Harmonized behaviour when point length is invalid.

[BearSSL] / src / ec / ec_c25519_i15.c

diff --git a/src/ec/ec_c25519_i15.c b/src/ec/ec_c25519_i15.c
index 361e75f..8fadcf4 100644 (file)
--- a/src/ec/ec_c25519_i15.c
+++ b/src/ec/ec_c25519_i15.c
@@ -239,11 +239,11 @@ api_mul(unsigned char *G, size_t Glen,
        x2[1] = 19;
        memcpy(z3, x2, ILEN);
 
-       memcpy(k, kb, kblen);
-       memset(k + kblen, 0, (sizeof k) - kblen);
-       k[0] &= 0xF8;
-       k[31] &= 0x7F;
-       k[31] |= 0x40;
+       memset(k, 0, (sizeof k) - kblen);
+       memcpy(k + (sizeof k) - kblen, kb, kblen);
+       k[31] &= 0xF8;
+       k[0] &= 0x7F;
+       k[0] |= 0x40;
 
        /* obsolete
        print_int_mont("x1", x1);
@@ -253,7 +253,7 @@ api_mul(unsigned char *G, size_t Glen,
        for (i = 254; i >= 0; i --) {
                uint32_t kt;
 
-               kt = (k[i >> 3] >> (i & 7)) & 1;
+               kt = (k[31 - (i >> 3)] >> (i & 7)) & 1;
                swap ^= kt;
                cswap(x2, x3, swap);
                cswap(z2, z3, swap);