Struct sequoia_openpgp::packet::user_attribute::UserAttribute

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pub struct UserAttribute { /* private fields */ }

Expand description

Holds a UserAttribute packet.

See Section 5.12 of RFC 4880 for details.

Implementations§

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impl UserAttribute

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pub fn new(subpackets: &[Subpacket]) -> Result<Self>

Returns a new UserAttribute packet.

Note: a valid UserAttribute has at least one subpacket.

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pub fn hash_algo_security(&self) -> HashAlgoSecurity

The security requirements of the hash algorithm for self-signatures.

A cryptographic hash algorithm usually has three security properties: pre-image resistance, second pre-image resistance, and collision resistance. If an attacker can influence the signed data, then the hash algorithm needs to have both second pre-image resistance, and collision resistance. If not, second pre-image resistance is sufficient.

In general, an attacker may be able to influence third-party signatures. But direct key signatures, and binding signatures are only over data fully determined by signer. And, an attacker’s control over self signatures over User IDs is limited due to their structure.

These observations can be used to extend the life of a hash algorithm after its collision resistance has been partially compromised, but not completely broken. For more details, please refer to the documentation for HashAlgoSecurity.

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pub fn value(&self) -> &[u8] ⓘ

Gets the user attribute packet’s raw, unparsed value.

Most likely you will want to use subpackets() to iterate over the subpackets.

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pub fn value_mut(&mut self) -> &mut Vec<u8> ⓘ

Gets a mutable reference to the user attribute packet’s raw value.

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pub fn subpackets(&self) -> SubpacketIterator<'_> ⓘ

Iterates over the subpackets.

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impl UserAttribute

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pub fn bind( &self, signer: &mut dyn Signer, cert: &Cert, signature: SignatureBuilder, ) -> Result<Signature>

Creates a binding signature.

The signature binds this user attribute to cert. signer will be used to create a signature using signature as builder. Thehash_algo defaults to SHA512, creation_time to the current time.

This function adds a creation time subpacket, a issuer fingerprint subpacket, and a issuer subpacket to the signature.

§Examples

This example demonstrates how to bind this user attribute to a Cert. Note that in general, the CertBuilder is a better way to add User IDs to a Cert.

// Generate a Cert, and create a keypair from the primary key.
let (cert, _) = CertBuilder::new()
    .generate()?;
let mut keypair = cert.primary_key().key().clone()
    .parts_into_secret()?.into_keypair()?;
assert_eq!(cert.userids().len(), 0);

// Generate a user attribute and a binding signature.
let user_attr = UserAttribute::new(&[
    Subpacket::Image(
        Image::Private(100, vec![0, 1, 2].into_boxed_slice())),
])?;
let builder =
    signature::SignatureBuilder::new(SignatureType::PositiveCertification);
let binding = user_attr.bind(&mut keypair, &cert, builder)?;

// Now merge the user attribute and binding signature into the Cert.
let cert = cert.insert_packets(vec![Packet::from(user_attr),
                                   binding.into()])?;

// Check that we have a user attribute.
assert_eq!(cert.user_attributes().count(), 1);

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pub fn certify<S, H, T>( &self, signer: &mut dyn Signer, cert: &Cert, signature_type: S, hash_algo: H, creation_time: T, ) -> Result<Signature>
where S: Into<Option<SignatureType>>, H: Into<Option<HashAlgorithm>>, T: Into<Option<SystemTime>>,

Returns a certification for the user attribute.

The signature binds this user attribute to cert. signer will be used to create a certification signature of type signature_type. signature_type defaults to SignatureType::GenericCertification, hash_algo to SHA512, creation_time to the current time.

This function adds a creation time subpacket, a issuer fingerprint subpacket, and a issuer subpacket to the signature.

§Errors

Returns Error::InvalidArgument if signature_type is not one of SignatureType::{Generic, Persona, Casual, Positive}Certification

§Examples

This example demonstrates how to certify a User ID.

// Generate a Cert, and create a keypair from the primary key.
let (alice, _) = CertBuilder::new()
    .add_userid("alice@example.org")
    .generate()?;
let mut keypair = alice.primary_key().key().clone()
    .parts_into_secret()?.into_keypair()?;

// Generate a Cert for Bob.
let user_attr = UserAttribute::new(&[
    Subpacket::Image(
        Image::Private(100, vec![0, 1, 2].into_boxed_slice())),
])?;
let (bob, _) = CertBuilder::new()
    .set_primary_key_flags(KeyFlags::empty().set_certification())
    .add_user_attribute(user_attr)
    .generate()?;

// Alice now certifies the binding between `bob@example.org` and `bob`.
let certification =
    bob.user_attributes().nth(0).unwrap()
    .certify(&mut keypair, &bob, SignatureType::PositiveCertification,
             None, None)?;

// `certification` can now be used, e.g. by merging it into `bob`.
let bob = bob.insert_packets(certification)?;

// Check that we have a certification on the User ID.
assert_eq!(bob.user_attributes().nth(0).unwrap()
           .certifications().count(),
           1);