SignatureSubpacket.java
// SPDX-FileCopyrightText: 2021 Paul Schaub <vanitasvitae@fsfe.org>
//
// SPDX-License-Identifier: Apache-2.0
package org.pgpainless.algorithm;
import static org.bouncycastle.bcpg.SignatureSubpacketTags.ATTESTED_CERTIFICATIONS;
import static org.bouncycastle.bcpg.SignatureSubpacketTags.CREATION_TIME;
import static org.bouncycastle.bcpg.SignatureSubpacketTags.EMBEDDED_SIGNATURE;
import static org.bouncycastle.bcpg.SignatureSubpacketTags.EXPIRE_TIME;
import static org.bouncycastle.bcpg.SignatureSubpacketTags.EXPORTABLE;
import static org.bouncycastle.bcpg.SignatureSubpacketTags.FEATURES;
import static org.bouncycastle.bcpg.SignatureSubpacketTags.INTENDED_RECIPIENT_FINGERPRINT;
import static org.bouncycastle.bcpg.SignatureSubpacketTags.ISSUER_FINGERPRINT;
import static org.bouncycastle.bcpg.SignatureSubpacketTags.ISSUER_KEY_ID;
import static org.bouncycastle.bcpg.SignatureSubpacketTags.KEY_EXPIRE_TIME;
import static org.bouncycastle.bcpg.SignatureSubpacketTags.KEY_FLAGS;
import static org.bouncycastle.bcpg.SignatureSubpacketTags.KEY_SERVER_PREFS;
import static org.bouncycastle.bcpg.SignatureSubpacketTags.NOTATION_DATA;
import static org.bouncycastle.bcpg.SignatureSubpacketTags.PLACEHOLDER;
import static org.bouncycastle.bcpg.SignatureSubpacketTags.POLICY_URL;
import static org.bouncycastle.bcpg.SignatureSubpacketTags.PREFERRED_AEAD_ALGORITHMS;
import static org.bouncycastle.bcpg.SignatureSubpacketTags.PREFERRED_COMP_ALGS;
import static org.bouncycastle.bcpg.SignatureSubpacketTags.PREFERRED_HASH_ALGS;
import static org.bouncycastle.bcpg.SignatureSubpacketTags.PREFERRED_KEY_SERV;
import static org.bouncycastle.bcpg.SignatureSubpacketTags.PREFERRED_SYM_ALGS;
import static org.bouncycastle.bcpg.SignatureSubpacketTags.PRIMARY_USER_ID;
import static org.bouncycastle.bcpg.SignatureSubpacketTags.REG_EXP;
import static org.bouncycastle.bcpg.SignatureSubpacketTags.REVOCABLE;
import static org.bouncycastle.bcpg.SignatureSubpacketTags.REVOCATION_KEY;
import static org.bouncycastle.bcpg.SignatureSubpacketTags.REVOCATION_REASON;
import static org.bouncycastle.bcpg.SignatureSubpacketTags.SIGNATURE_TARGET;
import static org.bouncycastle.bcpg.SignatureSubpacketTags.SIGNER_USER_ID;
import static org.bouncycastle.bcpg.SignatureSubpacketTags.TRUST_SIG;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
/**
* Enumeration of possible subpackets that might be found in the hashed and unhashed area of an OpenPGP signature.
*
* @see <a href="https://tools.ietf.org/html/rfc4880#section-5.2.3.1">RFC4880: Signature Subpacket Specification</a>
*/
public enum SignatureSubpacket {
/**
* The time the signature was made.
* MUST be present in the hashed area of the signature.
*
* @see <a href="https://tools.ietf.org/html/rfc4880#section-5.2.3.4">Signature Creation Time</a>
*/
signatureCreationTime(CREATION_TIME),
/**
* The validity period of the signature. This is the number of seconds
* after the signature creation time that the signature expires. If
* this is not present or has a value of zero, it never expires.
*
* @see <a href="https://tools.ietf.org/html/rfc4880#section-5.2.3.10">Signature Expiration Time</a>
*/
signatureExpirationTime(EXPIRE_TIME),
/**
* Denotes whether the signature is exportable for other users.
*
* @see <a href="https://tools.ietf.org/html/rfc4880#section-5.2.3.11">Exportable Certification</a>
*/
exportableCertification(EXPORTABLE),
/**
* Signer asserts that the key is not only valid but also trustworthy at
* the specified level. Level 0 has the same meaning as an ordinary
* validity signature. Level 1 means that the signed key is asserted to
* be a valid, trusted introducer, with the 2nd octet of the body
* specifying the degree of trust. Level 2 means that the signed key is
* asserted to be trusted to issue level 1 trust signatures, i.e., that
* it is a "meta introducer". Generally, a level n trust signature
* asserts that a key is trusted to issue level n-1 trust signatures.
* The trust amount is in a range from 0-255, interpreted such that
* values less than 120 indicate partial trust and values of 120 or
* greater indicate complete trust. Implementations SHOULD emit values
* of 60 for partial trust and 120 for complete trust.
*
* @see <a href="https://tools.ietf.org/html/rfc4880#section-5.2.3.13">Trust Signature</a>
*/
trustSignature(TRUST_SIG),
/**
* Used in conjunction with trust Signature packets (of level greater 0) to
* limit the scope of trust that is extended. Only signatures by the
* target key on User IDs that match the regular expression in the body
* of this packet have trust extended by the trust Signature subpacket.
* The regular expression uses the same syntax as the Henry Spencer's
* "almost public domain" regular expression [REGEX] package. A
* description of the syntax is found in Section 8 below.
*
* @see <a href="https://tools.ietf.org/html/rfc4880#section-5.2.3.14">Regular Expression</a>
*/
regularExpression(REG_EXP),
/**
* Signature's revocability status. The packet body contains a Boolean
* flag indicating whether the signature is revocable. Signatures that
* are not revocable have any later revocation signatures ignored. They
* represent a commitment by the signer that he cannot revoke his
* signature for the life of his key. If this packet is not present,
* the signature is revocable.
*
* @see <a href="https://tools.ietf.org/html/rfc4880#section-5.2.3.12">Revocable</a>
*/
revocable(REVOCABLE),
/**
* The validity period of the key. This is the number of seconds after
* the key creation time that the key expires. If this is not present
* or has a value of zero, the key never expires. This is found only on
* a self-signature.
*
* @see <a href="https://tools.ietf.org/html/rfc4880#section-5.2.3.6">Key Expiration Time</a>
*/
keyExpirationTime(KEY_EXPIRE_TIME),
/**
* Placeholder for backwards compatibility.
*/
placeholder(PLACEHOLDER),
/**
* Symmetric algorithm numbers that indicate which algorithms the keyholder
* prefers to use. The subpackets body is an ordered list of
* octets with the most preferred listed first. It is assumed that only
* algorithms listed are supported by the recipient's software.
* This is only found on a self-signature.
*
* @see <a href="https://tools.ietf.org/html/rfc4880#section-5.2.3.7">Preferred Symmetric Algorithms</a>
*/
preferredSymmetricAlgorithms(PREFERRED_SYM_ALGS),
/**
* Authorizes the specified key to issue revocation signatures for this
* key. Class octet must have bit 0x80 set. If the bit 0x40 is set,
* then this means that the revocation information is sensitive. Other
* bits are for future expansion to other kinds of authorizations. This
* is found on a self-signature.
*
* If the "sensitive" flag is set, the keyholder feels this subpacket
* contains private trust information that describes a real-world
* sensitive relationship. If this flag is set, implementations SHOULD
* NOT export this signature to other users except in cases where the
* data needs to be available: when the signature is being sent to the
* designated revoker, or when it is accompanied by a revocation
* signature from that revoker. Note that it may be appropriate to
* isolate this subpacket within a separate signature so that it is not
* combined with other subpackets that need to be exported.
*
* @see <a href="https://tools.ietf.org/html/rfc4880#section-5.2.3.15">Revocation Key</a>
*/
revocationKey(REVOCATION_KEY),
/**
* The OpenPGP Key ID of the key issuing the signature.
*
* @see <a href="https://tools.ietf.org/html/rfc4880#section-5.2.3.5">Issuer Key ID</a>
*/
issuerKeyId(ISSUER_KEY_ID),
/**
* This subpacket describes a "notation" on the signature that the
* issuer wishes to make. The notation has a name and a value, each of
* which are strings of octets. There may be more than one notation in
* a signature. Notations can be used for any extension the issuer of
* the signature cares to make. The "flags" field holds four octets of
* flags.
*
* @see <a href="https://tools.ietf.org/html/rfc4880#section-5.2.3.16">Notation Data</a>
*/
notationData(NOTATION_DATA),
/**
* Message digest algorithm numbers that indicate which algorithms the
* keyholder prefers to receive. Like the preferred symmetric
* algorithms, the list is ordered.
* This is only found on a self-signature.
*
* @see <a href="https://tools.ietf.org/html/rfc4880#section-5.2.3.8">Preferred Hash Algorithms</a>
*/
preferredHashAlgorithms(PREFERRED_HASH_ALGS),
/**
* Compression algorithm numbers that indicate which algorithms the
* keyholder prefers to use. Like the preferred symmetric algorithms, the
* list is ordered. If this subpacket is not included, ZIP is preferred.
* A zero denotes that uncompressed data is preferred; the keyholder's
* software might have no compression software in that implementation.
* This is only found on a self-signature.
*
* @see <a href="https://tools.ietf.org/html/rfc4880#section-5.2.3.9">Preferred Compressio Algorithms</a>
*/
preferredCompressionAlgorithms(PREFERRED_COMP_ALGS),
/**
* This is a list of one-bit flags that indicate preferences that the
* keyholder has about how the key is handled on a key server. All
* undefined flags MUST be zero.
* This is found only on a self-signature.
*
* @see <a href="https://tools.ietf.org/html/rfc4880#section-5.2.3.17">Key Server Preferences</a>
*/
keyServerPreferences(KEY_SERVER_PREFS),
/**
* This is a URI of a key server that the keyholder prefers be used for
* updates. Note that keys with multiple User IDs can have a preferred
* key server for each User ID. Note also that since this is a URI, the
* key server can actually be a copy of the key retrieved by ftp, http,
* finger, etc.
*
* @see <a href="https://tools.ietf.org/html/rfc4880#section-5.2.3.18">Preferred Key Server</a>
*/
preferredKeyServers(PREFERRED_KEY_SERV),
/**
* This is a flag in a User ID's self-signature that states whether this
* User ID is the main User ID for this key. It is reasonable for an
* implementation to resolve ambiguities in preferences, etc. by
* referring to the primary User ID. If this flag is absent, its value
* is zero. If more than one User ID in a key is marked as primary, the
* implementation may resolve the ambiguity in any way it sees fit, but
* it is RECOMMENDED that priority be given to the User ID with the most
* recent self-signature.
*
* When appearing on a self-signature on a User ID packet, this
* subpacket applies only to User ID packets. When appearing on a
* self-signature on a User Attribute packet, this subpacket applies
* only to User Attribute packets. That is to say, there are two
* different and independent "primaries" -- one for User IDs, and one
* for User Attributes.
*
* @see <a href="https://tools.ietf.org/html/rfc4880#section-5.2.3.19">Primary User-ID</a>
*/
primaryUserId(PRIMARY_USER_ID),
/**
* This subpacket contains a URI of a document that describes the policy
* under which the signature was issued.
*
* @see <a href="https://tools.ietf.org/html/rfc4880#section-5.2.3.20">Policy URL</a>
*/
policyUrl(POLICY_URL),
/**
* This subpacket contains a list of binary flags that hold information
* about a key. It is a string of octets, and an implementation MUST
* NOT assume a fixed size. This is so it can grow over time. If a
* list is shorter than an implementation expects, the unstated flags
* are considered to be zero.
*
* @see <a href="https://tools.ietf.org/html/rfc4880#section-5.2.3.21">Key Flags</a>
*/
keyFlags(KEY_FLAGS),
/**
* This subpacket allows a keyholder to state which User ID is
* responsible for the signing. Many keyholders use a single key for
* different purposes, such as business communications as well as
* personal communications. This subpacket allows such a keyholder to
* state which of their roles is making a signature.
*
* @see <a href="https://tools.ietf.org/html/rfc4880#section-5.2.3.22">Signer's User ID</a>
*/
signerUserId(SIGNER_USER_ID),
/**
* This subpacket is used only in key revocation and certification
* revocation signatures. It describes the reason why the key or
* certificate was revoked.
*
* The first octet contains a machine-readable code that denotes the
* reason for the revocation:
*
* 0 - No reason specified (key revocations or cert revocations)
* 1 - Key is superseded (key revocations)
* 2 - Key material has been compromised (key revocations)
* 3 - Key is retired and no longer used (key revocations)
* 32 - User ID information is no longer valid (cert revocations)
* 100-110 - Private Use
*
* @see <a href="https://tools.ietf.org/html/rfc4880#section-5.2.3.23">Reason for Revocation</a>
*/
revocationReason(REVOCATION_REASON),
/**
* The Features subpacket denotes which advanced OpenPGP features a
* user's implementation supports. This is so that as features are
* added to OpenPGP that cannot be backwards-compatible, a user can
* state that they can use that feature. The flags are single bits that
* indicate that a given feature is supported.
*
* This subpacket is similar to a preferences subpacket, and only
* appears in a self-signature.
*
* @see <a href="https://tools.ietf.org/html/rfc4880#section-5.2.3.24">Features</a>
*/
features(FEATURES),
/**
* This subpacket identifies a specific target signature to which a
* signature refers. For revocation signatures, this subpacket
* provides explicit designation of which signature is being revoked.
* For a third-party or timestamp signature, this designates what
* signature is signed. All arguments are an identifier of that target
* signature.
*
* The N octets of hash data MUST be the size of the hash of the
* signature. For example, a target signature with a SHA-1 hash MUST
* have 20 octets of hash data.
*
* @see <a href="https://tools.ietf.org/html/rfc4880#section-5.2.3.25">Signature Target</a>
*/
signatureTarget(SIGNATURE_TARGET),
/**
* This subpacket contains a complete Signature packet body as
* specified in Section 5.2 above. It is useful when one signature
* needs to refer to, or be incorporated in, another signature.
*
* @see <a href="https://tools.ietf.org/html/rfc4880#section-5.2.3.26">Embedded Signature</a>
*/
embeddedSignature(EMBEDDED_SIGNATURE),
/**
* The OpenPGP Key fingerprint of the key issuing the signature. This
* subpacket SHOULD be included in all signatures. If the version of
* the issuing key is 4 and an Issuer subpacket is also included in the
* signature, the key ID of the Issuer subpacket MUST match the low 64
* bits of the fingerprint.
*
* Note that the length N of the fingerprint for a version 4 key is 20
* octets; for a version 5 key N is 32.
*
* @see <a href="https://tools.ietf.org/html/draft-ietf-openpgp-rfc4880bis-10#section-5.2.3.28">Issuer Fingerprint</a>
*/
issuerFingerprint(ISSUER_FINGERPRINT),
/**
* AEAD algorithm numbers that indicate which AEAD algorithms the
* keyholder prefers to use. The subpackets body is an ordered list of
* octets with the most preferred listed first. It is assumed that only
* algorithms listed are supported by the recipient's software.
* This is only found on a self-signature.
* Note that support for the AEAD Encrypted Data packet in the general
* is indicated by a Feature Flag.
*
* @see <a href="https://tools.ietf.org/html/draft-ietf-openpgp-rfc4880bis-10#section-5.2.3.8">Preferred AEAD Algorithms</a>
*/
preferredAEADAlgorithms(PREFERRED_AEAD_ALGORITHMS),
/**
* The OpenPGP Key fingerprint of the intended recipient primary key.
* If one or more subpackets of this type are included in a signature,
* it SHOULD be considered valid only in an encrypted context, where the
* key it was encrypted to is one of the indicated primary keys, or one
* of their subkeys. This can be used to prevent forwarding a signature
* outside its intended, encrypted context.
*
* Note that the length N of the fingerprint for a version 4 key is 20
* octets; for a version 5 key N is 32.
*
* @see <a href="https://tools.ietf.org/html/draft-ietf-openpgp-rfc4880bis-10#section-5.2.3.29">Intended Recipient Fingerprint</a>
*/
intendedRecipientFingerprint(INTENDED_RECIPIENT_FINGERPRINT),
/**
* This subpacket MUST only appear as a hashed subpacket of an
* Attestation Key Signature. It has no meaning in any other signature
* type. It is used by the primary key to attest to a set of third-
* party certifications over the associated User ID or User Attribute.
* This enables the holder of an OpenPGP primary key to mark specific
* third-party certifications as re-distributable with the rest of the
* Transferable Public Key (see the "No-modify" flag in "Key Server
* Preferences", above). Implementations MUST include exactly one
* Attested Certification subpacket in any generated Attestation Key
* Signature.
*
* @see <a href="https://tools.ietf.org/html/draft-ietf-openpgp-rfc4880bis-10#section-5.2.3.30">Attested Certification</a>
*/
attestedCertification(ATTESTED_CERTIFICATIONS)
;
private static final Map<Integer, SignatureSubpacket> MAP = new ConcurrentHashMap<>();
static {
for (SignatureSubpacket p : values()) {
MAP.put(p.code, p);
}
}
private final int code;
SignatureSubpacket(int code) {
this.code = code;
}
/**
* Return the numerical identifier of the {@link SignatureSubpacket}.
* @return id
*/
public int getCode() {
return code;
}
/**
* Return the {@link SignatureSubpacket} that corresponds to the provided id.
*
* @param code id
* @return signature subpacket
*/
public static SignatureSubpacket fromCode(int code) {
SignatureSubpacket tag = MAP.get(code);
if (tag == null) {
throw new IllegalArgumentException("No SignatureSubpacket tag found with code " + code);
}
return tag;
}
/**
* Convert an array of signature subpacket tags into a list of {@link SignatureSubpacket SignatureSubpackets}.
*
* @param codes array of codes
* @return list of subpackets
*/
public static List<SignatureSubpacket> fromCodes(int[] codes) {
List<SignatureSubpacket> tags = new ArrayList<>();
for (int code : codes) {
tags.add(fromCode(code));
}
return tags;
}
}