crypto/ecdsa, crypto/rsa: use io.ReadFull to read from random source.

R=golang-dev, agl1
CC=golang-dev
https://golang.org/cl/4316057

src/pkg/crypto/ecdsa/ecdsa.go

@@ -37,7 +37,7 @@ var one = new(big.Int).SetInt64(1)
 // curve using the procedure given in [NSA] A.2.1.
 func randFieldElement(c *elliptic.Curve, rand io.Reader) (k *big.Int, err os.Error) {
 	b := make([]byte, c.BitSize/8+8)
-	_, err = rand.Read(b)
+	_, err = io.ReadFull(rand, b)
 	if err != nil {
 		return
 	}

src/pkg/crypto/rsa/pkcs1v15.go

@@ -127,7 +127,7 @@ func nonZeroRandomBytes(s []byte, rand io.Reader) (err os.Error) {
 
 	for i := 0; i < len(s); i++ {
 		for s[i] == 0 {
-			_, err = rand.Read(s[i : i+1])
+			_, err = io.ReadFull(rand, s[i:i+1])
 			if err != nil {
 				return
 			}