Pine Privacy Guard
Table of Contents
Pine Privacy Guard is a small perl
script to interface Pine
and GnuPG for the secure exchange
of email. It allows Pine users to conveniently:
- Encrypt email.
- Decrypt email.
- Clear-sign email.
- Verify clear-signed email.
- Securely remember secret key passphrases, so that the passphrase
need only be typed in once per Pine session.
- Aliases, so that mail sent to an email address can automatically be
encrypted with any number of specified public keys.
- Simple installation. The necessary files consist of only one perl script
called by Pine via four symbolic links, and an optional aliases file.
- A short script means no funny business. The compact, well-documented
code makes it easier to see what is going on for yourself, so you
don't need to trust the author to not put in backdoors or
Here is a sample session of using Pine with
Pine Privacy Guard.
GNU General Public License
The most recent versions of both Pine and GnuPG are preferred, as many
of the software upgrades are security updates.
The most recent version is Pine Privacy Guard 1.02. You can download it
If you haven't done so already, you will need to have generated your own
public/private GnuPG key pair in order to sign your messages. See this HOWTO for getting this setup
quickly. It is recommended however that the GnuPG documentation be
read in order to understand why the procedure is how it is.
- Unzip+untar the package to the installation directory.
- Verify path names are correct for your system in pine_privacy_guard.pl,
as well as the Unix permissions of pine_privacy_guard.pl.
- Set the two pine settings: display-filters and sending-filters. See below.
- Configure your own aliases file (optional).
- Unzip and untar the package to where you want to install the
installation directory. Where you install it need not be in
your $PATH, as it will only be called by pine by its full path.
For example, for single-user use, it would be appropriate to run
unzip and untar from your home directory.
will create a pinepg-x.x subdirectory. (If you are using a GNU version
of tar, as is the case on most Linux systems, then you can just do
"tar zxvf pinepg-x.x.tgz") To install system-wide, execute the above,
as root, from /usr/local/, for example.
gunzip -c pinepg-x.x.tgz | tar xvf -
- In the script pine_privacy_guard.pl, the top line should consist of
the full path to the perl executable, preceded by the 2 characters
"#!". Find out what it should be with the command "which perl".
Similarly, make sure the paths are correct for the variables under
"Set full paths to files". Also make sure the permissions are set
chmod 755 pine_privacy_guard.pl. There is
no loss of security if the script is made publicly readable and
executable. However, it would be a major security hole if the script
were to be world-writable.
- Set the Pine display-filters and sending-filters settings as given
below. From within pine, go to
Substitute /usr/local/pinepg below to where ever your installation
directory is. For example, if you installed to your home directory,
you may have /home/myusername/pinepg/decrypt below instead
of /usr/local/pinepg/decrypt. Everything else should not be changed.
(M)ain Menu >> (S)etup >> (C)onfig >> (W)hereIs
Word to find : display-filters
display-filters = _LEADING("-----BEGIN PGP MESSAGE-----")_ /usr/local/pinepg/decrypt _RESULTFILE_ _DATAFILE_ _PREPENDKEY_, _LEADING("-----BEGIN PGP SIGNED MESSAGE-----")_ /usr/local/pinepg/verify _TMPFILE_ _RESULTFILE_
(The variable names like _RESULTFILE_ are special tokens recognized
by Pine, that it will substitute for its own values.)
sending-filters = /usr/local/pinepg/clearsign _RESULTFILE_ _DATAFILE_ _PREPENDKEY_, /usr/local/pinepg/encrypt _RECIPIENTS_ _RESULTFILE_ _DATAFILE_ _PREPENDKEY_
- Pine Privacy Guard includes a feature in which email sent to any
particular address (email@example.com for example) can automatically
be encrypted using a specified set of email addresses from your public
GPG keyring (firstname.lastname@example.org and email@example.com for example).
This is done with an aliases file. The default location for the
aliases file is .pinepg_aliases in your home directory. Copy it
there by doing:
To enable the example, add the following line to the aliases file
(with no indentation):
cp pinepg_aliases ~/.pinepg_aliases
This feature can also be used for individual email addresses as well.
For example, the email address associated with Alice's public key
may be firstname.lastname@example.org but she prefers to receive email at
email@example.com. Then include the line (with no indentation)
firstname.lastname@example.org email@example.com firstname.lastname@example.org
in the aliases file. For users who have multiple public keys with
identical email addresses, the 8-digit hexadecimal ID for the key can be
used in place of the email address for distinguishing the public key in
the keyring. See the GPG documentation for more details on this ID.
Some Important Notes About Security
As with all security software, Pine Privacy Guard is a tool for
security, not a fool-proof solution. As with any tool, it must
be understood, at least in part, in order to be used effectively.
If complete security is the goal, there is no substitute for an
understanding of the underlying security protocols themselves.
An excellent text about security protocols and algorithms is Applied Cryptography
by Bruce Schneier.
For the user who wants to quickly setup and use Pine Privacy Guard,
here is an example of a few considerations that are no substitute for
understanding the underlying protocols:
- During the pine session, your passphrase will be asked for, and
you will need to type it in. Any component between your keyboard and
the machine on which pine is running may intercept your passphrase.
In particular, if you are running pine on a remote machine via an insecure
channel (telnet, for example) then you are susceptible to an eavesdropper
obtaining your passphrase.
- For convenience, Pine Privacy Guard encrypts your passphrase,
and writes it to the temp directory for automatic retrieval during the
pine session. Your passphrase is encrypted (using GPG) using the pine
session key, which is unique to each user-initiated pine session, (see
the pine documentation for details) and may exist in insecure memory.
To retrieve your passphrase, an attacker would have to get this session
key as well as the encrypted passphrase file, which is also protected
by the Unix permissions system.
- In general, if you believe the system administrator, root user, or
anyone who can obtain the super user permissions of your system may try
to circumvent these security measures, then you are using an insecure
system and no amount of cryptography will help. In such a situation,
the nosy administrator could, if they tried hard enough, capture all
key strokes from the keyboard, and all text sent to your terminal, in
the extreme case. In less extreme cases, they can simply read all of
your files, including email.
Tips, Suggestions, and Other Notes
Setting up GnuPG
In order to sign messages, you will need to have generated
your own public/private key pair with GnuPG. Here is a ``HOWTO Setup GnuPG Quickly'' page for the
impatient user. For those who are interested in real security, there is
no substitute for an understanding of the cryptographic protocols. It
is recommended that the GnuPG documentation be read.
Be careful using Bcc with encrypted email
If you send out an encrypted email while having someone receive a blind
carbon copy, for example:
then Pine Privacy Guard will encrypt the message with both Alice's and
Bob's public keys. When Alice decrypts the message, she will see that
the message was also encrypted with Bob's key even though he would not
be listed as a recipient in the email header. Thus if you truly want to
keep the Bcc recipients out of the picture when sending encrypted email,
the Bcc recipients should be emailed separately.
To: Alice <email@example.com>
Bcc: Bob <firstname.lastname@example.org>
Clear-signing when the word "From" starts a line in the email
Some email transport software look for a special line in the email header
which starts with a "From" in order to extract transport information.
In order to distinguish these special lines from a line in the email body
that may begin with a "From", some software will insert a prefix character
">" just before the "From" in the email body so that it doesn't confuse
other email software down the line as email gets passed along through
the Internet. This effect can produce what seem to be bad signatures
on clear-signed messages. That is, Alice may sign an email that says:
From the past to the present, the future is always ahead.
When Bob receives it, some email transport program between Alice and Bob
may have transformed it into:
>From the past to the present, the future is always ahead.
Alice signed the first version, but Bob is checking Alice's signature
against the second version. Since the versions are different, Bob sees
that the signature is bad.
Pine Privacy Guard solves this problem by automatically prefixing lines
that begin with a "From" with the ">" character before clear-signing
the message. This is a user-configurable feature; by default it
is on. To turn it off, set the $prefix_From variable near the top of
pine_privacy_guard.pl to 0 instead of 1.
Here's a FAQ.
Here are some links to other security software. These packages are not
endorsed, nor necessarily have been used by any of the developers of
Pine Privacy Guard; they are provided in the hope that anyone looking
to use a secure email program will find the best package for their
particular needs. If there are any additional software packages that
I missed of this variety that should be included here, please send an
email to pinepg at quantumlab.net.
``pgp4pine is an interactive program for using encryption within the
Pine email client. It is compatible with PGP 2/5/6 and GnuPG 1.0.''
``pgpenvelope is an interface to meld using Pine with GnuPG,
the GNU Privacy Guard. It allows one to sign/encrypt/decrypt/verify
one's mail messages using GnuPG from within Pine. Ease of installation
and use, and a nice interface are primary goals during development.''
``PinePgp is set of display and sending filters which enables
pine to send and receive signed and/or encrypted e-mails.''