Unix Systems Programming: Communication, Concurrency

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After a successful return from dup () or dup2 (),the old and new file descriptors may be used interchangeably. RETURN VALUES. If successful, dup2() returns a nonnegative integer; namely, the duplicated file descriptor, which is the lowest available descriptor. If failed, it returns a -1 and sets errno to the corresponding value.. EBADF .

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mov ebx, eax ; client_fd. dup2: mov al, 0x3f ; systemcall dup2. int 0x80. dec ecx. jns dup2. ;execve( "/bin/sh", NULL, NULL );.

I think (but am not 100% positive) that's subject to a race condition: the EINTR may indicate that the implicit close() was interrupted by a signal.

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int 0x80. ; dup2 demo->stdout. dec ebx.

segmentation fault in port-binding shellcode - Stack Overflow

https://www.andreafortuna.org/2018/02/05/some-thoughts dup2() The dup2() system call performs the same task as dup(), but instead of using the lowest-numbered unused file descriptor, it uses the file descriptor number specified in newfd. If the file descriptor newfd was previously open, it is silently closed before being reused. Se hela listan på linux.die.net The close-on-exec flag (FD_CLOEXEC ; see fcntl (2)) for the duplicate descriptor is off. dup2 () The dup2 () system call performs the same task as dup (), but instead of using the lowest-numbered unused file descriptor, it uses the descriptor number specified in newfd.

SYNOPSIS [Toc] [Back] . #include int dup(int oldfd); int dup2(int oldfd, int newfd);  Chapter 5 Question 4 Linux Programming Interface - Michael Kerrisk. Implement dup() and dup2() using fcntl() and, where necessary, close(). (You may ignore  EBUSY (Linux only) This may be returned by dup2() or dup3() during a race condition with open(2) and dup Note that we perform our dup2 call in the child so   Jul 9, 2020 But now I need to redirect stderr/stdout of the executed program into some file. It's obvious, that I should use some sort of dup2 Linux call after  dup, dup2 - 複製一個文件描述符SYNOPSIS #include int dup(int oldfd); int dup2( int oldfd, int newfd); DESCRIPTION dup () and dup2 () create a copy of the file  #include int dup2(int filedes, int filedes2); /* returns new file descriptor dup2() causes the file descriptor filedes2 to reference the same file as filedes . Programming in the UNIX Environment", by Richard Program 2: Program to use dup2() system call in linux to duplicate a file descriptor.
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The dup2() function has the advantage over its predecessor of closing and duplicating the file descriptor as a single atomic action.

int dup(int fd); // 复制一个已经存在的文件描述符，如果成功，返回复制成功后的文件描述符，失败返回-1 Linux/x86 - dup2(0,0) + dup2(0,1) + dup2(0,2) Shellcode (15 bytes).. shellcode exploit for Linux_x86 platform Linux Shell 1>devnull 2>&1 含义. dup2(1,2)open(file) ==3dup2(3,1)可以考虑一下不同的dup2()调用序列会产生怎样的文件共享结构。 (Linux seulement) Cette valeur peut être renvoyée par dup2() ou dup3() lors d’une concurrence critique avec open(2) et dup().
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EINTR The dup2() or dup3() call was interrupted by a signal; see signal(7). EINVAL (dup3()) flags contain an invalid value. EINVAL (dup3()) oldfd was equal to newfd. EMFILE The dup () and dup2 () functions provide an alternative interface to the service provided by fcntl () using the F_DUPFD command. dup2 () makes newfd be the copy of oldfd, closing newfd first if necessary. In this video, we illusrate the basics of dup() and dup2() and how you can use these system calls to modify the file descriptors of your system. Modifying th dup2()¶ The dup2() system call performs the same task as dup(), but instead of using the lowest-numbered unused file descriptor, it uses the file descriptor number specified in newfd.

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int 0x80. ; dup2 demo->stdout. dec ebx. runt om, nu är det så att jag ville lek lite med consolen i Linux via c++. the pipe since the child's fd is read-only dup2(fd[READ], 0); //Redirect  164, -extern ssize_t pwrite64(int, const void *, size_t, off64_t);.

However, sometimes there are other bottlenecks like memory or disk space. Aug 30, 2020 Using dup2() to redirect output. Sometimes, you want to redirect the output of your program to a file–maybe to record it for another program,  dup, dup2, dup3 − duplicate a file descriptor int dup2(int oldfd, int newfd); ( Linux only) This may be returned by dup2() or dup3() during a race condition  Linux/x86 - Reverse (192.168.227.129:4444/TCP) Shell (/bin/sh) oldfd, int newfd); dup2(sock_file_des, 0); // stdin dup2(sock_file_des,  Linux/x86 - Bind (1472/TCP) Shell (/bin/sh) + IPv6 Shellcode (1250 int 80h ;dup2(sd,1) xor eax,eax inc ecx mov ebx,esi mov al,63 int 80h  close(pp[0]) mov ebx, [ebp-8] mov al, byte 6h int 80h ; close(); ; dup2(pp[1], 0); dup2(pp[1], 1); dup2(pp[1], 2); lea ecx, [zero_reg+3] ; pp[1] == pp[0]+1 inc ebx .1:  egrep "execve|dup2|socketcall" /usr/include/i386-linux-gnu/asm/unistd_32.h #define __NR_execve 11 #define __NR_dup2 63 #define  egrep "execve|dup2|socketcall" /usr/include/i386-linux-gnu/asm/unistd_32.h #define __NR_execve 11 #define __NR_dup2 63 #define  sub ecx, 3 ; ecx = 2. mov ebx, eax ; client_fd. dup2: mov al, 0x3f ; systemcall dup2. int 0x80. dec ecx.