Struct sequoia_openpgp::packet::signature::subpacket::SubpacketArea

pub struct SubpacketArea { /* private fields */ }

Subpacket area.

A version 4 Signature contains two areas that can stored signature subpackets: a so-called hashed subpacket area, and a so-called unhashed subpacket area. The hashed subpacket area is protected by the signature; the unhashed area is not. This makes the unhashed subpacket area only appropriate for self-authenticating data, like the Issuer subpacket. The SubpacketAreas data structure understands these nuances and routes lookups appropriately. As such, it is usually better to work with subpackets using that interface.

Examples

fn sig_stats(sig: &Signature) {
    eprintln!("Hashed subpacket area has {} subpackets",
              sig.hashed_area().iter().count());
    eprintln!("Unhashed subpacket area has {} subpackets",
              sig.unhashed_area().iter().count());
}

Implementations

impl SubpacketArea

pub const MAX_SIZE: usize = 65_535usize

The maximum size of a subpacket area.

pub fn new(packets: Vec<Subpacket>) -> Result<SubpacketArea>

Returns a new subpacket area containing the given packets.

pub fn iter(&self) -> impl Iterator<Item = &Subpacket> + Send + Sync

Iterates over the subpackets.

Examples

Print the number of different types of subpackets in a Signature’s hashed subpacket area:

let mut tags: Vec<_> = sig.hashed_area().iter().map(|sb| {
    sb.tag()
}).collect();
tags.sort();
tags.dedup();

eprintln!("The hashed area contains {} types of subpackets",
          tags.len());

pub fn subpacket(&self, tag: SubpacketTag) -> Option<&Subpacket>

Returns a reference to the last instance of the specified subpacket, if any.

A given subpacket may occur multiple times. For some, like the Notation Data subpacket, this is reasonable. For others, like the Signature Creation Time subpacket, this results in an ambiguity. Section 5.2.4.1 of RFC 4880 says:

a signature may contain multiple copies of a preference or multiple expiration times. In most cases, an implementation SHOULD use the last subpacket in the signature, but MAY use any conflict resolution scheme that makes more sense.

This function implements the recommended strategy of returning the last subpacket.

Examples

All signatures must have a Signature Creation Time subpacket in the hashed subpacket area:

use sequoia_openpgp as openpgp;
use openpgp::packet::signature::subpacket::SubpacketTag;

if sig.hashed_area().subpacket(SubpacketTag::SignatureCreationTime).is_none() {
    eprintln!("Invalid signature.");
}

pub fn subpacket_mut(&mut self, tag: SubpacketTag) -> Option<&mut Subpacket>

Returns a mutable reference to the last instance of the specified subpacket, if any.

A given subpacket may occur multiple times. For some, like the Notation Data subpacket, this is reasonable. For others, like the Signature Creation Time subpacket, this results in an ambiguity. Section 5.2.4.1 of RFC 4880 says:

a signature may contain multiple copies of a preference or multiple expiration times. In most cases, an implementation SHOULD use the last subpacket in the signature, but MAY use any conflict resolution scheme that makes more sense.

This function implements the recommended strategy of returning the last subpacket.

Examples

All signatures must have a Signature Creation Time subpacket in the hashed subpacket area:

use sequoia_openpgp as openpgp;
use openpgp::packet::signature::subpacket::SubpacketTag;

if sig.hashed_area().subpacket(SubpacketTag::SignatureCreationTime).is_none() {
    eprintln!("Invalid signature.");
}

pub fn subpackets( &self, target: SubpacketTag, ) -> impl Iterator<Item = &Subpacket> + Send + Sync

Returns all instances of the specified subpacket.

For most subpackets, only a single instance of the subpacket makes sense. SubpacketArea::subpacket resolves this ambiguity by returning the last instance of the request subpacket type. But, for some subpackets, like the Notation Data subpacket, multiple instances of the subpacket are reasonable.

Examples

Count the number of Notation Data subpackets in the hashed subpacket area:

use sequoia_openpgp as openpgp;
use openpgp::packet::signature::subpacket::SubpacketTag;

eprintln!("Signature has {} notations.",
          sig.hashed_area().subpackets(SubpacketTag::NotationData).count());

pub fn add(&mut self, packet: Subpacket) -> Result<()>

Adds the given subpacket.

Adds the given subpacket to the subpacket area. If the subpacket area already contains subpackets with the same tag, they are left in place. If you want to replace them, you should instead use the SubpacketArea::replace method.

Errors

Returns Error::MalformedPacket if adding the packet makes the subpacket area exceed the size limit.

Examples

Adds an additional Issuer subpacket to the unhashed subpacket area. (This is useful if the key material is associated with multiple certificates, e.g., a v4 and a v5 certificate.) Because the subpacket is added to the unhashed area, the signature remains valid.

use sequoia_openpgp as openpgp;
use openpgp::KeyID;
use openpgp::packet::signature::subpacket::{
    Subpacket,
    SubpacketTag,
    SubpacketValue,
};

let mut sig: Signature = sig;
sig.unhashed_area_mut().add(
    Subpacket::new(
        SubpacketValue::Issuer(KeyID::from_hex("AAAA BBBB CCCC DDDD")?),
        false)?);

sig.verify_message(signer.public(), msg)?;

pub fn replace(&mut self, packet: Subpacket) -> Result<()>

Adds the given subpacket, replacing all other subpackets with the same tag.

Adds the given subpacket to the subpacket area. If the subpacket area already contains subpackets with the same tag, they are first removed. If you want to preserve them, you should instead use the SubpacketArea::add method.

Errors

Returns Error::MalformedPacket if adding the packet makes the subpacket area exceed the size limit.

Examples

Assuming we have a signature with an additional Issuer subpacket in the unhashed area (see the example for SubpacketArea::add, this replaces the Issuer subpacket in the unhashed area. Because the unhashed area is not protected by the signature, the signature remains valid:

use sequoia_openpgp as openpgp;
use openpgp::KeyID;
use openpgp::packet::signature::subpacket::{
    Subpacket,
    SubpacketTag,
    SubpacketValue,
};

// First, add a subpacket to the unhashed area.
let mut sig: Signature = sig;
sig.unhashed_area_mut().add(
    Subpacket::new(
        SubpacketValue::Issuer(KeyID::from_hex("DDDD CCCC BBBB AAAA")?),
        false)?);

// Now, replace it.
sig.unhashed_area_mut().replace(
    Subpacket::new(
        SubpacketValue::Issuer(KeyID::from_hex("AAAA BBBB CCCC DDDD")?),
    false)?);

sig.verify_message(signer.public(), msg)?;

pub fn remove_all(&mut self, tag: SubpacketTag)

Removes all subpackets with the given tag.

pub fn clear(&mut self)

Removes all subpackets.

pub fn sort(&mut self)

Sorts the subpackets by subpacket tag.

This normalizes the subpacket area, and accelerates lookups in implementations that sort the in-core representation and use binary search for lookups.

The subpackets are sorted by the numeric value of their tag. The sort is stable. So, if there are multiple Notation Data subpackets, for instance, they will remain in the same order.

The SignatureBuilder sorts the subpacket areas just before creating the signature.

Trait Implementations

impl Clone for SubpacketArea

fn clone(&self) -> SubpacketArea

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for SubpacketArea

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for SubpacketArea

fn default() -> Self

Returns the “default value” for a type.

impl Hash for SubpacketArea

fn hash<H: Hasher>(&self, state: &mut H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<'a> IntoIterator for &'a SubpacketArea

type Item = &'a Subpacket

The type of the elements being iterated over.

type IntoIter = Iter<'a, Subpacket>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl Marshal for SubpacketArea

fn serialize(&self, o: &mut dyn Write) -> Result<()>

Writes a serialized version of the object to o.

fn export(&self, o: &mut dyn Write) -> Result<()>

Exports a serialized version of the object to o.

impl MarshalInto for SubpacketArea

fn serialized_len(&self) -> usize

Computes the maximal length of the serialized representation.

fn serialize_into(&self, buf: &mut [u8]) -> Result<usize>

Serializes into the given buffer.

fn to_vec(&self) -> Result<Vec<u8>>

Serializes the packet to a vector.

fn export_into(&self, buf: &mut [u8]) -> Result<usize>

Exports into the given buffer.

fn export_to_vec(&self) -> Result<Vec<u8>>

Exports to a vector.

impl Ord for SubpacketArea

fn cmp(&self, other: &SubpacketArea) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized + PartialOrd,

Restrict a value to a certain interval.

impl PartialEq for SubpacketArea

fn eq(&self, other: &SubpacketArea) -> bool

This method tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd for SubpacketArea

fn partial_cmp(&self, other: &SubpacketArea) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

This method tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

This method tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator.

impl Eq for SubpacketArea