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messages: sign our requests with the public identity, not the IMSI IMPU

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Every request we originated — INVITE, CANCEL, both ACKs, in-dialog BYE and
friends — put the IMSI-derived temporary IMPU in From. 3GPP allows that
identity in REGISTER only; the same lesson was learned for the reg-event
SUBSCRIBE (480) and never carried to calls. Most P-CSCFs overwrite From
and hid it; a Telia node did not, and a reporter's IMSI appeared on the
callee's screen (field report 2026-09-01). A strict P-CSCF may reject the
INVITE outright.

CallerId(): the registered sip: public identity (P-Associated-URI), else
the tel: one, and the temporary IMPU only before either is learned. One
helper feeds all five builders, so a dialog's From never drifts. As UAS the
dialog's local URI is the INVITE's To (RFC 3261 12.2.1.1), stored on the
Dialog, so an incoming call's BYE is signed the way the network addressed
us. The identity is persisted in the state file and restored on warm
resume, so a call placed before the refresh 200 re-learns it cannot fall
back. DUMP_SIP now also writes the last outgoing INVITE
(imsd-invite-out.raw): the one request a field log could never show.

The byte-pinned INVITE fixture moves to the tel: identity its test context
knows; new scenarios cover the sip: identity, the tel: fallback, the
pre-learning case and the UAS BYE.

Bench-verified on KPN 2026-09-08: outgoing INVITE From is the registered
sip: identity, call accepted and carried; caller ID at the far end
unchanged.
This commit is contained in:
Jorijn van der Graaf 2026-09-08 20:37:47 +02:00
commit 7978b94502
6 changed files with 97 additions and 16 deletions
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30
interfaces/Imsd-Messages.cppm
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@ -290,8 +290,28 @@ export namespace imsd::msg {
std::optional<std::string> dialogTo; // remote To/From incl. tag, once known
std::vector<std::string> recordRoute; // route set, UAC order (see DialogRoute)
std::optional<std::string> remoteTarget; // remote Contact URI
std::string localUri; // our URI in this dialog: the UAS takes the
// INVITE's To URI; empty = CallerId(c) (UAC)
};
// The identity we sign our own requests with: the registered public
// identity (P-Associated-URI sip: entry), else the tel: one, and the
// IMSI-derived temporary IMPU only before either is learned. 3GPP allows
// the temporary IMPU in REGISTER alone; a P-CSCF that does not overwrite
// From shows it to the callee (Telia, 2026-09-01: the reporter's IMSI on
// the far phone) and a strict one may reject the request.
inline std::string_view CallerId(const Context& c) {
if (!c.aor.empty()) return c.aor;
if (!c.ppi.empty()) return c.ppi;
return c.id.impu;
}
// From URI of a request inside a dialog (RFC 3261 12.2.1.1: the dialog's
// local URI — as UAS that is the INVITE's To, as UAC our caller identity).
inline std::string_view FromUri(const Context& c, const Dialog& d) {
return d.localUri.empty() ? CallerId(c) : std::string_view(d.localUri);
}
// Dialog route set: the reversed Record-Route, or the registration Route
// when none was recorded (imsd._dialog_route).
inline std::string DialogRoute(const Context& c, const Dialog& d) {
@ -314,7 +334,7 @@ export namespace imsd::msg {
std::format("Via: SIP/2.0/TCP {};branch=z9hG4bK{};rport", imsd::util::HostPort(c.local, c.portUs), d.invBranch),
"Max-Forwards: 70",
std::format("Route: {}", c.route),
std::format("From: <{}>;tag={}", c.id.impu, d.itag),
std::format("From: <{}>;tag={}", FromUri(c, d), d.itag),
std::format("To: <{}>", d.ruri),
std::format("Call-ID: {}", d.callid),
"CSeq: 1 INVITE",
@ -347,7 +367,7 @@ export namespace imsd::msg {
ViaLine(c, "TCP", c.portUs, viaBranch),
"Max-Forwards: 70",
std::format("Route: {}", DialogRoute(c, d)),
std::format("From: <{}>;tag={}", c.id.impu, d.itag),
std::format("From: <{}>;tag={}", FromUri(c, d), d.itag),
std::format("To: {}", to),
std::format("Call-ID: {}", d.callid),
std::format("CSeq: {} {}", cseq, method),
@ -374,7 +394,7 @@ export namespace imsd::msg {
ViaLine(c, "TCP", c.portUs, viaBranch),
"Max-Forwards: 70",
std::format("Route: {}", DialogRoute(c, d)),
std::format("From: <{}>;tag={}", c.id.impu, d.itag),
std::format("From: <{}>;tag={}", FromUri(c, d), d.itag),
std::format("To: {}", to),
std::format("Call-ID: {}", d.callid),
"CSeq: 1 ACK",
@ -391,7 +411,7 @@ export namespace imsd::msg {
std::format("Via: SIP/2.0/TCP {};branch=z9hG4bK{};rport", imsd::util::HostPort(c.local, c.portUs), d.invBranch),
"Max-Forwards: 70",
std::format("Route: {}", c.route),
std::format("From: <{}>;tag={}", c.id.impu, d.itag),
std::format("From: <{}>;tag={}", FromUri(c, d), d.itag),
std::format("To: {}", toHeader),
std::format("Call-ID: {}", d.callid),
"CSeq: 1 ACK",
@ -407,7 +427,7 @@ export namespace imsd::msg {
std::format("Via: SIP/2.0/TCP {};branch=z9hG4bK{};rport", imsd::util::HostPort(c.local, c.portUs), d.invBranch),
"Max-Forwards: 70",
std::format("Route: {}", c.route),
std::format("From: <{}>;tag={}", c.id.impu, d.itag),
std::format("From: <{}>;tag={}", FromUri(c, d), d.itag),
std::format("To: <{}>", d.ruri),
std::format("Call-ID: {}", d.callid),
"CSeq: 1 CANCEL",