Some more extra casts to avoid alignment warnings with Clang and -Wcast-align on...

[BearSSL] / src / rsa / rsa_i15_priv.c

diff --git a/src/rsa/rsa_i15_priv.c b/src/rsa/rsa_i15_priv.c
index 8dc839a..e692da4 100644 (file)
--- a/src/rsa/rsa_i15_priv.c
+++ b/src/rsa/rsa_i15_priv.c
@@ -24,7 +24,7 @@
 
 #include "inner.h"
 
-#define U      (1 + ((BR_MAX_RSA_FACTOR + 14) / 15))
+#define U      (2 + ((BR_MAX_RSA_FACTOR + 14) / 15))
 #define TLEN   (8 * U)
 
 /* obsolete
@@ -54,7 +54,7 @@ br_rsa_i15_private(unsigned char *x, const br_rsa_private_key *sk)
        size_t fwlen;
        uint16_t p0i, q0i;
        size_t xlen;
-       uint16_t tmp[TLEN];
+       uint16_t tmp[1 + TLEN];
        long z;
        uint16_t *mp, *mq, *s1, *s2, *t1, *t2, *t3;
        uint32_t r;
@@ -86,6 +86,10 @@ br_rsa_i15_private(unsigned char *x, const br_rsa_private_key *sk)
                z -= 15;
                fwlen ++;
        }
+       /*
+        * Round up the word length to an even number.
+        */
+       fwlen += (fwlen & 1);
 
        /*
         * We need to fit at least 6 values in the stack buffer.
@@ -100,34 +104,41 @@ br_rsa_i15_private(unsigned char *x, const br_rsa_private_key *sk)
        xlen = (sk->n_bitlen + 7) >> 3;
 
        /*
-        * Decode q.
+        * Ensure 32-bit alignment for value words.
         */
        mq = tmp;
+       if (((uintptr_t)mq & 2) == 0) {
+               mq ++;
+       }
+
+       /*
+        * Decode q.
+        */
        br_i15_decode(mq, q, qlen);
 
        /*
         * Compute s2 = x^dq mod q.
         */
        q0i = br_i15_ninv15(mq[1]);
-       s2 = tmp + fwlen;
+       s2 = mq + fwlen;
        br_i15_decode_reduce(s2, x, xlen, mq);
        r = br_i15_modpow_opt(s2, sk->dq, sk->dqlen, mq, q0i,
-               tmp + 2 * fwlen, TLEN - 2 * fwlen);
+               mq + 2 * fwlen, TLEN - 2 * fwlen);
 
        /*
         * Decode p.
         */
-       mp = tmp + 2 * fwlen;
+       mp = mq + 2 * fwlen;
        br_i15_decode(mp, p, plen);
 
        /*
         * Compute s1 = x^dq mod q.
         */
        p0i = br_i15_ninv15(mp[1]);
-       s1 = tmp + 3 * fwlen;
+       s1 = mq + 3 * fwlen;
        br_i15_decode_reduce(s1, x, xlen, mp);
        r &= br_i15_modpow_opt(s1, sk->dp, sk->dplen, mp, p0i,
-               tmp + 4 * fwlen, TLEN - 4 * fwlen);
+               mq + 4 * fwlen, TLEN - 4 * fwlen);
 
        /*
         * Compute:
@@ -142,8 +153,8 @@ br_rsa_i15_private(unsigned char *x, const br_rsa_private_key *sk)
         * inverse of q modulo p), we also tolerate improperly large
         * values for this parameter.
         */
-       t1 = tmp + 4 * fwlen;
-       t2 = tmp + 5 * fwlen;
+       t1 = mq + 4 * fwlen;
+       t2 = mq + 5 * fwlen;
        br_i15_reduce(t2, s2, mp);
        br_i15_add(s1, mp, br_i15_sub(s1, t2, 1));
        br_i15_to_monty(s1, mp);