Minor code tidy and bug fix: need to set t = s after first pass and

t and s do not need to have independent values after the first pass
so set t = s.

diff --git a/fips/rand/fips_drbg_ec.c b/fips/rand/fips_drbg_ec.c
index 0b674199bbb032e37d0827f0daa8a16d30a720bd..ccdab03cf97687cb5c53c0db2853015435f6d748 100644 (file)
--- a/fips/rand/fips_drbg_ec.c
+++ b/fips/rand/fips_drbg_ec.c
@@ -287,17 +287,19 @@ static int drbg_ec_generate(DRBG_CTX *dctx,
                }
 
        BN_CTX_start(ectx->bctx);
-       t = BN_CTX_get(ectx->bctx);
        r = BN_CTX_get(ectx->bctx);
        if (!r)
                goto err;
        if (adin && adin_len)
                {
                size_t i;
+               t = BN_CTX_get(ectx->bctx);
+               if (!t)
+                       goto err;
                /* Convert s to buffer */
                if (ectx->exbits)
-                       BN_lshift(ectx->s, ectx->s, ectx->exbits);
-               bn2binpad(ectx->sbuf, dctx->seedlen, ectx->s);
+                       BN_lshift(s, s, ectx->exbits);
+               bn2binpad(ectx->sbuf, dctx->seedlen, s);
                /* Step 2 */
                if (!hash_df(dctx, ectx->tbuf, adin, adin_len,
                                NULL, 0, NULL, 0))
@@ -309,11 +311,13 @@ static int drbg_ec_generate(DRBG_CTX *dctx,
                        return 0;
                }
        else
-               if (!BN_copy(t, ectx->s))
-                       goto err;
+               /* Note if no additional input t and s the algorithm never
+                * needs separate values for t and s.
+                */
+               t = s;
 
 #ifdef EC_DRBG_TRACE
-       bnprint(stderr, "s at start of generate: ", ectx->s);
+       bnprint(stderr, "s at start of generate: ", s);
 #endif
 
        for (;;)
@@ -360,6 +364,8 @@ static int drbg_ec_generate(DRBG_CTX *dctx,
                if (!outlen)
                        break;
                out += dctx->blocklength;
+               /* Step #5 after first pass */
+               t = s;
 #ifdef EC_DRBG_TRACE
                fprintf(stderr, "Random bits written:\n");
                hexprint(stderr, out, dctx->blocklength);