17.4. taler-auditor-offline(1)

17.4.1. Name

taler-auditor-offline - operations using the auditor’s private key

17.4.2. Synopsis

taler-auditor-offline [-c FILENAME | ––config=FILENAME] [-h | ––help] [-L LOGLEVEL | ––loglevel=LOGLEVEL] [-l FILENAME | ––logfile=FILENAME] [-v | ––version] [subcommand …]

17.4.3. Description

taler-auditor-offline is a command-line tool to be used by an auditor to sign that he is aware of certain keys being used by a exchange. Using this signature, the auditor affirms that he will verify that the exchange is properly accounting for coins of those denominations. The tool takes a list of subcommands as arguments which are then processed sequentially.

The tool includes two subcommands to interact online with the exchange’s REST APIs. The download subcommand downloads current public keys from the running exchange. Note that this only includes keys that the exchange operator has previously validated using the taler-exchange-offline tool. The resulting data serves as input to the sign and show subcommands.

The upload subcommand uploads the signatures created with the private key to the exchange. It handles the output of all subcommands (except download). The download and upload subcommands must naturally be run “online” and do not require access to the auditor’s private key, which should be kept offline.

All other subcommands are intended to be run “offline”. However, especially when testing, it is of course possible to run the subcommands online as well. Generally, subcommands read inputs (beyond command-line arguments) from stdin. However, they may also consume outputs of previous subcommands. The outputs of multiple subcommands are automatically combined, and if not consumed the final output is printed to stdout.

The general options for taler-auditor-offline are:

-c FILENAME | ––config=FILENAME
Use the configuration and other resources for the merchant to operate from FILENAME.
-h | ––help
Print short help on options.
-L LOGLEVEL | ––loglevel=LOGLEVEL
Specifies the log level to use. Accepted values are: DEBUG, INFO, WARNING, ERROR.
-l FILENAME | ––logfile=FILENAME
Send logging output to FILENAME.
-v | ––version
Print version information.

17.4.4. Configuration

The exchange and the taler-auditor-httpd must both be provided with the auditor’s public key, such that they can validate messages signed by the auditor. To obtain the auditor’s public key, use:

$ AUDITOR_PRIV_FILE=`taler-config -f -c $CONF -s AUDITOR -o AUDITOR_PRIV_FILE`
$ gnunet-ecc -p $AUDITOR_PRIV_FILE

Note that if the private key file does not yet exist, the above will fail. In this case, create the private key using:

$ AUDITOR_PRIV_FILE=`taler-config -f -c $CONF -s AUDITOR -o AUDITOR_PRIV_FILE`
$ AUDITOR_PRIV_DIR=`dirname $AUDITOR_PRIV_FILE`
$ mkdir -p $AUDITOR_PRIV_DIR
$ gnunet-ecc -g1 $AUDITOR_PRIV_FILE

Relevant configuration options for taler-auditor-offline are:

  • [auditor/AUDITOR_PRIV_FILE] — where to store the private key

17.4.5. Subcommands

download

This subcommand must be run online. It downloads future signing and denomination keys with the associated meta data from the exchange and outputs the resulting JSON (for consumption by subsequent subcommands, or to stdout).

show

This subcommand outputs information about future signing and denomination keys for manual checking against the business-approved fee structure, lifetimes and other parameters.

It consumes the output of the download subcommand, either from stdin or directly.

Its output always goes to stdout for human consumption (not in JSON). It is usually a bad idea (but possible) to combine show with other subcommands, except maybe for testing.

sign

This subcommand signs information about future signing and denomination keys.

It consumes the output of the download subcommand, either from stdin or directly.

It outputs the signatures over all denomination and signing keys present in the input, in a format suitable for the upload subcommand.

revoke-denomination

This subcommand signs a revocation message for a denomination key.

The hash of the denomination public key must be given in the usual base32-encoding as the first and only argument to the subcommand.

It outputs the signature affirming the revocation of the denomination key, in a format suitable for the upload subcommand.

revoke-signkey

This subcommand signs a revocation message for an exchange online signing key.

The online signing public key must be given in the usual base32-encoding as the first and only argument to the subcommand.

It outputs the signature affirming the revocation of the online signing key, in a format suitable for the upload subcommand.

enable-auditor

This subcommand informs an exchange that an auditor is to be activated. Afterwards, the exchange will accept inputs from that auditor’s taler-auditor-offline tool. Note that the auditor also must add the exchange to the list of exchanges that it audits via taler-auditor-exchange. Furthermore, the exchange’s database will need to be provided to the auditor. This subcommand only informs the exchange about the auditor, but does not perform those additional mandatory steps for a working auditor.

The auditor’s public key must be given in the usual base32-encoding as the first argument.

The auditor’s REST API base URL must be given as the second argument. The tool performs a minimal sanity check, namely that the URL begins with “http” (this also allows “https”), but as it runs offline does not perform any further validation!

The third argument must be a human-readable name for the auditor. This may be shown to users and should identify the auditor’s business entity. If the name includes spaces, the argument should be quoted.

The subcommand takes no inputs from stdin or other subcommands.

It outputs the signature affirming the addition of the auditor, in a format suitable for the upload subcommand.

disable-auditor

This subcommand informs an exchange that an auditor is to be deactivated. Afterwards, the exchange will refuse inputs from that auditor’s taler-auditor-offline tool.

The auditor’s public key must be given in the usual base32-encoding as the first argument.

The subcommand takes no inputs from stdin or other subcommands.

It outputs the signature affirming the removal of the auditor, in a format suitable for the upload subcommand.

enable-account

This subcommand informs an exchange that it should advertise a bank account as belonging to the exchange on its /wire endpoint. Note that this does not ensure that the exchange will use this bank account for incoming or outgoing wire transfers! For this, the taler-exchange-transfer and taler-exchange-wirewatch tools must be configured. Furthermore, the bank account information advertised could theoretically differ from that which these tool actually use, for example if the public bank account is only a front for the actual internal business acounts.

The payto:// URI (RFC 8905) of the exchange’s bank account must be given as the first argument to the subcommand.

The subcommand takes no inputs from stdin or other subcommands.

It outputs the signature affirming the addition of the wire account, in a format suitable for the upload subcommand.

disable-account

This subcommand informs an exchange that it should stop advertising a bank account as belonging to the exchange on its /wire endpoint.

The payto:// URI (RFC 8905) of the exchange’s (former) bank account must be given as the first argument to the subcommand.

The subcommand takes no inputs from stdin or other subcommands.

It outputs the signature affirming the deletion of the wire account, in a format suitable for the upload subcommand.

wire-fee

This subcommand informs an exchange about the desired wire fee (and closing fee) structure for particular wire method and a calendar year (!). The tool does not permit changing wire fees during a calendar year. Also, once the wire fee has been set for a calendar year, it cannot be changed.

The subcommand takes the year, wire-method (see RFC 8905, examples include x-taler-bank or iban), wire fee and closing fee as arguments. Instead of a year, the string now can be given for the current year (this is mostly useful for test cases). The wire-method should follow the GANA registry as given in RFC 8905. The fees must be given in the usual Taler format of CURRENCY:NUMBER.FRACTION.

The subcommand takes no inputs from stdin or other subcommands.

It outputs the signature affirming the wire fees, in a format suitable for the upload subcommand.

upload

This subcommand uploads outputs from other subcommands (except download and show) to the exchange. Note that it is possible that some uploads succeed, while others fail, as the operation is not atomic.

The subcommand takes no arguments and has no output.

help

This subcommand shows a summary of all available subcommands with the required arguments.

17.4.6. Examples

Download public keys from an exchange (online)

$ taler-auditor-offline download > keys.json

Show information about public keys (offline or online)

$ taler-auditor-offline show < keys.json

Sign public keys (offline)

$ taler-auditor-offline sign < keys.json > sigs.json

Upload auditor signatures (online)

$ taler-auditor-offline upload < sigs.json

Download, sign and upload, all in one (online)

Note that doing this is only recommended in non-production deployments.

$ taler-auditor-offline download sign upload

17.4.7. Security considerations

The taler-auditor-offline tool assumes that it is run on a high-security system, especially for the sign subcommand.

The auditor should first use the show subcommand on the offline system to check that the keys being signed are acceptable. This process requires manual work: the auditor should check with the exchange operator that the keys (and meta data) matches that previously seen by the exchange operator when they used the taler-exchange-offline tool.

17.4.8. See Also

gnunet-ecc(1), taler-auditor-exchange(1), taler-exchange-offline(1), taler.conf(5)

17.4.9. Bugs

Report bugs by using https://bugs.taler.net/ or by sending electronic mail to <taler@gnu.org>.