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80 lines
2.7 KiB
Go
80 lines
2.7 KiB
Go
package omemo
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import (
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"fmt"
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"dev.narayana.im/narayana/telegabber/e2ee/omemo/libsignal"
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)
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// Version identifies which OMEMO wire-format generation a message, device
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// list, or bundle uses - the full namespace+XML dialect, not just the
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// underlying crypto-engine version (see libsignal.ProtocolVersionV3/V4,
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// which is a strictly coarser, two-way distinction shared by two of the
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// three versions below).
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type Version int
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const (
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// Omemo0 is the original "siacs" OMEMO (eu.siacs.conversations.axolotl,
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// XEP-0384 <= 0.3.0): libsignal.ProtocolVersionV3, AES-128-GCM directly
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// on the plaintext body, key||tag distributed per-device, <iv> element
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// present. Still the most widely deployed version as of this writing,
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// and the current implementation priority.
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Omemo0 Version = iota
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// Omemo1 is urn:xmpp:omemo:1 (XEP-0384 0.4.0-0.7.x, introduced
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// 2020-03-08): libsignal.ProtocolVersionV4, AES-256-CBC+HMAC-SHA256
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// (via HKDF) over an SCE envelope using the OLD (pre-0.4.0) XEP-0420
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// dialect: root element <content xmlns='urn:xmpp:sce:0'>, inner
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// wrapper <payload/>. Confirmed by reading the archived XEP-0420 0.3.2
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// spec directly (https://xmpp.org/extensions/attic/xep-0420-0.3.2.html),
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// not assumed - see sceEncodeV0/sceDecodeV0.
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Omemo1
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// Omemo2 is urn:xmpp:omemo:2 (XEP-0384 0.8.0+, current spec):
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// libsignal.ProtocolVersionV4, the same AES-256-CBC+HMAC-SHA256 scheme
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// as Omemo1, but over the NEW (XEP-0420 0.4.0+) dialect: root element
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// <envelope xmlns='urn:xmpp:sce:1'>, inner wrapper <content/>.
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Omemo2
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)
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func (v Version) String() string {
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switch v {
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case Omemo0:
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return "omemo0"
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case Omemo1:
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return "omemo1"
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case Omemo2:
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return "omemo2"
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default:
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return "omemo?"
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}
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}
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// ParseVersion maps an e2ee.Variant string (omemo0/omemo1/omemo2 - see
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// Version.String()) back to a Version, at every point the generic
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// e2ee.Backend interface hands one in (DeviceListNode, BundleNode,
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// PublishedIdentity, PublishedBundle).
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func ParseVersion(s string) (Version, error) {
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switch s {
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case "omemo0":
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return Omemo0, nil
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case "omemo1":
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return Omemo1, nil
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case "omemo2":
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return Omemo2, nil
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default:
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return 0, fmt.Errorf("omemo: unknown version %q (want omemo0, omemo1, or omemo2)", s)
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}
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}
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// libsignalVersion returns the underlying Signal-protocol wire version
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// this OMEMO version uses. Omemo1 and Omemo2 share the same crypto-engine
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// version - libomemo-c itself only branches on "message_version >= 4", not
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// on which OMEMO namespace is in play (confirmed by reading protocol.c) -
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// they differ only in the outer XML/SCE dialect (see envelope.go).
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func (v Version) libsignalVersion() int {
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if v == Omemo0 {
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return libsignal.ProtocolVersionV3
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}
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return libsignal.ProtocolVersionV4
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}
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