT_LIKELY(curve25519_use_ed == 1)) { + curved25519_scalarmult_basepoint_donna(output, secret); + r = 0; + } else { + static const uint8_t basepoint[32] = {9}; + r = curve25519_impl(output, secret, basepoint); + } + return r; +} + +void +curve25519_set_impl_params(int use_ed) +{ + curve25519_use_ed = use_ed; +} + /* ============================== Part 2: Wrap curve25519_impl with some convenience types and functions. ============================== */ @@ -113,9 +147,7 @@ void curve25519_public_key_generate(curve25519_public_key_t *key_out, const curve25519_secret_key_t *seckey) { - static const uint8_t basepoint[32] = {9}; - - curve25519_impl(key_out->public_key, seckey->secret_key, basepoint); + curve25519_basepoint_impl(key_out->public_key, seckey->secret_key); } int @@ -283,3 +315,84 @@ curve25519_handshake(uint8_t *output, curve25519_impl(output, skey->secret_key, pkey->public_key); } +/** Check whether the ed25519-based curve25519 basepoint optimization seems to + * be working. If so, return 0; otherwise return -1. */ +static int +curve25519_basepoint_spot_check(void) +{ + static const uint8_t alicesk[32] = { + 0x77,0x07,0x6d,0x0a,0x73,0x18,0xa5,0x7d, + 0x3c,0x16,0xc1,0x72,0x51,0xb2,0x66,0x45, + 0xdf,0x4c,0x2f,0x87,0xeb,0xc0,0x99,0x2a, + 0xb1,0x77,0xfb,0xa5,0x1d,0xb9,0x2c,0x2a + }; + static const uint8_t alicepk[32] = { + 0x85,0x20,0xf0,0x09,0x89,0x30,0xa7,0x54, + 0x74,0x8b,0x7d,0xdc,0xb4,0x3e,0xf7,0x5a, + 0x0d,0xbf,0x3a,0x0d,0x26,0x38,0x1a,0xf4, + 0xeb,0xa4,0xa9,0x8e,0xaa,0x9b,0x4e,0x6a + }; + const int loop_max=200; + int save_use_ed = curve25519_use_ed; + unsigned char e1[32] = { 5 }; + unsigned char e2[32] = { 5 }; + unsigned char x[32],y[32]; + int i; + int r=0; + + /* Check the most basic possible sanity via the test secret/public key pair + * used in "Cryptography in NaCl - 2. Secret keys and public keys". This + * may catch catastrophic failures on systems where Curve25519 is expensive, + * without requiring a ton of key generation. + */ + curve25519_use_ed = 1; + r |= curve25519_basepoint_impl(x, alicesk); + if (fast_memneq(x, alicepk, 32)) + goto fail; + + /* Ok, the optimization appears to produce passable results, try a few more + * values, maybe there's something subtle wrong. + */ + for (i = 0; i < loop_max; ++i) { + curve25519_use_ed = 0; + r |= curve25519_basepoint_impl(x, e1); + curve25519_use_ed = 1; + r |= curve25519_basepoint_impl(y, e2); + if (fast_memneq(x,y,32)) + goto fail; + memcpy(e1, x, 32); + memcpy(e2, x, 32); + } + + goto end; + fail: + r = -1; + end: + curve25519_use_ed = save_use_ed; + return r; +} + +/** Choose whether to use the ed25519-based curve25519-basepoint + * implementation. */ +static void +pick_curve25519_basepoint_impl(void) +{ + curve25519_use_ed = 1; + + if (curve25519_basepoint_spot_check() == 0) + return; + + log_warn(LD_CRYPTO, "The ed25519-based curve25519 basepoint " + "multiplication seems broken; using the curve25519 " + "implementation."); + curve25519_use_ed = 0; +} + +/** Initialize the curve25519 implementations. This is necessary if you're + * going to use them in a multithreaded setting, and not otherwise. */ +void +curve25519_init(void) +{ + pick_curve25519_basepoint_impl(); +} + |