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Cover and document the client KEX role check #1223

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Merged
philljj merged 1 commit into from
Sep 3, 2026
Merged

Cover and document the client KEX role check #1223

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8 changes: 7 additions & 1 deletion src/internal.c
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Original file line number Diff line number Diff line change
Expand Up @@ -945,7 +945,13 @@ INLINE static int IsMessageAllowedClient(WOLFSSH *ssh, byte msg)


/* 'state' argument is for if trying to send a message or receive one.
* Returns 1 if allowed 0 if not allowed. */
* Returns 1 if allowed 0 if not allowed.
*
* The side helpers implement the receive policy only; 'state' is unused,
* and both WS_MSG_SEND callers ask about channel messages that no role
* list names. IDs 30 to 49 are per KEX method, so those lists hold for
* the methods in cannedKexAlgoNames, not the ids; RFC 4432 and RFC 4462
* send some of those ids the other way. */
INLINE static int IsMessageAllowed(WOLFSSH *ssh, byte msg, byte state)
{
#ifndef NO_WOLFSSH_SERVER
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27 changes: 27 additions & 0 deletions tests/regress.c
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Expand Up @@ -2274,6 +2274,9 @@ static void TestClientOnlyKexMsgsBlocked(WOLFSSH* ssh)
ssh->isKeying = WOLFSSH_PEER_IS_KEYING;
ssh->handshake = AllocHandshake(ssh);
ssh->handshake->kexId = ID_DH_GEX_SHA256;
/* The client expects no particular message yet, so the expectMsgId
* check cannot catch these, the role check has to. */
AssertIntEQ(ssh->handshake->expectMsgId, MSGID_NONE);

allowed = wolfSSH_TestIsMessageAllowed(ssh, MSGID_KEXDH_INIT,
WS_MSG_RECV);
Expand All @@ -2300,11 +2303,35 @@ static void TestClientOnlyKexMsgsBlocked(WOLFSSH* ssh)
WS_MSG_RECV);
AssertTrue(allowed);
AssertIntEQ(ssh->handshake->expectMsgId, MSGID_NONE);
AssertIntEQ(ssh->error, WS_SUCCESS);

/* 33 sits between the two blocked ids and has to stay allowed. Assert
* it where the client actually expects it, once it has sent its GEX
* init. */
ssh->error = 0;
ssh->handshake->expectMsgId = MSGID_KEXDH_GEX_REPLY;
allowed = wolfSSH_TestIsMessageAllowed(ssh, MSGID_KEXDH_GEX_REPLY,
WS_MSG_RECV);
AssertTrue(allowed);
AssertIntEQ(ssh->handshake->expectMsgId, MSGID_NONE);
AssertIntEQ(ssh->error, WS_SUCCESS);

/* Same answer during a rekey on an established session. */
ssh->error = 0;
ssh->connectState = CONNECT_DONE;

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

ssh->error = 0;
allowed = wolfSSH_TestIsMessageAllowed(ssh, MSGID_KEXDH_GEX_INIT,
WS_MSG_RECV);
AssertFalse(allowed);
AssertIntEQ(ssh->error, WS_MSGID_NOT_ALLOWED_E);

ssh->error = 0;
allowed = wolfSSH_TestIsMessageAllowed(ssh, MSGID_KEXDH_GEX_REQUEST,
WS_MSG_RECV);
AssertFalse(allowed);
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