cedula-uy-pdf-sign

Sign PDF documents locally using a Uruguayan national ID card (cédula) through PKCS#11, producing PDF digital signatures compatible with standard PDF signature validators.

Overview

cedula-uy-pdf-sign provides a local, developer-oriented workflow for signing PDF documents with a Uruguayan national ID card using PKCS#11 middleware.

The CLI tool is invoked as firmauy and supports:

• signing individual PDF documents
• batch-signing multiple PDFs with a single PKCS#11 session
• configuring the visible signature position
• selecting the signature page
• discovering available PKCS#11 tokens and certificates
• non-interactive PIN sources for controlled automation workflows

Project status and limitations

This project is copyright-registered, experimental, community-maintained, and not officially certified.

It is intended for developers and technically proficient users who understand the implications of using smart cards, PKCS#11 middleware, and digital signatures.

Legal / Compliance Notice

⚠️ Important

This project:

• is not affiliated with or endorsed by AGESIC
• does not claim official certification or compliance
• is provided for technical and educational purposes

While it uses standard cryptographic mechanisms and aims to align with Uruguayan digital signature practices, it should not be assumed to be valid for legal or regulatory use without independent verification.

Users are solely responsible for ensuring that the generated signatures meet any legal or regulatory requirements applicable to their use case.

Intended use

This project is intended for local, developer-oriented PDF signing workflows using a Uruguayan ID card through PKCS#11.

It is especially aimed at users who want to:

• sign PDF documents locally
• understand and reproduce a PKCS#11-based signing workflow
• experiment with smart card integration on Linux
• build automation around PDF signing under their own responsibility

It is not intended to replace official, certified, or legally guaranteed signing platforms.

Scope

This tool focuses on:

• technical integration with PKCS#11
• PDF signing workflows
• reproducibility of signature appearance

It does not:

• validate certificates against official trust lists
• provide legal guarantees
• replace certified signing platforms

Requirements

Hardware

• Smart card reader compatible with your OS
• Uruguayan ID card (cédula) with active certificate

Operating system

This tool is primarily designed and tested for Arch Linux.

Other Linux distributions may work if the required smart card stack, PKCS#11 middleware, and Python environment are correctly configured.

PKCS#11 middleware

The default PKCS#11 module expected by this tool is:

/usr/lib/pkcs11/libgclib.so

On Arch Linux, this is provided by the cedula-uruguay-pkcs11 AUR package.

Setup on Arch Linux

1. Install smart card stack

sudo pacman -S pcsclite ccid pcsc-tools opensc
sudo systemctl enable --now pcscd

2. Install PKCS#11 library for the Uruguayan ID card

Install the PKCS#11 module from AUR:

yay -S cedula-uruguay-pkcs11
# or manually:
# https://aur.archlinux.org/packages/cedula-uruguay-pkcs11

This is a community-maintained AUR package that repackages the official cédula drivers distributed by the Uruguayan government. It is not an official government package.

It provides the default PKCS#11 module used by this tool:

/usr/lib/pkcs11/libgclib.so

Installation

Installation with uv

uv tool install cedula-uy-pdf-sign

Usage

The CLI tool is invoked as firmauy.

CLI help

Use --help on any command to see all available options:

firmauy --help
firmauy sign --help
firmauy sign-batch --help

Sign a single PDF

firmauy sign input.pdf output_signed.pdf

The tool will prompt for the PKCS#11 PIN interactively.

If the output path is omitted, the signed file is saved as:

<input>_firmado.pdf

Custom signature position

firmauy sign input.pdf output_signed.pdf --x1 20 --y1 20 --x2 225 --y2 90

Specify page

Pages are 0-indexed. Use -1 to sign the last page.

firmauy sign input.pdf output_signed.pdf --page 0

Non-interactive PIN

PIN can be supplied without an interactive prompt via --pin-source:

# From an environment variable
firmauy sign input.pdf output_signed.pdf --pin-source env --pin-env-var MY_PIN

# From stdin
echo "1234" | firmauy sign input.pdf output_signed.pdf --pin-source stdin

# From a file descriptor
firmauy sign input.pdf output_signed.pdf --pin-source fd --pin-fd 3

⚠️ Avoid exposing the PIN in shell history or process lists.

Sign batch

Sign multiple PDFs with a single PKCS#11 session. The card PIN is entered only once.

# Explicit file list
firmauy sign-batch file1.pdf file2.pdf file3.pdf --output-dir ~/signed

# Whole directory
firmauy sign-batch --input-dir ~/docs --output-dir ~/signed

# Whole directory, recursively
firmauy sign-batch --input-dir ~/docs --recursive --output-dir ~/signed

# Both can be combined
firmauy sign-batch extra.pdf --input-dir ~/docs --output-dir ~/signed

Output files are named <original-name>_firmado.pdf by default.

Change the suffix with --suffix:

firmauy sign-batch --input-dir ~/docs --output-dir ~/signed --suffix _signed

The output directory is created automatically if it does not exist.

All options available for sign — position, PIN source, reason, TSA, etc. — are also available for sign-batch.

⚠️ This tool produces cryptographic signatures. Legal validity depends on applicable regulations and use context.

Make sure you have reviewed all documents before signing them in batch.

Discover tokens and certificates

List all visible PKCS#11 tokens:

firmauy list-tokens

List certificates available on a token:

firmauy list-certs

Security considerations

• Never pass the PIN directly as a command-line argument.
• Prefer interactive PIN entry for manual use.
• For automation, prefer protected file descriptors or controlled environments.
• Review every document before signing it.
• Use batch signing only in trusted workflows.
• Keep your smart card, reader, PIN, and PKCS#11 middleware under your own control.

Privacy

This tool is designed to run entirely locally.

It does not collect, transmit, or store any user data externally.

All cryptographic operations are performed on the user's machine and/or the connected smart card.

Note: Optional features such as timestamping (TSA) may involve external network requests, depending on user configuration.

Signature verification

Signed documents can be independently verified using external tools, such as the official validator provided by AGESIC:

https://firma.gub.uy/

No affiliation with or endorsement by AGESIC is implied.

A successful technical verification does not necessarily imply legal validity for every use case. Users should independently verify the legal and regulatory requirements applicable to their situation.

Known issues

Incorrect PIN may crash the process (middleware bug)

On Arch Linux, entering an incorrect PIN may cause the process to terminate abruptly with:

*** stack smashing detected ***: terminated

This is a bug in the PKCS#11 middleware (libgclib.so), not in cedula-uy-pdf-sign.

The middleware correctly returns CKR_PIN_INCORRECT to the caller, but then appears to corrupt its own memory during error handling.

This is independently reproducible with pkcs11-tool:

pkcs11-tool --module /usr/lib/pkcs11/libgclib.so --login --test
# With wrong PIN -> process crashes with stack smash

Because the crash occurs inside native code, it cannot be caught or recovered from at the Python level.

Practical advice: double-check your PIN before invoking firmauy.

This behavior is outside the control of this application.

Additional notes

• The default visual signature appearance was derived by analyzing documents signed with official software.
• This project focuses on practical interoperability rather than strict compliance with any specific implementation.

Copyright / software registration

This software has been registered as a computer program with the Uruguayan Dirección Nacional de la Propiedad Industrial y Registro de Software.

The registration was published in the official Boletín de la Propiedad Industrial Nº 357:

• Entry: Software (w/000235)
• Filing date: 2026-04-15
• Applicant: Carlos Andrés Planchón Prestes [UY]
• Title: cedula-uy-pdf-sign
• Classification: Programa de ordenador
• Official publication: Boletín de la Propiedad Industrial Nº 357

This registration refers to the authorship and registration of the software as a copyrighted work.

It does not imply official certification, endorsement, legal validity of generated signatures, or regulatory compliance of any specific use case.

Contributing & reporting issues

Bug reports, questions, and pull requests are welcome.

Feel free to open an issue on GitHub.

Acknowledgements

• @nicolasgutierrezdev — provided reference for signature appearance inspired by signatures generated using the Uruguayan ID card (cédula).

License

This project is licensed under the Apache License 2.0.