jmcarbo / go-imap-sql

SQL-based storage backend for go-imap.

go-imap-sql

SQL-based storage backend for go-imap library.

Building

Go 1.13 is required due to use of Go 1.13 error inspection features.

RDBMS support

go-imap-sql is known to work with (and constantly being tested against) following RDBMS:

• SQLite 3.25.0
• PostgreSQL 9.6

Following RDBMS was actively supported in the past, it's unknown whether they still work with go-imap-sql:

• MariaDB 10.2

IMAP Extensions Supported

• CHILDREN
• APPEND-LIMIT
• MOVE
• SPECIAL-USE

Usernames case-insensitivity

Usernames are always converted to lower-case before doing anything. This means that if you type imapsql-ctl ... users create FOXCPP. Account with username foxcpp will be created. Also this means that you can use any case in account settings in your IMAP client.

Passwords hashing

go-imap-sql uses bcrypt hash function for account passwords. This makes passwords hard to brute-force, but also significantly increases CPU load.

Backend users should either change hash function to sha3-512 (see Opts structure documentation) or implement restrictions on authentication attempts that will block access after certain number of attempts.

secure_delete

You may want to overwrite deleted messages and theirs meta-data with zeroes for security/privacy reasons. For MySQL, PostgreSQL - consult documentation (AFAIK, there is no such option).

For SQLite3, you should build go-imap-sql with sqlite_secure_delete build tag. It will enable corresponding SQLite3 feature by default for all databases.

If you want to enable it per-database - you can use file:PATH?_secure_delete=ON in DSN.

UIDVALIDITY

go-imap-sql never invalidates UIDs in an existing mailbox. If mailbox is DELETE'd then UIDVALIDITY value changes.

Unlike many popular IMAP server implementations, go-imap-sql uses randomly generated UIDVALIDITY values instead of timestamps.

This makes several things easier to implement with less edge cases. And answer to the question you are already probably asked: To make go-imap-sql malfunction you need to get Go's PRNG to generate two equal integers in range of [1, 2^32-1] just at right moment (seems unlikely enough to ignore it). Even then, it will not cause much problems due to the way most client implementations work.

go-imap-sql uses separate math/rand.Rand instance and seeds it with system time on initialization (in New).

You can provide custom pre-seeded struct implementing math/rand.Source in Opts struct (PRNG field).

Maddy

You can use go-imap-sql as part of the maddy mail server.

imapsql-ctl

For direct access to database you can use imapsql-ctl console utility. See more information in separate README here.

go install github.com/foxcpp/go-imap-sql/cmd/imapsql-ctl