[management] remove old math rand lib (#6836)

management/server/types/network.go

@@ -1,18 +1,18 @@
 package types
 
 import (
+	"crypto/rand"
 	"encoding/binary"
 	"fmt"
-	"math/rand"
 	"net"
 	"net/netip"
 	"slices"
 	"sync"
-	"time"
 
 	"github.com/c-robinson/iplib"
 	"github.com/rs/xid"
 
+	"github.com/netbirdio/netbird/management/server/util"
 	"github.com/netbirdio/netbird/shared/management/status"
 )
 
@@ -47,14 +47,12 @@ func NewNetwork() *Network {
 	n := iplib.NewNet4(net.ParseIP("100.64.0.0"), NetSize)
 	sub, _ := n.Subnet(SubnetSize)
 
-	s := rand.NewSource(time.Now().UnixNano())
-	r := rand.New(s)
-	intn := r.Intn(len(sub))
+	intn := util.RandIntn(len(sub))
 
 	return &Network{
 		Identifier: xid.New().String(),
 		Net:        sub[intn].IPNet,
-		NetV6:      AllocateIPv6Subnet(r),
+		NetV6:      AllocateIPv6Subnet(),
 		Dns:        "",
 		Serial:     0,
 	}
@@ -64,18 +62,13 @@ func NewNetwork() *Network {
 // The format follows RFC 4193 section 3.1: fd + 40-bit Global ID + 16-bit Subnet ID.
 // The Global ID and Subnet ID are randomized (simplified from the SHA-1 algorithm
 // in section 3.2.2), giving 2^56 possible /64 subnets across all accounts.
-func AllocateIPv6Subnet(r *rand.Rand) net.IPNet {
+func AllocateIPv6Subnet() net.IPNet {
 	ip := make(net.IP, 16)
 	ip[0] = 0xfd
-	// Bytes 1-5: 40-bit random Global ID
-	ip[1] = byte(r.Intn(256))
-	ip[2] = byte(r.Intn(256))
-	ip[3] = byte(r.Intn(256))
-	ip[4] = byte(r.Intn(256))
-	ip[5] = byte(r.Intn(256))
-	// Bytes 6-7: 16-bit random Subnet ID
-	ip[6] = byte(r.Intn(256))
-	ip[7] = byte(r.Intn(256))
+	// Bytes 1-5: 40-bit random Global ID, bytes 6-7: 16-bit random Subnet ID
+	if _, err := rand.Read(ip[1:8]); err != nil {
+		panic(err)
+	}
 
 	return net.IPNet{
 		IP:   ip,
@@ -109,10 +102,22 @@ func (n *Network) Copy() *Network {
 	}
 }
 
+// validateIPv4Prefix ensures the prefix is an IPv4 network with assignable host addresses.
+func validateIPv4Prefix(prefix netip.Prefix) error {
+	if !prefix.IsValid() || !prefix.Addr().Is4() || prefix.Bits() < 1 || prefix.Bits() >= 31 {
+		return fmt.Errorf("invalid IPv4 subnet: %s", prefix.String())
+	}
+	return nil
+}
+
 // AllocatePeerIP picks an available IP from a netip.Prefix.
 // This method considers already taken IPs and reuses IPs if there are gaps in takenIps.
 // E.g. if prefix=100.30.0.0/16 and takenIps=[100.30.0.1, 100.30.0.4] then the result would be 100.30.0.2 or 100.30.0.3.
 func AllocatePeerIP(prefix netip.Prefix, takenIps []netip.Addr) (netip.Addr, error) {
+	if err := validateIPv4Prefix(prefix); err != nil {
+		return netip.Addr{}, err
+	}
+
 	b := prefix.Masked().Addr().As4()
 	baseIP := binary.BigEndian.Uint32(b[:])
 	hostBits := 32 - prefix.Bits()
@@ -123,15 +128,17 @@ func AllocatePeerIP(prefix netip.Prefix, takenIps []netip.Addr) (netip.Addr, err
 	taken[baseIP+totalIPs-1] = struct{}{} // reserve broadcast IP
 
 	for _, ip := range takenIps {
+		if !ip.Is4() {
+			continue
+		}
 		ab := ip.As4()
 		taken[binary.BigEndian.Uint32(ab[:])] = struct{}{}
 	}
 
-	rng := rand.New(rand.NewSource(time.Now().UnixNano()))
 	maxAttempts := (int(totalIPs) - len(taken)) / 100
 
 	for i := 0; i < maxAttempts; i++ {
-		offset := uint32(rng.Intn(int(totalIPs-2))) + 1
+		offset := uint32(util.RandIntn(int(totalIPs-2))) + 1
 		candidate := baseIP + offset
 		if _, exists := taken[candidate]; !exists {
 			return uint32ToIP(candidate), nil
@@ -150,13 +157,16 @@ func AllocatePeerIP(prefix netip.Prefix, takenIps []netip.Addr) (netip.Addr, err
 
 // AllocateRandomPeerIP picks a random available IP from a netip.Prefix.
 func AllocateRandomPeerIP(prefix netip.Prefix) (netip.Addr, error) {
+	if err := validateIPv4Prefix(prefix); err != nil {
+		return netip.Addr{}, err
+	}
+
 	b := prefix.Masked().Addr().As4()
 	baseIP := binary.BigEndian.Uint32(b[:])
 	hostBits := 32 - prefix.Bits()
 	totalIPs := uint32(1 << hostBits)
 
-	rng := rand.New(rand.NewSource(time.Now().UnixNano()))
-	offset := uint32(rng.Intn(int(totalIPs-2))) + 1
+	offset := uint32(util.RandIntn(int(totalIPs-2))) + 1
 
 	candidate := baseIP + offset
 	return uint32ToIP(candidate), nil
@@ -172,23 +182,26 @@ func AllocateRandomPeerIPv6(prefix netip.Prefix) (netip.Addr, error) {
 
 	ip := prefix.Addr().As16()
 
-	rng := rand.New(rand.NewSource(time.Now().UnixNano()))
-
 	// Determine which byte the host bits start in
 	firstHostByte := ones / 8
 	// If the prefix doesn't end on a byte boundary, handle the partial byte
 	partialBits := ones % 8
 
+	var rnd [16]byte
+	if _, err := rand.Read(rnd[firstHostByte:]); err != nil {
+		return netip.Addr{}, err
+	}
+
 	if partialBits > 0 {
 		// Keep the network bits in the partial byte, randomize the rest
 		hostMask := byte(0xff >> partialBits)
-		ip[firstHostByte] = (ip[firstHostByte] & ^hostMask) | (byte(rng.Intn(256)) & hostMask)
+		ip[firstHostByte] = (ip[firstHostByte] & ^hostMask) | (rnd[firstHostByte] & hostMask)
 		firstHostByte++
 	}
 
 	// Randomize remaining full host bytes
 	for i := firstHostByte; i < 16; i++ {
-		ip[i] = byte(rng.Intn(256))
+		ip[i] = rnd[i]
 	}
 
 	// Avoid all-zeros and all-ones host parts by checking only host bits.

management/server/types/network_test.go

@@ -143,6 +143,34 @@ func TestAllocatePeerIPVariousCIDRs(t *testing.T) {
 	}
 }
 
+func TestAllocateIPv4InvalidPrefixes(t *testing.T) {
+	prefixes := []netip.Prefix{
+		{},
+		netip.MustParsePrefix("0.0.0.0/0"),
+		netip.MustParsePrefix("192.168.1.0/31"),
+		netip.MustParsePrefix("192.168.1.1/32"),
+		netip.MustParsePrefix("fd12:3456:7890:abcd::/64"),
+	}
+
+	for _, prefix := range prefixes {
+		t.Run(prefix.String(), func(t *testing.T) {
+			_, err := AllocatePeerIP(prefix, nil)
+			assert.Error(t, err)
+
+			_, err = AllocateRandomPeerIP(prefix)
+			assert.Error(t, err)
+		})
+	}
+}
+
+func TestAllocatePeerIPIgnoresNonIPv4TakenIPs(t *testing.T) {
+	prefix := netip.MustParsePrefix("192.168.1.0/29")
+
+	ip, err := AllocatePeerIP(prefix, []netip.Addr{netip.MustParseAddr("fd12:3456:7890:abcd::1")})
+	require.NoError(t, err)
+	assert.True(t, prefix.Contains(ip))
+}
+
 func TestGenerateIPs(t *testing.T) {
 	ipNet := net.IPNet{IP: net.ParseIP("100.64.0.0"), Mask: net.IPMask{255, 255, 255, 0}}
 	ips, ipsLen := generateIPs(&ipNet, map[string]struct{}{"100.64.0.0": {}})