Struct sequoia_openpgp::packet::UserID

pub struct UserID { /* fields omitted */ }

Holds a UserID packet.

The standard imposes no structure on UserIDs, but suggests to follow RFC 2822. See Section 5.11 of RFC 4880 for details. In practice though, implementations do not follow RFC 2822, or do not even help their users in producing well-formed User IDs. Experience has shown that parsing User IDs using RFC 2822 does not work, so we are taking a more pragmatic approach and define what we call Conventional User IDs.

Using this definition, we provide methods to extract the name, comment, email address, or URI from UserID packets. Furthermore, we provide a way to canonicalize the email address found in a UserID packet. We provide two constructors that create well-formed User IDs from email address, and optional name and comment.

Conventional User IDs

Informally, conventional User IDs are of the form:

• First Last (Comment) <name@example.org>

• First Last <name@example.org>

• First Last

• name@example.org <name@example.org>

• <name@example.org>

• name@example.org

• Name (Comment) <scheme://hostname/path>

• Name (Comment) <mailto:user@example.org>

• Name <scheme://hostname/path>

• <scheme://hostname/path>

• scheme://hostname/path

Names consist of UTF-8 non-control characters and may include punctuation. For instance, the following names are valid:

• Acme Industries, Inc.
• Michael O'Brian
• Smith, John
• e.e. cummings

(Note: according to RFC 2822 and its successors, all of these would need to be quoted. Conventionally, no implementation quotes names.)

Conventional User IDs are UTF-8. RFC 2822 only covers US-ASCII and allows character set switching using RFC 2047. For example, an RFC 2822 parser would parse:

• Bj=?utf-8?q?=C3=B6?=rn Bj=?utf-8?q?=C3=B6?=rnson

“Björn Björnson”. Nobody uses this in practice, and, as such, this extension is not supported by this parser.

Comments can include any UTF-8 text except parentheses. Thus, the following is not a valid comment even though the parentheses are balanced:

• (foo (bar))

URIs

The URI parser recognizes URIs using a regular expression similar to the one recommended in RFC 3986 with the following extensions and restrictions:

• UTF-8 characters are in the range \u{80}-\u{10ffff} are allowed wherever percent-encoded characters are allowed (i.e., everywhere but the schema).

• The scheme component and its trailing : are required.

• The URI must have an authority component (//domain) or a path component (/path/to/resource).

• Although the RFC does not allow it, in practice, the [ and ] characters are allowed wherever percent-encoded characters are allowed (i.e., everywhere but the schema).

URIs are neither normalized nor interpreted. For instance, dot segments are not removed, escape sequences are not decoded, etc.

Note: the recommended regular expression is less strict than the grammar. For instance, a percent encoded character must consist of three characters: the percent character followed by two hex digits. The parser that we use does not enforce this either.

Formal Grammar

Formally, the following grammar is used to decompose a User ID:

  WS                 = 0x20 (space character)

  comment-specials   = "<" / ">" /   ; RFC 2822 specials - "(" and ")"
                       "[" / "]" /
                       ":" / ";" /
                       "@" / "\" /
                       "," / "." /
                       DQUOTE

  atext-specials     = "(" / ")" /   ; RFC 2822 specials - "<" and ">".
                       "[" / "]" /
                       ":" / ";" /
                       "@" / "\" /
                       "," / "." /
                       DQUOTE

  atext              = ALPHA / DIGIT /   ; Any character except controls,
                       "!" / "#" /       ;  SP, and specials.
                       "$" / "%" /       ;  Used for atoms
                       "&" / "'" /
                       "*" / "+" /
                       "-" / "/" /
                       "=" / "?" /
                       "^" / "_" /
                       "`" / "{" /
                       "|" / "}" /
                       "~" /
                       \u{80}-\u{10ffff} ; Non-ascii, non-control UTF-8

  dot_atom_text      = 1*atext *("." *atext)

  name-char-start    = atext / atext-specials

  name-char-rest     = atext / atext-specials / WS

  name               = name-char-start *name-char-rest

  comment-char       = atext / comment-specials / WS

  comment-content    = *comment-char

  comment            = "(" *WS comment-content *WS ")"

  addr-spec          = dot-atom-text "@" dot-atom-text

  uri                = See [RFC 3986] and the note on URIs above.

  pgp-uid-convention = addr-spec /
                       uri /
                       *WS [name] *WS [comment] *WS "<" addr-spec ">" /
                       *WS [name] *WS [comment] *WS "<" uri ">" /
                       *WS name *WS [comment] *WS

Implementations

impl UserID

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.

In the case of self signatures over User IDs, an attacker may be able to control the content of the User ID packet. However, unlike an image, there is no easy way to hide large amounts of arbitrary data (e.g., the 512 bytes needed by the SHA-1 is a Shambles attack) from the user. Further, normal User IDs are short and encoded using UTF-8.

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. Specifically for the case of User IDs, we relax the requirement for strong collision resistance for self signatures over User IDs if:

• The User ID is at most 96 bytes long,
• It contains valid UTF-8, and
• It doesn’t contain a UTF-8 control character (this includes the NUL byte).

For more details, please refer to the documentation for HashAlgoSecurity.

pub fn from_address<O, S>(name: O, comment: O, email: S) -> Result<Self> where
    S: AsRef<str>,
    O: Into<Option<S>>, 

Constructs a User ID.

This does a basic check and any necessary escaping to form a conventional User ID.

Only the address is required. If a comment is supplied, then a name is also required.

If you already have a User ID value, then you can just use UserID::from().

assert_eq!(UserID::from_address(
               "John Smith".into(),
               None, "boat@example.org")?.value(),
           &b"John Smith <boat@example.org>"[..]);

pub fn from_unchecked_address<O, S>(
    name: O,
    comment: O,
    address: S
) -> Result<Self> where
    S: AsRef<str>,
    O: Into<Option<S>>, 

Constructs a User ID.

This does a basic check and any necessary escaping to form a conventional User ID modulo the address, which is not checked.

This is useful when you want to specify a URI instead of an email address.

If you already have a User ID value, then you can just use UserID::from().

assert_eq!(UserID::from_unchecked_address(
               "NAS".into(),
               None, "ssh://host.example.org")?.value(),
           &b"NAS <ssh://host.example.org>"[..]);

pub fn value(&self) -> &[u8]

Gets the user ID packet’s value.

This returns the raw, uninterpreted value. See UserID::name, UserID::email, UserID::email_normalized, UserID::uri, and UserID::comment for how to extract parts of conventional User IDs.

pub fn name(&self) -> Result<Option<String>>

Parses the User ID according to de facto conventions, and returns the name component, if any.

See conventional User ID for more information.

pub fn comment(&self) -> Result<Option<String>>

Parses the User ID according to de facto conventions, and returns the comment field, if any.

See conventional User ID for more information.

pub fn email(&self) -> Result<Option<String>>

Parses the User ID according to de facto conventions, and returns the email address, if any.

See conventional User ID for more information.

pub fn uri(&self) -> Result<Option<String>>

Parses the User ID according to de facto conventions, and returns the URI, if any.

See conventional User ID for more information.

pub fn email_normalized(&self) -> Result<Option<String>>

Returns a normalized version of the UserID’s email address.

Normalized email addresses are primarily needed when email addresses are compared.

Note: normalized email addresses are still valid email addresses.

This function normalizes an email address by doing puny-code normalization on the domain, and lowercasing the local part in the so-called empty locale.

Note: this normalization procedure is the same as the normalization procedure recommended by Autocrypt.

impl UserID

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

Creates a binding signature.

The signature binds this userid 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 userid to a Cert. Note that in general, the CertBuilder is a better way to add userids 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 userid and a binding signature.
let userid = UserID::from("test@example.org");
let builder =
    signature::SignatureBuilder::new(SignatureType::PositiveCertification);
let binding = userid.bind(&mut keypair, &cert, builder)?;

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

// Check that we have a userid.
assert_eq!(cert.userids().len(), 1);

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 id.

The signature binds this userid 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 userid.

// Generate a Cert, and create a keypair from the primary key.
let (alice, _) = CertBuilder::new()
    .set_primary_key_flags(KeyFlags::empty().set_certification())
    .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 (bob, _) = CertBuilder::new()
    .set_primary_key_flags(KeyFlags::empty().set_certification())
    .add_userid("bob@example.org")
    .generate()?;

// Alice now certifies the binding between `bob@example.org` and `bob`.
let certification =
    bob.userids().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 userid.
assert_eq!(bob.userids().nth(0).unwrap()
           .certifications().count(), 1);

Trait Implementations

impl Clone for UserID

fn clone(&self) -> Self

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for UserID

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

Formats the value using the given formatter.

impl Display for UserID

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

Formats the value using the given formatter.

impl From<&'_ [u8]> for UserID

fn from(u: &[u8]) -> Self

Performs the conversion.

impl<'a> From<&'a str> for UserID

fn from(u: &'a str) -> Self

Performs the conversion.

impl<'a> From<Cow<'a, str>> for UserID

fn from(u: Cow<'a, str>) -> Self

Performs the conversion.

impl From<String> for UserID

fn from(u: String) -> Self

Performs the conversion.

impl From<UserID> for Packet

fn from(s: UserID) -> Self

Performs the conversion.

impl From<Vec<u8, Global>> for UserID

fn from(u: Vec<u8>) -> Self

Performs the conversion.

impl Hash for UserID

fn hash(&self, hash: &mut dyn Digest)

Updates the given hash with this object.

impl Hash for UserID

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, 

Feeds a slice of this type into the given Hasher.

impl IntoIterator for UserID

Implement IntoIterator so that cert::insert_packets(sig) just works.

type Item = UserID

The type of the elements being iterated over.

type IntoIter = Once<UserID>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl Marshal for UserID

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 UserID

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 UserID

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

This method returns an Ordering between self and other.

#[must_use]

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

Compares and returns the maximum of two values.

#[must_use]

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

Compares and returns the minimum of two values.

#[must_use]

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

Restrict a value to a certain interval.

impl<'a> Parse<'a, UserID> for UserID

fn from_reader<R: 'a + Read + Send + Sync>(reader: R) -> Result<Self>

Reads from the given reader.

fn from_file<P: AsRef<Path>>(path: P) -> Result<T>

Reads from the given file.

fn from_bytes<D: AsRef<[u8]> + ?Sized + Send + Sync>(data: &'a D) -> Result<T>

Reads from the given slice.

impl PartialEq<UserID> for UserID

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

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

#[must_use]

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

This method tests for !=.

impl PartialOrd<UserID> for UserID

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

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

#[must_use]

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

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

#[must_use]

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

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

#[must_use]

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

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

#[must_use]

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 UserID