From e73040d0bfad0cca0f25f78f896d3043277f8204 Mon Sep 17 00:00:00 2001
From: Karol <2004karol@gmail.com>
Date: Mon, 21 Jun 2021 13:59:06 +0200
Subject: [PATCH] [lib] Fix pipes and redirections

Right after running  fork() child doesn't know if it is "part of pipe".
However at the time of running execve() process already know if it is "part of pipe" or not.
---
 lib/bash/src/nhi.c | 35 ++++++++++++++++++++++++++---------
 1 file changed, 26 insertions(+), 9 deletions(-)

diff --git a/lib/bash/src/nhi.c b/lib/bash/src/nhi.c
index 09d24b8..9848520 100644
--- a/lib/bash/src/nhi.c
+++ b/lib/bash/src/nhi.c
@@ -28,6 +28,8 @@ int bash_history_fd;
 
 bool completion, long_completion, after_question;
 
+bool *is_stdout_terminal, *is_stderr_terminal;
+
 /*
  * set_is_bash checks if current process is bash and
  * if so sets is_bash global variable to true
@@ -269,6 +271,9 @@ pid_t fork(void)
     sem_t *sem = mmap(NULL, sizeof(sem_t), PROT_READ|PROT_WRITE, MAP_SHARED|MAP_ANONYMOUS, -1, 0);
     sem_init(sem, 1, 0);
 
+    is_stdout_terminal = mmap(NULL, sizeof(bool), PROT_READ|PROT_WRITE, MAP_SHARED|MAP_ANONYMOUS, -1, 0);
+    is_stderr_terminal = mmap(NULL, sizeof(bool), PROT_READ|PROT_WRITE, MAP_SHARED|MAP_ANONYMOUS, -1, 0);
+
     pid_t tracer_pid = original_fork();
     if (!tracer_pid) {
       /*
@@ -286,14 +291,6 @@ pid_t fork(void)
 
       add_start_time(db, table_name);
 
-      bool is_stdout_terminal, is_stderr_terminal;
-      if (isatty(STDOUT_FILENO)) {
-        is_stdout_terminal = true;
-      }
-      if (isatty(STDERR_FILENO)) {
-        is_stderr_terminal = true;
-      }
-
       pid_t tracee_pid = getppid();
 
       int wstatus;
@@ -308,6 +305,8 @@ pid_t fork(void)
         waitpid(tracee_pid, &wstatus, 0);
 
         if (errno == ECHILD) {
+          munmap(is_stdout_terminal, sizeof(bool));
+          munmap(is_stderr_terminal, sizeof(bool));
           break;
         }
 
@@ -322,7 +321,7 @@ pid_t fork(void)
         struct user_regs_struct regs;
         ptrace(PTRACE_GETREGS, tracee_pid, NULL, &regs);
         if (regs.orig_rax == SYS_write &&
-            ((regs.rdi == STDOUT_FILENO && is_stdout_terminal) || (regs.rdi == STDERR_FILENO && is_stderr_terminal))) {
+            ((regs.rdi == STDOUT_FILENO && *is_stdout_terminal) || (regs.rdi == STDERR_FILENO && *is_stderr_terminal))) {
           /*
            * Quick solution for receiving the same syscall 2 times in a row
            * When I have more free time I will try to figure it out and fix it in more elegant way.
@@ -357,3 +356,21 @@ pid_t fork(void)
   }
   return tracee_pid;
 }
+
+/*
+ * execve sets "inter-process" variables indicating if fd refers to tty and executes original shared library call.
+ * execve is used by bash to execute program(s) defined in command.
+ */
+int execve(const char *pathname, char *const argv[], char *const envp[])
+{
+  if (isatty(STDOUT_FILENO)) {
+    *is_stdout_terminal = true;
+  }
+  if (isatty(STDERR_FILENO)) {
+    *is_stderr_terminal = true;
+  }
+
+  int (*original_execve)() = (int (*)())dlsym(RTLD_NEXT, "execve");
+  int status = original_execve(pathname, argv, envp);
+  return status;
+}