From ba943cb682c1efde252fa68ac7c871f5fa78b445 Mon Sep 17 00:00:00 2001
From: James Hillyerd <james@hillyerd.com>
Date: Sun, 3 Nov 2013 10:25:34 -0800
Subject: [PATCH] Initial version of ValidateLocalPart

Does not support any quoting yet, not RFC compliant
---
 smtpd/utils.go      | 38 ++++++++++++++++++++++++++++++++++++++
 smtpd/utils_test.go | 35 ++++++++++++++++++++++++++++++++---
 2 files changed, 70 insertions(+), 3 deletions(-)

diff --git a/smtpd/utils.go b/smtpd/utils.go
index 0e4c2e3..133c1bb 100644
--- a/smtpd/utils.go
+++ b/smtpd/utils.go
@@ -1,6 +1,7 @@
 package smtpd
 
 import (
+	"bytes"
 	"container/list"
 	"crypto/sha1"
 	"fmt"
@@ -89,3 +90,40 @@ func ValidateDomainPart(domain string) bool {
 
 	return true
 }
+
+// ValidateLocalPart returns true if the string complies with RFC3696 recommendations
+func ValidateLocalPart(local string) bool {
+	length := len(local)
+	if 1 > length || length > 64 {
+		// Invalid length
+		return false
+	}
+	if local[length-1] == '.' {
+		// Cannot end with a period
+		return false
+	}
+
+	prev := byte('.')
+	for i := 0; i < length; i++ {
+		c := local[i]
+		switch {
+		case ('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z'):
+			// Letters are OK
+		case '0' <= c && c <= '9':
+			// Numbers are OK
+		case bytes.IndexByte([]byte("!#$%&'*+-/=?^_`{|}~"), c) >= 0:
+			// These specials can be used unquoted
+		case c == '.':
+			// A single period is OK
+			if prev == '.' {
+				// Sequence of periods is not permitted
+				return false
+			}
+		default:
+			return false
+		}
+		prev = c
+	}
+
+	return true
+}
diff --git a/smtpd/utils_test.go b/smtpd/utils_test.go
index cc30d8f..47940e8 100644
--- a/smtpd/utils_test.go
+++ b/smtpd/utils_test.go
@@ -17,9 +17,6 @@ func TestHashMailboxName(t *testing.T) {
 }
 
 func TestValidateDomain(t *testing.T) {
-	assert.True(t, ValidateDomainPart("jhillyerd.github.com"),
-		"Simple domain failed")
-	assert.False(t, ValidateDomainPart(""), "Empty domain is not valid")
 	assert.False(t, ValidateDomainPart(strings.Repeat("a", 256)),
 		"Max domain length is 255")
 	assert.False(t, ValidateDomainPart(strings.Repeat("a", 64)+".com"),
@@ -32,6 +29,7 @@ func TestValidateDomain(t *testing.T) {
 		expect bool
 		msg    string
 	}{
+		{"", false, "Empty domain is not valid"},
 		{"hostname", true, "Just a hostname is valid"},
 		{"github.com", true, "Two labels should be just fine"},
 		{"my-domain.com", true, "Hyphen is allowed mid-label"},
@@ -52,3 +50,34 @@ func TestValidateDomain(t *testing.T) {
 		}
 	}
 }
+
+func TestValidateLocal(t *testing.T) {
+	var testTable = []struct {
+		input string
+		expect bool
+		msg string
+	}{
+		{"", false, "Empty local is not valid"},
+		{"a", true, "Single letter should be fine"},
+		{strings.Repeat("a", 65), false, "Only valid up to 64 characters"},
+		{"FirstLast", true, "Mixed case permitted"},
+		{"user123", true, "Numbers permitted"},
+		{"a!#$%&'*+-/=?^_`{|}~", true, "Any of !#$%&'*+-/=?^_`{|}~ are permitted"},
+		{"james@mail", false, "Unquoted @ not permitted"},
+		{"first.last", true, "Embedded period is permitted"},
+		{"first..last", false, "Sequence of periods is not allowed"},
+		{".user", false, "Cannot lead with a period"},
+		{"user.", false, "Cannot end with a period"},
+		{"user+mailbox", true, "RFC3696 test case should be valid"},
+		{"customer/department=shipping", true, "RFC3696 test case should be valid"},
+		{"$A12345", true, "RFC3696 test case should be valid"},
+		{"!def!xyz%abc", true, "RFC3696 test case should be valid"},
+		{"_somename", true, "RFC3696 test case should be valid"},
+	}
+
+	for _, tt := range testTable {
+		if ValidateLocalPart(tt.input) != tt.expect {
+			t.Errorf("Expected %v for %q: %s", tt.expect, tt.input, tt.msg)
+		}
+	}
+}