11.1. Nexus Manual¶
LibEuFin Nexus is an EBICS facilitator. It offers a command line interface to setup EBICS access, download banking records, and submit payments. Today, the LibEuFin implementation supports EBICS 2.5 and 3.0 and has been tested with the Postfinance (CHF). Please note that banks tend to have their own dialects of finance messages and thus other retail banks may or may not work. Contact us if you need support for another bank or core banking protocol.
Future versions will offer a Web API to allow Taler exchanges to talk to their banks.
In this manual, we explain how to setup an EBICS subscriber. We assume that the bank has already granted EBICS access to the subscriber.
11.1.1. Installing Nexus¶
The following section was tested on an OpenJDK 17 environment.
11.1.1.1. Installing the libeufin-nexus binary packages on Debian¶
To install the GNU Taler Debian packages, first ensure that you have the right Debian distribution. At this time, the packages are built for Debian bookworm.
You need to add a file to import the GNU Taler packages. Typically,
this is done by adding a file /etc/apt/sources.list.d/taler.list that
looks like this:
deb [signed-by=/etc/apt/keyrings/taler-systems.gpg] https://deb.taler.net/apt/debian bookworm main
Next, you must import the Taler Systems SA public package signing key into your keyring and update the package lists:
# wget -O /etc/apt/keyrings/taler-systems.gpg \
https://taler.net/taler-systems.gpg
# apt update
Note
You may want to verify the correctness of the Taler Systems SA key out-of-band.
Now your system is ready to install the official GNU Taler binary packages using apt.
To install libeufin-nexus, you can now simply run:
# apt install libeufin-nexus
11.1.1.2. Installing the libeufin-nexus binary packages on Ubuntu¶
To install the GNU Taler Ubuntu packages, first ensure that you have
the right Ubuntu distribution. At this time, the packages are built for
Ubuntu Lunar and Ubuntu Jammy. Make sure to have universe in your
/etc/apt/sources.list (after main) as we depend on some packages
from Ubuntu universe.
A typical /etc/apt/sources.list.d/taler.list file for this setup
would look like this for Ubuntu Lunar:
deb [signed-by=/etc/apt/keyrings/taler-systems.gpg] https://deb.taler.net/apt/ubuntu/ lunar taler-lunar
For Ubuntu Mantic use this instead:
deb [signed-by=/etc/apt/keyrings/taler-systems.gpg] https://deb.taler.net/apt/ubuntu/ mantic taler-mantic
For Ubuntu Noble use this instead:
deb [signed-by=/etc/apt/keyrings/taler-systems.gpg] https://deb.taler.net/apt/ubuntu/ noble taler-noble
Next, you must import the Taler Systems SA public package signing key into your keyring and update the package lists:
# wget -O /etc/apt/keyrings/taler-systems.gpg \
https://taler.net/taler-systems.gpg
# apt update
Note
You may want to verify the correctness of the Taler Systems key out-of-band.
Now your system is ready to install the official GNU Taler binary packages using apt.
To install libeufin-nexus, you can now simply run:
# apt install libeufin-nexus
11.1.1.3. Building from source¶
Nexus belongs to the LibEuFin project, and can be downloaded via Git:
$ git clone git://git.taler.net/libeufin
Note that Kotlin and Gradle should already work on the host system.
Navigate into the libeufin local repository, and from top-level run:
$ ./bootstrap
$ ./configure --prefix=$PREFIX
$ make install
If the previous steps succeeded, the libeufin-nexus command should
be found in the $PATH.
11.1.2. Database setup¶
The configuration file must include a connection string that tells Nexus how it should connect to the database. The default is:
[libeufin-nexusdb-postgres]
config = postgres:///libeufin
You must make sure that this database exists and is accessible to the user running Nexus before continuing. Then, the Nexus database schema must be created (or updated) to the current Nexus version using the following command:
$ libeufin-nexus-dbinit -c "$CONFIG_FILE"
where $CONFIG_FILE is again the path to a configuration that contains at
least the above [libeufin-nexusdb-postgres] section.
11.1.3. Setting up the EBICS subscriber¶
When you sign up for an EBICS-enabled bank account, the bank will provide you
with various credentials. Those must be provided in the
/etc/libeufin/libeufin-nexus.conf configuration file together with the
name of the fiat currency.
Note
As legacy transactions in that bank account would likely confuse the system, it is advisable to use a fresh bank account with an empty transaction history.
The following snippet shows the mandatory configuration values:
[nexus-ebics]
CURRENCY = CHF
# Bank
HOST_BASE_URL = https://ebics.postfinance.ch/ebics/ebics.aspx
BANK_DIALECT = postfinance
# EBICS IDs
HOST_ID = PFEBICS
USER_ID = PFC00563
PARTNER_ID = PFC00563
# Account information
IBAN = CH7789144474425692816
BIC = POFICHBEXXX
NAME = John Smith S.A.
Note
Refer to the manpage libeufin-nexus.conf(5)
for the full array of configuration values.
Warning
This combination of HOST_ID, USER_ID and PARTNER_ID must never be used by another instance of libeufin-nexus or by other EBICS clients, otherwise data will be lost.
11.1.3.1. Reuse existing client keys¶
If you have client keys from a previous EBICS setup you can copy the JSON file to the configured path CLIENT_PRIVATE_KEYS_FILE (/var/lib/libeufin-nexus/client-ebics-keys.json with the default config).
Make sure this file is accessible to the user running libeufin-nexus, for the default services you should run:
$ chown libeufin-nexus:libeufin-nexus /var/lib/libeufin-nexus/client-ebics-keys.json
11.1.3.2. Create new client keys¶
Assuming that the configuration file exists at $CONFIG_FILE, the following
command should start the EBICS setup process:
$ libeufin-nexus ebics-setup -c "$CONFIG_FILE"
If the previous command failed when running EBICS INI with an error code of
EBICS_INVALID_USER_OR_USER_STATE, you need to confirm your keys to your bank to
activate your account.
To that end, the previous run should have left a PDF document that you can
print, sign and send to the bank. Look for the message that looks like PDF
file with keys created at '/tmp/libeufin-nexus-keys-$TIMESTAMP.pdf'.
Once the bank has received and processed this document you can continue.
11.1.3.3. Get bank keys¶
Assuming that the configuration file exists at $CONFIG_FILE, the following
command will finish the EBICS setup process:
$ libeufin-nexus ebics-setup -c "$CONFIG_FILE"
The EBICS setup is finished once the bank keys have been accepted.
Make sure this bank keys are accessible to the user running libeufin-nexus, for the default services you should run:
$ chown libeufin-nexus:libeufin-nexus /var/lib/libeufin-nexus/bank-ebics-keys.json
11.1.4. Sending payments¶
Sending payments must follow a successful EBICS subscriber setup, where the bank obtained the subscriber keys, and the subscriber accepted the bank keys. Furthermore, the database has to be set up. Right now, some other process must queue payments to be submitted to the database, so this section only discusses how such queued payments will be executed.
The responsible subcommand for sending payments is ebics-submit, and its
configuration is a superset of core-config. On top of that, it expects
the database connection string and optionally a frequency at which it will
check for submittable payments in the database.
The frequency may be specified as
[nexus-submit]
FREQUENCY = 5m
The supported time units are s (seconds), m (minutes), h (hours).
11.1.4.1. For testing¶
The ebics-submit subcommand is not suitable to send arbitrary
payments, but rather to submit initiated payments that are already queued for
submission in the Nexus database.
Such queued payments may originate from bounces of incoming payments with a subject that would be invalid for a Taler withdrawal, or from a Taler exchange that needs to send a payment to a merchant.
For testing purposes it is possible to manually initiate a payment using the
initiate-payment subcommand.
The following invocation pays 1 CHF to the CH987654321 with an “Hello, Nexus!”
subject:
$ libeufin-nexus initiate-payment -c "$CONFIG_FILE" --subject "Hello, Nexus!" "payto://iban/CH987654321?receiver-name=Name&amount=CHF:1"
$CONFIG_FILE is the path to Nexus’ configuration file and it does not need
the FREQUENCY value. If the previous command worked, now the database should
contain a new row in the initiated_outgoing_transactions table, with an
unsubmitted submission state.
The following command would now pick such an unsubmitted initiated payment and send it to the bank.
$ libeufin-nexus ebics-submit -c "$CONFIG_FILE" --transient
The --transient flag instructs the software to perform only one pass on
the database, submit what is submittable, and return.
The --debug-ebics $SAVEDIR flag will cause EBICS transactions steps and payloads to be stored in $SAVEDIR/$YYYY-MM-DD where $YYYY-MM-DD represents the date when the upload took place. This is mostly useful for debugging.
11.1.4.2. For production¶
The ebics-submit subcommand can run in fixed frequency, or transient mode.
The fixed frequency mode causes the command to check the database every time the
frequency period expires. To activate this mode, and – for example – set a frequency
of five minutes, set the configuration value FREQUENCY to 5m. Assuming that
FREQUENCY is set as described above, the following invocation would
make ebics-submit check the database every five minutes, and submit any initiated
payment according to their submission state.
$ libeufin-nexus ebics-submit -c "$CONFIG_FILE"
Transient mode causes ebics-submit to check the database only once, submit any
initiated payment according to their submission state, and return.
$ libeufin-nexus ebics-submit -c "$CONFIG_FILE"
11.1.5. Downloading payment records¶
Downloading payments must follow a successful EBICS subscriber setup, where the bank obtained the subscriber keys, and the subscriber accepted the bank keys. Furthermore, the database has to be set up.
The responsible subcommand for fetching and registering payments is
ebics-fetch, and its configuration is a superset of core-config. On
top of that, it expects the database connection string and optionally a
frequency and a checkpoint time of day.
For the best user experience, new transactions should be registered as soon as they are booked. This is especially important for instant transactions, which reach final status in ~10 seconds. On the other hand, EBICS document fetches are slow and expensive and should not be performed more than necessary.
ebics-fetch will run a periodical fetch of pending documents (documents
that have never been fetched before). If the bank server supports it, it will
also listen to real-time document availability notifications and fetch
documents as soon as they are announced. This enables instant registration of
instant transactions. If your bank server does not support real-time
notifications, it is recommended that you fetch more often; otherwise, you can
reduce the fetch frequency.
Only fetching pending documents is not always reliable, if other EBICS clients
use the same connection settings as libeufin-nexus, they can consume documents before they are ingested. In case of bank downtime, the status of
documents can be lost. This is why ebics-fetch will run a checkpoint every
day to download all documents generated since the last checkpoint.
If the bank supports real-time notifications, you can expect transactions to be registered as soon as they are booked: ~10s for instant transactions and 24 to 72h for other transactions. Otherwise, expect a latency corresponding to the fetch frequency for instant transactions. Thanks to checkpointing, latency should not exceed one day.
The frequency may be specified as
[nexus-fetch]
FREQUENCY = 5m
The supported time units are s (seconds), m (minutes), h (hours).
The checkpoint time of day may be specified as
[nexus-fetch]
CHECKPOINT_TIME_OF_DAY = 19:00
Assuming that $CONFIG_FILE contains all required options, the following
command would download any unseen EBICS files:
$ libeufin-nexus ebics-fetch -c "$CONFIG_FILE" --transient
The ebics-fetch subcommand will always cause libeufin-nexus to download
then parse EBICS files and register their content statements into its local
database.
The --transient flag makes the command download and import EBICS files only
once and return immediately afterwards. Without the flag, Nexus
will download at the frequency specified in the configuration or when it receive real time notifications.
The --debug-ebics $SAVEDIR flag will cause EBICS transactions steps and payloads to be stored in $SAVEDIR/$YYYY-MM-DD where $YYYY-MM-DD represents the date when the download took place. This is mostly useful for debugging.
11.1.5.1. For Testing¶
If the bank account history has transactions that are useful for testing, it is
possible to re-download them via the --pinned-start argument.
The following command redownloads transactions from the pinned start until the present:
$ libeufin-nexus ebics-fetch -c "$CONFIG_FILE" --pinned-start 2023-11-01
Note
If the Nexus database already contains the bank account history, you might need to reset the database in order to have the re-downloaded transactions be properly registered.
Be careful when resetting the database: resetting the wrong database might cause DATA LOSS!
Use the IGNORE_BOUNCES_BEFORE configuration to prevent malformed transactions from being bounced a second time when they are registered again.