diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/Makefile.am | 1 | ||||
| -rw-r--r-- | src/exec.c | 238 |
2 files changed, 239 insertions, 0 deletions
diff --git a/src/Makefile.am b/src/Makefile.am index 99432811..eeb3f7df 100644 --- a/src/Makefile.am +++ b/src/Makefile.am @@ -27,6 +27,7 @@ libosmocore_la_SOURCES = context.c timer.c timer_gettimeofday.c timer_clockgetti tdef.c \ sockaddr_str.c \ use_count.c \ + exec.c \ $(NULL) if HAVE_SSSE3 diff --git a/src/exec.c b/src/exec.c new file mode 100644 index 00000000..a9d8ce0f --- /dev/null +++ b/src/exec.c @@ -0,0 +1,238 @@ +/* (C) 2019 by Harald Welte <laforge@gnumonks.org> + * + * All Rights Reserved + * + * SPDX-License-Identifier: GPL-2.0+ + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License along + * with this program; if not, write to the Free Software Foundation, Inc., + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. + * + */ + +#include "config.h" +#ifndef EMBEDDED + +#include <unistd.h> + +#include <errno.h> +#include <string.h> + +#include <stdio.h> +#include <dirent.h> +#include <sys/types.h> + +#include <osmocom/core/logging.h> +#include <osmocom/core/utils.h> +#include <osmocom/core/exec.h> + +/*! suggested list of environment variables to pass (if they exist) to a sub-process/script */ +const char *osmo_environment_whitelist[] = { + "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 +}; + +static bool str_in_list(const char **list, const char *key) +{ + const char **ent; + + for (ent = list; *ent; ent++) { + if (!strcmp(*ent, key)) + return true; + } + return false; +} + +/*! 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. + * + * \oaram[out] out caller-allocated array of pointers for the generated output + * \param[in] out_len size of out (number of pointers) + * \param[in] in input environment (NULL-terminated list of pointers like **environ) + * \param[in] whitelist whitelist of permitted keys in environment (like **environ) + * \returns number of entries filled in 'out'; negtive on error */ +int osmo_environment_filter(char **out, size_t out_len, char **in, const char **whitelist) +{ + char tmp[256]; + char **ent; + size_t out_used = 0; + + /* invalid calls */ + if (!out || out_len == 0 || !whitelist) + return -EINVAL; + + /* legal, but unusual: no input to filter should generate empty, terminated out */ + if (!in) { + out[0] = NULL; + return 1; + } + + /* iterate over input entries */ + for (ent = in; *ent; ent++) { + char *eq = strchr(*ent, '='); + unsigned long eq_pos; + if (!eq) { + /* no '=' in string, skip it */ + continue; + } + eq_pos = eq - *ent; + if (eq_pos >= ARRAY_SIZE(tmp)) + continue; + strncpy(tmp, *ent, eq_pos); + tmp[eq_pos] = '\0'; + if (str_in_list(whitelist, tmp)) { + if (out_used == out_len-1) + break; + /* append to output */ + out[out_used++] = *ent; + } + } + OSMO_ASSERT(out_used < out_len); + out[out_used++] = NULL; + return out_used; +} + +/*! 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. + * + * \oaram[out] out caller-allocated array of pointers for the generated output + * \param[in] out_len size of out (number of pointers) + * \param[in] in input environment (NULL-terminated list of pointers like **environ) + * \returns number of entries filled in 'out'; negative on error */ +int osmo_environment_append(char **out, size_t out_len, char **in) +{ + size_t out_used = 0; + + if (!out || out_len == 0) + return -EINVAL; + + /* seek to end of existing output */ + for (out_used = 0; out[out_used]; out_used++) {} + + if (!in) { + if (out_used == 0) + out[out_used++] = NULL; + return out_used; + } + + for (; *in && out_used < out_len-1; in++) + out[out_used++] = *in; + + OSMO_ASSERT(out_used < out_len); + out[out_used++] = NULL; + + return out_used; +} + +/* Iterate over files in /proc/self/fd and close all above lst_fd_to_keep */ +int osmo_close_all_fds_above(int last_fd_to_keep) +{ + struct dirent *ent; + DIR *dir; + int rc; + + dir = opendir("/proc/self/fd"); + if (!dir) { + LOGP(DLGLOBAL, LOGL_ERROR, "Cannot open /proc/self/fd: %s\n", strerror(errno)); + return -ENODEV; + } + + while ((ent = readdir(dir))) { + int fd = atoi(ent->d_name); + if (fd <= last_fd_to_keep) + continue; + if (fd == dirfd(dir)) + continue; + rc = close(fd); + if (rc) + LOGP(DLGLOBAL, LOGL_ERROR, "Error closing fd=%d: %s\n", fd, strerror(errno)); + } + closedir(dir); + return 0; +} + +/* Seems like POSIX has no header file for this, and even glibc + __USE_GNU doesn't help */ +extern char **environ; + +/*! 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 + * + * \param[in] command the shell command to be executed, see system(3) + * \param[in] env_whitelist A white-list of keys for environment variables + * \param[in] addl_env any additional environment variables to be appended + * \returns PID of generated child process; negative on error + */ +int osmo_system_nowait(const char *command, const char **env_whitelist, char **addl_env) +{ + int rc; + + rc = fork(); + if (rc == 0) { + /* we are in the child */ + char *new_env[1024]; + + /* close all file descriptors above stdio */ + osmo_close_all_fds_above(2); + + /* build the new environment */ + if (env_whitelist) + osmo_environment_filter(new_env, ARRAY_SIZE(new_env), environ, env_whitelist); + if (addl_env) + osmo_environment_append(new_env, ARRAY_SIZE(new_env), addl_env); + + /* if we want to behave like system(3), we must go via the shell */ + execle("/bin/sh", "sh", "-c", command, (char *) NULL, new_env); + /* only reached in case of error */ + LOGP(DLGLOBAL, LOGL_ERROR, "Error executing command '%s' after fork: %s\n", + command, strerror(errno)); + return -EIO; + } else { + /* we are in the parent */ + return rc; + } +} + +#endif /* EMBEDDED */ |