emacs/lisp/gnus/smime.el

;;; smime.el --- S/MIME support library  -*- lexical-binding:t -*-

;; Copyright (C) 2000-2021 Free Software Foundation, Inc.

;; Author: Simon Josefsson <simon@josefsson.org>
;; Keywords: SMIME X.509 PEM OpenSSL

;; This file is part of GNU Emacs.

;; GNU Emacs is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.

;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.

;;; Commentary:

;; This library perform S/MIME operations from within Emacs.
;;
;; Functions for fetching certificates from public repositories are
;; provided, currently from DNS and LDAP.
;;
;; It uses OpenSSL (tested with version 0.9.5a and 0.9.6) for signing,
;; encryption and decryption.
;;
;; Some general knowledge of S/MIME, X.509, PKCS#12, PEM etc is
;; probably required to use this library in any useful way.
;; Especially, don't expect this library to buy security for you.  If
;; you don't understand what you are doing, you're as likely to lose
;; security than gain any by using this library.
;;
;; This library is not intended to provide a "raw" API for S/MIME,
;; PKCSx or similar, it's intended to perform common operations
;; done on messages encoded in these formats.  The terminology chosen
;; reflect this.
;;
;; The home of this file is in Gnus, but also available from
;; http://josefsson.org/smime.html.

;;; Quick introduction:

;; Get your S/MIME certificate from VeriSign or someplace.  I used
;; Netscape to generate the key and certificate request and stuff, and
;; Netscape can export the key into PKCS#12 format.
;;
;; Enter OpenSSL.  To be able to use this library, it need to have the
;; SMIME key readable in PEM format.  OpenSSL is used to convert the
;; key:
;;
;; $ openssl pkcs12 -in mykey.p12 -clcerts -nodes > mykey.pem
;; ...
;;
;; Now, use M-x customize-variable smime-keys and add mykey.pem as
;; a key.
;;
;; Now you should be able to sign messages!  Create a buffer and write
;; something and run M-x smime-sign-buffer RET RET and you should see
;; your message MIME armored and a signature.  Encryption, M-x
;; smime-encrypt-buffer, should also work.
;;
;; To be able to verify messages you need to build up trust with
;; someone.  Perhaps you trust the CA that issued your certificate, at
;; least I did, so I export its certificates from my PKCS#12
;; certificate with:
;;
;; $ openssl pkcs12 -in mykey.p12 -cacerts -nodes > cacert.pem
;; ...
;;
;; Now, use M-x customize-variable smime-CAs and add cacert.pem as a
;; CA certificate.
;;
;; You should now be able to sign messages, and even verify messages
;; sent by others that use the same CA as you.

;; Bugs:
;;
;; Don't complain that this package doesn't do encrypted PEM files,
;; submit a patch instead.  I store my keys in a safe place, so I
;; didn't need the encryption.  Also, programming was made easier by
;; that decision.  One might think that this even influenced were I
;; store my keys, and one would probably be right. :-)
;;
;; Update: Mathias Herberts sent the patch.  However, it uses
;; environment variables to pass the password to OpenSSL, which is
;; slightly insecure. Hence a new todo: use a better -passin method.
;;
;; Cache password for e.g. 1h
;;
;; Suggestions and comments are appreciated, mail me at simon@josefsson.org.

;; begin rant
;;
;; I would include pointers to introductory text on concepts used in
;; this library here, but the material I've read are so horrible I
;; don't want to recommend them.
;;
;; Why can't someone write a simple introduction to all this stuff?
;; Until then, much of this resemble security by obscurity.
;;
;; Also, I'm not going to mention anything about the wonders of
;; cryptopolitics.  Oops, I just did.
;;
;; end rant

;;; Revision history:

;; 2000-06-05  initial version, committed to Gnus CVS contrib/
;; 2000-10-28  retrieve certificates via DNS CERT RRs
;; 2001-10-14  posted to gnu.emacs.sources
;; 2005-02-13  retrieve certificates via LDAP

;;; Code:

(require 'dig)

(require 'password-cache)

(eval-when-compile (require 'cl-lib))

(defgroup smime nil
  "S/MIME configuration."
  :group 'mime)

(defcustom smime-keys nil
  "Map mail addresses to a file containing Certificate (and private key).
The file is assumed to be in PEM format.  You can also associate additional
certificates to be sent with every message to each address."
  :type '(repeat (list (string :tag "Mail address")
		       (file :tag "File name")
		       (repeat :tag "Additional certificate files"
			       (file :tag "File name")))))

(defcustom smime-CA-directory nil
  "Directory containing certificates for CAs you trust.
Directory should contain files (in PEM format) named to the X.509
hash of the certificate.  This can be done using OpenSSL such as:

$ ln -s ca.pem \\=`openssl x509 -noout -hash -in ca.pem\\=`.0

where `ca.pem' is the file containing a PEM encoded X.509 CA
certificate."
  :type '(choice (const :tag "none" nil)
		 directory))

(defcustom smime-CA-file nil
  "Files containing certificates for CAs you trust.
File should contain certificates in PEM format."
  :version "22.1"
  :type '(choice (const :tag "none" nil)
		 file))

(defcustom smime-certificate-directory "~/Mail/certs/"
  "Directory containing other people's certificates.
It should contain files named to the X.509 hash of the certificate,
and the files themselves should be in PEM format."
;The S/MIME library provide simple functionality for fetching
;certificates into this directory, so there is no need to populate it
;manually.
  :type 'directory)

(defcustom smime-openssl-program
  (and (condition-case ()
	   (eq 0 (call-process "openssl" nil nil nil "version"))
	 (error nil))
       "openssl")
  "Name of OpenSSL binary or nil if none."
  :type '(choice string
                 (const :tag "none" nil)))

;; OpenSSL option to select the encryption cipher

(defcustom smime-encrypt-cipher "-des3"
  "Cipher algorithm used for encryption."
  :version "22.1"
  :type '(choice (const :tag "Triple DES" "-des3")
		 (const :tag "DES"  "-des")
		 (const :tag "AES 256 bits" "-aes256")
		 (const :tag "AES 192 bits" "-aes192")
		 (const :tag "AES 128 bits" "-aes128")
		 (const :tag "RC2 40 bits" "-rc2-40")
		 (const :tag "RC2 64 bits" "-rc2-64")
		 (const :tag "RC2 128 bits" "-rc2-128")))

(defcustom smime-crl-check nil
  "Check revocation status of signers certificate using CRLs.
Enabling this will have OpenSSL check the signers certificate
against a certificate revocation list (CRL).

For this to work the CRL must be up-to-date and since they are
normally updated quite often (i.e., several times a day) you
probably need some tool to keep them up-to-date.  Unfortunately
Gnus cannot do this for you.

The CRL should either be appended (in PEM format) to your
`smime-CA-file' or be located in a file (also in PEM format) in
your `smime-certificate-directory' named to the X.509 hash of the
certificate with .r0 as file name extension.

At least OpenSSL version 0.9.7 is required for this to work."
  :type '(choice (const :tag "No check" nil)
		 (const :tag "Check certificate" "-crl_check")
		 (const :tag "Check certificate chain" "-crl_check_all")))

(defcustom smime-dns-server nil
  "DNS server to query certificates from.
If nil, use system defaults."
  :version "22.1"
  :type '(choice (const :tag "System defaults")
		 string))

(defcustom smime-ldap-host-list nil
  "A list of LDAP hosts with S/MIME user certificates.
If needed search base, binddn, passwd, etc. for the LDAP host
must be set in `ldap-host-parameters-alist'."
  :type '(repeat (string :tag "Host name"))
  :version "23.1") ;; No Gnus

(defvar smime-details-buffer "*OpenSSL output*")

(defun smime-ask-passphrase (&optional cache-key)
  "Asks the passphrase to unlock the secret key.
If `cache-key' and `password-cache' is non-nil then cache the
password under `cache-key'."
  (let ((passphrase
	 (password-read
	  "Passphrase for secret key (RET for no passphrase): " cache-key)))
    (if (string= passphrase "")
	nil
      ;; FIXME test passphrase works before caching it.
      (and passphrase cache-key (password-cache-add cache-key passphrase))
      passphrase)))

;; OpenSSL wrappers.

(defun smime-call-openssl-region (b e buf &rest args)
  (pcase (apply #'call-process-region b e smime-openssl-program nil buf nil args)
    (0 t)
    (1 (message "OpenSSL: An error occurred parsing the command options.") nil)
    (2 (message "OpenSSL: One of the input files could not be read.") nil)
    (3 (message "OpenSSL: An error occurred creating the PKCS#7 file or when reading the MIME message.") nil)
    (4 (message "OpenSSL: An error occurred decrypting or verifying the message.") nil)
    (_ (error "Unknown OpenSSL exitcode"))))

(defun smime-make-certfiles (certfiles)
  (if certfiles
      (append (list "-certfile" (expand-file-name (car certfiles)))
	      (smime-make-certfiles (cdr certfiles)))))

;; Sign+encrypt region

(defun smime-sign-region (b e keyfile)
  "Sign region with certified key in KEYFILE.
If signing fails, the buffer is not modified.  Region is assumed to
have proper MIME tags.  KEYFILE is expected to contain a PEM encoded
private key and certificate as its car, and a list of additional
certificates to include in its caar.  If no additional certificates is
included, KEYFILE may be the file containing the PEM encoded private
key and certificate itself."
  (smime-new-details-buffer)
  (let* ((certfiles (and (cdr-safe keyfile) (cadr keyfile)))
	 (keyfile (or (car-safe keyfile) keyfile))
	 (buffer (generate-new-buffer " *smime*"))
	 (passphrase (smime-ask-passphrase (expand-file-name keyfile)))
	 (tmpfile (make-temp-file "smime")))
    (if passphrase
	(setenv "GNUS_SMIME_PASSPHRASE" passphrase))
    (prog1
	(when (prog1
		  (apply #'smime-call-openssl-region b e (list buffer tmpfile)
			 "smime" "-sign" "-signer" (expand-file-name keyfile)
			 (append
			  (smime-make-certfiles certfiles)
			  (if passphrase
			      (list "-passin" "env:GNUS_SMIME_PASSPHRASE"))))
		(if passphrase
		    (setenv "GNUS_SMIME_PASSPHRASE" "" t))
		(with-current-buffer smime-details-buffer
		  (insert-file-contents tmpfile)
		  (delete-file tmpfile)))
	  (delete-region b e)
	  (insert-buffer-substring buffer)
	  (goto-char b)
	  (when (looking-at "^MIME-Version: 1.0$")
	    (delete-region (point) (progn (forward-line 1) (point))))
	  t)
      (with-current-buffer smime-details-buffer
	(goto-char (point-max))
	(insert-buffer-substring buffer))
      (kill-buffer buffer))))

(defun smime-encrypt-region (b e certfiles)
  "Encrypt region for recipients specified in CERTFILES.
If encryption fails, the buffer is not modified.  Region is assumed to
have proper MIME tags.  CERTFILES is a list of filenames, each file
is expected to contain of a PEM encoded certificate."
  (smime-new-details-buffer)
  (let ((buffer (generate-new-buffer " *smime*"))
	(tmpfile (make-temp-file "smime")))
    (prog1
	(when (prog1
		  (apply #'smime-call-openssl-region b e (list buffer tmpfile)
			 "smime" "-encrypt" smime-encrypt-cipher
			 (mapcar #'expand-file-name certfiles))
		(with-current-buffer smime-details-buffer
		  (insert-file-contents tmpfile)
		  (delete-file tmpfile)))
	  (delete-region b e)
	  (insert-buffer-substring buffer)
	  (goto-char b)
	  (when (looking-at "^MIME-Version: 1.0$")
	    (delete-region (point) (progn (forward-line 1) (point))))
	  t)
      (with-current-buffer smime-details-buffer
	(goto-char (point-max))
	(insert-buffer-substring buffer))
      (kill-buffer buffer))))

;; Sign+encrypt buffer

(defun smime-sign-buffer (&optional keyfile buffer)
  "S/MIME sign BUFFER with key in KEYFILE.
KEYFILE should contain a PEM encoded key and certificate."
  (interactive)
  (with-current-buffer (or buffer (current-buffer))
    (unless (smime-sign-region
	     (point-min) (point-max)
	     (if keyfile
		 keyfile
	       (smime-get-key-with-certs-by-email
		(gnus-completing-read
		 "Sign using key"
		 smime-keys nil (car-safe (car-safe smime-keys))))))
      (error "Signing failed"))))

(defun smime-encrypt-buffer (&optional certfiles buffer)
  "S/MIME encrypt BUFFER for recipients specified in CERTFILES.
CERTFILES is a list of filenames, each file is expected to consist of
a PEM encoded key and certificate.  Uses current buffer if BUFFER is
nil."
  (interactive)
  (with-current-buffer (or buffer (current-buffer))
    (unless (smime-encrypt-region
	     (point-min) (point-max)
	     (or certfiles
		 (list (read-file-name "Recipient's S/MIME certificate: "
				       smime-certificate-directory nil))))
      (error "Encryption failed"))))

;; Verify+decrypt region

(defun smime-verify-region (b e)
  "Verify S/MIME message in region between B and E.
Returns non-nil on success.
Any details (stdout and stderr) are left in the buffer specified by
`smime-details-buffer'."
  (smime-new-details-buffer)
  (let ((CAs (append (if smime-CA-file
			 (list "-CAfile"
			       (expand-file-name smime-CA-file)))
		     (if smime-CA-directory
			 (list "-CApath"
			       (expand-file-name smime-CA-directory)))))
	(input-buffer (current-buffer)))
    (unless CAs
      (error "No CA configured"))
    (if smime-crl-check
	(cl-pushnew smime-crl-check CAs :test #'equal))
    (with-temp-buffer
      (let ((result-buffer (current-buffer)))
	(with-current-buffer input-buffer
	  (if (apply #'smime-call-openssl-region b e (list result-buffer
							  smime-details-buffer)
		     "smime" "-verify" "-out" "-" CAs)
	      (with-current-buffer result-buffer
		(buffer-string))
	    nil))))))

(defun smime-noverify-region (b e)
  "Verify integrity of S/MIME message in region between B and E.
Returns non-nil on success.
Any details (stdout and stderr) are left in the buffer specified by
`smime-details-buffer'."
  (smime-new-details-buffer)
  (if (apply #'smime-call-openssl-region b e (list smime-details-buffer t)
	     "smime" "-verify" "-noverify" "-out" `(,null-device))
      t
    (insert-buffer-substring smime-details-buffer)
    nil))

(defun smime-decrypt-region (b e keyfile &optional from)
  "Decrypt S/MIME message in region between B and E with key in KEYFILE.
Optional FROM specifies sender's mail address.
On success, replaces region with decrypted data and return non-nil.
Any details (stderr on success, stdout and stderr on error) are left
in the buffer specified by `smime-details-buffer'."
  (smime-new-details-buffer)
  (let ((buffer (generate-new-buffer " *smime*"))
	(passphrase (smime-ask-passphrase (expand-file-name keyfile)))
	(tmpfile (make-temp-file "smime")))
    (if passphrase
	(setenv "GNUS_SMIME_PASSPHRASE" passphrase))
    (if (prog1
	    (apply #'smime-call-openssl-region b e
		   (list buffer tmpfile)
		   "smime" "-decrypt" "-recip" (expand-file-name keyfile)
		   (if passphrase
		       (list "-passin" "env:GNUS_SMIME_PASSPHRASE")))
	  (if passphrase
	      (setenv "GNUS_SMIME_PASSPHRASE" "" t))
	  (with-current-buffer smime-details-buffer
	    (insert-file-contents tmpfile)
	    (delete-file tmpfile)))
	(progn
	  (delete-region b e)
	  (when from
	    (insert "From: " from "\n"))
	  (insert-buffer-substring buffer)
	  (kill-buffer buffer)
	  t)
      (with-current-buffer smime-details-buffer
	(insert-buffer-substring buffer))
      (kill-buffer buffer)
      (delete-region b e)
      (insert-buffer-substring smime-details-buffer)
      nil)))

;; Verify+Decrypt buffer

(defun smime-verify-buffer (&optional buffer)
  "Verify integrity of S/MIME message in BUFFER.
Uses current buffer if BUFFER is nil.  Returns non-nil on success.
Any details (stdout and stderr) are left in the buffer specified by
`smime-details-buffer'."
  (interactive)
  (with-current-buffer (or buffer (current-buffer))
    (smime-verify-region (point-min) (point-max))))

(defun smime-noverify-buffer (&optional buffer)
  "Verify integrity of S/MIME message in BUFFER.
Does NOT verify validity of certificate (only message integrity).
Uses current buffer if BUFFER is nil.  Returns non-nil on success.
Any details (stdout and stderr) are left in the buffer specified by
`smime-details-buffer'."
  (interactive)
  (with-current-buffer (or buffer (current-buffer))
    (smime-noverify-region (point-min) (point-max))))

(defun smime-decrypt-buffer (&optional buffer keyfile)
  "Decrypt S/MIME message in BUFFER using KEYFILE.
Uses current buffer if BUFFER is nil, and query user of KEYFILE if it's nil.
On success, replaces data in buffer and return non-nil.
Any details (stderr on success, stdout and stderr on error) are left
in the buffer specified by `smime-details-buffer'."
  (interactive)
  (with-current-buffer (or buffer (current-buffer))
    (smime-decrypt-region
     (point-min) (point-max)
     (expand-file-name
      (or keyfile
	  (smime-get-key-by-email
	   (gnus-completing-read
	    "Decipher using key"
	    smime-keys nil (car-safe (car-safe smime-keys)))))))))

;; Various operations

(defun smime-new-details-buffer ()
  (with-current-buffer (get-buffer-create smime-details-buffer)
    (erase-buffer)))

(defun smime-pkcs7-region (b e)
  "Convert S/MIME message between points B and E into a PKCS7 message."
  (smime-new-details-buffer)
  (when (smime-call-openssl-region b e smime-details-buffer "smime" "-pk7out")
    (delete-region b e)
    (insert-buffer-substring smime-details-buffer)
    t))

(defun smime-pkcs7-certificates-region (b e)
  "Extract any certificates enclosed in PKCS7 message between points B and E."
  (smime-new-details-buffer)
  (when (smime-call-openssl-region
	 b e smime-details-buffer "pkcs7" "-print_certs" "-text")
    (delete-region b e)
    (insert-buffer-substring smime-details-buffer)
    t))

(defun smime-pkcs7-email-region (b e)
  "Get email addresses contained in certificate between points B and E.
A string or a list of strings is returned."
  (smime-new-details-buffer)
  (when (smime-call-openssl-region
	 b e smime-details-buffer "x509" "-email" "-noout")
    (delete-region b e)
    (insert-buffer-substring smime-details-buffer)
    t))

;; Utility functions

(defun smime-get-certfiles (keyfile keys)
  (if keys
      (let ((curkey (car keys))
	    (otherkeys (cdr keys)))
	(if (string= keyfile (cadr curkey))
	    (nth 2 curkey)
	  (smime-get-certfiles keyfile otherkeys)))))

(defun smime-buffer-as-string-region (b e)
  "Return each line in region between B and E as a list of strings."
  (save-excursion
    (goto-char b)
    (let (res)
      (while (< (point) e)
	(let ((str (buffer-substring (point) (point-at-eol))))
	  (unless (string= "" str)
	    (push str res)))
	(forward-line))
      res)))

;; Find certificates

(defun smime-mail-to-domain (mailaddr)
  (if (string-match "@" mailaddr)
      (replace-match "." 'fixedcase 'literal mailaddr)
    mailaddr))

(defun smime-cert-by-dns (mail)
  "Find certificate via DNS for address MAIL."
  (let* ((dig-dns-server smime-dns-server)
	 (digbuf (dig-invoke (smime-mail-to-domain mail) "cert" nil nil "+vc"))
	 (retbuf (generate-new-buffer (format "*certificate for %s*" mail)))
	 (certrr (with-current-buffer digbuf
		   (dig-extract-rr (smime-mail-to-domain mail) "cert")))
	 (cert (and certrr (dig-rr-get-pkix-cert certrr))))
      (if cert
	  (with-current-buffer retbuf
	    (insert "-----BEGIN CERTIFICATE-----\n")
	    (let ((i 0) (len (length cert)))
	      (while (> (- len 64) i)
		(insert (substring cert i (+ i 64)) "\n")
		(setq i (+ i 64)))
	      (insert (substring cert i len) "\n"))
	    (insert "-----END CERTIFICATE-----\n"))
	(kill-buffer retbuf)
	(setq retbuf nil))
      (kill-buffer digbuf)
      retbuf))

(declare-function ldap-search "ldap"
		  (filter &optional host attributes attrsonly withdn))

(defun smime-cert-by-ldap-1 (mail host)
  "Get certificate for MAIL from the ldap server at HOST."
  (let ((ldapresult
	 (funcall
	  (progn
	    (require 'ldap)
	    'ldap-search)
	  (concat "mail=" mail)
	  host '("userCertificate") nil))
	(retbuf (generate-new-buffer (format "*certificate for %s*" mail)))
        ldapstr
	cert)
    (if (and (consp ldapresult)
             ;; FIXME: This seems to expect a format rather different from
             ;; the list of alists described in ldap.el.
             (setq ldapstr (cadr (caar ldapresult)))
             (> (length ldapstr) 0))
	(with-current-buffer retbuf
	  ;; Certificates on LDAP servers _should_ be in DER format,
	  ;; but there are some servers out there that distributes the
	  ;; certificates in PEM format (with or without
	  ;; header/footer) so we try to handle them anyway.
	  (if (or (string= (substring ldapstr 0 27)
			   "-----BEGIN CERTIFICATE-----")
		  (string= (substring ldapstr 0 3)
			   "MII"))
	      (setq cert
		    (replace-regexp-in-string
		     (concat "\\(\n\\|\r\\|-----BEGIN CERTIFICATE-----\\|"
			     "-----END CERTIFICATE-----\\)")
		     ""
		     ldapstr nil t))
	    (setq cert (base64-encode-string ldapstr t)))
	  (insert "-----BEGIN CERTIFICATE-----\n")
	  (let ((i 0) (len (length cert)))
	    (while (> (- len 64) i)
	      (insert (substring cert i (+ i 64)) "\n")
	      (setq i (+ i 64)))
	    (insert (substring cert i len) "\n"))
	  (insert "-----END CERTIFICATE-----\n"))
      (kill-buffer retbuf)
      (setq retbuf nil))
    retbuf))

(defun smime-cert-by-ldap (mail)
  "Find certificate via LDAP for address MAIL."
  (if smime-ldap-host-list
      (catch 'certbuf
	(dolist (host smime-ldap-host-list)
	  (let ((retbuf (smime-cert-by-ldap-1 mail host)))
	    (when retbuf
	      (throw 'certbuf retbuf)))))))

;; User interface.

(defvar smime-buffer "*SMIME*")

(defvar smime-mode-map
  (let ((map (make-sparse-keymap)))
    (suppress-keymap map)
    (define-key map "q" 'smime-exit)
    (define-key map "f" 'smime-certificate-info)
    map))

(autoload 'gnus-completing-read "gnus-util")

(put 'smime-mode 'mode-class 'special)
(define-derived-mode smime-mode fundamental-mode ;special-mode
  "SMIME"
  "Major mode for browsing, viewing and fetching certificates.

All normal editing commands are switched off.
\\<smime-mode-map>

The following commands are available:

\\{smime-mode-map}"
  (setq mode-line-process nil)
  (buffer-disable-undo)
  (setq truncate-lines t)
  (setq buffer-read-only t))

(defun smime-certificate-info (certfile)
  (interactive "fCertificate file: ")
  (let ((buffer (get-buffer-create (format "*certificate %s*" certfile))))
    (switch-to-buffer buffer)
    (erase-buffer)
    (call-process smime-openssl-program nil buffer 'display
		  "x509" "-in" (expand-file-name certfile) "-text")
    (fundamental-mode)
    (set-buffer-modified-p nil)
    (setq buffer-read-only t)
    (goto-char (point-min))))

(defun smime-draw-buffer ()
  (with-current-buffer smime-buffer
    (let (buffer-read-only)
      (erase-buffer)
      (insert "\nYour keys:\n")
      (dolist (key smime-keys)
	(insert
	 (format "\t\t%s: %s\n" (car key) (cadr key))))
      (insert "\nTrusted Certificate Authorities:\n")
      (insert "\nKnown Certificates:\n"))))

(defun smime ()
  "Go to the SMIME buffer."
  (interactive)
  (unless (get-buffer smime-buffer)
    (with-current-buffer (get-buffer-create smime-buffer)
      (smime-mode)))
  (smime-draw-buffer)
  (switch-to-buffer smime-buffer))

(defun smime-exit ()
  "Quit the S/MIME buffer."
  (interactive nil smime-mode)
  (kill-buffer (current-buffer)))

;; Other functions

(defun smime-get-key-by-email (email)
  (cadr (assoc email smime-keys)))

(defun smime-get-key-with-certs-by-email (email)
  (cdr (assoc email smime-keys)))

(provide 'smime)

;;; smime.el ends here