exec.c File Reference

#include "config.h"
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <stdio.h>
#include <dirent.h>
#include <sys/types.h>
#include <pwd.h>
#include <osmocom/core/logging.h>
#include <osmocom/core/utils.h>
#include <osmocom/core/exec.h>

Macros
#define	_GNU_SOURCE

Functions
static bool	str_in_list (const char **list, const char *key)
int	osmo_environment_filter (char **out, size_t out_len, char **in, const char **whitelist)
	filtered a process environment by whitelist; only copying pointers, no actual strings. More...
int	osmo_environment_append (char **out, size_t out_len, char **in)
	append one environment to another; only copying pointers, not actual strings. More...
int	osmo_close_all_fds_above (int last_fd_to_keep)
int	osmo_system_nowait2 (const char *command, const char **env_whitelist, char **addl_env, const char *user)
	call an external shell command as 'user' without waiting for it. More...
int	osmo_system_nowait (const char *command, const char **env_whitelist, char **addl_env)
	call an external shell command without waiting for it. More...

Variables
const char *	osmo_environment_whitelist []
	suggested list of environment variables to pass (if they exist) to a sub-process/script More...
char **	environ

Macro Definition Documentation

_GNU_SOURCE

#define _GNU_SOURCE

Function Documentation

osmo_close_all_fds_above()

int osmo_close_all_fds_above

(

int

last_fd_to_keep

)

References DLGLOBAL, LOGL_ERROR, and LOGP.

Referenced by osmo_system_nowait2().

osmo_environment_append()

int osmo_environment_append	(	char **	out,
		size_t	out_len,
		char **	in
	)

append one environment to another; only copying pointers, not actual strings.

This function is useful if you'd like to append soem entries to an environment befoer passing it to exec*e() functions.

It will append all entries from 'in' to the environment in 'out', as long as 'out' has space (determined by 'out_len').

Constraints: If the same key exists in 'out' and 'in', duplicate keys are generated. It is a simple append, without any duplicate checks.

Parameters

[out]	out	caller-allocated array of pointers for the generated output
[in]	out_len	size of out (number of pointers)
[in]	in	input environment (NULL-terminated list of pointers like **environ)

Returns

number of entries filled in 'out'; negative on error

References OSMO_ASSERT.

Referenced by osmo_system_nowait2().

osmo_environment_filter()

int osmo_environment_filter	(	char **	out,
		size_t	out_len,
		char **	in,
		const char **	whitelist
	)

filtered a process environment by whitelist; only copying pointers, no actual strings.

This function is useful if you'd like to generate an environment to pass exec*e() functions. It will create a new environment containing only those entries whose keys (as per environment convention KEY=VALUE) are contained in the whitelist. The function will not copy the actual strings, but just create a new pointer array, pointing to the same memory as the input strings.

Constraints: Keys up to a maximum length of 255 characters are supported.

Parameters

[out]	out	caller-allocated array of pointers for the generated output
[in]	out_len	size of out (number of pointers)
[in]	in	input environment (NULL-terminated list of pointers like **environ)
[in]	whitelist	whitelist of permitted keys in environment (like **environ)

Returns

number of entries filled in 'out'; negtive on error

References ARRAY_SIZE, OSMO_ASSERT, and str_in_list().

Referenced by osmo_system_nowait2().

osmo_system_nowait()

int osmo_system_nowait	(	const char *	command,
		const char **	env_whitelist,
		char **	addl_env
	)

call an external shell command without waiting for it.

This mimics the behavior of system(3), with the following differences:

• it doesn't wait for completion of the child process
• it closes all non-stdio file descriptors by iterating /proc/self/fd
• it constructs a reduced environment where only whitelisted keys survive
• it (optionally) appends additional variables to the environment

Parameters

[in]	command	the shell command to be executed, see system(3)
[in]	env_whitelist	A white-list of keys for environment variables
[in]	addl_env	any additional environment variables to be appended

Returns

PID of generated child process; negative on error

References osmo_system_nowait2().

osmo_system_nowait2()

int osmo_system_nowait2	(	const char *	command,
		const char **	env_whitelist,
		char **	addl_env,
		const char *	user
	)

call an external shell command as 'user' without waiting for it.

This mimics the behavior of system(3), with the following differences:

• it doesn't wait for completion of the child process
• it closes all non-stdio file descriptors by iterating /proc/self/fd
• it constructs a reduced environment where only whitelisted keys survive
• it (optionally) appends additional variables to the environment
• it (optionally) changes the user ID to that of 'user' (requires execution as root)

Parameters

[in]	command	the shell command to be executed, see system(3)
[in]	env_whitelist	A white-list of keys for environment variables
[in]	addl_env	any additional environment variables to be appended
[in]	user	name of the user to which we should switch before executing the command

Returns

PID of generated child process; negative on error

References ARRAY_SIZE, DLGLOBAL, environ, LOGL_ERROR, LOGP, osmo_close_all_fds_above(), osmo_environment_append(), and osmo_environment_filter().

Referenced by osmo_system_nowait().

str_in_list()

static bool str_in_list ( const char **  list, const char *  key  )

static

References list.

Referenced by osmo_environment_filter().

Variable Documentation

environ

char** environ

extern

Referenced by osmo_system_nowait2().

osmo_environment_whitelist

const char* osmo_environment_whitelist[]

Initial value:

= {
        "USER", "LOGNAME", "HOME",
        "LANG", "LC_ALL", "LC_COLLATE", "LC_CTYPE", "LC_MESSAGES", "LC_MONETARY", "LC_NUMERIC", "LC_TIME",
        "PATH",
        "PWD",
        "SHELL",
        "TERM",
        "TMPDIR",
        "LD_LIBRARY_PATH",
        "LD_PRELOAD",
        "POSIXLY_CORRECT",
        "HOSTALIASES",
        "TZ", "TZDIR",
        "TERMCAP",
        "COLUMNS", "LINES",
        NULL
}

suggested list of environment variables to pass (if they exist) to a sub-process/script