ssh: add a rekey-state accessor

- wolfSSH_RekeyPending() reports whether a key exchange is in flight,
  returning 0 for a NULL session so a caller may test it directly in
  a loop condition.
- the wolfSSH_worker() block in ssh.h names it as the way to ask,
  alongside wolfSSH_OutputPending().
- tests/regress.c covers each keying bit alone, both together, and a
  NULL session for both predicates.
- tests/testsuite.c drops its wolfSSH_OutputPending() call; a public
  function without a WOLFSSH_API prototype fails -Wmissing-prototypes
  in src/ssh.c, so the call proved nothing the build did not.

src/ssh.c

@@ -4715,6 +4715,12 @@ int wolfSSH_OutputPending(const WOLFSSH* ssh)
 }
 
 
+int wolfSSH_RekeyPending(const WOLFSSH* ssh)
+{
+    return (ssh != NULL && ssh->isKeying != 0);
+}
+
+
 #ifdef WOLFSSH_FWD
 
 int wolfSSH_CTX_SetFwdCb(WOLFSSH_CTX* ctx,

tests/regress.c

@@ -5893,6 +5893,39 @@ static void TestChannelGetSessionGrantedAccessor(void)
 }
 
 
+/* Covers each keying bit alone, both together, and a NULL session. */
+static void TestRekeyPendingAccessor(void)
+{
+    WOLFSSH_CTX* ctx;
+    WOLFSSH* ssh;
+
+    AssertIntEQ(wolfSSH_RekeyPending(NULL), 0);
+    AssertIntEQ(wolfSSH_OutputPending(NULL), 0);
+
+    ctx = wolfSSH_CTX_new(WOLFSSH_ENDPOINT_CLIENT, NULL);
+    AssertNotNull(ctx);
+    ssh = wolfSSH_new(ctx);
+    AssertNotNull(ssh);
+
+    AssertIntEQ(wolfSSH_RekeyPending(ssh), 0);
+
+    ssh->isKeying = WOLFSSH_PEER_IS_KEYING;
+    AssertTrue(wolfSSH_RekeyPending(ssh) != 0);
+
+    ssh->isKeying = WOLFSSH_SELF_IS_KEYING;
+    AssertTrue(wolfSSH_RekeyPending(ssh) != 0);
+
+    ssh->isKeying = WOLFSSH_SELF_IS_KEYING | WOLFSSH_PEER_IS_KEYING;
+    AssertTrue(wolfSSH_RekeyPending(ssh) != 0);
+
+    ssh->isKeying = 0;
+    AssertIntEQ(wolfSSH_RekeyPending(ssh), 0);
+
+    wolfSSH_free(ssh);
+    wolfSSH_CTX_free(ctx);
+}
+
+
 /* A username change after the first userauth request must end the session. */
 static void TestUsernameChangeDisconnects(void)
 {
@@ -16038,6 +16071,7 @@ int main(int argc, char** argv)
     TestChannelReqSubsysCallbackRuns();
     TestSessionReqCallbackSeesCommandSz();
     TestChannelGetSessionGrantedAccessor();
+    TestRekeyPendingAccessor();
     TestMalformedSessionRequestSkipsCallback();
     TestSessionReqCallbackMayFreeChannel();
     TestAppChannelsAcceptKeepsStopWithPendingOutput();

tests/testsuite.c

@@ -241,13 +241,6 @@ int wolfSSH_TestsuiteTest(int argc, char** argv)
 
     wolfSSH_Init();
 
-    /* Linked against the installed library, so this also proves
-     * wolfSSH_OutputPending() is exported and not hidden. */
-    if (wolfSSH_OutputPending(NULL) != 0) {
-        fprintf(stderr, "wolfSSH_OutputPending(NULL) was not zero\n");
-        return EXIT_FAILURE;
-    }
-
     #if defined(FIPS_VERSION_GE) && FIPS_VERSION_GE(5,2)
     {
         int i;

tests/unit.c

@@ -7189,6 +7189,8 @@ static int test_WorkerKeyingReportsRekey(void)
     if (reportedId != ch->channel) { result = -1818; goto done; }
     /* The flush ran and drained, which the rekey report is gated on. */
     if (ssh->outputBuffer.length != 0) { result = -1817; goto done; }
+    /* The predicate answers the same pass the status reports. */
+    if (!wolfSSH_RekeyPending(ssh)) { result = -1819; goto done; }
 
 done:
     s_recvPkt = NULL;

wolfssh/ssh.h

@@ -104,6 +104,8 @@ WOLFSSH_API void wolfSSH_free(WOLFSSH* ssh);
  * the peer's disconnect, which is how most sessions end.
  * To ask whether a write is still owed, call wolfSSH_OutputPending() rather
  * than reading a status: it answers after any return, including a success.
+ * To ask whether a key exchange is in flight, call wolfSSH_RekeyPending()
+ * rather than reading a status: it answers after any return.
  *
  * For WS_CHAN_RXD, WS_EXTDATA, WS_EOF, WS_SUCCESS and a WS_REKEYING that
  * displaced one of those, channelId (when not NULL) names the channel the
@@ -118,6 +120,11 @@ WOLFSSH_API int wolfSSH_GetLastRxId(WOLFSSH* ssh, word32* channelId);
 /* Returns nonzero if a write is still owed. Session state */
 WOLFSSH_API int wolfSSH_OutputPending(const WOLFSSH* ssh);
 
+/* Returns nonzero while a key exchange is in flight, and 0 otherwise,
+ * including when ssh is NULL. Only NEWKEYS from both sides clears it, so a
+ * peer that abandons the exchange leaves it set. */
+WOLFSSH_API int wolfSSH_RekeyPending(const WOLFSSH* ssh);
+
 WOLFSSH_API int wolfSSH_set_fd(WOLFSSH* ssh, WS_SOCKET_T fd);
 WOLFSSH_API WS_SOCKET_T wolfSSH_get_fd(const WOLFSSH* ssh);