PySequoia
This library provides OpenPGP facilities in Python through the
Sequoia PGP library. If you need to work with encryption and
digital signatures using an IETF standardized protocol, this
package is for you!
Note: This is a work in progress. The API is not stable!
Building
set -euxo pipefail
python -m venv .env
source .env/bin/activate
pip install maturin
maturin develop
Installing
PySequoia can be installed through pip
:
pip install pysequoia
Note that since pysequoia
is implemented largely in Rust, a Rust
toolchain is necessary for the installation to succeed.
Testing
This entire document is used for end-to-end integration tests that
exercise the package's API surface.
The tests assume that these keys exist:
gpg --batch --pinentry-mode loopback --passphrase hunter22 --quick-gen-key passwd@example.com
gpg --batch --pinentry-mode loopback --passphrase hunter22 --export-secret-key passwd@example.com > passwd.pgp
gpg --batch --pinentry-mode loopback --passphrase '' --quick-gen-key no-passwd@example.com future-default
gpg --batch --pinentry-mode loopback --passphrase '' --export-secret-key no-passwd@example.com > no-passwd.pgp
Functions
All examples assume that these basic classes have been imported:
from pysequoia import Cert
sign
Signs data and returns armored output:
from pysequoia import sign
s = Cert.from_file("signing-key.asc")
signed = sign(s.secrets.signer(), "data to be signed".encode("utf8"))
print(f"Signed data: {signed}")
assert "PGP MESSAGE" in str(signed)
verify
Verifies signed data and returns verified data:
from pysequoia import verify
signing_key = Cert.from_file("signing-key.asc")
signed = sign(s.secrets.signer(), "data to be signed".encode("utf8"))
def get_certs(key_ids):
print(f"For verification, we need these keys: {key_ids}")
return [signing_key]
result = verify(signed, get_certs)
assert result.bytes.decode("utf8") == "data to be signed"
assert result.valid_sigs[0].certificate == "afcf5405e8f49dbcd5dc548a86375b854b86acf9"
assert result.valid_sigs[0].signing_key == "afcf5405e8f49dbcd5dc548a86375b854b86acf9"
The function that returns certificates (here get_certs
) may return more certificates than necessary.
verify
succeeds if at least one correct signature has been made by any of the certificates supplied. If you need more advanced policies they can be implemented by inspecting the valid_sigs
property.
encrypt
Signs and encrypts a string to one or more recipients:
from pysequoia import encrypt
s = Cert.from_file("passwd.pgp")
r = Cert.from_bytes(open("wiktor.asc", "rb").read())
bytes = "content to encrypt".encode("utf8")
encrypted = encrypt(signer = s.secrets.signer("hunter22"), recipients = [r], bytes = bytes).decode("utf8")
print(f"Encrypted data: {encrypted}")
The signer
argument is optional and when omitted the function will return an unsigned (but encrypted) message.
decrypt
Decrypts plain data:
from pysequoia import decrypt
sender = Cert.from_file("no-passwd.pgp")
receiver = Cert.from_file("passwd.pgp")
content = "Red Green Blue"
encrypted = encrypt(recipients = [receiver], bytes = content.encode("utf8"))
decrypted = decrypt(decryptor = receiver.secrets.decryptor("hunter22"), bytes = encrypted)
assert content == decrypted.bytes.decode("utf8");
assert len(decrypted.valid_sigs) == 0
Decrypt can also verify signatures while decrypting:
from pysequoia import decrypt
sender = Cert.from_file("no-passwd.pgp")
receiver = Cert.from_file("passwd.pgp")
content = "Red Green Blue"
encrypted = encrypt(signer = sender.secrets.signer(), recipients = [receiver], bytes = content.encode("utf8"))
def get_certs(key_ids):
print(f"For verification after decryption, we need these keys: {key_ids}")
return [sender]
decrypted = decrypt(decryptor = receiver.secrets.decryptor("hunter22"), bytes = encrypted, store = get_certs)
assert content == decrypted.bytes.decode("utf8");
assert decrypted.valid_sigs[0].certificate == sender.fingerprint
assert decrypted.valid_sigs[0].signing_key == sender.fingerprint
Here, the same remarks as to verify
also apply.
Certificates
The Cert
class represents one OpenPGP certificate (commonly called a
"public key").
This package additionally verifies the certificate using Sequoia PGP's
StandardPolicy
. This means that certificates using weak
cryptography can fail to load, or present a different view than in
other OpenPGP software (e.g. if a User ID uses SHA-1 in its
back-signature, it may be missing from the list of User IDs returned
by this package).
Certificates have two forms, one is ASCII armored and one is raw bytes:
cert = Cert.generate("Test <test@example.com>")
print(f"Armored cert: {cert}")
print(f"Bytes of the cert: {cert.bytes()}")
Parsing
Certificates can be parsed from files (Cert.from_file
) or bytes in
memory (Cert.from_bytes
).
cert1 = Cert.generate("Test <test@example.com>")
buffer = cert1.bytes()
parsed_cert = Cert.from_bytes(buffer)
assert str(parsed_cert.user_ids[0]) == "Test <test@example.com>"
They can also be picked from "keyring" files (Cert.split_file
) or
bytes in memory (Cert.split_bytes
) which are collections of binary
certificates.
cert1 = Cert.generate("Test 1 <test-1@example.com>")
cert2 = Cert.generate("Test 2 <test-2@example.com>")
cert3 = Cert.generate("Test 3 <test-3@example.com>")
buffer = cert1.bytes() + cert2.bytes() + cert3.bytes()
certs = Cert.split_bytes(buffer)
assert len(certs) == 3
generate
Creates a new general purpose key with a given User ID:
alice = Cert.generate("Alice <alice@example.com>")
fpr = alice.fingerprint
print(f"Generated cert with fingerprint {fpr}:\n{alice}")
Multiple User IDs can be passed as a list to the generate
function:
cert = Cert.generate(user_ids = ["First", "Second", "Third"])
assert len(cert.user_ids) == 3
Newly generated certificates are usable in both encryption and signing
contexts:
alice = Cert.generate("Alice <alice@example.com>")
bob = Cert.generate("Bob <bob@example.com>")
bytes = "content to encrypt".encode("utf8")
encrypted = encrypt(signer = alice.secrets.signer(), recipients = [bob], bytes = bytes)
print(f"Encrypted data: {encrypted}")
merge
Merges packets from a new version into an old version of a certificate:
old = Cert.from_file("wiktor.asc")
new = Cert.from_file("wiktor-fresh.asc")
merged = old.merge(new)
User IDs
Listing existing User IDs:
cert = Cert.from_file("wiktor.asc")
user_id = cert.user_ids[0]
assert str(user_id).startswith("Wiktor Kwapisiewicz")
Adding new User IDs:
cert = Cert.generate("Alice <alice@example.com>")
assert len(cert.user_ids) == 1;
cert = cert.add_user_id(value = "Alice <alice@company.invalid>", certifier = cert.secrets.certifier())
assert len(cert.user_ids) == 2;
Revoking User IDs:
cert = Cert.generate("Bob <bob@example.com>")
cert = cert.add_user_id(value = "Bob <bob@company.invalid>", certifier = cert.secrets.certifier())
assert len(cert.user_ids) == 2
revocation = cert.revoke_user_id(user_id = cert.user_ids[1], certifier = cert.secrets.certifier())
cert = Cert.from_bytes(cert.bytes() + revocation.bytes())
assert len(cert.user_ids) == 1
Notations
Notations are small pieces of data that can be attached to signatures (and, indirectly, to User IDs).
The following example reads and displays a Keyoxide proof URI:
cert = Cert.from_file("wiktor.asc")
user_id = cert.user_ids[0]
notation = user_id.notations[0]
assert notation.key == "proof@metacode.biz";
assert notation.value == "dns:metacode.biz?type=TXT";
Notations can also be added:
from pysequoia import Notation
cert = Cert.from_file("signing-key.asc")
assert len(cert.user_ids[0].notations) == 0;
cert = cert.set_notations(cert.secrets.certifier(), [Notation("proof@metacode.biz", "dns:metacode.biz")])
print(str(cert.user_ids[0].notations))
assert len(cert.user_ids[0].notations) == 1;
notation = cert.user_ids[0].notations[0]
assert notation.key == "proof@metacode.biz";
assert notation.value == "dns:metacode.biz";
Key expiration
Certs have an expiration
getter for retrieving the current key
expiry time:
cert = Cert.from_file("signing-key.asc")
assert cert.expiration is None
cert = Cert.from_file("wiktor.asc")
assert str(cert.expiration) == "2022-12-31 12:00:02+00:00"
Key expiration can also be adjusted with set_expiration
:
from datetime import datetime
cert = Cert.from_file("signing-key.asc")
assert cert.expiration is None
expiration = datetime.fromisoformat("2021-11-04T00:05:23+00:00")
cert = cert.set_expiration(expiration = expiration, certifier = cert.secrets.certifier())
assert str(cert.expiration) == "2021-11-04 00:05:23+00:00"
Key revocation
Certs can be revoked. While expiration makes the key unusable
temporarily to encourage the user to refresh a copy revocation is
irreversible.
cert = Cert.generate("Test Revocation <revoke@example.com>")
revocation = cert.revoke(certifier = cert.secrets.certifier())
assert not cert.is_revoked
revoked_cert = Cert.from_bytes(cert.bytes() + revocation.bytes())
assert revoked_cert.is_revoked
Secret keys
Certificates generated through Cert.generate()
contain secret keys
and can be used for signing and decryption.
To avoid accidental leakage secret keys are never directly printed
when the Cert is written to a string. To enable this behavior use
Cert.secrets
. secrets
returns None
on certificates which do
not contain any secret key material ("public keys").
c = Cert.generate("Testing key <test@example.com>")
assert c.has_secret_keys
public_parts = Cert.from_bytes(f"{c}".encode("utf8"))
assert not public_parts.has_secret_keys
assert public_parts.secrets is None
private_parts = Cert.from_bytes(f"{c.secrets}".encode("utf8"))
assert private_parts.has_secret_keys
Signatures
Detached signatures can be read directly from files (Sig.from_file
) or bytes in memory (Sig.from_bytes
):
from pysequoia import Sig
sig = Sig.from_file("sig.pgp")
print(f"Parsed signature: {repr(sig)}")
assert sig.issuer_fpr == "e8f23996f23218640cb44cbe75cf5ac418b8e74c"
assert sig.created == datetime.fromisoformat("2023-07-19T18:14:01+00:00")
License
This project is licensed under Apache License, Version 2.0.
Contribution
Unless you explicitly state otherwise, any contribution intentionally
submitted for inclusion in the package by you shall be under the terms
and conditions of this license, without any additional terms or
conditions.