queue: Use a PRNG to generate IDs

The queue IDs are internal to chasquid, and we don't need them to be
cryptographically secure, so this patch changes the ID generation to use
the PRNG.

This also helps avoid entropy issues.

internal/queue/queue.go

@@ -7,11 +7,10 @@ package queue
 
 import (
 	"context"
-	"crypto/rand"
 	"encoding/base64"
 	"expvar"
 	"fmt"
-	mathrand "math/rand"
+	"math/rand"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -66,20 +65,19 @@ var (
 var newID chan string
 
 func generateNewIDs() {
+	// The IDs are only used internally, we are ok with using a PRNG.
+	// We create our own to avoid relying on external sources initializing it
+	// properly.
+	prng := rand.New(rand.NewSource(time.Now().UnixNano()))
+
 	// IDs are base64(8 random bytes), but the code doesn't care.
-	var err error
 	buf := make([]byte, 8)
 	id := ""
 	for {
-		_, err = rand.Read(buf)
-		if err != nil {
-			panic(err)
-		}
-
+		prng.Read(buf)
 		id = base64.RawURLEncoding.EncodeToString(buf)
 		newID <- id
 	}
-
 }
 
 func init() {
@@ -469,7 +467,7 @@ func nextDelay(createdAt time.Time) time.Duration {
 
 	// Perturb the delay, to avoid all queued emails to be retried at the
 	// exact same time after a restart.
-	delay += time.Duration(mathrand.Intn(60)) * time.Second
+	delay += time.Duration(rand.Intn(60)) * time.Second
 	return delay
 }