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 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 1.1 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-decrypt-region "pgg"
 102   "Decrypt the current region." t)
 103 (autoload 'pgg-sign-region "pgg"
 104   "Sign the current region." t)
 105 (autoload 'pgg-verify-region "pgg"
 106   "Verify the current region." t)
 107 (autoload 'pgg-insert-key "pgg"
 108   "Insert the ASCII armored public key." t)
 109 (autoload 'pgg-snarf-keys-region "pgg"
 110   "Import public keys in the current region." t)
 111 @end lisp
 112
 113 @menu
 114 * User Commands::
 115 * Selecting an implementation::
 116 * Caching passphrase::
 117 * Default user identity::
 118 @end menu
 119
 120 @node User Commands
 121 @section User Commands
 122
 123 At this time you can use some cryptographic commands.  The behavior of
 124 these commands relies on a fashion of invocation because they are also
 125 intended to be used as library functions.  In case you don't have the
 126 signer's public key, for example, the function @code{pgg-verify-region}
 127 fails immediately, but if the function had been called interactively, it
 128 would ask you to retrieve the signer's public key from the server.
 129
 130 @deffn Command pgg-encrypt-region start end recipients &optional sign
 131 Encrypt the current region between @var{start} and @var{end} for
 132 @var{recipients}.  When the function were called interactively, you
 133 would be asked about the recipients.
 134
 135 If encryption is successful, it replaces the current region contents (in
 136 the accessible portion) with the resulting data.
 137
 138 If optional argument @var{sign} is non-nil, the function is request to
 139 do a combined sign and encrypt.  This currently only work with GnuPG.
 140 @end deffn
 141
 142 @deffn Command pgg-decrypt-region start end
 143 Decrypt the current region between @var{start} and @var{end}.  If
 144 decryption is successful, it replaces the current region contents (in
 145 the accessible portion) with the resulting data.
 146 @end deffn
 147
 148 @deffn Command pgg-sign-region start end &optional cleartext
 149 Make the signature from text between @var{start} and @var{end}.  If the
 150 optional third argument @var{cleartext} is non-@code{nil}, or the
 151 function is called interactively, it does not create a detached
 152 signature.  In such a case, it replaces the current region contents (in
 153 the accessible portion) with the resulting data.
 154 @end deffn
 155
 156 @deffn Command pgg-verify-region start end &optional signature fetch
 157 Verify the current region between @var{start} and @var{end}.  If the
 158 optional third argument @var{signature} is non-@code{nil}, or the function
 159 is called interactively, it is treated as the detached signature of the
 160 current region.
 161
 162 If the optional 4th argument @var{fetch} is non-@code{nil}, or the
 163 function is called interactively, we attempt to fetch the signer's
 164 public key from the key server.
 165 @end deffn
 166
 167 @deffn Command pgg-insert-key
 168 Retrieve the user's public key and insert it as ASCII-armored format.
 169 @end deffn
 170
 171 @deffn Command pgg-snarf-keys-region start end
 172 Collect public keys in the current region between @var{start} and
 173 @var{end}, and add them into the user's keyring.
 174 @end deffn
 175
 176 @node Selecting an implementation
 177 @section Selecting an implementation
 178
 179 Since PGP has a long history and there are a number of PGP
 180 implementations available today, the function which each one has differs
 181 considerably.  For example, if you are using GnuPG, you know you can
 182 select cipher algorithm from 3DES, CAST5, BLOWFISH, and so on, but on
 183 the other hand the version 2 of PGP only supports IDEA.
 184
 185 By default, if the variable @code{pgg-scheme} is not set, PGG searches the
 186 registered scheme for an implementation of the requested service
 187 associated with the named algorithm.  If there are no match, PGG uses
 188 @code{pgg-default-scheme}.  In other words, there are two options to
 189 control which command is used to process the incoming PGP armors.  One
 190 is for encrypting and signing, the other is for decrypting and
 191 verifying.
 192
 193 @defvar pgg-scheme
 194 Force specify the scheme of PGP implementation for decrypting and verifying.
 195 The value can be @code{gpg}, @code{pgp}, and @code{pgp5}.
 196 @end defvar
 197
 198 @defvar pgg-default-scheme
 199 Force specify the scheme of PGP implementation for encrypting and signing.
 200 The value can be @code{gpg}, @code{pgp}, and @code{pgp5}.
 201 @end defvar
 202
 203 @node Caching passphrase
 204 @section Caching passphrase
 205
 206 PGG provides a simple passphrase caching mechanism.  If you want to
 207 arrange the interaction, set the variable @code{pgg-read-passphrase}.
 208
 209 @defvar pgg-cache-passphrase
 210 If non-@code{nil}, store passphrases.  The default value of this
 211 variable is @code{t}.  If you were worry about security issue, however,
 212 you could stop caching with setting it @code{nil}.
 213 @end defvar
 214
 215 @defvar pgg-passphrase-cache-expiry
 216 Elapsed time for expiration in seconds.
 217 @end defvar
 218
 219 @node Default user identity
 220 @section Default user identity
 221
 222 The PGP implementation is usually able to select the proper key to use
 223 for signing and decryption, but if you have more than one key, you may
 224 need to specify the key id to use.
 225
 226 @defvar pgg-default-user-id
 227 User ID of your default identity.  It defaults to the value returned
 228 by @samp{(user-login-name)}.  You can customize this variable.
 229 @end defvar
 230
 231 @defvar pgg-gpg-user-id
 232 User ID of the GnuPG default identity.  It defaults to @samp{nil}.
 233 This overrides @samp{pgg-default-user-id}.  You can customize this
 234 variable.
 235 @end defvar
 236
 237 @defvar pgg-pgp-user-id
 238 User ID of the PGP 2.x/6.x default identity.  It defaults to
 239 @samp{nil}.  This overrides @samp{pgg-default-user-id}.  You can
 240 customize this variable.
 241 @end defvar
 242
 243 @defvar pgg-pgp5-user-id
 244 User ID of the PGP 5.x default identity.  It defaults to @samp{nil}.
 245 This overrides @samp{pgg-default-user-id}.  You can customize this
 246 variable.
 247 @end defvar
 248
 249 @node Architecture
 250 @chapter Architecture
 251
 252 PGG introduces the notion of a "scheme of PGP implementation" (used
 253 interchangeably with "scheme" in this document).  This term refers to a
 254 singleton object wrapped with the luna object system.
 255
 256 Since PGG was designed for accessing and developing PGP functionality,
 257 the architecture had to be designed not just for interoperability but
 258 also for extensiblity.  In this chapter we explore the architecture
 259 while finding out how to write the PGG backend.
 260
 261 @menu
 262 * Initializing::
 263 * Backend methods::
 264 * Getting output::
 265 @end menu
 266
 267 @node Initializing
 268 @section Initializing
 269
 270 A scheme must be initialized before it is used.
 271 It had better guarantee to keep only one instance of a scheme.
 272
 273 The following code is snipped out of @file{pgg-gpg.el}.  Once an
 274 instance of @code{pgg-gpg} scheme is initialized, it's stored to the
 275 variable @code{pgg-scheme-gpg-instance} and will be reused from now on.
 276
 277 @lisp
 278 (defvar pgg-scheme-gpg-instance nil)
 279
 280 (defun pgg-make-scheme-gpg ()
 281   (or pgg-scheme-gpg-instance
 282       (setq pgg-scheme-gpg-instance
 283             (luna-make-entity 'pgg-scheme-gpg))))
 284 @end lisp
 285
 286 The name of the function must follow the
 287 regulation---@code{pgg-make-scheme-} follows the backend name.
 288
 289 @node Backend methods
 290 @section Backend methods
 291
 292 In each backend, these methods must be present.  The output of these
 293 methods is stored in special buffers (@ref{Getting output}), so that
 294 these methods must tell the status of the execution.
 295
 296 @deffn Method pgg-scheme-lookup-key scheme string &optional type
 297 Return keys associated with @var{string}.  If the optional third
 298 argument @var{type} is non-@code{nil}, it searches from the secret
 299 keyrings.
 300 @end deffn
 301
 302 @deffn Method pgg-scheme-encrypt-region scheme start end recipients &optional sign
 303 Encrypt the current region between @var{start} and @var{end} for
 304 @var{recipients}.  If @var{sign} is non-nil, do a combined sign and
 305 encrypt.  If encryption is successful, it returns @code{t}, otherwise
 306 @code{nil}.
 307 @end deffn
 308
 309 @deffn Method pgg-scheme-decrypt-region scheme start end
 310 Decrypt the current region between @var{start} and @var{end}.  If
 311 decryption is successful, it returns @code{t}, otherwise @code{nil}.
 312 @end deffn
 313
 314 @deffn Method pgg-scheme-sign-region scheme start end &optional cleartext
 315 Make the signature from text between @var{start} and @var{end}.  If the
 316 optional third argument @var{cleartext} is non-@code{nil}, it does not
 317 create a detached signature.  If signing is successful, it returns
 318 @code{t}, otherwise @code{nil}.
 319 @end deffn
 320
 321 @deffn Method pgg-scheme-verify-region scheme start end &optional signature
 322 Verify the current region between @var{start} and @var{end}.  If the
 323 optional third argument @var{signature} is non-@code{nil}, it is treated
 324 as the detached signature of the current region.  If the signature is
 325 successfully verified, it returns @code{t}, otherwise @code{nil}.
 326 @end deffn
 327
 328 @deffn Method pgg-scheme-insert-key scheme
 329 Retrieve the user's public key and insert it as ASCII-armored format.
 330 On success, it returns @code{t}, otherwise @code{nil}.
 331 @end deffn
 332
 333 @deffn Method pgg-scheme-snarf-keys-region scheme start end
 334 Collect public keys in the current region between @var{start} and
 335 @var{end}, and add them into the user's keyring.
 336 On success, it returns @code{t}, otherwise @code{nil}.
 337 @end deffn
 338
 339 @node Getting output
 340 @section Getting output
 341
 342 The output of the backend methods (@ref{Backend methods}) is stored in
 343 special buffers, so that these methods must tell the status of the
 344 execution.
 345
 346 @defvar pgg-errors-buffer
 347 The standard error output of the execution of the PGP command is stored
 348 here.
 349 @end defvar
 350
 351 @defvar pgg-output-buffer
 352 The standard output of the execution of the PGP command is stored here.
 353 @end defvar
 354
 355 @defvar pgg-status-buffer
 356 The rest of status information of the execution of the PGP command is
 357 stored here.
 358 @end defvar
 359
 360 @node Parsing OpenPGP packets
 361 @chapter Parsing OpenPGP packets
 362
 363 The format of OpenPGP messages is maintained in order to publish all
 364 necessary information needed to develop interoperable applications.
 365 The standard is documented in RFC 2440.
 366
 367 PGG has its own parser for the OpenPGP packets.
 368
 369 @defun pgg-parse-armor string
 370 List the sequence of packets in @var{string}.
 371 @end defun
 372
 373 @defun pgg-parse-armor-region start end
 374 List the sequence of packets in the current region between @var{start}
 375 and @var{end}.
 376 @end defun
 377
 378 @defvar pgg-ignore-packet-checksum
 379 If non-@code{nil}, don't check the checksum of the packets.
 380 @end defvar
 381
 382 @node Function Index
 383 @chapter Function Index
 384 @printindex fn
 385
 386 @node Variable Index
 387 @chapter Variable Index
 388 @printindex vr
 389
 390 @summarycontents
 391 @contents
 392 @bye
 393
 394 @c End:
 395
 396 @ignore
 397    arch-tag: 0c205838-34b9-41a5-b9d7-49ae57ccac85
 398 @end ignore