diff options
Diffstat (limited to 'src/exec.c')
| -rw-r--r-- | src/exec.c | 67 |
1 files changed, 61 insertions, 6 deletions
@@ -23,6 +23,7 @@ #include "config.h" #ifndef EMBEDDED +#define _GNU_SOURCE #include <unistd.h> #include <errno.h> @@ -31,6 +32,7 @@ #include <stdio.h> #include <dirent.h> #include <sys/types.h> +#include <pwd.h> #include <osmocom/core/logging.h> #include <osmocom/core/utils.h> @@ -192,23 +194,34 @@ int osmo_close_all_fds_above(int last_fd_to_keep) /* 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. +/*! 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) * * \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 + * \param[in] user name of the user to which we should switch before executing the command * \returns PID of generated child process; negative on error */ -int osmo_system_nowait(const char *command, const char **env_whitelist, char **addl_env) +int osmo_system_nowait2(const char *command, const char **env_whitelist, char **addl_env, const char *user) { + struct passwd _pw, *pw; + int getpw_buflen = sysconf(_SC_GETPW_R_SIZE_MAX); int rc; + if (user) { + char buf[getpw_buflen]; + getpwnam_r(user, &_pw, buf, sizeof(buf), &pw); + if (!pw) + return -EINVAL; + } + rc = fork(); if (rc == 0) { /* we are in the child */ @@ -217,11 +230,34 @@ int osmo_system_nowait(const char *command, const char **env_whitelist, char **a /* close all file descriptors above stdio */ osmo_close_all_fds_above(2); + /* man execle: "an array of pointers *must* be terminated by a null pointer" */ + new_env[0] = NULL; + /* 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 (env_whitelist) { + rc = osmo_environment_filter(new_env, ARRAY_SIZE(new_env), environ, env_whitelist); + if (rc < 0) + return rc; + } + if (addl_env) { + rc = osmo_environment_append(new_env, ARRAY_SIZE(new_env), addl_env); + if (rc < 0) + return rc; + } + + /* drop privileges */ + if (pw) { + if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) < 0) { + perror("setresgid() during privilege drop"); + exit(1); + } + + if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) < 0) { + perror("setresuid() during privilege drop"); + exit(1); + } + + } /* if we want to behave like system(3), we must go via the shell */ execle("/bin/sh", "sh", "-c", command, (char *) NULL, new_env); @@ -235,4 +271,23 @@ int osmo_system_nowait(const char *command, const char **env_whitelist, char **a } } +/*! 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) +{ + return osmo_system_nowait2(command, env_whitelist, addl_env, NULL); +} + + #endif /* EMBEDDED */ |