pkg: remove random package

The unnecessary `random` package has been removed in favor of using the
`math/rand` package directly. Seeding of the random value from crypto
has been added to the `stringid` package to account for the change.

May need to add an equivalent seed to `namesgenerator`, but this is
often used with `stringid` and has collision protection.

Signed-off-by: Stephen J Day <stephen.day@docker.com>
Upstream-commit: 66cfe61f71252f528ddb458d554cd241e996d9f1
Component: engine

components/engine/pkg/stringid/stringid.go

@@ -2,15 +2,17 @@
 package stringid
 
 import (
-	"crypto/rand"
+	cryptorand "crypto/rand"
 	"encoding/hex"
 	"fmt"
 	"io"
+	"math"
+	"math/big"
+	"math/rand"
 	"regexp"
 	"strconv"
 	"strings"
-
-	"github.com/docker/docker/pkg/random"
+	"time"
 )
 
 const shortLen = 12
@@ -39,12 +41,8 @@ func TruncateID(id string) string {
 	return id
 }
 
-func generateID(crypto bool) string {
+func generateID(r io.Reader) string {
 	b := make([]byte, 32)
-	r := random.Reader
-	if crypto {
-		r = rand.Reader
-	}
 	for {
 		if _, err := io.ReadFull(r, b); err != nil {
 			panic(err) // This shouldn't happen
@@ -62,14 +60,14 @@ func generateID(crypto bool) string {
 
 // GenerateRandomID returns a unique id.
 func GenerateRandomID() string {
-	return generateID(true)
+	return generateID(cryptorand.Reader)
 }
 
 // GenerateNonCryptoID generates unique id without using cryptographically
 // secure sources of random.
 // It helps you to save entropy.
 func GenerateNonCryptoID() string {
-	return generateID(false)
+	return generateID(readerFunc(rand.Read))
 }
 
 // ValidateID checks whether an ID string is a valid image ID.
@@ -79,3 +77,23 @@ func ValidateID(id string) error {
 	}
 	return nil
 }
+
+func init() {
+	// safely set the seed globally so we generate random ids. Tries to use a
+	// crypto seed before falling back to time.
+	var seed int64
+	if cryptoseed, err := cryptorand.Int(cryptorand.Reader, big.NewInt(math.MaxInt64)); err != nil {
+		// This should not happen, but worst-case fallback to time-based seed.
+		seed = time.Now().UnixNano()
+	} else {
+		seed = cryptoseed.Int64()
+	}
+
+	rand.Seed(seed)
+}
+
+type readerFunc func(p []byte) (int, error)
+
+func (fn readerFunc) Read(p []byte) (int, error) {
+	return fn(p)
+}