Commit | Line | Data |
---|---|---|
23f87bed MB |
1 | \input texinfo @c -*-texinfo-*- |
2 | ||
3 | @setfilename ../info/pgg | |
4 | ||
5 | @set VERSION 0.1 | |
6 | ||
7 | ||
8 | @copying | |
b223e22d | 9 | This file describes PGG, an Emacs interface to various PGP implementations. |
23f87bed | 10 | |
01dd4a91 GM |
11 | Copyright @copyright{} 2001, 2003, 2004, 2005, 2006, 2007 Free Software |
12 | Foundation, Inc. | |
23f87bed MB |
13 | |
14 | @quotation | |
15 | Permission is granted to copy, distribute and/or modify this document | |
678e7c71 | 16 | under the terms of the GNU Free Documentation License, Version 1.2 or |
23f87bed MB |
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 | |
5a7f4c1b | 20 | Free Documentation License.'' |
23f87bed MB |
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:: | |
84247bb5 | 55 | * GNU Free Documentation License:: The license for this documentation. |
23f87bed MB |
56 | * Function Index:: |
57 | * Variable Index:: | |
58 | @end menu | |
59 | ||
60 | @node Overview | |
61 | @chapter Overview | |
62 | ||
63 | PGG is an interface library between Emacs and various tools for secure | |
64 | communication. Even though Mailcrypt has similar feature, it does not | |
65 | deal with detached PGP messages, normally used in PGP/MIME | |
66 | infrastructure. This was the main reason why I wrote the new library. | |
67 | ||
68 | PGP/MIME is an application of MIME Object Security Services (RFC1848). | |
69 | The standard is documented in RFC2015. | |
70 | ||
71 | @node Prerequisites | |
72 | @chapter Prerequisites | |
73 | ||
74 | PGG requires at least one implementation of privacy guard system. | |
75 | This document assumes that you have already obtained and installed them | |
76 | and that you are familiar with its basic functions. | |
77 | ||
84d921c4 CY |
78 | By default, PGG uses GnuPG. If you are new to such a system, I |
79 | recommend that you should look over the GNU Privacy Handbook (GPH) | |
80 | which is available at @uref{http://www.gnupg.org/documentation/}. | |
24ec9db6 | 81 | |
84d921c4 CY |
82 | When using GnuPG, we recommend the use of the @code{gpg-agent} |
83 | program, which is distributed with versions 2.0 and later of GnuPG. | |
84 | This is a daemon to manage private keys independently from any | |
85 | protocol, and provides the most secure way to input and cache your | |
86 | passphrases (@pxref{Caching passphrase}). By default, PGG will | |
87 | attempt to use @code{gpg-agent} if it is running. @xref{Invoking | |
88 | GPG-AGENT,,,gnupg,Using the GNU Privacy Guard}. | |
89 | ||
90 | PGG also supports Pretty Good Privacy version 2 or version 5. | |
23f87bed MB |
91 | |
92 | @node How to use | |
93 | @chapter How to use | |
94 | ||
95 | The toplevel interface of this library is quite simple, and only | |
96 | intended to use with public-key cryptographic operation. | |
97 | ||
98 | To use PGG, evaluate following expression at the beginning of your | |
99 | application program. | |
100 | ||
101 | @lisp | |
102 | (require 'pgg) | |
103 | @end lisp | |
104 | ||
105 | If you want to check existence of pgg.el at runtime, instead you can | |
106 | list autoload setting for desired functions as follows. | |
107 | ||
108 | @lisp | |
109 | (autoload 'pgg-encrypt-region "pgg" | |
110 | "Encrypt the current region." t) | |
df5725c5 EZ |
111 | (autoload 'pgg-encrypt-symmetric-region "pgg" |
112 | "Encrypt the current region with symmetric algorithm." t) | |
23f87bed MB |
113 | (autoload 'pgg-decrypt-region "pgg" |
114 | "Decrypt the current region." t) | |
115 | (autoload 'pgg-sign-region "pgg" | |
116 | "Sign the current region." t) | |
117 | (autoload 'pgg-verify-region "pgg" | |
118 | "Verify the current region." t) | |
119 | (autoload 'pgg-insert-key "pgg" | |
120 | "Insert the ASCII armored public key." t) | |
121 | (autoload 'pgg-snarf-keys-region "pgg" | |
122 | "Import public keys in the current region." t) | |
123 | @end lisp | |
124 | ||
125 | @menu | |
126 | * User Commands:: | |
127 | * Selecting an implementation:: | |
128 | * Caching passphrase:: | |
129 | * Default user identity:: | |
130 | @end menu | |
131 | ||
132 | @node User Commands | |
133 | @section User Commands | |
134 | ||
135 | At this time you can use some cryptographic commands. The behavior of | |
136 | these commands relies on a fashion of invocation because they are also | |
137 | intended to be used as library functions. In case you don't have the | |
138 | signer's public key, for example, the function @code{pgg-verify-region} | |
139 | fails immediately, but if the function had been called interactively, it | |
140 | would ask you to retrieve the signer's public key from the server. | |
141 | ||
98e330e6 | 142 | @deffn Command pgg-encrypt-region start end recipients &optional sign passphrase |
23f87bed MB |
143 | Encrypt the current region between @var{start} and @var{end} for |
144 | @var{recipients}. When the function were called interactively, you | |
145 | would be asked about the recipients. | |
146 | ||
147 | If encryption is successful, it replaces the current region contents (in | |
148 | the accessible portion) with the resulting data. | |
149 | ||
f4dd4ae8 | 150 | If optional argument @var{sign} is non-@code{nil}, the function is |
98e330e6 EZ |
151 | request to do a combined sign and encrypt. This currently is |
152 | confirmed to work with GnuPG, but might not work with PGP or PGP5. | |
153 | ||
154 | If optional @var{passphrase} is @code{nil}, the passphrase will be | |
155 | obtained from the passphrase cache or user. | |
23f87bed MB |
156 | @end deffn |
157 | ||
98e330e6 | 158 | @deffn Command pgg-encrypt-symmetric-region &optional start end passphrase |
df5725c5 EZ |
159 | Encrypt the current region between @var{start} and @var{end} using a |
160 | symmetric cipher. After invocation you are asked for a passphrase. | |
161 | ||
98e330e6 EZ |
162 | If optional @var{passphrase} is @code{nil}, the passphrase will be |
163 | obtained from the passphrase cache or user. | |
164 | ||
165 | symmetric-cipher encryption is currently only implemented for GnuPG. | |
df5725c5 EZ |
166 | @end deffn |
167 | ||
98e330e6 | 168 | @deffn Command pgg-decrypt-region start end &optional passphrase |
23f87bed MB |
169 | Decrypt the current region between @var{start} and @var{end}. If |
170 | decryption is successful, it replaces the current region contents (in | |
171 | the accessible portion) with the resulting data. | |
98e330e6 EZ |
172 | |
173 | If optional @var{passphrase} is @code{nil}, the passphrase will be | |
174 | obtained from the passphrase cache or user. | |
23f87bed MB |
175 | @end deffn |
176 | ||
98e330e6 | 177 | @deffn Command pgg-sign-region start end &optional cleartext passphrase |
23f87bed MB |
178 | Make the signature from text between @var{start} and @var{end}. If the |
179 | optional third argument @var{cleartext} is non-@code{nil}, or the | |
180 | function is called interactively, it does not create a detached | |
181 | signature. In such a case, it replaces the current region contents (in | |
182 | the accessible portion) with the resulting data. | |
98e330e6 EZ |
183 | |
184 | If optional @var{passphrase} is @code{nil}, the passphrase will be | |
185 | obtained from the passphrase cache or user. | |
23f87bed MB |
186 | @end deffn |
187 | ||
188 | @deffn Command pgg-verify-region start end &optional signature fetch | |
189 | Verify the current region between @var{start} and @var{end}. If the | |
58090a8d MB |
190 | optional third argument @var{signature} is non-@code{nil}, it is treated |
191 | as the detached signature file of the current region. | |
23f87bed MB |
192 | |
193 | If the optional 4th argument @var{fetch} is non-@code{nil}, or the | |
194 | function is called interactively, we attempt to fetch the signer's | |
195 | public key from the key server. | |
196 | @end deffn | |
197 | ||
198 | @deffn Command pgg-insert-key | |
199 | Retrieve the user's public key and insert it as ASCII-armored format. | |
200 | @end deffn | |
201 | ||
202 | @deffn Command pgg-snarf-keys-region start end | |
203 | Collect public keys in the current region between @var{start} and | |
204 | @var{end}, and add them into the user's keyring. | |
205 | @end deffn | |
206 | ||
207 | @node Selecting an implementation | |
208 | @section Selecting an implementation | |
209 | ||
210 | Since PGP has a long history and there are a number of PGP | |
211 | implementations available today, the function which each one has differs | |
212 | considerably. For example, if you are using GnuPG, you know you can | |
213 | select cipher algorithm from 3DES, CAST5, BLOWFISH, and so on, but on | |
214 | the other hand the version 2 of PGP only supports IDEA. | |
215 | ||
58090a8d MB |
216 | Which implementation is used is controlled by the @code{pgg-scheme} |
217 | variable. If it is @code{nil} (the default), the value of the | |
218 | @code{pgg-default-scheme} variable will be used instead. | |
23f87bed MB |
219 | |
220 | @defvar pgg-scheme | |
58090a8d MB |
221 | Force specify the scheme of PGP implementation. The value can be set to |
222 | @code{gpg}, @code{pgp}, and @code{pgp5}. The default is @code{nil}. | |
23f87bed MB |
223 | @end defvar |
224 | ||
225 | @defvar pgg-default-scheme | |
58090a8d MB |
226 | The default scheme of PGP implementation. The value should be one of |
227 | @code{gpg}, @code{pgp}, and @code{pgp5}. The default is @code{gpg}. | |
23f87bed MB |
228 | @end defvar |
229 | ||
230 | @node Caching passphrase | |
231 | @section Caching passphrase | |
232 | ||
05b405c9 CY |
233 | When using GnuPG (gpg) as the PGP scheme, we recommend using a program |
234 | called @code{gpg-agent} for entering and caching | |
235 | passphrases@footnote{Actually, @code{gpg-agent} does not cache | |
236 | passphrases but private keys. On the other hand, from a user's point | |
237 | of view, this technical difference isn't visible.}. | |
238 | ||
239 | @defvar pgg-gpg-use-agent | |
240 | If non-@code{nil}, attempt to use @code{gpg-agent} whenever possible. | |
241 | The default is @code{t}. If @code{gpg-agent} is not running, or GnuPG | |
242 | is not the current PGP scheme, PGG's own passphrase-caching mechanism | |
243 | is used (see below). | |
244 | @end defvar | |
245 | ||
246 | To use @code{gpg-agent} with PGG, you must first ensure that | |
247 | @code{gpg-agent} is running. For example, if you are running in the X | |
248 | Window System, you can do this by putting the following line in your | |
249 | @file{.xsession} file: | |
250 | ||
251 | @smallexample | |
252 | eval "$(gpg-agent --daemon)" | |
253 | @end smallexample | |
254 | ||
255 | For more details on invoking @code{gpg-agent}, @xref{Invoking | |
256 | GPG-AGENT,,,gnupg,Using the GNU Privacy Guard}. | |
257 | ||
258 | Whenever you perform a PGG operation that requires a GnuPG passphrase, | |
259 | GnuPG will contact @code{gpg-agent}, which prompts you for the | |
260 | passphrase. Furthermore, @code{gpg-agent} ``caches'' the result, so | |
261 | that subsequent uses will not require you to enter the passphrase | |
262 | again. (This cache usually expires after a certain time has passed; | |
263 | you can change this using the @code{--default-cache-ttl} option when | |
264 | invoking @code{gpg-agent}.) | |
265 | ||
266 | If you are running in a X Window System environment, @code{gpg-agent} | |
267 | prompts for a passphrase by opening a graphical window. However, if | |
268 | you are running Emacs on a text terminal, @code{gpg-agent} has trouble | |
269 | receiving input from the terminal, since it is being sent to Emacs. | |
270 | One workaround for this problem is to run @code{gpg-agent} on a | |
271 | different terminal from Emacs, with the @code{--keep-tty} option; this | |
272 | tells @code{gpg-agent} use its own terminal to prompt for passphrases. | |
273 | ||
274 | When @code{gpg-agent} is not being used, PGG prompts for a passphrase | |
275 | through Emacs. It also has its own passphrase caching mechanism, | |
d2d64bc3 | 276 | which is controlled by the variable @code{pgg-cache-passphrase} (see |
05b405c9 CY |
277 | below). |
278 | ||
279 | There is a security risk in handling passphrases through PGG rather | |
280 | than @code{gpg-agent}. When you enter your passphrase into an Emacs | |
281 | prompt, it is temporarily stored as a cleartext string in the memory | |
282 | of the Emacs executable. If the executable memory is swapped to disk, | |
283 | the root user can, in theory, extract the passphrase from the | |
284 | swapfile. Furthermore, the swapfile containing the cleartext | |
285 | passphrase might remain on the disk after the system is discarded or | |
286 | stolen. @code{gpg-agent} avoids this problem by using certain tricks, | |
287 | such as memory locking, which have not been implemented in Emacs. | |
23f87bed MB |
288 | |
289 | @defvar pgg-cache-passphrase | |
290 | If non-@code{nil}, store passphrases. The default value of this | |
fc23c3c6 AS |
291 | variable is @code{t}. If you are worried about security issues, |
292 | however, you could stop the caching of passphrases by setting this | |
293 | variable to @code{nil}. | |
23f87bed MB |
294 | @end defvar |
295 | ||
296 | @defvar pgg-passphrase-cache-expiry | |
297 | Elapsed time for expiration in seconds. | |
298 | @end defvar | |
299 | ||
815b81c8 | 300 | If your passphrase contains non-ASCII characters, you might need to |
68790809 RS |
301 | specify the coding system to be used to encode your passphrases, since |
302 | GnuPG treats them as a byte sequence, not as a character sequence. | |
815b81c8 MB |
303 | |
304 | @defvar pgg-passphrase-coding-system | |
68790809 | 305 | Coding system used to encode passphrase. |
815b81c8 MB |
306 | @end defvar |
307 | ||
23f87bed MB |
308 | @node Default user identity |
309 | @section Default user identity | |
310 | ||
311 | The PGP implementation is usually able to select the proper key to use | |
312 | for signing and decryption, but if you have more than one key, you may | |
313 | need to specify the key id to use. | |
314 | ||
315 | @defvar pgg-default-user-id | |
316 | User ID of your default identity. It defaults to the value returned | |
317 | by @samp{(user-login-name)}. You can customize this variable. | |
318 | @end defvar | |
319 | ||
320 | @defvar pgg-gpg-user-id | |
321 | User ID of the GnuPG default identity. It defaults to @samp{nil}. | |
322 | This overrides @samp{pgg-default-user-id}. You can customize this | |
323 | variable. | |
324 | @end defvar | |
325 | ||
326 | @defvar pgg-pgp-user-id | |
327 | User ID of the PGP 2.x/6.x default identity. It defaults to | |
328 | @samp{nil}. This overrides @samp{pgg-default-user-id}. You can | |
329 | customize this variable. | |
330 | @end defvar | |
331 | ||
332 | @defvar pgg-pgp5-user-id | |
333 | User ID of the PGP 5.x default identity. It defaults to @samp{nil}. | |
334 | This overrides @samp{pgg-default-user-id}. You can customize this | |
335 | variable. | |
336 | @end defvar | |
337 | ||
338 | @node Architecture | |
339 | @chapter Architecture | |
340 | ||
341 | PGG introduces the notion of a "scheme of PGP implementation" (used | |
342 | interchangeably with "scheme" in this document). This term refers to a | |
343 | singleton object wrapped with the luna object system. | |
344 | ||
345 | Since PGG was designed for accessing and developing PGP functionality, | |
346 | the architecture had to be designed not just for interoperability but | |
347 | also for extensiblity. In this chapter we explore the architecture | |
348 | while finding out how to write the PGG backend. | |
349 | ||
350 | @menu | |
351 | * Initializing:: | |
352 | * Backend methods:: | |
353 | * Getting output:: | |
354 | @end menu | |
355 | ||
356 | @node Initializing | |
357 | @section Initializing | |
358 | ||
359 | A scheme must be initialized before it is used. | |
360 | It had better guarantee to keep only one instance of a scheme. | |
361 | ||
362 | The following code is snipped out of @file{pgg-gpg.el}. Once an | |
363 | instance of @code{pgg-gpg} scheme is initialized, it's stored to the | |
364 | variable @code{pgg-scheme-gpg-instance} and will be reused from now on. | |
365 | ||
366 | @lisp | |
367 | (defvar pgg-scheme-gpg-instance nil) | |
368 | ||
369 | (defun pgg-make-scheme-gpg () | |
370 | (or pgg-scheme-gpg-instance | |
371 | (setq pgg-scheme-gpg-instance | |
372 | (luna-make-entity 'pgg-scheme-gpg)))) | |
373 | @end lisp | |
374 | ||
375 | The name of the function must follow the | |
376 | regulation---@code{pgg-make-scheme-} follows the backend name. | |
377 | ||
378 | @node Backend methods | |
379 | @section Backend methods | |
380 | ||
381 | In each backend, these methods must be present. The output of these | |
382 | methods is stored in special buffers (@ref{Getting output}), so that | |
383 | these methods must tell the status of the execution. | |
384 | ||
385 | @deffn Method pgg-scheme-lookup-key scheme string &optional type | |
386 | Return keys associated with @var{string}. If the optional third | |
387 | argument @var{type} is non-@code{nil}, it searches from the secret | |
388 | keyrings. | |
389 | @end deffn | |
390 | ||
98e330e6 | 391 | @deffn Method pgg-scheme-encrypt-region scheme start end recipients &optional sign passphrase |
23f87bed | 392 | Encrypt the current region between @var{start} and @var{end} for |
f4dd4ae8 MB |
393 | @var{recipients}. If @var{sign} is non-@code{nil}, do a combined sign |
394 | and encrypt. If encryption is successful, it returns @code{t}, | |
395 | otherwise @code{nil}. | |
23f87bed MB |
396 | @end deffn |
397 | ||
98e330e6 | 398 | @deffn Method pgg-scheme-encrypt-symmetric-region scheme start end &optional passphrase |
df5725c5 EZ |
399 | Encrypt the current region between @var{start} and @var{end} using a |
400 | symmetric cipher and a passphrases. If encryption is successful, it | |
401 | returns @code{t}, otherwise @code{nil}. This function is currently only | |
402 | implemented for GnuPG. | |
403 | @end deffn | |
404 | ||
98e330e6 | 405 | @deffn Method pgg-scheme-decrypt-region scheme start end &optional passphrase |
23f87bed MB |
406 | Decrypt the current region between @var{start} and @var{end}. If |
407 | decryption is successful, it returns @code{t}, otherwise @code{nil}. | |
408 | @end deffn | |
409 | ||
98e330e6 | 410 | @deffn Method pgg-scheme-sign-region scheme start end &optional cleartext passphrase |
23f87bed MB |
411 | Make the signature from text between @var{start} and @var{end}. If the |
412 | optional third argument @var{cleartext} is non-@code{nil}, it does not | |
413 | create a detached signature. If signing is successful, it returns | |
414 | @code{t}, otherwise @code{nil}. | |
415 | @end deffn | |
416 | ||
417 | @deffn Method pgg-scheme-verify-region scheme start end &optional signature | |
418 | Verify the current region between @var{start} and @var{end}. If the | |
419 | optional third argument @var{signature} is non-@code{nil}, it is treated | |
420 | as the detached signature of the current region. If the signature is | |
421 | successfully verified, it returns @code{t}, otherwise @code{nil}. | |
422 | @end deffn | |
423 | ||
424 | @deffn Method pgg-scheme-insert-key scheme | |
425 | Retrieve the user's public key and insert it as ASCII-armored format. | |
426 | On success, it returns @code{t}, otherwise @code{nil}. | |
427 | @end deffn | |
428 | ||
429 | @deffn Method pgg-scheme-snarf-keys-region scheme start end | |
430 | Collect public keys in the current region between @var{start} and | |
431 | @var{end}, and add them into the user's keyring. | |
432 | On success, it returns @code{t}, otherwise @code{nil}. | |
433 | @end deffn | |
434 | ||
435 | @node Getting output | |
436 | @section Getting output | |
437 | ||
438 | The output of the backend methods (@ref{Backend methods}) is stored in | |
439 | special buffers, so that these methods must tell the status of the | |
440 | execution. | |
441 | ||
442 | @defvar pgg-errors-buffer | |
443 | The standard error output of the execution of the PGP command is stored | |
444 | here. | |
445 | @end defvar | |
446 | ||
447 | @defvar pgg-output-buffer | |
448 | The standard output of the execution of the PGP command is stored here. | |
449 | @end defvar | |
450 | ||
451 | @defvar pgg-status-buffer | |
452 | The rest of status information of the execution of the PGP command is | |
453 | stored here. | |
454 | @end defvar | |
455 | ||
456 | @node Parsing OpenPGP packets | |
457 | @chapter Parsing OpenPGP packets | |
458 | ||
459 | The format of OpenPGP messages is maintained in order to publish all | |
460 | necessary information needed to develop interoperable applications. | |
461 | The standard is documented in RFC 2440. | |
462 | ||
463 | PGG has its own parser for the OpenPGP packets. | |
464 | ||
465 | @defun pgg-parse-armor string | |
466 | List the sequence of packets in @var{string}. | |
467 | @end defun | |
468 | ||
469 | @defun pgg-parse-armor-region start end | |
470 | List the sequence of packets in the current region between @var{start} | |
471 | and @var{end}. | |
472 | @end defun | |
473 | ||
474 | @defvar pgg-ignore-packet-checksum | |
475 | If non-@code{nil}, don't check the checksum of the packets. | |
476 | @end defvar | |
477 | ||
84247bb5 CY |
478 | @node GNU Free Documentation License |
479 | @appendix GNU Free Documentation License | |
480 | @include doclicense.texi | |
481 | ||
23f87bed | 482 | @node Function Index |
84247bb5 | 483 | @unnumbered Function Index |
23f87bed MB |
484 | @printindex fn |
485 | ||
486 | @node Variable Index | |
84247bb5 | 487 | @unnumbered Variable Index |
23f87bed MB |
488 | @printindex vr |
489 | ||
490 | @summarycontents | |
491 | @contents | |
492 | @bye | |
493 | ||
494 | @c End: | |
495 | ||
496 | @ignore | |
497 | arch-tag: 0c205838-34b9-41a5-b9d7-49ae57ccac85 | |
498 | @end ignore |