Lua based authentication ¶

New in version v2.3.0.

You can implement passdb and userdb using Lua script.

Contents

Lua based authentication

Known bugs ¶

Before 2.3.4 when returning a table with values, the table values are mistakenly converted into a number if they seem like a number. So if you are using values like 012345, this would get converted into 12345
Before 2.3.4 returning password without scheme would cause a crash.

Lua based authentication ¶

When used in authentication, additional module dovecot.auth is added, which contains constants for passdb and userdb.

For details about Dovecot Lua, see Dovecot Lua support.

When used in authentication, additional module dovecot.auth is added, which contains constants for passdb and userdb.

List of constants ¶

dovecot.auth.PASSDB_RESULT_INTERNAL_FAILURE
dovecot.auth.PASSDB_RESULT_SCHEME_NOT_AVAILABLE - indicates password scheme that cannot be understood
dovecot.auth.PASSDB_RESULT_USER_UNKNOWN
dovecot.auth.PASSDB_RESULT_USER_DISABLED
dovecot.auth.PASSDB_RESULT_PASS_EXPIRED
dovecot.auth.PASSDB_RESULT_NEXT - indicates that this passdb did not authenticate user, next passdb should do it
dovecot.auth.PASSDB_RESULT_PASSWORD_MISMATCH
dovecot.auth.PASSDB_RESULT_OK
dovecot.auth.USERDB_RESULT_INTERNAL_FAILURE
dovecot.auth.USERDB_RESULT_USER_UNKNOWN
dovecot.auth.USERDB_RESULT_OK

Also, it registers object struct auth_request* which lets access various parts of the auth request. You should use the loggers associated with auth_request when possible.

Auth request methods

Functions:

auth_request#log_debug(text) - logs debug message (if debug is enabled, noop otherwise)
auth_request#log_error(text) - logs error message
auth_request#log_info(text) - logs informational message
auth_request#log_warning(text) - logs warning message
auth_request#response_from_template(template) - takes in key=value template and expands it using var_expand and produces table suitable for passdb result
auth_request#var_expand(template) - performs var expansion on the template using Variables
auth_request#password_verify(crypted_password, plain_password) - checks if the plain password matches the crypted or hashed password

New in version v2.3.6.

auth_request#event() - Returns child event for the auth request, can be used for logging and other events. Comes with a prefix.

Members:¶

See Variables for details

auth_request#auth_domain
auth_request#auth_user
auth_request#auth_username
auth_request#cert
auth_request#client_id
auth_request#domain
auth_request#domain_first
auth_request#domain_last
auth_request#home
auth_request#lip
auth_request#local_name
auth_request#login_domain
auth_request#login_user
auth_request#login_username
auth_request#lport
auth_request#master_user
auth_request#mech
auth_request#orig_domain
auth_request#orig_user
auth_request#orig_username
auth_request#password
auth_request#pid
auth_request#real_lip
auth_request#real_lport
auth_request#real_rip
auth_request#real_rport
auth_request#rip
auth_request#rport
auth_request#secured
auth_request#service
auth_request#session
auth_request#session_pid
auth_request#user
auth_request#username

Additionally you can access

skip_password_check - Set if the password has already been validated by another passdb
passdbs_seen_user_unknown - If some previous passdb has not found this user
passdbs_seen_internal_failure - If some previous passdb has had internal failure
userdbs_seen_internal_failure - If some previous userdb has had internal failure

Password database

Lua passdb supports two modes of function. It can behave as lookup database, or password verification database.

Lookup function signature is auth_passdb_lookup(request) and the password verification signature is auth_password_verify(request, password)

Both functions must return a tuple, which contains a return code, and also additionally string or table. Table must be in key-value format, it will be imported into auth request. The string must be in key=value format, except if return code indicates internal error, the second parameter can be used as error string.

If auth_verify_password is found, it’s always used.

To configure passdb in dovecot, use

passdb {
  driver = lua
  args = file=/path/to/lua blocking=yes # default is yes
}

By default, dovecot runs Lua scripts in auth-worker processes. If you do not want this, you can disable blocking, and Lua script will be ran in auth process. This can degrade performance if your script is slow or makes external lookups.

User database ¶

Lua userdb supports both single user lookup and iteration. Note that iteration will hold the whole user database in memory during iteration.

User lookup function signature is auth_userdb_lookup(request). The function must return a tuple, which contains a return code, and also additionally string or table. Table must be in key-value format, it will be imported into auth request. The string must be in key=value format, except if return code indicates internal error, the second parameter can be used as error string.

User iteration function signature is auth_userdb_iterate, which is expected to return table of usernames. Key names are ignored.

Lua userdb supports both single user lookup and iteration.

Note

The iteration will hold the whole user database in memory during iteration.

To configure userdb in dovecot, use

userdb {
  driver = lua
  args = file=/path/to/lua blocking=yes # default is yes
}

Examples ¶

function auth_passdb_lookup(req)
  if req.user == "testuser1" then
    return dovecot.auth.PASSDB_RESULT_OK, "password=pass"
  end
  return dovecot.auth.PASSDB_RESULT_USER_UNKNOWN, "no such user"
end

function auth_userdb_lookup(req)
  if req.user == "testuser1" then
    return dovecot.auth.USERDB_RESULT_OK, "uid=vmail gid=vmail"
  end
  return dovecot.auth.USERDB_RESULT_USER_UNKNOWN, "no such user"
end

function script_init()
  return 0
end

function script_deinit()
end

function auth_userdb_iterate()
  return {"testuser1"}
end

Simple username password database (such as opensmtpd)¶

The example uses whitespace separated username and password. As a special caution, the way Lua is used here means you can have multiple user password per line, instead of just one. This can be extended to more complicated separators or multiple fields per user.

If you only want to autenticate users, and don’t care about user listing, you can use

function auth_passdb_lookup(req)
   for line in io.lines("/path/to/file") do
       for user, pass in string.gmatch(line, "(%w+)%s(.+)") do
           if (user == req.username) then
               -- you can add additional information here, like userdb_uid
               return dovecot.auth.PASSDB_RESULT_OK, "password=" .. pass
           end
       end
   end
   return dovecot.auth.PASSDB_RESULT_USER_UNKNOWN, ""
end

If you also want to be able to list users, so that you could use doveadm cmd -A

local database = "/path/to/file"

function db_lookup(username)
   for line in io.lines(database) do
       for user, pass in string.gmatch(line, "(%w+)%s(.+)") do
           if (user == username) then
               return {result=0, password=pass}
           end
       end
   end
   return {result=-1}
end

function auth_passdb_lookup(req)
   res = db_lookup(req.username)
   if res.result == 0 then
       -- you can add additional information here for passdb
       return dovecot.auth.PASSDB_RESULT_OK, "password=" .. res.password
   end
   return dovecot.auth.PASSDB_RESULT_USER_UNKNOWN, ""
end

function auth_userdb_lookup(req)
   res = db_lookup(req.username)
   if res.result == 0 then
       -- you can add additional information here for userdb, like uid or home
       return dovecot.auth.USERDB_RESULT_OK, "uid=vmail gid=vmail"
   end
   return dovecot.auth.USERDB_RESULT_USER_UNKNOWN, ""
end

function auth_userdb_iterate()
  users = {}
  for line in io.lines(database) do
       for user in string.gmatch(line, "(%w+)%s.+") do
           table.insert(users, user)
       end
  end
  return users
end

Lua based authentication ¶

Known bugs ¶

Lua based authentication ¶

List of constants ¶

Subtables:¶

Members:¶

User database ¶

Examples ¶

Simple username password database (such as opensmtpd)¶

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