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//-----------------------------------------------------------------------------
// <copyright file="MailAddressParser.cs" company="Microsoft">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
//-----------------------------------------------------------------------------
namespace System.Net.Mail
{
using System;
using System.Text;
using System.Net.Mime;
using System.Globalization;
using System.Collections;
using System.Diagnostics;
using System.Collections.Generic;
//
// This class is responsible for parsing E-mail addresses as described in RFC 2822.
//
// Ideally, addresses are formatted as ("Display name" <username@domain>), but we still try to read several
// other formats, including common invalid formats like (Display name username@domain).
//
// To make the detection of invalid address formats simpler, all address parsing is done in reverse order,
// including lists. This way we know that the domain must be first, then the local-part, and then whatever
// remains must be the display-name.
//
internal static class MailAddressParser
{
// Parse a single MailAddress from the given string.
//
// Throws a FormatException if any part of the MailAddress is invalid.
internal static MailAddress ParseAddress(string data)
{
int index = data.Length - 1;
MailAddress parsedAddress = MailAddressParser.ParseAddress(data, false, ref index);
Debug.Assert(index == -1, "The index indicates that part of the address was not parsed: " + index);
return parsedAddress;
}
// Parse a comma separated list of MailAddress's
//
// Throws a FormatException if any MailAddress is invalid.
internal static IList<MailAddress> ParseMultipleAddresses(string data)
{
IList<MailAddress> results = new List<MailAddress>();
int index = data.Length - 1;
while (index >= 0)
{
// Because we're parsing in reverse, we must make an effort to preserve the order of the addresses.
results.Insert(0, MailAddressParser.ParseAddress(data, true, ref index));
Debug.Assert(index == -1 || data[index] == MailBnfHelper.Comma,
"separator not found while parsing multiple addresses");
index--;
}
return results;
}
//
// Parse a single MailAddress, potentially from a list.
//
// Preconditions:
// - Index must be within the bounds of the data string.
// - The data string must not be null or empty
//
// Postconditions:
// - Returns a valid MailAddress object parsed from the string
// - For a single MailAddress index is set to -1
// - For a list data[index] is the comma separator or -1 if the end of the data string was reached.
//
// Throws a FormatException if any part of the MailAddress is invalid.
private static MailAddress ParseAddress(string data, bool expectMultipleAddresses, ref int index)
{
Debug.Assert(!String.IsNullOrEmpty(data));
Debug.Assert(index >= 0 && index < data.Length, "Index out of range: " + index + ", " + data.Length);
// Parsed components to be assembled as a MailAddress later
string domain = null;
string localPart = null;
string displayName = null;
// Skip comments and whitespace
index = ReadCfwsAndThrowIfIncomplete(data, index);
// Do we expect angle brackets around the address?
// e.g. ("display name" <user@domain>)
bool expectAngleBracket = false;
if (data[index] == MailBnfHelper.EndAngleBracket)
{
expectAngleBracket = true;
index--;
}
domain = ParseDomain(data, ref index);
// The next character after the domain must be the '@' symbol
if (data[index] != MailBnfHelper.At)
{
throw new FormatException(SR.GetString(SR.MailAddressInvalidFormat));
}
// Skip the '@' symbol
index--;
localPart = ParseLocalPart(data, ref index, expectAngleBracket, expectMultipleAddresses);
// Check for a matching angle bracket around the address
if (expectAngleBracket)
{
if (index >= 0 && data[index] == MailBnfHelper.StartAngleBracket)
{
index--; // Skip the angle bracket
// Skip white spaces, but leave comments, as they may be part of the display name.
index = WhitespaceReader.ReadFwsReverse(data, index);
}
else
{
// Mismatched angle brackets, throw
throw new FormatException(SR.GetString(SR.MailHeaderFieldInvalidCharacter,
(index >= 0 ? data[index] : MailBnfHelper.EndAngleBracket)));
}
}
// Is there anything left to parse?
// There could still be a display name or another address
if (index >= 0 && !(expectMultipleAddresses && data[index] == MailBnfHelper.Comma))
{
displayName = ParseDisplayName(data, ref index, expectMultipleAddresses);
}
else
{
displayName = String.Empty;
}
return new MailAddress(displayName, localPart, domain);
}
// Read through a section of CFWS. If we reach the end of the data string then throw because not enough of the
// MailAddress components were found.
private static int ReadCfwsAndThrowIfIncomplete(string data, int index)
{
index = WhitespaceReader.ReadCfwsReverse(data, index);
if (index < 0)
{
// More components were expected. Incomplete address, invalid
throw new FormatException(SR.GetString(SR.MailAddressInvalidFormat));
}
return index;
}
// Parses the domain section of an address. The domain may be in dot-atom format or surrounded by square
// brackets in domain-literal format.
// e.g. <user@domain.com> or <user@[whatever I want]>
//
// Preconditions:
// - data[index] is just inside of the angle brackets (if any).
//
// Postconditions:
// - data[index] should refer to the '@' symbol
// - returns the parsed domain, including any square brackets for domain-literals
//
// Throws a FormatException:
// - For invalid un-escaped chars, including Unicode
// - If the start of the data string is reached
private static string ParseDomain(string data, ref int index)
{
// Skip comments and whitespace
index = ReadCfwsAndThrowIfIncomplete(data, index);
// Mark one end of the domain component
int startingIndex = index;
// Is the domain component in domain-literal format or dot-atom format?
if (data[index] == MailBnfHelper.EndSquareBracket)
{
index = DomainLiteralReader.ReadReverse(data, index);
}
else
{
index = DotAtomReader.ReadReverse(data, index);
}
string domain = data.Substring(index + 1, startingIndex - index);
// Skip comments and whitespace
index = ReadCfwsAndThrowIfIncomplete(data, index);
return NormalizeOrThrow(domain);
}
// Parses the local-part section of an address. The local-part may be in dot-atom format or
// quoted-string format. e.g. <user.name@domain> or <"user name"@domain>
// We do not support the obsolete formats of user."name"@domain, "user".name@domain, or "user"."name"@domain.
//
// Preconditions:
// - data[index + 1] is the '@' symbol
//
// Postconditions:
// - data[index] should refer to the '<', if any, otherwise the next non-CFWS char.
// - index == -1 if the beginning of the data string has been reached.
// - returns the parsed local-part, including any bounding quotes around quoted-strings
//
// Throws a FormatException:
// - For invalid un-escaped chars, including Unicode
// - If the final value of data[index] is not a valid character to precede the local-part
private static string ParseLocalPart(string data, ref int index, bool expectAngleBracket,
bool expectMultipleAddresses)
{
// Skip comments and whitespace
index = ReadCfwsAndThrowIfIncomplete(data, index);
// Mark the start of the local-part
int startingIndex = index;
// Is the local-part component in quoted-string format or dot-atom format?
if (data[index] == MailBnfHelper.Quote)
{
index = QuotedStringFormatReader.ReadReverseQuoted(data, index, true);
}
else
{
index = DotAtomReader.ReadReverse(data, index);
// Check that the local-part is properly separated from the next component. It may be separated by a
// comment, white space, an expected angle bracket, a quote for the display-name, or an expected comma
// before the next address.
if (index >= 0 &&
!(
MailBnfHelper.Whitespace.Contains(data[index]) // < local@domain >
|| data[index] == MailBnfHelper.EndComment // <(comment)local@domain>
|| (expectAngleBracket && data[index] == MailBnfHelper.StartAngleBracket) // <local@domain>
|| (expectMultipleAddresses && data[index] == MailBnfHelper.Comma) // local@dom,local@dom
// Note: The following condition is more lax than the RFC. This is done so we could support
// a common invalid formats as shown below.
|| data[index] == MailBnfHelper.Quote // "display"local@domain
)
)
{
throw new FormatException(SR.GetString(SR.MailHeaderFieldInvalidCharacter, data[index]));
}
}
string localPart = data.Substring(index + 1, startingIndex - index);
index = WhitespaceReader.ReadCfwsReverse(data, index);
return NormalizeOrThrow(localPart);
}
// Parses the display-name section of an address. In departure from the RFC, we attempt to read data in the
// quoted-string format even if the bounding quotes are omitted. We also permit Unicode, which the RFC does
// not allow for.
// e.g. ("display name" <user@domain>) or (display name <user@domain>)
//
// Preconditions:
//
// Postconditions:
// - data[index] should refer to the comma ',' separator, if any
// - index == -1 if the beginning of the data string has been reached.
// - returns the parsed display-name, excluding any bounding quotes around quoted-strings
//
// Throws a FormatException:
// - For invalid un-escaped chars, except Unicode
// - If the postconditions cannot be met.
private static string ParseDisplayName(string data, ref int index, bool expectMultipleAddresses)
{
string displayName;
// Whatever is left over must be the display name. The display name should be a single word/atom or a
// quoted string, but for robustness we allow the quotes to be omitted, so long as we can find the comma
// separator before the next address.
// Read the comment (if any). If the display name is contained in quotes, the surrounding comments are
// omitted. Otherwise, mark this end of the comment so we can include it as part of the display name.
int firstNonCommentIndex = WhitespaceReader.ReadCfwsReverse(data, index);
// Check to see if there's a quoted-string display name
if (firstNonCommentIndex >= 0 && data[firstNonCommentIndex] == MailBnfHelper.Quote)
{
// The preceding comment was not part of the display name. Read just the quoted string.
index = QuotedStringFormatReader.ReadReverseQuoted(data, firstNonCommentIndex, true);
Debug.Assert(data[index + 1] == MailBnfHelper.Quote, "Mis-alligned index: " + index);
// Do not include the bounding quotes on the display name
int leftIndex = index + 2;
displayName = data.Substring(leftIndex, firstNonCommentIndex - leftIndex);
// Skip any CFWS after the display name
index = WhitespaceReader.ReadCfwsReverse(data, index);
// Check for completion. We are valid if we hit the end of the data string or if the rest of the data
// belongs to another address.
if (index >= 0 && !(expectMultipleAddresses && data[index] == MailBnfHelper.Comma))
{
// If there was still data, only a comma could have been the next valid character
throw new FormatException(SR.GetString(SR.MailHeaderFieldInvalidCharacter, data[index]));
}
}
else
{
// The comment (if any) should be part of the display name.
int startingIndex = index;
// Read until the dividing comma or the end of the line.
index = QuotedStringFormatReader.ReadReverseUnQuoted(data, index, true, expectMultipleAddresses);
Debug.Assert(index < 0 || data[index] == MailBnfHelper.Comma, "Mis-alligned index: " + index);
// Do not include the Comma (if any)
displayName = data.Substring(index + 1, startingIndex - index);
// Because there were no bounding quotes, trim extra whitespace
displayName = displayName.Trim();
}
return NormalizeOrThrow(displayName);
}
internal static string NormalizeOrThrow(string input)
{
try
{
return input.Normalize(NormalizationForm.FormC);
}
catch (ArgumentException argEx)
{
throw new FormatException(SR.GetString(SR.MailAddressInvalidFormat), argEx);
}
}
}
}