lei-security - Man Page

security information

Synopsis

lei(1) is intended for use with both publicly-archived and “private” mail in personal mailboxes.  This document is intended to give an overview of security implications and lower^Wmanage user expectations.

Description

lei expects to be run as a regular user on a Unix-like system. It expects a case-sensitive filesystem with standard Unix permissions support.

It does not use POSIX ACLs, extended attributes, nor any other security-related functions which require non-standard Perl modules.

There is preliminary support for “virtual users”, but it is incomplete and undocumented.

Internal Files

lei runs with a umask of 077 to prevent other users on the system from accessing each other's mail.

The git storage and Xapian databases are located at $XDG_DATA_HOME/lei/store (typically ~/.local/share/lei/store). Any personal mail imported will reside here, so this should be on an encrypted filesystem or block device.

$XDG_RUNTIME_DIR/lei (typically /run/user/$UID/lei or /tmp/lei-$UID) contain the socket used to access the lei daemon.  It must only be accessible to the owner (mode 0700).

$XDG_CACHE_HOME/lei (typically ~/.cache/lei) will contain IMAP and Maildir folder names which could leak sensitive information as well as git repository names.

$XDG_DATA_HOME/lei/saved-searches (typically ~/.local/share/lei/saved-searches) will contain aforementioned folder names as well as (removable) search history.

The configuration for lei resides at $XDG_CONFIG_HOME/lei/config (typically ~/.config/lei/config).  It may contain sensitive pathnames and hostnames in the config if a user chooses to configure them.

lei itself will never write credentials to the filesystem.  However, git-credential(1) may be configured to do so.  lei will only read ~/.netrc if --netrc is used (and it will never write to ~/.netrc).

$XDG_CACHE_HOME/public-inbox (typically ~/.cache/public-inbox) can contain data and Inline::C-built modules which can be shared with public-facing public-inbox-daemon(8) instances; so no private data should be in “public-inbox” paths.

External Files

Locations set by lei-add-external(1) can be shared with public-facing public-inbox-daemon(8) processes.  They may reside on shared storage and may be made world-readable to other users on the local system.

Core Dumps

In case any process crashes, a core dumps may contain passwords or contents of sensitive messages.  Please report these so they can be fixed (see “Contact”).

Network Access

lei currently uses the curl(1) and git(1) executables in $PATH for HTTP and HTTPS network access.  Interactive authentication for HTTP and HTTPS is not-yet-supported since all currently supported HTTP/HTTPS sources are PublicInbox::WWW instances.

The Mail::IMAPClient library is used for IMAP and IMAPS. Net::NNTP (standard library) is used for NNTP and NNTPS.

Mail::IMAPClient and Net::NNTP will use IO::Socket::SSL for TLS if available.  In turn, IO::Socket::SSL uses the widely-installed OpenSSL library.

STARTTLS will be attempted if advertised by the server unless IMAPS or NNTPS are used.  -c imap.starttls=0 and -c nntp.startls=0 may be used to disable STARTTLS.

IO::Socket::Socks will be used if -c imap.proxy or -c nntp.proxy point to a socks5h://$HOST:$PORT address (common for Tor).

The --netrc switch may be passed to curl and used for NNTP/IMAP access (via Net::Netrc).

Credential Data

lei uses git-credential(1) to prompt users for IMAP and NNTP usernames and passwords.  These passwords are not encrypted in memory and get transferred across processes via anonymous UNIX sockets and pipes.  They may be exposed via syscall tracing tools (e.g. strace(1)), kernel and hardware bugs/attacks.

While credentials are not written to the filesystem by default, it is possible for them to end up on disk if processes are swapped out.  Use of an encrypted swap partition is recommended.

Authentication Methods

LOGIN (username + password) is known to work over IMAP(S), as does AUTH=ANONYMOUS (which is used by public-inbox-imapd(1) as part of our test suite).  AUTHINFO may work for NNTP, but is untested.  Testers will be needed for other authentication methods.

Denial-of-Service Vectors

lei uses the same MIME parsing library as public-inbox-mda(1) with limits header sizes, parts, nesting and boundary limits similar to those found in SpamAssassin and postfix.

Email address parsing is handled by Email::Address::XS if available, but may fall back to regular expressions which favor speed and predictable execution times over correctness.

Encrypted Emails

Not yet supported, but it should eventually be possible to configure decryption and indexing of encrypted messages and attachments.  When supported, decrypted terms will be stored in Xapian DBs under $XDG_DATA_HOME/lei/store.

Contact

Feedback welcome via plain-text mail to <mailto:meta@public-inbox.org>

The mail archives are hosted at <https://public-inbox.org/meta/> and <http://4uok3hntl7oi7b4uf4rtfwefqeexfzil2w6kgk2jn5z2f764irre7byd.onion/meta/>

See Also

lei-overview(7), lei(1)

Info

1993-10-02 public-inbox.git public-inbox user manual