X-Git-Url: http://git.chise.org/gitweb/?a=blobdiff_plain;f=README;h=3c13257560799f84c763dd848476ceabd9bc6852;hb=116cf83f4957f12852882e9f5aef8766cbee3711;hp=e231330cd6b256fdddcf68adf805ad03bd5bc6c7;hpb=3d4d9b0ed010b57ec3e9d4f8a6f15e3a55251133;p=elisp%2Fepg.git diff --git a/README b/README index e231330..3c13257 100644 --- a/README +++ b/README @@ -1,71 +1,125 @@ * What's this? -EasyPG is yet another GnuPG interface for Emacs. It consists of three -parts: transparent file encryption utility, Gnus/PGG backend, and -elisp library to interact with GnuPG. +EasyPG is an all-in-one GnuPG interface for Emacs. It has two +aspects: convenient tools which allow to use GnuPG from Emacs (EasyPG +Assistant), and a fully functional interface library to GnuPG (EasyPG +Library). -* Requirements +* Features -** GNU Emacs 21.4 or later +The EasyPG Assistant provides the following features: -** XEmacs 21.4 or later +- Keyring browser. +- Cryptographic operations on regions. +- Cryptographic operations on files. +- Dired integration. +- Encryption/decryption of *.gpg files. -** GnuPG 1.4.3 or later +The EasyPG Library provides the following features: + +- The API covers most functions of GnuPG like GPGME. +- S/MIME support using gpgsm. +- Designed to avoid potential security pitfalls around Emacs + +* Requirements -** Gnus 5.10.8 or later (optional) +** GNU Emacs 21.4, XEmacs 21.4, or later + +** GnuPG 1.4.3 or later + If you are using earlier versions, you will need to specify + --disable-gpg-test when ./configure. * Quick start ** Installation -$ ./configure -$ sudo make install + $ ./configure + $ sudo make install + +Add the following line to your ~/.emacs + + (require 'epa-setup) + +Restart emacs and type `M-x epa- TAB', and you will see a lot of +commands available. For example, + +- To browse your keyring, type `M-x epa-list-keys' +- To create a cleartext signature of the region, type `M-x epa-sign-region' + +You can also do some cryptographic operations from dired. + + M-x dired + (mark some files) + : e (or M-x epa-dired-do-encrypt) + (select recipients by 'm' and click [OK]) + +* MUA Integration + +The EasyPG Library can be used in combination with various MUA (Mail +User Agents). + +** CVS version of Gnus + +CVS version of Gnus uses EasyPG by default. To make sure of that, +check mml2015-use set to 'epg. Other options which affect on the +EasyPG are + + mml2015-signers + mml2015-encrypt-to-self + mml2015-cache-passphrase + mml2015-passphrase-cache-expiry + mml2015-verbose + +NOTE: You don't need pgg-epg.el in this case. + +** PGG based MUA -** Transparent file encryption utility +PGG is outdated PGP library used by old Gnus (<= v5.11), MH-E, etc. -EasyPG provides transparent file encryption utility similar to -crypt++, alpaca.el, hedgehog. To try this, add the following line to -your ~/.emacs and C-x C-f ~/test.txt.gpg. +There is a PGG backend written using EasyPG called pgg-epg.el. +However, EasyPG API is a superset of PGG and pgg-epg.el provides +nothing but compatibility with PGG. -(require 'epg-file) +*** Limitations of PGG -** Gnus/PGG backend +As I noted "PGG is outdated PGP library" above, PGG has several +limitations. For example -EasyPG provides an implementation of the backend interface of -Gnus/PGG. To use EasyPG instead of pgg-gpg, install pgg-epg.el and -add the following line to your ~/.gnus. +- PGG can't handle a message signed with multiple keys. +- PGG can't prompt a user which key is being used. +- PGG can't create a binary PGP messages. +- PGG doesn't provide a way to select keys per cryptographic operation. +- PGG ignores GnuPG's trust metrics. -(setq pgg-scheme 'epg) +** SEMI based MUA -* Advantages over other competitors +SEMI is the MIME library used by Wanderlust, cmail, T-gnus, etc. -There are many competitors of EasyPG such as Mailcrypt, Gnus/PGG, -gpg.el, etc. EasyPG has some advantages over them. +There is an EasyPG capable SEMI library called EMIKO-EasyPG. It can +be downloaded from the same site of the EasyPG distribution point. -** EasyPG avoides potential security flaws of Emacs +* Security -*** `call-process-region' writes data in region to temporary files +There are security pitfalls around Emacs. EasyPG is written with +avoiding them. -`call-process-region' writes data in region to temporary files. -EasyPG do _not_ use `call-process-region' to communicate with a gpg -subprocess. +** Passphrase may leak to a temporary file. -*** `(fillarray string 0)' is not enough to clear passphrases +The function call-process-region writes data in region to a temporary +file. If your PGP library used this function, your passphrases would +leak to the filesystem. -If Emacs crashed and dumps core, passphrase strings in memory are also -dumped within the core file. `read-passwd' function clears passphrase -strings by `(fillarray string 0)'. However, Emacs performs compaction -in gc_sweep phase. If GC happens before `fillarray', passphrase -strings may be moved elsewhere in memory. +The EasyPG Library does not use call-process-region to communicate +with a gpg subprocess. -Fortunately, there is gpg-agent to cache passphrases in more secure -way, so EasyPG dares _not_ to cache passphrase. Elisp programs can -set `epg-context-passphrase-callback' to cache user's passphrases. +** Passphrase may be stolen from a core file. -** GnuPG features are directly accessible from Emacs +If Emacs crashes and dumps core, Lisp strings in memory are also +dumped within the core file. read-passwd function clears passphrase +strings by (fillarray string 0) to avoid this risk. However, Emacs +performs compaction in gc_sweep phase. If GC happens before fillarray, +passphrase strings may be moved elsewhere in memory. Therefore, +passphrase caching in elisp is generally a bad idea. -Other competitors provide only specific features of GnuPG since they -still support PGP 2.*, 5.*, 6.*. As the name indicates, EasyPG is -inspired by GPGME (GnuPG Made Easy), and the library interface is -close to GPGME. With EasyPG you can benefit from a lot of features of -GnuPG. +The EasyPG Library dares to disable passphrase caching. Fortunately, +there is more secure way to cache passphrases - use gpg-agent.