From c0283a2028317d3fb6574f9a06e68443cf6b89cd Mon Sep 17 00:00:00 2001
From: Alexey Naidyonov <alexey.naidyonov@gmail.com>
Date: Fri, 5 Oct 2018 20:30:27 +0300
Subject: [PATCH] Allows larger offset in $GENERATE (#776)

Although BIND9 documentations does not specify the possible size of offset
in $GENERATE clause, it clearly says that range must be a positive integer
between 0 and (2^31)-1. Moreover, BIND perfectly supports large offsets
which might be really handy when you're dealing with large intranets. I.e.
consider following case

```
$GENERATE 0-255 dhcp-${0,4,d}   A 10.0.0.$
$GENERATE 0-255 dhcp-${256,4,d} A 10.0.1.$
$GENERATE 0-255 dhcp-${512,4,d} A 10.0.2.$
...
```

This change removes offset size check and introduces check that
0 >= (start + offset) and (end + offset) < (2^31)-1.
---
 generate.go      |  4 +++-
 generate_test.go | 39 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/generate.go b/generate.go
index 3a559793..91d928c8 100644
--- a/generate.go
+++ b/generate.go
@@ -107,6 +107,8 @@ BuildRR:
 					mod, offset, err = modToPrintf(s[j+2 : j+2+sep])
 					if err != nil {
 						return err.Error()
+					} else if start + offset < 0 || end + offset > 1<<31-1 {
+						return "bad offset in $GENERATE"
 					}
 					j += 2 + sep // Jump to it
 				}
@@ -152,7 +154,7 @@ func modToPrintf(s string) (string, int, error) {
 		return "", 0, errors.New("bad base in $GENERATE")
 	}
 	offset, err := strconv.Atoi(xs[0])
-	if err != nil || offset > 255 {
+	if err != nil {
 		return "", 0, errors.New("bad offset in $GENERATE")
 	}
 	width, err := strconv.Atoi(xs[1])
diff --git a/generate_test.go b/generate_test.go
index 1df6abd6..e224c1b8 100644
--- a/generate_test.go
+++ b/generate_test.go
@@ -2,8 +2,46 @@ package dns
 
 import (
 	"testing"
+	"strings"
 )
 
+func TestGenerateRangeGuard(t *testing.T) {
+	var tests = [...]struct {
+		zone string
+		fail bool
+	}{{
+		`@ IN SOA ns.test. hostmaster.test. ( 1 8h 2h 7d 1d )
+$GENERATE 0-1 dhcp-${0,4,d} A 10.0.0.$
+`, false},{
+		`@ IN SOA ns.test. hostmaster.test. ( 1 8h 2h 7d 1d )
+$GENERATE 128-129 dhcp-${-128,4,d} A 10.0.0.$
+`, false},{
+		`@ IN SOA ns.test. hostmaster.test. ( 1 8h 2h 7d 1d )
+$GENERATE 128-129 dhcp-${-129,4,d} A 10.0.0.$
+`, true},{
+		`@ IN SOA ns.test. hostmaster.test. ( 1 8h 2h 7d 1d )
+$GENERATE 0-2 dhcp-${2147483647,4,d} A 10.0.0.$
+`, true},{
+		`@ IN SOA ns.test. hostmaster.test. ( 1 8h 2h 7d 1d )
+$GENERATE 0-1 dhcp-${2147483646,4,d} A 10.0.0.$
+`, false},
+	}
+Outer:
+	for i := range tests {
+		for tok := range ParseZone(strings.NewReader(tests[i].zone), "test.", "test") {
+			if tok.Error != nil {
+				if !tests[i].fail {
+					t.Errorf("expected \n\n%s\nto be parsed, but got %v", tests[i].zone, tok.Error)
+				}
+				continue Outer
+			}
+		}
+		if tests[i].fail {
+			t.Errorf("expected \n\n%s\nto fail, but got no error", tests[i].zone)
+		}
+	}
+}
+
 func TestGenerateModToPrintf(t *testing.T) {
 	tests := []struct {
 		mod        string
@@ -22,6 +60,7 @@ func TestGenerateModToPrintf(t *testing.T) {
 		{"0,0,X", "%0X", 0, false},
 		{"0,0,z", "", 0, true},
 		{"0,0,0,d", "", 0, true},
+		{"-100,0,d", "%0d", -100, false},
 	}
 	for _, test := range tests {
 		gotFmt, gotOffset, err := modToPrintf(test.mod)