This is a tool to make custom web interfaces to PostgreSQL databases
(aka [dynamic websites](https://defanor.uberspace.net/notes/dynamic-websites.xhtml)),
using simple and standard technologies:
- SQL for querying
- XSLT for templating
- HTML forms for user input
- Optional HTTP basic authentication for PostgreSQL authentication
URL query parameters are available for use from XSLTs. SQL query
templates can use those too, as well as HTML form data submitted with
the POST method.
Request timeouts are enforced and do cancel DB queries, but otherwise
it relies on PostgreSQL for access permissions and security policies,
as well as for any business logic that may be needed.
The used environment variables are:
- `TIMEOUT`: request timeout in seconds, 10 by default.
- `XSLT_DIR`: a directory to read XSLT files from, current working
directory by default.
Regular [libpq environment
are used for database connections.
URL query parameters are made visible to XSLTs as `xsl:param`
parameters. The documents they get applied to are either the results
of SQL queries (which are expected to return a single XML document,
using `query_to_xml` or similar functions), or error documents (which
contain error details) in case of an error.
The XSLTs are taken from `XSLT_DIR`, using file name from the `t` URL
query parameter, with added `xsl` extension.
SQL queries provided in the `q` URL query parameter get executed, with
some substitutions to handle HTML forms:
- `f:<name>` for "POST" (serialised form data in message body)
- `q:<name>` for "GET" (serialised form data in URI query) parameters
- `:fields` for "POST" parameter names
- `:values` for "POST" parameter values (in the same order as the
`:fields` and `:values` are unnecessary, but are provided for
convenience of insert/upsert operations.
SQL queries get tokenized by splitting into words and reassembled
afterwards, hence some whitespace separation is needed.
HTTP methods (and corresponding conventions) are currently ignored,
since they are of little use with HTML 5 forms.
Presence of `auth=on` in the URL query requires HTTP basic
authentication, and the provided credentials are used directly for
PostgreSQL authentication. HTTP authentication also gets requested if
a database connection failure was password-related.
With `auth=try` pgxhtml would serve pages composed using defaults if
no credentials are provided, but with 401 status code.
`auth=fail` would ignore user-provided credentials and serve pages
with 401 status code. It can be used to circumvent poor authentication
handling by some web browsers.
### Web server
This is intended to be used with an HTTP server, which would take care
of encryption, compression, static files, redirects, and so on, while
pgxhtml only focuses on providing a web interface to a database.
### Security checklist
- Regular privileges (see
should be set appropriately.
- [Row Security
should be defined and enabled.
are useful for data validation.
- [REVOKE CREATE ON SCHEMA public FROM
would likely be desired (perhaps granting `CREATE` just to the
- Possibly web server rules (such as nginx rewrites), if it's desired
to strictly limit available queries.
## See also
- [PostgREST](http://postgrest.org/), "a standalone web server that
turns your PostgreSQL database directly into a RESTful API".
- [automatic-api](https://github.com/dbohdan/automatic-api/), a list
of tools for automatic HTTP-based API generation.