Fix SendPacketType to not advance state when negotiation fails

SendPacketType() set the state to SFTP_SEND_PACKET even when
wolfSSH_SFTP_negotiate() returned a retry or an error. No request
buffer was built in that case, so an empty buffer was sent and the
caller could wait for a response to a request that was never sent.

Move to SFTP_SEND_PACKET only when the request has been
built, and return the negotiation result otherwise. Keep the state
for retryable errors.

Add the wolfSSH_TestSftpSendPacketType() test hook and an API test
that fails without this change.

F-13904

src/wolfsftp.c

@@ -711,6 +711,15 @@ int wolfSSH_TestSftpRecvSizeCheck(int sz)
 {
     return SFTP_CheckRecvSz(sz);
 }
+
+
+/* Test hook: exposes the static SendPacketType() so the unit tests can
+ * check that no request is sent when SFTP negotiation did not succeed. */
+int wolfSSH_TestSftpSendPacketType(WOLFSSH* ssh, byte type, byte* buf,
+        word32 bufSz)
+{
+    return SendPacketType(ssh, type, buf, bufSz);
+}
 #endif
 
 
@@ -6905,8 +6914,15 @@ int SendPacketType(WOLFSSH* ssh, byte type, byte* buf, word32 bufSz)
 
                 /* reset state for sending data */
                 wolfSSH_SFTP_buffer_rewind(&state->buffer);
+                state->state = SFTP_SEND_PACKET;
             }
-            state->state = SFTP_SEND_PACKET;
+            else {
+                if(!NoticeError(ssh)){
+                    wolfSSH_SFTP_ClearState(ssh, STATE_ID_SEND);
+                }
+                return ret;
+            }
+
             FALL_THROUGH;
 
         case SFTP_SEND_PACKET:

tests/api.c

@@ -6267,6 +6267,32 @@ static void test_wolfSSH_SFTP_SaveOfst(void)
 }
 
 
+/* SendPacketType must not send a request when negotiation did not succeed */
+static void test_wolfSSH_SFTP_SendPacketType_negotiate(void)
+{
+#ifdef WOLFSSH_TEST_INTERNAL
+    WOLFSSH_CTX* ctx = NULL;
+    WOLFSSH*     ssh = NULL;
+    byte         payload[4] = { 0x00, 0x01, 0x02, 0x03 };
+    int          ret;
+
+    AssertNotNull(ctx = wolfSSH_CTX_new(WOLFSSH_ENDPOINT_CLIENT, NULL));
+    AssertNotNull(ssh = wolfSSH_new(ctx));
+
+    ret = wolfSSH_TestSftpSendPacketType(ssh, WOLFSSH_FTP_REALPATH,
+            payload, (word32)sizeof(payload));
+
+    /* The SFTP connection was not established, so negotiation cannot succeed.
+     * SendPacketType() must report that failure instead of returning WS_SUCCESS */
+    AssertIntNE(ret, WS_SUCCESS);
+
+    wolfSSH_free(ssh);
+    wolfSSH_CTX_free(ctx);
+#endif /* WOLFSSH_TEST_INTERNAL */
+}
+
+
+
 #if !defined(NO_FILESYSTEM) && !defined(WOLFSSH_USER_FILESYSTEM) && \
     !defined(WOLFSSH_ZEPHYR)
 
@@ -6690,6 +6716,7 @@ static void test_wolfSSH_SFTP_StartPathNotConfined(void) { ; }
 static void test_wolfSSH_SFTP_SetConfinePath(void) { ; }
 static void test_wolfSSH_SFTP_SetDefaultPath(void) { ; }
 static void test_wolfSSH_SFTP_SaveOfst(void) { ; }
+static void test_wolfSSH_SFTP_SendPacketType_negotiate(void) { ; }
 static void test_wolfSSH_SFTP_PutResume(void) { ; }
 static void test_wolfSSH_SFTP_GetResume(void) { ; }
 #endif /* WOLFSSH_SFTP && !NO_WOLFSSH_CLIENT && !SINGLE_THREADED */
@@ -8823,6 +8850,7 @@ int wolfSSH_ApiTest(int argc, char** argv)
     test_wolfSSH_SFTP_SetConfinePath();
     test_wolfSSH_SFTP_SetDefaultPath();
     test_wolfSSH_SFTP_SaveOfst();
+    test_wolfSSH_SFTP_SendPacketType_negotiate();
     test_wolfSSH_SFTP_PutResume();
     test_wolfSSH_SFTP_GetResume();
 

wolfssh/wolfsftp.h

@@ -360,6 +360,8 @@ WOLFSSH_LOCAL void wolfSSH_SFTP_ShowSizes(void);
             WS_SFTP_FILEATRB* atr, word32* idx);
     WOLFSSH_API int wolfSSH_TestSftpSendCap(WOLFSSH* ssh, word32 cap);
     WOLFSSH_API int wolfSSH_TestSftpStallPending(WOLFSSH* ssh, word32 count);
+    WOLFSSH_API int wolfSSH_TestSftpSendPacketType(WOLFSSH* ssh, byte type,
+           byte* buf, word32 bufSz);
     #if !defined(NO_WOLFSSH_SERVER) && !defined(NO_FILESYSTEM)
         WOLFSSH_API int wolfSSH_SFTP_TestRecvStateInit(WOLFSSH* ssh);
         WOLFSSH_API const byte* wolfSSH_SFTP_TestRecvReply(WOLFSSH* ssh,