process: Provide an abstraction to spawn child processes with redirected I/O
This commit is contained in:
Martin Willi
@@ -0,0 +1,232 @@
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/*
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* Copyright (C) 2014 Martin Willi
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* Copyright (C) 2014 revosec AG
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2 of the License, or (at your
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* option) any later version. See <http://www.fsf.org/copyleft/gpl.txt>.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* for more details.
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*/
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#include "process.h"
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#include <utils/debug.h>
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#include <fcntl.h>
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typedef struct private_process_t private_process_t;
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/**
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* Ends of a pipe()
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*/
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enum {
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PIPE_READ = 0,
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PIPE_WRITE = 1,
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PIPE_ENDS,
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};
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#ifndef WIN32
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#include <unistd.h>
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#include <errno.h>
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#include <sys/wait.h>
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/**
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* Private data of an process_t object.
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*/
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struct private_process_t {
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/**
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* Public process_t interface.
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*/
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process_t public;
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/**
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* child stdin pipe
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*/
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int in[PIPE_ENDS];
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/**
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* child stdout pipe
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*/
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int out[PIPE_ENDS];
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/**
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* child stderr pipe
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*/
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int err[PIPE_ENDS];
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/**
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* child process
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*/
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int pid;
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};
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/**
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* Close a file descriptor if it is not -1
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*/
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static void close_if(int *fd)
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{
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if (*fd != -1)
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{
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close(*fd);
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*fd = -1;
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}
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}
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/**
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* Destroy a process structure, close all pipes
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*/
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static void process_destroy(private_process_t *this)
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{
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close_if(&this->in[PIPE_READ]);
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close_if(&this->in[PIPE_WRITE]);
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close_if(&this->out[PIPE_READ]);
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close_if(&this->out[PIPE_WRITE]);
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close_if(&this->err[PIPE_READ]);
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close_if(&this->err[PIPE_WRITE]);
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free(this);
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}
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METHOD(process_t, wait_, bool,
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private_process_t *this, int *code)
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{
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int status, ret;
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ret = waitpid(this->pid, &status, 0);
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process_destroy(this);
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if (ret == -1)
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{
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return FALSE;
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}
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if (!WIFEXITED(status))
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{
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return FALSE;
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}
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if (code)
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{
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*code = WEXITSTATUS(status);
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}
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return TRUE;
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}
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/**
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* See header
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*/
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process_t* process_start(char *const argv[], char *const envp[],
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int *in, int *out, int *err, bool close_all)
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{
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private_process_t *this;
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char *empty[] = { NULL };
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INIT(this,
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.public = {
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.wait = _wait_,
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},
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.in = { -1, -1 },
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.out = { -1, -1 },
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.err = { -1, -1 },
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);
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if (in && pipe(this->in) != 0)
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{
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DBG1(DBG_LIB, "creating stdin pipe failed: %s", strerror(errno));
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process_destroy(this);
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return NULL;
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}
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if (out && pipe(this->out) != 0)
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{
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DBG1(DBG_LIB, "creating stdout pipe failed: %s", strerror(errno));
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process_destroy(this);
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return NULL;
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}
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if (err && pipe(this->err) != 0)
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{
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DBG1(DBG_LIB, "creating stderr pipe failed: %s", strerror(errno));
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process_destroy(this);
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return NULL;
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}
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this->pid = fork();
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switch (this->pid)
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{
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case -1:
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DBG1(DBG_LIB, "forking process failed: %s", strerror(errno));
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process_destroy(this);
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return NULL;
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case 0:
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/* child */
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close_if(&this->in[PIPE_WRITE]);
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close_if(&this->out[PIPE_READ]);
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close_if(&this->err[PIPE_READ]);
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if (this->in[PIPE_READ] != -1)
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{
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if (dup2(this->in[PIPE_READ], 0) == -1)
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{
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raise(SIGKILL);
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}
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}
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if (this->out[PIPE_WRITE] != -1)
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{
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if (dup2(this->out[PIPE_WRITE], 1) == -1)
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{
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raise(SIGKILL);
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}
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}
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if (this->err[PIPE_WRITE] != -1)
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{
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if (dup2(this->err[PIPE_WRITE], 2) == -1)
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{
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raise(SIGKILL);
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}
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}
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if (close_all)
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{
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closefrom(3);
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}
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if (execve(argv[0], argv, envp ?: empty) == -1)
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{
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raise(SIGKILL);
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}
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/* not reached */
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default:
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/* parent */
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close_if(&this->in[PIPE_READ]);
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close_if(&this->out[PIPE_WRITE]);
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close_if(&this->err[PIPE_WRITE]);
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if (in)
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{
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*in = this->in[PIPE_WRITE];
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this->in[PIPE_WRITE] = -1;
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}
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if (out)
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{
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*out = this->out[PIPE_READ];
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this->out[PIPE_READ] = -1;
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}
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if (err)
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{
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*err = this->err[PIPE_READ];
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this->err[PIPE_READ] = -1;
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}
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return &this->public;
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}
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}
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#else /* WIN32 */
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/**
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* See header
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*/
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process_t* process_start(char *const argv[], char *const envp[],
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int *in, int *out, int *err, bool close_all)
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{
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return NULL;
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}
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#endif /* WIN32 */
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@@ -0,0 +1,80 @@
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/*
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* Copyright (C) 2014 Martin Willi
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* Copyright (C) 2014 revosec AG
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2 of the License, or (at your
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* option) any later version. See <http://www.fsf.org/copyleft/gpl.txt>.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* for more details.
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*/
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/**
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* @defgroup process process
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* @{ @ingroup utils
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*/
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#ifndef PROCESS_H_
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#define PROCESS_H_
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#include <utils/utils.h>
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typedef struct process_t process_t;
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/**
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* Child process spawning abstraction
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*/
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struct process_t {
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/**
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* Wait for a started process to terminate.
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*
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* The process object gets destroyed by this call, regardless of the
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* return value.
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*
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* The returned code is the exit code, not the status returned by waitpid().
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* If the program could not be executed or has terminated abnormally
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* (by signals etc.), FALSE is returned.
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*
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* @param code process exit code, set only if TRUE returned
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* @return TRUE if program exited normally through exit()
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*/
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bool (*wait)(process_t *this, int *code);
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};
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/**
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* Spawn a child process with redirected I/O.
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*
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* Forks the current process, optionally redirects stdin/out/err to the current
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* process, and executes the provided program with arguments.
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*
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* The process to execute is specified as argv[0], followed by the process
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* arguments, followed by NULL. envp[] has a NULL terminated list of arguments
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* to invoke the process with.
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*
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* If any of in/out/err is given, stdin/out/err from the child process get
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* connected over pipe()s to the caller. If close_all is TRUE, all other
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* open file descriptors get closed, regardless of any CLOEXEC setting.
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*
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* A caller must close all of the returned file descriptors to avoid file
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* descriptor leaks.
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*
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* A non-NULL return value does not guarantee that the process has been
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* invoked successfully.
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*
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* @param argv NULL terminated process arguments, with argv[0] as program
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* @param envp NULL terminated list of environment variables
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* @param in pipe fd returned for redirecting data to child stdin
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* @param out pipe fd returned to redirect child stdout data to
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* @param err pipe fd returned to redirect child stderr data to
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* @param close_all close all open file descriptors above 2 before execve()
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* @return process, NULL on failure
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*/
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process_t* process_start(char *const argv[], char *const envp[],
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int *in, int *out, int *err, bool close_all);
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#endif /** PROCESS_H_ @}*/
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