code.delx.au - gnu-emacs/blob - man/pgg.texi

   1 \input texinfo                  @c -*-texinfo-*-
   2
   3 @setfilename ../info/pgg
   4
   5 @set VERSION 0.1
   6
   7
   8 @copying
   9 This file describes the PGG.
  10
  11 Copyright (C) 2003, 2004, 2005 Free Software Foundation, Inc.
  12 Copyright (C) 2001 Daiki Ueno.
  13
  14 @quotation
  15 Permission is granted to copy, distribute and/or modify this document
  16 under the terms of the GNU Free Documentation License, Version 1.2 or
  17 any later version published by the Free Software Foundation; with no
  18 Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
  19 Texts.  A copy of the license is included in the section entitled ``GNU
  20 Free Documentation License''.
  21 @end quotation
  22 @end copying
  23
  24 @dircategory Emacs
  25 @direntry
  26 * PGG: (pgg).   Emacs interface to various PGP implementations.
  27 @end direntry
  28
  29 @settitle PGG @value{VERSION}
  30
  31
  32 @titlepage
  33 @title PGG
  34
  35 @author by Daiki Ueno
  36 @page
  37
  38 @vskip 0pt plus 1filll
  39 @insertcopying
  40 @end titlepage
  41 @page
  42
  43 @node Top
  44 @top PGG
  45 This manual describes PGG.  PGG is an interface library between Emacs
  46 and various tools for secure communication.  PGG also provides a simple
  47 user interface to encrypt, decrypt, sign, and verify MIME messages.
  48
  49 @menu
  50 * Overview::                    What PGG is.
  51 * Prerequisites::               Complicated stuff you may have to do.
  52 * How to use::                  Getting started quickly.
  53 * Architecture::
  54 * Parsing OpenPGP packets::
  55 * Function Index::
  56 * Variable Index::
  57 @end menu
  58
  59 @node Overview
  60 @chapter Overview
  61
  62 PGG is an interface library between Emacs and various tools for secure
  63 communication.  Even though Mailcrypt has similar feature, it does not
  64 deal with detached PGP messages, normally used in PGP/MIME
  65 infrastructure.  This was the main reason why I wrote the new library.
  66
  67 PGP/MIME is an application of MIME Object Security Services (RFC1848).
  68 The standard is documented in RFC2015.
  69
  70 @node Prerequisites
  71 @chapter Prerequisites
  72
  73 PGG requires at least one implementation of privacy guard system.
  74 This document assumes that you have already obtained and installed them
  75 and that you are familiar with its basic functions.
  76
  77 By default, PGG uses GnuPG, but Pretty Good Privacy version 2 or version
  78 5 are also supported.  If you are new to such a system, I recommend that
  79 you should look over the GNU Privacy Handbook (GPH) which is available
  80 at @uref{http://www.gnupg.org/gph/}.
  81
  82 @node How to use
  83 @chapter How to use
  84
  85 The toplevel interface of this library is quite simple, and only
  86 intended to use with public-key cryptographic operation.
  87
  88 To use PGG, evaluate following expression at the beginning of your
  89 application program.
  90
  91 @lisp
  92 (require 'pgg)
  93 @end lisp
  94
  95 If you want to check existence of pgg.el at runtime, instead you can
  96 list autoload setting for desired functions as follows.
  97
  98 @lisp
  99 (autoload 'pgg-encrypt-region "pgg"
 100   "Encrypt the current region." t)
 101 (autoload 'pgg-encrypt-symmetric-region "pgg"
 102   "Encrypt the current region with symmetric algorithm." t)
 103 (autoload 'pgg-decrypt-region "pgg"
 104   "Decrypt the current region." t)
 105 (autoload 'pgg-sign-region "pgg"
 106   "Sign the current region." t)
 107 (autoload 'pgg-verify-region "pgg"
 108   "Verify the current region." t)
 109 (autoload 'pgg-insert-key "pgg"
 110   "Insert the ASCII armored public key." t)
 111 (autoload 'pgg-snarf-keys-region "pgg"
 112   "Import public keys in the current region." t)
 113 @end lisp
 114
 115 @menu
 116 * User Commands::
 117 * Selecting an implementation::
 118 * Caching passphrase::
 119 * Default user identity::
 120 @end menu
 121
 122 @node User Commands
 123 @section User Commands
 124
 125 At this time you can use some cryptographic commands.  The behavior of
 126 these commands relies on a fashion of invocation because they are also
 127 intended to be used as library functions.  In case you don't have the
 128 signer's public key, for example, the function @code{pgg-verify-region}
 129 fails immediately, but if the function had been called interactively, it
 130 would ask you to retrieve the signer's public key from the server.
 131
 132 @deffn Command pgg-encrypt-region start end recipients &optional sign passphrase
 133 Encrypt the current region between @var{start} and @var{end} for
 134 @var{recipients}.  When the function were called interactively, you
 135 would be asked about the recipients.
 136
 137 If encryption is successful, it replaces the current region contents (in
 138 the accessible portion) with the resulting data.
 139
 140 If optional argument @var{sign} is non-@code{nil}, the function is
 141 request to do a combined sign and encrypt.  This currently is
 142 confirmed to work with GnuPG, but might not work with PGP or PGP5.
 143
 144 If optional @var{passphrase} is @code{nil}, the passphrase will be
 145 obtained from the passphrase cache or user.
 146 @end deffn
 147
 148 @deffn Command pgg-encrypt-symmetric-region &optional start end passphrase
 149 Encrypt the current region between @var{start} and @var{end} using a
 150 symmetric cipher.  After invocation you are asked for a passphrase.
 151
 152 If optional @var{passphrase} is @code{nil}, the passphrase will be
 153 obtained from the passphrase cache or user.
 154
 155 symmetric-cipher encryption is currently only implemented for GnuPG.
 156 @end deffn
 157
 158 @deffn Command pgg-decrypt-region start end &optional passphrase
 159 Decrypt the current region between @var{start} and @var{end}.  If
 160 decryption is successful, it replaces the current region contents (in
 161 the accessible portion) with the resulting data.
 162
 163 If optional @var{passphrase} is @code{nil}, the passphrase will be
 164 obtained from the passphrase cache or user.
 165 @end deffn
 166
 167 @deffn Command pgg-sign-region start end &optional cleartext passphrase
 168 Make the signature from text between @var{start} and @var{end}.  If the
 169 optional third argument @var{cleartext} is non-@code{nil}, or the
 170 function is called interactively, it does not create a detached
 171 signature.  In such a case, it replaces the current region contents (in
 172 the accessible portion) with the resulting data.
 173
 174 If optional @var{passphrase} is @code{nil}, the passphrase will be
 175 obtained from the passphrase cache or user.
 176 @end deffn
 177
 178 @deffn Command pgg-verify-region start end &optional signature fetch
 179 Verify the current region between @var{start} and @var{end}.  If the
 180 optional third argument @var{signature} is non-@code{nil}, it is treated
 181 as the detached signature file of the current region.
 182
 183 If the optional 4th argument @var{fetch} is non-@code{nil}, or the
 184 function is called interactively, we attempt to fetch the signer's
 185 public key from the key server.
 186 @end deffn
 187
 188 @deffn Command pgg-insert-key
 189 Retrieve the user's public key and insert it as ASCII-armored format.
 190 @end deffn
 191
 192 @deffn Command pgg-snarf-keys-region start end
 193 Collect public keys in the current region between @var{start} and
 194 @var{end}, and add them into the user's keyring.
 195 @end deffn
 196
 197 @node Selecting an implementation
 198 @section Selecting an implementation
 199
 200 Since PGP has a long history and there are a number of PGP
 201 implementations available today, the function which each one has differs
 202 considerably.  For example, if you are using GnuPG, you know you can
 203 select cipher algorithm from 3DES, CAST5, BLOWFISH, and so on, but on
 204 the other hand the version 2 of PGP only supports IDEA.
 205
 206 Which implementation is used is controlled by the @code{pgg-scheme}
 207 variable.  If it is @code{nil} (the default), the value of the
 208 @code{pgg-default-scheme} variable will be used instead.
 209
 210 @defvar pgg-scheme
 211 Force specify the scheme of PGP implementation.  The value can be set to
 212 @code{gpg}, @code{pgp}, and @code{pgp5}.  The default is @code{nil}.
 213 @end defvar
 214
 215 @defvar pgg-default-scheme
 216 The default scheme of PGP implementation.  The value should be one of
 217 @code{gpg}, @code{pgp}, and @code{pgp5}.  The default is @code{gpg}.
 218 @end defvar
 219
 220 @node Caching passphrase
 221 @section Caching passphrase
 222
 223 PGG provides a simple passphrase caching mechanism.  If you want to
 224 arrange the interaction, set the variable @code{pgg-read-passphrase}.
 225
 226 @defvar pgg-cache-passphrase
 227 If non-@code{nil}, store passphrases.  The default value of this
 228 variable is @code{t}.  If you were worry about security issue, however,
 229 you could stop caching with setting it @code{nil}.
 230 @end defvar
 231
 232 @defvar pgg-passphrase-cache-expiry
 233 Elapsed time for expiration in seconds.
 234 @end defvar
 235
 236 @node Default user identity
 237 @section Default user identity
 238
 239 The PGP implementation is usually able to select the proper key to use
 240 for signing and decryption, but if you have more than one key, you may
 241 need to specify the key id to use.
 242
 243 @defvar pgg-default-user-id
 244 User ID of your default identity.  It defaults to the value returned
 245 by @samp{(user-login-name)}.  You can customize this variable.
 246 @end defvar
 247
 248 @defvar pgg-gpg-user-id
 249 User ID of the GnuPG default identity.  It defaults to @samp{nil}.
 250 This overrides @samp{pgg-default-user-id}.  You can customize this
 251 variable.
 252 @end defvar
 253
 254 @defvar pgg-pgp-user-id
 255 User ID of the PGP 2.x/6.x default identity.  It defaults to
 256 @samp{nil}.  This overrides @samp{pgg-default-user-id}.  You can
 257 customize this variable.
 258 @end defvar
 259
 260 @defvar pgg-pgp5-user-id
 261 User ID of the PGP 5.x default identity.  It defaults to @samp{nil}.
 262 This overrides @samp{pgg-default-user-id}.  You can customize this
 263 variable.
 264 @end defvar
 265
 266 @node Architecture
 267 @chapter Architecture
 268
 269 PGG introduces the notion of a "scheme of PGP implementation" (used
 270 interchangeably with "scheme" in this document).  This term refers to a
 271 singleton object wrapped with the luna object system.
 272
 273 Since PGG was designed for accessing and developing PGP functionality,
 274 the architecture had to be designed not just for interoperability but
 275 also for extensiblity.  In this chapter we explore the architecture
 276 while finding out how to write the PGG backend.
 277
 278 @menu
 279 * Initializing::
 280 * Backend methods::
 281 * Getting output::
 282 @end menu
 283
 284 @node Initializing
 285 @section Initializing
 286
 287 A scheme must be initialized before it is used.
 288 It had better guarantee to keep only one instance of a scheme.
 289
 290 The following code is snipped out of @file{pgg-gpg.el}.  Once an
 291 instance of @code{pgg-gpg} scheme is initialized, it's stored to the
 292 variable @code{pgg-scheme-gpg-instance} and will be reused from now on.
 293
 294 @lisp
 295 (defvar pgg-scheme-gpg-instance nil)
 296
 297 (defun pgg-make-scheme-gpg ()
 298   (or pgg-scheme-gpg-instance
 299       (setq pgg-scheme-gpg-instance
 300             (luna-make-entity 'pgg-scheme-gpg))))
 301 @end lisp
 302
 303 The name of the function must follow the
 304 regulation---@code{pgg-make-scheme-} follows the backend name.
 305
 306 @node Backend methods
 307 @section Backend methods
 308
 309 In each backend, these methods must be present.  The output of these
 310 methods is stored in special buffers (@ref{Getting output}), so that
 311 these methods must tell the status of the execution.
 312
 313 @deffn Method pgg-scheme-lookup-key scheme string &optional type
 314 Return keys associated with @var{string}.  If the optional third
 315 argument @var{type} is non-@code{nil}, it searches from the secret
 316 keyrings.
 317 @end deffn
 318
 319 @deffn Method pgg-scheme-encrypt-region scheme start end recipients &optional sign passphrase
 320 Encrypt the current region between @var{start} and @var{end} for
 321 @var{recipients}.  If @var{sign} is non-@code{nil}, do a combined sign
 322 and encrypt.  If encryption is successful, it returns @code{t},
 323 otherwise @code{nil}.
 324 @end deffn
 325
 326 @deffn Method pgg-scheme-encrypt-symmetric-region scheme start end &optional passphrase
 327 Encrypt the current region between @var{start} and @var{end} using a
 328 symmetric cipher and a passphrases.  If encryption is successful, it
 329 returns @code{t}, otherwise @code{nil}.  This function is currently only
 330 implemented for GnuPG.
 331 @end deffn
 332
 333 @deffn Method pgg-scheme-decrypt-region scheme start end &optional passphrase
 334 Decrypt the current region between @var{start} and @var{end}.  If
 335 decryption is successful, it returns @code{t}, otherwise @code{nil}.
 336 @end deffn
 337
 338 @deffn Method pgg-scheme-sign-region scheme start end &optional cleartext passphrase
 339 Make the signature from text between @var{start} and @var{end}.  If the
 340 optional third argument @var{cleartext} is non-@code{nil}, it does not
 341 create a detached signature.  If signing is successful, it returns
 342 @code{t}, otherwise @code{nil}.
 343 @end deffn
 344
 345 @deffn Method pgg-scheme-verify-region scheme start end &optional signature
 346 Verify the current region between @var{start} and @var{end}.  If the
 347 optional third argument @var{signature} is non-@code{nil}, it is treated
 348 as the detached signature of the current region.  If the signature is
 349 successfully verified, it returns @code{t}, otherwise @code{nil}.
 350 @end deffn
 351
 352 @deffn Method pgg-scheme-insert-key scheme
 353 Retrieve the user's public key and insert it as ASCII-armored format.
 354 On success, it returns @code{t}, otherwise @code{nil}.
 355 @end deffn
 356
 357 @deffn Method pgg-scheme-snarf-keys-region scheme start end
 358 Collect public keys in the current region between @var{start} and
 359 @var{end}, and add them into the user's keyring.
 360 On success, it returns @code{t}, otherwise @code{nil}.
 361 @end deffn
 362
 363 @node Getting output
 364 @section Getting output
 365
 366 The output of the backend methods (@ref{Backend methods}) is stored in
 367 special buffers, so that these methods must tell the status of the
 368 execution.
 369
 370 @defvar pgg-errors-buffer
 371 The standard error output of the execution of the PGP command is stored
 372 here.
 373 @end defvar
 374
 375 @defvar pgg-output-buffer
 376 The standard output of the execution of the PGP command is stored here.
 377 @end defvar
 378
 379 @defvar pgg-status-buffer
 380 The rest of status information of the execution of the PGP command is
 381 stored here.
 382 @end defvar
 383
 384 @node Parsing OpenPGP packets
 385 @chapter Parsing OpenPGP packets
 386
 387 The format of OpenPGP messages is maintained in order to publish all
 388 necessary information needed to develop interoperable applications.
 389 The standard is documented in RFC 2440.
 390
 391 PGG has its own parser for the OpenPGP packets.
 392
 393 @defun pgg-parse-armor string
 394 List the sequence of packets in @var{string}.
 395 @end defun
 396
 397 @defun pgg-parse-armor-region start end
 398 List the sequence of packets in the current region between @var{start}
 399 and @var{end}.
 400 @end defun
 401
 402 @defvar pgg-ignore-packet-checksum
 403 If non-@code{nil}, don't check the checksum of the packets.
 404 @end defvar
 405
 406 @node Function Index
 407 @chapter Function Index
 408 @printindex fn
 409
 410 @node Variable Index
 411 @chapter Variable Index
 412 @printindex vr
 413
 414 @summarycontents
 415 @contents
 416 @bye
 417
 418 @c End:
 419
 420 @ignore
 421    arch-tag: 0c205838-34b9-41a5-b9d7-49ae57ccac85
 422 @end ignore