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fix: reject service messages while keying #1200

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Merged
philljj merged 1 commit into from
Aug 28, 2026
Merged

fix: reject service messages while keying #1200

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26 changes: 22 additions & 4 deletions src/internal.c
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Original file line number Diff line number Diff line change
Expand Up @@ -710,6 +710,15 @@ INLINE static int IsMessageAllowedServer(WOLFSSH *ssh, byte msg)
}

if (msg == MSGID_SERVICE_REQUEST) {
/* RFC 4253 section 7.1: no service request once the peer's KEXINIT
* lands. acceptState doesn't track a rekey. */
if (ssh->isKeying & WOLFSSH_PEER_IS_KEYING) {
WLOG(WS_LOG_DEBUG, "Message ID %u not allowed by %s %s",
msg, "server", "when keying");
ssh->error = WS_MSGID_NOT_ALLOWED_E;
return 0;
}

if (ssh->acceptState == ACCEPT_KEYED) {
return 1;
}
Expand All @@ -732,7 +741,7 @@ INLINE static int IsMessageAllowedServer(WOLFSSH *ssh, byte msg)
if (msg == MSGID_KEXINIT) {
WLOG(WS_LOG_DEBUG, "Message ID %u not allowed by %s %s",
msg, "server", "when keying");
ssh->error = WS_REKEYING;
ssh->error = WS_MSGID_NOT_ALLOWED_E;
return 0;
}

Expand All @@ -744,7 +753,7 @@ INLINE static int IsMessageAllowedServer(WOLFSSH *ssh, byte msg)
WLOG(WS_LOG_DEBUG,
"Message ID %u not the expected message %u",
msg, ssh->handshake->expectMsgId);
ssh->error = WS_REKEYING;
ssh->error = WS_MSGID_NOT_ALLOWED_E;
return 0;
}
else {
Expand Down Expand Up @@ -823,6 +832,15 @@ INLINE static int IsMessageAllowedClient(WOLFSSH *ssh, byte msg)
}

if (msg == MSGID_SERVICE_ACCEPT) {
/* RFC 4253 section 7.1: no service accept once the peer's KEXINIT
* lands. connectState doesn't track a rekey. */
if (ssh->isKeying & WOLFSSH_PEER_IS_KEYING) {
WLOG(WS_LOG_DEBUG, "Message ID %u not allowed by %s %s",
msg, "client", "when keying");
ssh->error = WS_MSGID_NOT_ALLOWED_E;
return 0;
}

if (ssh->connectState == CONNECT_CLIENT_USERAUTH_REQUEST_SENT) {
return 1;
}
Expand All @@ -845,7 +863,7 @@ INLINE static int IsMessageAllowedClient(WOLFSSH *ssh, byte msg)
if (msg == MSGID_KEXINIT) {
WLOG(WS_LOG_DEBUG, "Message ID %u not allowed by %s %s",
msg, "client", "when keying");
ssh->error = WS_REKEYING;
ssh->error = WS_MSGID_NOT_ALLOWED_E;
return 0;
}

Expand All @@ -857,7 +875,7 @@ INLINE static int IsMessageAllowedClient(WOLFSSH *ssh, byte msg)
WLOG(WS_LOG_DEBUG,
"Message ID %u not the expected message %u",
msg, ssh->handshake->expectMsgId);
ssh->error = WS_REKEYING;
ssh->error = WS_MSGID_NOT_ALLOWED_E;
return 0;
}
else {
Expand Down
93 changes: 93 additions & 0 deletions tests/regress.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2142,6 +2142,39 @@ static void TestChannelAllowedAfterAuth(WOLFSSH* ssh)
}


/* A service accept is allowed only when no key exchange is in flight.
* connectState does not see a rekey, so isKeying is checked too. */
static void TestClientServiceAcceptBlockedDuringKeying(WOLFSSH* ssh)
{
int allowed;

ResetSession(ssh);
ssh->connectState = CONNECT_CLIENT_USERAUTH_REQUEST_SENT;

allowed = wolfSSH_TestIsMessageAllowed(ssh, MSGID_SERVICE_ACCEPT,
WS_MSG_RECV);
AssertTrue(allowed);

/* Same connectState, peer's rekey KEXINIT arrived first. */
ssh->isKeying = WOLFSSH_PEER_IS_KEYING;

allowed = wolfSSH_TestIsMessageAllowed(ssh, MSGID_SERVICE_ACCEPT,
WS_MSG_RECV);
AssertFalse(allowed);
AssertIntEQ(ssh->error, WS_MSGID_NOT_ALLOWED_E);

/* Allowed when only this side has started a rekey: RFC 4253 section 7.1
* requires tolerating what the peer sent before it saw our KEXINIT. */
ResetSession(ssh);
ssh->connectState = CONNECT_CLIENT_USERAUTH_REQUEST_SENT;
ssh->isKeying = WOLFSSH_SELF_IS_KEYING;

allowed = wolfSSH_TestIsMessageAllowed(ssh, MSGID_SERVICE_ACCEPT,
WS_MSG_RECV);
AssertTrue(allowed);
}


/* Drive the whole receive path with a CHANNEL_OPEN sent from a pre-auth
* connectState: no channel created, no reply emitted. The connectState
* gate does the rejecting; isKeying below is scene-setting only. */
Expand Down Expand Up @@ -2300,6 +2333,64 @@ static void TestServerServiceRequestStateGated(WOLFSSH* ssh)
}


/* Drive the receive path with a SERVICE_REQUEST arriving mid-rekey.
* acceptState sits at ACCEPT_KEYED throughout, so only isKeying catches
* it. */
static void TestServerServiceRequestRejectedDuringKeying(void)
{
WOLFSSH_CTX* ctx;
WOLFSSH* ssh;
MemIo io;
byte payload[64];
byte pkt[128];
byte out[128];
word32 pktSz;
word32 idx = 0;

idx = AppendString(payload, sizeof(payload), idx, "ssh-userauth");
pktSz = WrapPacket(MSGID_SERVICE_REQUEST, payload, idx, pkt, sizeof(pkt));

ctx = wolfSSH_CTX_new(WOLFSSH_ENDPOINT_SERVER, NULL);
AssertNotNull(ctx);
wolfSSH_SetIORecv(ctx, MemRecv);
wolfSSH_SetIOSend(ctx, MemSend);

ssh = wolfSSH_new(ctx);
AssertNotNull(ssh);

MemIoInit(&io, pkt, pktSz, out, sizeof(out));
wolfSSH_SetIOReadCtx(ssh, &io);
wolfSSH_SetIOWriteCtx(ssh, &io);

ssh->acceptState = ACCEPT_KEYED;
/* The peer's rekey KEXINIT arrived, its NEWKEYS has not. */
ssh->isKeying = WOLFSSH_PEER_IS_KEYING;

AssertIntEQ(wolfSSH_TestDoReceive(ssh), WS_FATAL_ERROR);
AssertIntEQ(ssh->error, WS_MSGID_NOT_ALLOWED_E);
/* Not dispatched, so acceptState did not advance. */
AssertIntEQ(ssh->clientState, CLIENT_BEGIN);
AssertIntEQ(ssh->acceptState, ACCEPT_KEYED);
/* Nothing emitted in reply. */
AssertIntEQ(io.outSz, 0);

/* Allowed when only this side has started a rekey. */
ssh->error = 0;
ssh->isKeying = WOLFSSH_SELF_IS_KEYING;
AssertTrue(wolfSSH_TestIsMessageAllowed(ssh, MSGID_SERVICE_REQUEST,
WS_MSG_RECV));

/* Allowed once the key exchange is done. */
ssh->error = 0;
ssh->isKeying = 0;
AssertTrue(wolfSSH_TestIsMessageAllowed(ssh, MSGID_SERVICE_REQUEST,
WS_MSG_RECV));

wolfSSH_free(ssh);
wolfSSH_CTX_free(ctx);
}


static void TestChannelOpenCallbackRejectSendsOpenFail(void)
{
ChannelOpenHarness harness;
Expand Down Expand Up @@ -8006,6 +8097,7 @@ int main(int argc, char** argv)
TestChannelBlockedBeforeAuth(ssh);
TestChannelBlockedEveryPreAuthState(ssh);
TestChannelAllowedAfterAuth(ssh);
TestClientServiceAcceptBlockedDuringKeying(ssh);
TestChannelOpenRejectedBeforeKex(CONNECT_CLIENT_KEXINIT_SENT);
TestChannelOpenRejectedBeforeKex(CONNECT_CLIENT_KEXDH_INIT_SENT);
#ifndef NO_WOLFSSH_SERVER
Expand All @@ -8014,6 +8106,7 @@ int main(int argc, char** argv)
TestServerUserauthBlockedBeforeKeyed(serverSsh);
TestServerOnlyUserauthMsgsBlocked(serverSsh);
TestServerServiceRequestStateGated(serverSsh);
TestServerServiceRequestRejectedDuringKeying();
TestChannelOpenCallbackRejectSendsOpenFail();
TestSecondSessionChannelRejected();
TestUsernameChangeDisconnects();
Expand Down
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