S-nailのソースを表示

[[Category:メールクライアント]]
[[en:S-nail]]
S-nail (heirloom-mailx のフォーク) は ed と同じようなコマンド構文が使えるメール処理システムです。ed における行がメッセージになります。POSIX の mailx コマンドの機能を実現し行編集や IDNA, MIME, S/MIME, SMTP, POP3 (IMAP) などの拡張を提供します。メールバッチ言語として使うことが可能です。

S-nail は Unix のメールシステムの''ユーザーサイド''を担うものであり、''システムサイド''は伝統的に [[sendmail]] が使われていました。
	
Arch Linux では S-nail は SMTP によるメールの直接配達に対応しているため、外部の SMTP サーバーに直接メッセージを送信することができます。その場合、ローカルのメール転送エージェント (MTA) は''システムサイド''には不要です。ただし、S-nail にはメールキュー機構が存在しません。SMTP で直接かつ即座にメッセージを送るだけです。

== インストール ==

{{Pkg|s-nail}} パッケージは Arch Linux の {{Pkg|base}} グループに含まれているため、最初からインストールされています。

== 使用例 ==

システム全体の設定ファイル ({{ic|/etc/mail.rc}}) には最初から有用な設定が含まれており、以下のように [[sendmail]] や [[postfix]] などのローカルメール転送エージェント (MTA) でメールを送信できます:

 # echo 'Message body' | mailx -d -s 'A subject' -a an_attachment.txt foo1@bar.example 'Foo2 <foo2@bar.example>'

{{ic|-d}} フラグを付けることでドライランとなり実際にはメールは送信されません ({{ic|save}} や {{ic|record}} 設定も無視されます)。{{ic|sendmail}} 変数を設定することで MTA として使用するプログラムを調整できます ({{ic|sendmail-arguments}}, {{ic|sendmail-no-default-arguments}}, {{ic|sendmail-progname}} など詳しくはマニュアルの "Sending mail" を参照):

 # < /etc/passwd mailx -Ssendmail=/usr/bin/sendmail -Ssendwait -s 'My password file content!' public-foo@bar.example
 # echo Message was passed successfully: $?

デフォルトではメールの配達は非同期となっており、メッセージが配達システム (MTA など) に渡されると S-nail はすぐに終了します。メッセージの準備ができたかどうかだけ出力します。{{ic|sendwait}} オプションを設定した場合、S-nail は起動した MTA インスタンスが終了するまで待機し、MTA の終了ステータスを確認してメールの配達が成功したか失敗したか判断します。

{{ic|expandaddr}} オプションを設定した場合、ファイルやコマンドにメッセージを送信することができます:

 # echo bla | mailx -Sexpandaddr -s test ./mbox.mbox
 # echo bla | mailx -Sexpandaddr -s test '|cat >> ./mbox.mbox'

プログラム環境のメンバーと構成ファイルの設定がプログラムの動作を変更するのを避けるために、スクリプトを構成ファイルから切り離し、{{ic|-S}} および {{ic|-X}} コマンドライン フラグを使用できます (そしてそうすべきです)。それぞれ独自のセットアップを作成し、必要なコマンドを実行します。

{{ic|expandaddr}} に値を指定して、アドレス検証に使用できます。たとえば、次の ''only'' はネットワーク アドレスを許可します。 {{ic|-.}} コマンド ライン オプションは、オプション処理を終了し、メッセージ送信モードをオンにします。これらが一緒になってアクティブなバリアを形成し、アドレス引数をコマンドラインオプションとして誤って解釈したり、その他のインジェクション攻撃を防止したりします。
次の例は、''somefile.pdf'' がどこかにある場合、{ic|-d}} を除いてそのまま使用できます。 {{ic|record}} 変数を、すべての送信メールの記録に使用されるフォルダーのパス名に設定します。これにより、生成されたメールを調べることができます。
メッセージ:

 # echo Body |
 #   LC_ALL=C MAILRC=/dev/null \
 #   mailx -d -n -Sv15-compat -Ssendwait \
 #     -Sexpandaddr=fail,-all,+addr \
 #     -Snosave -Srecord=/tmp/out.mbox \
 #     -Smimetypes-load-control \
 #     -X'mimetype "application/pdf pdf"' \
 #     -Sfrom='Me <me@home>' \
 #     -a '''somefile.pdf''' -s Subject \
 #      -. '(foo2bar) <foo2@bar.example>' bob@hey.example
 # mailx -Rf /tmp/out.mbox

マニュアルページの ''はじめに''、''メールを送信する''、''メールを読む'' のセクションは、さらに ''クイック ショット'' を探す場合に一見の価値があります。

次の ''USER'' と ''PASS'' が URL の一部として指定されている場合 (その場合のみ)、それらは URL パーセントでエンコードされる必要があります。 S-nail は、これを行う {{ic|urlcodec}} コマンドを提供しています。

 # printf 'urlcodec encode ''USER'' ''PASS''\nx\n' | mailx -#

printf と S-nail / mailx は、ロケール設定の影響を受けます。

 # # In UTF-8:
 # printf 'urlcodec encode SPAß\nx\n' | mailx -#
   in: <SPAß> (5 bytes)
   out: <SPA%C3%9F> (9 bytes)
 # # In ISO-8859-1:
 # printf 'urlc enc SPAß\nx\n' | mailx -#
   in: <SPAß> (4 bytes)
   out: <SPA%DF> (6 bytes)

== 設定 ==

設定ファイルは各ユーザー個別の {{ic|$HOME/.mailrc}} と全ユーザー共通の {{ic|/etc/mail.rc}} があり、後者のファイルは Arch Linux でアップデートしたときに変わる可能性があるため、変更や追加は前者のファイルに行ってください。

{{Tip|{{ic|-n}} コマンド ライン オプションを使用するか、{{ic|NAIL_NO_SYSTEM_RC}} を設定することにより、起動時に {{ic|/etc/mail.rc}} を読み取ることを禁止できます。また、{{ic|MAILRC}} 環境変数を {{ic|/dev/null}} に設定することにより、構成ファイルがロードされないことが保証されるため、次のように、スクリプトを実行するための再現可能な環境が作成されます。}}

基本的なセキュリティや送信モードを設定する設定例:

 # All the examples require v15-compat!
 set v15-compat
 
 # ArchLinux-specific locations of certificates.
 # Since these are subject to the ArchLinux update mechanism,
 # use only those, don't try to load OpenSSL builtin ones.
 # And use the TLS specific set: see "man 8 update-ca-trust"
 #set ssl-ca-dir=/etc/ssl/certs
 set ssl-ca-file=/etc/ssl/certs/ca-certificates.crt
 set ssl-no-default-ca
 
 # Don't use protocols older than TLS v1.2.
 # Change this only when the remote server doesn't support it:
 # maybe use ssl-protocol-HOST (or -USER@HOST) syntax to define
 # such explicit exceptions, then, e.g.
 #     ssl-protocol-USER@archlinux.org="-ALL,+TLSv1.2"
 set ssl-protocol="-ALL,+TLSv1.2"
 
 # Explicitly define the list of ciphers, which may improve security,
 # especially with protocols older than TLS v1.2.  See ciphers(1).
 # Hint: it is important to include "@STRENGTH": only with it the
 # final list will be sorted by algorithm strength.
 # This is an example: in reality it is possibly best to only use
 # ssl-cipher-list-HOST (or -USER@HOST), as necessary, again..
 set ssl-cipher-list="ALL:!aNULL:!eNULL:!MEDIUM:!LOW:!MD5:!RC4:!EXPORT:@STRENGTH"
 
 # Request strict transport security checks
 set ssl-verify=strict
 
 # Essential setting: select allowed character sets
 # (Have a look at the "CHARACTER SETS" manual section)
 set sendcharsets=utf-8,iso-8859-1
 
 # A very kind option: when replying to a message, first try to
 # use the same encoding that the original poster used herself!
 set reply-in-same-charset
 
 # When replying to or forwarding a message the comment and name
 # parts of email addresses are removed unless this variable is set
 set fullnames
 
 # When sending messages, wait until the Mail-Transfer-Agent finishs.
 # Only like this you'll be able to see errors reported through the exit
 # status of the MTA (including the builtin SMTP one)!
 set sendwait
 
 # Only use builtin MIME types, no mime.types(5) files.
 # That set is often sufficient, but look at the output of the
 # mimetype command to ensure this is true for you, too
 set mimetypes-load-control
 
 # Default directory where we act in (relative to $HOME if not absolute)
 set folder=mail
 # A leading "+" (often) means: under folder
 # record is used to save copies of sent messages, DEAD is error storage
 # inbox: system mailbox, by default /var/mail/$USER: '''file %'''
 # MBOX: secondary mailbox: '''file &'''
 set MBOX=+mbox.mbox record=+sent.mbox DEAD=+dead.mbox
 set inbox=+system.mbox
 
 # Define some shortcuts; now one may say, e.g., file mymbo
 shortcut mymbo %:+mbox.mbox \
          myrec +sent.mbox
 
 # This is optional, but you should get the big picture
 # by reading the manual before you leave that off
 set from="''Your Name <youremail@domain>''" 
 
 # Mailing-list specifics (manual: "Mailing lists"):
 set followup-to followup-to-honour=ask-yes reply-to-honour=ask-yes
 # And teach some non-subscribed / some subscribed lists, too
 mlist @xyz-editor.xyz$ @xyzf.xyz$
 mlsubscribe ^xfans@xfans.xyz$

上記の SSL/TLS 構成の組み合わせにより、可能な限り最も安全なエンドツーエンド TLS トランスポートが実現します。

== 外部 SMTP サーバーでメールを送信 ==

To send messages via the built-in SMTP (Simple Mail Transfer Protocol) client to an external SMTP server, several options have to be set or adjusted.
Add the following as appropriate to the configuration as above, changing bold strings.
Reading the manual section "On URL syntax and credential lookup" is worthwhile.

 # It can be as easy as
 # (Remember '''USER''' and '''PASS''' must be URL percent encoded)
 set smtp=smtp://'''USER''':'''PASS'''@'''HOST''' \
     smtp-use-starttls
 
 # It may be necessary to set ''hostname'' and/or ''smtp-hostname''
 # if the "SERVER" of ''smtp'' and "domain" of ''from'' don't match.
 # Reading the "ON URL SYNTAX.." and ''smtp'' manual entries may be worthwhile
 set smtp='''(smtp[s]/submission)://[USER[:PASS]@]SERVER[:PORT]''' \
     smtp-auth='''login[/plain]...''' \
     smtp-use-starttls
 
 # E.g. here is a real life example of a very huge free mail provider
 # (Activate this account via ''mailx -AXooglX'' from the command line,
 # or use the ''? acc[ount] XooglX'' command in interactive mode)
 account XooglX {
    # Localize options, forget them when changing the account
    localopts yes
    # (The plain smtp:// proto is optional)
    set smtp='''USER:PASS'''@smtp.gmXil.com smtp-use-starttls
    set from="'''Your Name <youremail@domain>'''"
 }
 
 # And here is a pretty large one which does not allow sending mails
 # if there is a domain name mismatch ''on the SMTP protocol level'',
 # which would bite us if the value of ''from'' does not match, e.g.,
 # for people who have a sXXXXeforge project and want to speak
 # with the mailing list under their project account (in ''from''),
 # still sending the message through their normal mail provider
 account XandeX {
    localopts yes
    set smtp=smtps://'''USER:PASS'''@smtp.yaXXex.ru:465 \
        hostname=yaXXex.com smtp-hostname=
    set from="'''Your Name <youremail@domain>'''"
 }

{{Tip|If you have enabled two-step authentication in Gmail, and you have added an application specific password for S-nail, you will want to use that password rather than your regular Gmail password, which may work without enabling the otherwise necessary "less secure apps".}}

Note that, when storing passwords in {{ic|$HOME/.mailrc}}, you should set appropriate permissions with {{ic|chmod 0600}}.
You can also set the ''netrc-lookup'' option and store user credentials in {{ic|$HOME/.netrc}} (or ''$NETRC'') instead; e.g., here is a real life example that sets up SMTP, POP3 as well as IMAP, storing all user credentials in there:

 account XandeX {
    localopts yes
    set from="Your Name <youremail@domain>"
    set netrc-lookup
    #set agent-shell-lookup="gpg -d .pass.gpg"
    set smtp=smtps://smtp.yXXXXx.ru:465 \
        smtp-hostname= hostname=yXXXXx.com
    set pop3-keepalive=240
    shortcut pop pop3s://pop.yXXXXx.ru
    # Type '''xp''' to login to the POP3 account
    ghost xp 'fi pop'
    set imap-keepalive=240
    shortcut imap imaps://imap.yXXXXx.ru
    # Type '''xi''' to login to the IMAP account
    ghost xi 'fi imap'
  }

and, in {{ic|$HOME/.netrc}}:

 machine *.yXXXXx.ru login '''USER''' password '''PASS'''

In this case '''USER''' and '''PASS''' are clear text, not URL encoded. You can further diversify things and use encrypted password storage, since ArchLinux compiles in password agent support.
To adjust the example, simply do not specify the ''password '''PASS''''' token in {{ic|$HOME/.netrc}} but instead uncomment the ''agent-shell-lookup'' line in the example account above.
The encrypted password storage {{ic|.pass.gpg}} can be created like this:

 # echo '''PASS''' > .pass
 # gpg -e .pass
 # eval `gpg-agent --daemon --pinentry-program=/usr/bin/pinentry-curses --max-cache-ttl 99999 --default-cache-ttl 99999`

Test the configuration (use the ''-d'' command line option for a dry-run):

 # echo test-body | mailx -vv -A XandeX -s test-subject '''some@where'''

== インタラクティブな使用方法 ==

Arch Linux の S-nail にはコマンドラインエディタが組み込まれており、履歴機能や正規表現、メッセージのカラー表示が使えます。S-nail は POSIX 標準に準拠しているためインタラクティブに使う前に設定を変更する必要があります。全ての設定に手を入れる必要はありませんがマニュアルは必ず読んでください。最低でも設定の一番上に以下を追加してください:

 # (The global configuration /etc/mail.rc provides some commented basics;
 # in particular it shows all options that POSIX mandates as defaults.)
 
 # Start into interactive mode even if the system mailbox is empty or
 # doesn't exist.  S-nail would exit immediately without that one
 set emptystart
 
 # When composing a message, let period `.' on a line by itself finalize
 # composition, before start directly into ''$EDITOR''
 set dot 
 set editalong
 
 # Start ''$PAGER'' when a message is longer than VALUE lines;
 # without VALUE: screen ''$LINES''
 set crt=
 
 # Colourize headers when displaying messages (note that ''$PAGER'' may
 # require special flags, e.g., less(1) needs the -R option; S-nail will
 # however set the ''$LESS'' environment variable accordingly, but only if
 # that was not set before..)
 set colour-pager
 
 # A nicer prompt for a modern terminal
 set prompt="\033[31m?\?[\$ \@]\& \033[0m"
 
 # Add more entries to the history, and make that persistent
 set history-gabby NAIL_HISTFILE=+.s-nailhist NAIL_HISTSIZE=-1
 
 # When '''p'''rinting messages, show only these headers
 # (Easier to '''retain''' what you want than to '''ignore'''
 # what you don't; use '''P'''rint to see all headers and '''S'''how
 # to see the raw message content)
 retain date from to cc subject
 
 # Try to get around weird MIME attachment specifications
 # (This option can take a value, see the manual for more)
 set mime-counter-evidence
 
 # Display HTML parts inline, nicer than what the builtin viewer can achieve
 #set pipe-text/html="lynx -stdin -dump -force_html"
 # Learn another mimetype
 mimetype 'model/vrml wrl vrml'
 
 # Create some new commands so that, e.g., `ls /tmp' will..
 ghost ls !ls -latro
 ghost ps !ps axu

Once you're in it use '''list''' to print all available builtin commands.
ArchLinux compiles in the "DOCSTRINGS" feature, so that typing `?X' tries to expand "X" and print a help string; since S-nail will allow abbreviations of all commands this is sometimes handy; try, e.g., '''?h''', '''?he''' and '''?hel''' ...
The command '''help''' will print a short summary of the most frequent used commands.

=== コマンド ===

When starting into interactive mode a summary of the content of the initially opened mailbox is printed, as via the '''headers''' command.
In the header display messages are given numbers (starting at 1) which uniquely identify messages.
Messages can be printed with the '''print''' command, or short: '''p'''.
Whereas '''p''' honours '''retain'''ed (or '''ignore'''d) list of headers to be displayed, the '''P'''rint command will not and display all headers;
the '''Sh'''ow command will print raw message content.

By default the current message (dot) is printed, but just like with many other commands it is possible to specify lists of messages, as is documented in the manual section "Specifying messages"; e.g., '''p:u''' will display all unread messages, '''p.''' will print the dot, '''p 1 5''' will print the messages 1 and 5 and '''p-''' and '''p+''' will print the last and the next message, respectively.
Note that simply typing RETURN in an empty line acts like '''next''' ('''n'''), and thus prints the next message.

The command '''from''' ('''f''') is nice for an overview, e.g., '''f '@<@arch linux'''' will print the header summary of all messages that contain the string "arch linux" in some message header, whereas '''f '@arch linux'''' will only match those with "arch linux" in their subject;
finally, the regular expression '''f @^A[^[:space:]]+''' finds... 
that is, be aware that quoting may be necessary when there is whitespace in search expressions etc.

* '''file''' and '''File''' open a new mailbox, the latter in readonly mode (which can be handy to avoid flag updates etc.)
* '''newmail''' (dependent on the mailbox, checks for new mail and) prints a listing of new messages
* '''he''' (headers) reprints the message list
* '''z-''', '''z+''', '''z0''', '''z$''' scroll through the header display (dependent on the terminal you are using the Home/End/PageUp/PageDown keys will be working aliases)
* '''folders''' shows a listing of mailboxes under the currently set ''folder''
* '''r''' replies to all addressees of the given message(s)
* '''R''' replies to the sender of the given message(s)
* '''Lreply''' "mailing-list" reply to the given message(s)
* '''move''' or '''mv''' moves (a) message(s)
* '''(un)flag''' marks (a) message(s) as (un)flagged
* '''new''' marks (a) message(s) unread
* '''seen''' marks (a) message(s) read
* '''P''' prints (a) message(s) with all headers
* '''p''' prints (a) message(s) and all non-ignored headers.
* '''show''' prints the raw message of content of (a) message(s)

=== メッセージの作成 ===

Composition is started by typing '''mail user@host''' or by replying to a message.
When you return from ''$EDITOR'' (assuming ''editalong'' is set) you'll find yourself in the native editor, where many operations can be performed using tilde escapes (short help available via '''~?''').
Of particular interest is '''~@''', which either allows interactive editing of the attachment list, or, when given arguments, to add a(n) (comma-separated list of) additional attachment(s).

To send the mail, signal EOT with {{ic|Ctrl+d}} or type "." on its own line (the latter requires the ''dot'' option).

== S/MIME を使う ==

The manual contains a step-by-step example of how to create your certificates etc. ("Signed and encrypted messages with S/MIME").
Assuming you have your private key and signed certificate already, just create the paired file we need

 # cat private-key.pem signed-certificate.pem > ~/pair.pem

and setup S-nail via

 set smime-sign-cert=~/pair.pem \
     smime-sign-message-digest=SHA256 \
     smime-sign

From now any message that is sent will be signed.
The default message digest would be SHA1, as mandated by RFC 5751.
Note that S/MIME always works relative to the setting of the variable ''from'', so it seems best to instead place the above settings in an '''account'''.
The '''verify''' command verifies S/MIME messages, but note that S/MIME decryption and verification is solely based upon OpenSSL for now, which only supports messages with a simplicistic MIME structure.  Sorry.
By the way, if you miss hyperlinks and a table-of-content to get yourself going, the manual on the projects' website offers this; and the manual that ships with ArchLinux does, too, but needs the mdocmx(7) extension to be visible.

== OpenPGP のサポート ==

S-nail は OpenPGP をサポートしていませんが、マクロを使うことで自動的に ''--clearsign'' されたメッセージを検証することができます。リソースファイルで以下を使うことで '''V''' を押すだけでメッセージを検証することが可能です:

  define V {
    localopts yes
    set pipe-text/plain="set -C;\
      : > \"${TMPDIR}/${NAIL_FILENAME_GENERATED}\";\
      trap \"rm -f \\\"${TMPDIR}/${NAIL_FILENAME_GENERATED}\\\"\" EXIT;\
      trap \"exit 75\" INT QUIT TERM;\
      set +C;\
      cat > \"${TMPDIR}/${NAIL_FILENAME_GENERATED}\";\
      < \"${TMPDIR}/${NAIL_FILENAME_GENERATED}\" awk \
          -v TMPFILE=\"${TMPDIR}/${NAIL_FILENAME_GENERATED}\" '\
        BEGIN {done=0}\
        /^-----BEGIN PGP SIGNED MESSAGE-----/,/^$/ {\
          if (done++ != 0)\
            next;\
          print \"--- GPG --verify ---\";\
          system(\"gpg --verify \" TMPFILE \" 2>&1\");\
          print \"--- GPG --verify ---\";\
          print \"\";\
          next;\
        }\
        /^-----BEGIN PGP SIGNATURE-----/,/^-----END PGP SIGNATURE-----/ {\
          next;\
        }\
        {print}\
        '"
    print
  }
  define RK {
    !printf 'Key IDs to gpg --recv-keys: ';\
      read keyids;\
      gpg --recv-keys ${keyids};
  }
  ghost V call V
  ghost RK call RK

== IMAP メールボックスを使う ==

以下は簡単なヒントです。たとえば、''folder'' と ''inbox'' を定義して IMAP サーバーフォルダーを指すようにすることもできます。
国際化された名前がサポートされています。

 set v15-compat
 
 # or many servers will expire the session
 set imap-keepalive=240
 set imap-cache=~/.imap_cache
 
 # You may want to define shortcuts to folders, for example:
 shortcut myimap "'''imaps://USER:PASS@server:port"
 set inbox=myimap