fixed bodyhash missmatch issue in relax mode described in issue emers…

…ion#38

dkim/canonical.go

@@ -27,12 +27,15 @@ var canonicalizers = map[Canonicalization]canonicalizer{
 }
 
 // Fix any \n without a matching \r
-func fixCRLF(b []byte) []byte {
+func fixCRLF(b []byte, isRelaxed bool) []byte {
 	res := make([]byte, 0, len(b))
 	for i := range b {
 		if b[i] == '\n' && (i == 0 || b[i-1] != '\r') {
 			res = append(res, '\r')
 		}
+		if isRelaxed && i == len(b)-1 && b[i] == '\r' {
+			break
+		}
 		res = append(res, b[i])
 	}
 	return res
@@ -53,7 +56,7 @@ func (c *simpleBodyCanonicalizer) Write(b []byte) (int, error) {
 	written := len(b)
 	b = append(c.crlfBuf, b...)
 
-	b = fixCRLF(b)
+	b = fixCRLF(b, false)
 
 	end := len(b)
 	// If it ends with \r, maybe the next write will begin with \n
@@ -125,7 +128,7 @@ type relaxedBodyCanonicalizer struct {
 func (c *relaxedBodyCanonicalizer) Write(b []byte) (int, error) {
 	written := len(b)
 
-	b = fixCRLF(b)
+	b = fixCRLF(b, true)
 
 	canonical := make([]byte, 0, len(b))
 	for _, ch := range b {

dkim/canonical_test.go

@@ -2,6 +2,7 @@ package dkim
 
 import (
 	"bytes"
+	"reflect"
 	"testing"
 )
 
@@ -168,3 +169,33 @@ func TestRelaxedCanonicalizer_CanonicalBody(t *testing.T) {
 		}
 	}
 }
+
+func Test_fixCRLF(t *testing.T) {
+
+	tests := []struct {
+		name      string
+		got       string
+		want      string
+		isRelaxed bool
+	}{
+		{
+			name:      "t1",
+			got:       "test\r\ntest\r\ntest\r\ntest\r\ntest\r\ntest\r\ntest\r\ntest\r\ntest\r",
+			want:      "test\r\ntest\r\ntest\r\ntest\r\ntest\r\ntest\r\ntest\r\ntest\r\ntest",
+			isRelaxed: true,
+		},
+		{
+			name:      "t2",
+			got:       "test\r\ntest\r\ntest\r\ntest\r\ntest\r\ntest\r\ntest\r\ntest\r\ntest\r",
+			want:      "test\r\ntest\r\ntest\r\ntest\r\ntest\r\ntest\r\ntest\r\ntest\r\ntest\r",
+			isRelaxed: false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := fixCRLF([]byte(tt.got), tt.isRelaxed); !reflect.DeepEqual(got, []byte(tt.want)) {
+				t.Errorf("Expected fixCRLF for body %q to be %q, but got %q", []byte(tt.got), []byte(tt.want), got)
+			}
+		})
+	}
+}