exec.c

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/*
 *   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 St, Fifth Floor, Boston, MA 02110-1301, USA
 */
 
/**
 * $Id: 72785d1af35bada4ba37209e16a75f50ba3a4b31 $
 *
 * @file src/lib/server/exec.c
 * @brief Execute external programs.
 *
 * @copyright 2022-2023 Arran Cudbard-Bell (a.cudbardb@freeradius.org)
 * @copyright 2000-2004,2006 The FreeRADIUS server project
 */
RCSID("$Id: 72785d1af35bada4ba37209e16a75f50ba3a4b31 $")
 
#include <stdint.h>
 
#include <freeradius-devel/server/log.h>
#include <freeradius-devel/server/exec.h>
#include <freeradius-devel/server/exec_priv.h>
#include <freeradius-devel/server/main_config.h>
#include <freeradius-devel/server/util.h>
 
#define MAX_ENVP 1024
 
static _Thread_local char *env_exec_arr[MAX_ENVP];      /* Avoid allocing 8k on the stack */
 
/** Flatten a list into individual "char *" argv-style array
 *
 * @param[in] ctx       to allocate boxes in.
 * @param[out] argv_p   where output strings go
 * @param[in] in        boxes to flatten
 * @return
 *      - >= 0 number of array elements in argv
 *      - <0 on error
 */
int fr_exec_value_box_list_to_argv(TALLOC_CTX *ctx, char ***argv_p, fr_value_box_list_t const *in)
{
        char                    **argv;
        unsigned int            i = 0;
        size_t                  argc = fr_value_box_list_num_elements(in);
        fr_value_box_t const    *first;
 
        /*
         *      Check that we're not trying to run a program from
         *      a tainted source.
         */
        first = fr_value_box_list_head(in);
        if (!first) {
        missing:
                fr_strerror_const("No program to run");
                return -1;
        }
        if (first->type == FR_TYPE_GROUP) first = fr_value_box_list_head(&first->vb_group);
        if (!first) goto missing;
        if (first->tainted) {
                fr_strerror_printf("Program to run comes from tainted source - %pV", first);
                return -1;
        }
 
        argv = talloc_zero_array(ctx, char *, argc + 1);
        if (!argv) return -1;
 
        fr_value_box_list_foreach(in, vb) {
                /*
                 *      Print the children of each group into the argv array.
                 */
                argv[i] = fr_value_box_list_aprint(argv, &vb->vb_group, NULL, NULL);
                if (!argv[i]) {
                        talloc_free(argv);
                        return -1;
                }
                i++;
        }
 
        *argv_p = argv;
 
        return argc;
}
 
/** Print debug information showing the arguments and environment for a process
 *
 * @param[in] request           The current request, may be NULL.
 * @param[in] argv_in           arguments to pass to process.
 * @param[in] env_in            environment to pass to process.
 * @param[in] env_inherit       print debug for the environment from the environment.
 */
static inline CC_HINT(always_inline) void exec_debug(request_t *request, char **argv_in, char **env_in, bool env_inherit)
{
        char **p;
 
        if (argv_in) for (p = argv_in; *p; p++) ROPTIONAL(RDEBUG3, DEBUG3, "arg[%d] %s", (unsigned int)(p - argv_in), *p);
        if (env_in) for (p = env_in; *p; p++) ROPTIONAL(RDEBUG3, DEBUG3, "export %s", *p);
        if (env_inherit) for (p = environ; *p; p++) ROPTIONAL(RDEBUG3, DEBUG3, "export %s", *p);
}
 
/** Convert pairs from a request and a list of pairs into environmental variables
 *
 * @param[out] env_p            Where to write an array of \0 terminated strings.
 * @param[in] env_len           Length of env_p.
 * @param[out] env_sbuff        To write environmental variables too. Each variable
 *                              will be written to the buffer, and separated with
 *                              a '\0'.
 * @param[in] env_m             an array of markers of the same length as env_len.
 * @param[in] request           Will look for &control.Exec-Export items to convert to
 *                              env vars.
 * @param[in] env_pairs         Other items to convert to environmental variables.
 *                              The dictionary attribute name will be converted to
 *                              uppercase, and all '-' converted to '_' and will form
 *                              the variable name.
 * @param[in] env_escape        Wrap string values in double quotes, and apply doublequote
 *                              escaping to all environmental variable values.
 * @return
 *      - The number of environmental variables created.
 *      - -1 on failure.
 */
static inline CC_HINT(nonnull(1,3,4,5)) CC_HINT(always_inline)
int exec_pair_to_env(char **env_p, size_t env_len,
                     fr_sbuff_t *env_sbuff, fr_sbuff_marker_t env_m[],
                     request_t *request, fr_pair_list_t *env_pairs, bool env_escape)
{
        char                    *p;
        size_t                  i, j;
        fr_dcursor_t            cursor;
        fr_dict_attr_t const    *da;
        fr_sbuff_t              sbuff = FR_SBUFF_BIND_CURRENT(env_sbuff);
 
        if (!env_pairs) {
                env_p[0] = NULL;
                return 0;
        }
 
        /*
         *      Set up the environment variables in the
         *      parent, so we don't call libc functions that
         *      hold mutexes.  They might be locked when we fork,
         *      and will remain locked in the child.
         */
        i = 0;
        fr_pair_list_foreach_leaf(env_pairs, vp) {
                fr_sbuff_marker(&env_m[i], &sbuff);
 
                if (fr_sbuff_in_strcpy(&sbuff, vp->da->name) <= 0) {
                        fr_strerror_printf("Out of buffer space adding attribute name");
                        return -1;
                }
 
                /*
                 *      POSIX only allows names to contain
                 *      uppercase chars, digits, and
                 *      underscores.  Digits are not allowed
                 *      for the first char.
                 */
                p = fr_sbuff_current(&env_m[i]);
                if (isdigit((uint8_t)*p)) *p++ = '_';
                for (; p < fr_sbuff_current(&sbuff); p++) {
                        if (isalpha((uint8_t)*p)) *p = toupper((uint8_t) *p);
                        else if (*p == '-') *p = '_';
                        else if (isdigit((uint8_t)*p)) goto next;
                        else *p = '_';
                }
 
                if (fr_sbuff_in_char(&sbuff, '=') <= 0) {
                        fr_strerror_printf("Out of buffer space");
                        return -1;
                }
 
                if (env_escape) {
                        if (fr_value_box_print_quoted(&sbuff, &vp->data, T_DOUBLE_QUOTED_STRING) < 0) {
                                fr_strerror_printf("Out of buffer space adding attribute value for %pV", &vp->data);
                                return -1;
                        }
                } else {
                        /*
                         *      This can be zero length for empty strings
                         *
                         *      Note we don't do double quote escaping here,
                         *      we just escape unprintable chars.
                         *
                         *      Environmental variable values are not
                         *      restricted we likely wouldn't need to do
                         *      any escaping if we weren't dealing with C
                         *      strings.
                         *
                         *      If we end up passing binary data through
                         *      then the user can unescape the octal
                         *      sequences on the other side.
                         *
                         *      We unfortunately still need to escape '\'
                         *      because of this.
                         */
                        if (fr_value_box_print(&sbuff, &vp->data, &fr_value_escape_unprintables) < 0) {
                                fr_strerror_printf("Out of buffer space adding attribute value for %pV", &vp->data);
                                return -1;
                        }
                }
                if (fr_sbuff_in_char(&sbuff, '\0') <= 0) {
                        fr_strerror_printf("Out of buffer space");
                        return -1;
                }
 
        next:
                i++;
                if (i == (env_len - 1)) break;
        }
 
        /*
         *      Do this as a separate step so that if env_sbuff
         *      is extended at any point during the conversion
         *      the sbuff we use is the final one.
         */
        for (j = 0; j < i; j++) {
                env_p[j] = fr_sbuff_current(&env_m[j]);
        }
 
        da = fr_dict_attr_child_by_num(fr_dict_root(fr_dict_internal()), FR_EXEC_EXPORT);
        if (da) {
                fr_pair_t *vp;
 
                for (vp = fr_pair_dcursor_by_da_init(&cursor, &request->control_pairs, da);
                     vp;
                     vp = fr_dcursor_next(&cursor)) {
                        env_p[i++] = UNCONST(char *, vp->vp_strvalue);
                }
        }
 
        if (unlikely(i == (env_len - 1))) {
                fr_strerror_printf("Out of space for environmental variables");
                return -1;
        }
 
        /*
         *      NULL terminate for execve
         */
        env_p[i] = NULL;
 
        return i;
}
 
/** Convert env_pairs into an array of environmental variables using thread local buffers
 *
 * @param[in] request           Will be searched for control.Exec-Export pairs.
 * @param[in] env_pairs         env_pairs to put into into the environment.  May be NULL.
 * @param[in] env_escape        Wrap string values in double quotes, and apply doublequote
 *                              escaping to all environmental variable values.
 * @return
 *      - An array of environmental variable definitions, valid until the next call
 *        to fr_exec_pair_to_env within the same thread.
 *      - NULL on error.  Error retrievable fr_strerror().
 */
char **fr_exec_pair_to_env(request_t *request, fr_pair_list_t *env_pairs, bool env_escape)
{
        static _Thread_local char *env_arr[MAX_ENVP];                           /* Avoid allocing 8k on the stack */
        static _Thread_local char env_buff[NUM_ELEMENTS(env_arr) * 128];        /* Avoid allocing 128k on the stack */
        static _Thread_local fr_sbuff_marker_t env_m[NUM_ELEMENTS(env_arr)];
 
        if (exec_pair_to_env(env_arr, NUM_ELEMENTS(env_arr),
                             &FR_SBUFF_OUT(env_buff, sizeof(env_buff)), env_m,
                             request, env_pairs, env_escape) < 0) return NULL;
 
        return env_arr;
}
 
/** Start a child process
 *
 * We try to be fail-safe here. So if ANYTHING goes wrong, we exit with status 1.
 *
 * @param[in] argv              array of arguments to pass to child.
 * @param[in] envp              array of environment variables in form `<attr>=<val>`
 * @param[in] exec_wait         if true, redirect child process' stdin, stdout, stderr
 *                              to the pipes provided, redirecting any to /dev/null
 *                              where no pipe was provided.  If false redirect
 *                              stdin, and stdout to /dev/null.
 * @param[in] debug             If true, and !exec_wait, don't molest stderr.
 * @param[in] stdin_pipe        the pipe used to write data to the process. STDIN will
 *                              be set to stdin_pipe[0], stdin_pipe[1] will be closed.
 * @param[in] stdout_pipe       the pipe used to read data from the process.
 *                              STDOUT will be set to stdout_pipe[1], stdout_pipe[0]
 *                              will be closed.
 * @param[in] stderr_pipe       the pipe used to read error text from the process.
 *                              STDERR will be set to stderr_pipe[1], stderr_pipe[0]
 *                              will be closed.
 */
static NEVER_RETURNS void exec_child(char **argv, char **envp,
                                     bool exec_wait, bool debug,
                                     int stdin_pipe[static 2], int stdout_pipe[static 2], int stderr_pipe[static 2])
{
        int devnull;
 
        /*
         *      Open STDIN to /dev/null
         */
        devnull = open("/dev/null", O_RDWR);
        if (devnull < 0) {
                fprintf(stderr, "Failed opening /dev/null: %s\n", fr_syserror(errno));
 
                /*
                 *      Where the status code is interpreted as a module rcode
                 *      one is subtracted from it, to allow 0 to equal success
                 *
                 *      2 is RLM_MODULE_FAIL + 1
                 */
                exit(2);
        }
 
        /*
         *      Only massage the pipe handles if the parent
         *      has created them.
         */
        if (exec_wait) {
                if (stdin_pipe[1] >= 0) {
                        close(stdin_pipe[1]);
                        dup2(stdin_pipe[0], STDIN_FILENO);
                } else {
                        dup2(devnull, STDIN_FILENO);
                }
 
                if (stdout_pipe[1] >= 0) {
                        close(stdout_pipe[0]);
                        dup2(stdout_pipe[1], STDOUT_FILENO);
                } else {
                        dup2(devnull, STDOUT_FILENO);
                }
 
                if (stderr_pipe[1] >= 0) {
                        close(stderr_pipe[0]);
                        dup2(stderr_pipe[1], STDERR_FILENO);
                } else {
                        dup2(devnull, STDERR_FILENO);
                }
        } else {        /* no pipe, STDOUT should be /dev/null */
                dup2(devnull, STDIN_FILENO);
                dup2(devnull, STDOUT_FILENO);
 
                /*
                 *      If we're not debugging, then we can't do
                 *      anything with the error messages, so we throw
                 *      them away.
                 *
                 *      If we are debugging, then we want the error
                 *      messages to go to the STDERR of the server.
                 */
                if (!debug) dup2(devnull, STDERR_FILENO);
        }
 
        close(devnull);
 
        /*
         *      The server may have MANY FD's open.  We don't
         *      want to leave dangling FD's for the child process
         *      to play funky games with, so we close them.
         */
        fr_closefrom(STDERR_FILENO + 1);
 
        /*
         *      Disarm the thread local destructors
         *
         *      It's not safe to free memory between fork and exec.
         */
        fr_atexit_thread_local_disarm_all();
 
        /*
         *      Disarm the global destructors for the same reason
         */
        fr_atexit_global_disarm_all();
 
        /*
         *      I swear the signature for execve is wrong and should
         *      take 'char const * const argv[]'.
         *
         *      Note: execve(), unlike system(), treats all the space
         *      delimited arguments as literals, so there's no need
         *      to perform additional escaping.
         */
        execve(argv[0], argv, envp);
        printf("Failed to execute \"%s\": %s", argv[0], fr_syserror(errno)); /* fork output will be captured */
 
        /*
         *      Where the status code is interpreted as a module rcode
         *      one is subtracted from it, to allow 0 to equal success
         *
         *      2 is RLM_MODULE_FAIL + 1
         */
        exit(2);
}
 
/** Merge extra environmental variables and potentially the inherited environment
 *
 * @param[in] env_in            to merge.
 * @param[in] env_inherit       inherite environment from radiusd.
 * @return merged environmental variables.
 */
static
char **exec_build_env(char **env_in, bool env_inherit)
{
        size_t num_in, num_environ;
 
        /*
         *      Not inheriting the radiusd environment, just return whatever we were given.
         */
        if (!env_inherit) {
                return env_in;
        }
 
        /*
         *      No additional environment variables, just return the ones from radiusd.
         */
        if (!env_in) return environ;
 
        for (num_environ = 0; environ[num_environ] != NULL; num_environ++) {
                /* nothing */
        }
 
        /*
         *      No room to copy anything after the environment variables.
         */
        if (((num_environ + 1) >= NUM_ELEMENTS(env_exec_arr))) {
                return environ;
        }
 
        /*
         *      Copy the radiusd environment to the local array
         */
        memcpy(env_exec_arr, environ, (num_environ + 1) * sizeof(environ[0]));
 
        for (num_in = 0; env_in[num_in] != NULL; num_in++) {
                if ((num_environ + num_in + 1) >= NUM_ELEMENTS(env_exec_arr)) break;
        }
 
        memcpy(env_exec_arr + num_environ, env_in, num_in * sizeof(environ[0]));
        env_exec_arr[num_environ + num_in] = NULL;
 
        return env_exec_arr;
}
 
static bool fr_exec_allowed(char const *filename)
{
        size_t i, num_files, len;
 
        if (!main_config->limit_exec) return true;
 
        num_files = talloc_array_length(main_config->limit_exec);
        if (!num_files) goto fail;
 
        len = strlen(filename);
 
        for (i = 0; i < num_files; i++) {
                size_t alen = talloc_array_length(main_config->limit_exec[i]);
 
                /*
                 *      The allowed directory is longer than the filename, it's not allowed.
                 */
                if (alen > len) continue;
 
                /*
                 *      No leading match, it's not allowed.
                 */
                if (memcmp(filename, main_config->limit_exec[i], alen) != 0) continue;
 
                if (alen == len) return true;
 
                /*
                 *      Setting "allow = foo/bar" does NOT mean that
                 *      we allow "foo/bard".  It MUST be "foo/bar/bad"
                 */
                if (filename[alen] != '/') break;
 
                return true;
        }
 
fail:
        EDEBUG("Failed running program %s - it is outside of 'limit exec { ... }'", filename);
        return false;
}
 
/** Execute a program without waiting for the program to finish.
 *
 * @param[in] el                event list to insert reaper child into.
 * @param[in] argv_in           arg[0] is the path to the program, arg[...] are arguments
 *                              to pass to the program.
 * @param[in] env_in            any additional environmental variables to pass to the program.
 * @param[in] env_inherit       Inherit the environment from the current process.
 *                              This will be merged with any variables from env_pairs.
 * @param[in] debug             If true, STDERR will be left open and pointing to the stderr
 *                              descriptor of the parent.
 * @return
 *      - <0 on error.  Error retrievable fr_strerror().
 *      - 0 on success
 *
 *  @todo - maybe take an fr_dcursor_t instead of env_pairs?  That
 *  would allow finer-grained control over the attributes to put into
 *  the environment.
 */
int fr_exec_fork_nowait(fr_event_list_t *el, char **argv_in, char **env_in, bool env_inherit, bool debug)
{
        char            **env;
        pid_t           pid;
 
        if (!fr_exec_allowed(argv_in[0])) return -1;
 
        env = exec_build_env(env_in, env_inherit);
        pid = fork();
        /*
         *      The child never returns from calling exec_child();
         */
        if (pid == 0) {
                int unused[2] = { -1, -1 };
 
                exec_child(argv_in, env, false, debug, unused, unused, unused);
        }
 
        if (pid < 0) {
                fr_strerror_printf("Couldn't fork %s", argv_in[0]);
        error:
                return -1;
        }
 
        /*
         *      Ensure that we can clean up any child processes.  We
         *      don't want them left over as zombies.
         */
        if (fr_event_pid_reap(el, pid, NULL, NULL) < 0) {
                int status;
 
                /*
                 *      Try and cleanup... really we have
                 *      no idea what state things are in.
                 */
                kill(pid, SIGKILL);
                waitpid(pid, &status, WNOHANG);
                goto error;
        }
 
        return 0;
}
 
/** Execute a program assuming that the caller waits for it to finish.
 *
 * The caller takes responsibility for calling waitpid() on the returned PID.
 *
 * The caller takes responsibility for reading from the returned FD,
 * and closing it.
 *
 * @param[out] pid_p            The PID of the child
 * @param[out] stdin_fd         The stdin FD of the child.
 * @param[out] stdout_fd        The stdout FD of the child.
 * @param[out] stderr_fd        The stderr FD of the child.
 * @param[in] argv_in           arg[0] is the path to the program, arg[...] are arguments
 *                              to pass to the program.
 * @param[in] env_in            Environmental variables to pass to the program.
 * @param[in] env_inherit       Inherit the environment from the current process.
 *                              This will be merged with any variables from env_pairs.
 * @param[in] debug             If true, STDERR will be left open and pointing to the stderr
 *                              descriptor of the parent, if no stderr_fd pointer is provided.
 * @return
 *      - <0 on error.  Error retrievable fr_strerror().
 *      - 0 on success.
 *
 *  @todo - maybe take an fr_dcursor_t instead of env_pairs?  That
 *  would allow finer-grained control over the attributes to put into
 *  the environment.
 */
int fr_exec_fork_wait(pid_t *pid_p,
                      int *stdin_fd, int *stdout_fd, int *stderr_fd,
                      char **argv_in, char **env_in, bool env_inherit, bool debug)
{
        char            **env;
        pid_t           pid;
        int             stdin_pipe[2] = {-1, -1};
        int             stderr_pipe[2] = {-1, -1};
        int             stdout_pipe[2] = {-1, -1};
 
        if (!fr_exec_allowed(argv_in[0])) return -1;
 
        if (stdin_fd) {
                if (pipe(stdin_pipe) < 0) {
                        fr_strerror_const("Failed opening pipe to write to child");
 
                error1:
                        return -1;
                }
                if (fr_nonblock(stdin_pipe[1]) < 0) {
                        fr_strerror_const("Error setting stdin to nonblock");
                        goto error2;
                }
        }
 
        if (stdout_fd) {
                if (pipe(stdout_pipe) < 0) {
                        fr_strerror_const("Failed opening pipe to read from child");
 
                error2:
                        close(stdin_pipe[0]);
                        close(stdin_pipe[1]);
                        goto error1;
                }
                if (fr_nonblock(stdout_pipe[0]) < 0) {
                        fr_strerror_const("Error setting stdout to nonblock");
                        goto error3;
                }
        }
 
        if (stderr_fd) {
                if (pipe(stderr_pipe) < 0) {
                        fr_strerror_const("Failed opening pipe to read from child");
 
                error3:
                        close(stdout_pipe[0]);
                        close(stdout_pipe[1]);
                        goto error2;
                }
                if (fr_nonblock(stderr_pipe[0]) < 0) {
                        fr_strerror_const("Error setting stderr to nonblock");
                        close(stderr_pipe[0]);
                        close(stderr_pipe[1]);
                        goto error3;
                }
        }
 
        env = exec_build_env(env_in, env_inherit);
        pid = fork();
 
        /*
         *      The child never returns from calling exec_child();
         */
        if (pid == 0) exec_child(argv_in, env, true, debug, stdin_pipe, stdout_pipe, stderr_pipe);
        if (pid < 0) {
                fr_strerror_printf("Couldn't fork %s", argv_in[0]);
                *pid_p = -1;    /* Ensure the PID is set even if the caller didn't check the return code */
                if (stderr_fd) {
                        close(stderr_pipe[0]);
                        close(stderr_pipe[1]);
                }
                goto error3;
        }
 
        /*
         *      Tell the caller the childs PID, and the FD to read from.
         */
        *pid_p = pid;
 
        if (stdin_fd) {
                *stdin_fd = stdin_pipe[1];
                close(stdin_pipe[0]);
        }
 
        if (stdout_fd) {
                *stdout_fd = stdout_pipe[0];
                close(stdout_pipe[1]);
        }
 
        if (stderr_fd) {
                *stderr_fd = stderr_pipe[0];
                close(stderr_pipe[1]);
        }
 
        return 0;
}
 
/** Similar to fr_exec_oneshot, but does not attempt to parse output
 *
 * @param[in] request           currently being processed, may be NULL.
 * @param[in] args              to call as a fr_value_box_list_t.  Program will
 *                              be the first box and arguments in the subsequent boxes.
 * @param[in] env_pairs         list of pairs to be presented as environment variables
 *                              to the child.
 * @param[in] env_escape        Wrap string values in double quotes, and apply doublequote
 *                              escaping to all environmental variable values.
 * @param[in] env_inherit       Inherit the environment from the current process.
 *                              This will be merged with any variables from env_pairs.
 * @return
 *      - 0 on success.
 *      - -1 on error.
 */
int fr_exec_oneshot_nowait(request_t *request,
                           fr_value_box_list_t *args, fr_pair_list_t *env_pairs,
                           bool env_escape, bool env_inherit)
{
        char **argv = NULL;
        char **env = NULL;
        int ret;
 
        if (unlikely(fr_exec_value_box_list_to_argv(unlang_interpret_frame_talloc_ctx(request), &argv, args) < 0)) {
                RPEDEBUG("Failed converting boxes to argument strings");
                return -1;
        }
 
        if (env_pairs) {
                env = fr_exec_pair_to_env(request, env_pairs, env_escape);
                if (unlikely(env == NULL)) {
                        RPEDEBUG("Failed creating environment pairs");
                        return -1;
                }
        }
 
        if (RDEBUG_ENABLED3) exec_debug(request, argv, env, env_inherit);
        ret = fr_exec_fork_nowait(unlang_interpret_event_list(request), argv, env,
                                  env_inherit, ROPTIONAL_ENABLED(RDEBUG_ENABLED2, DEBUG_ENABLED2));
        talloc_free(argv);
        if (unlikely(ret < 0)) RPEDEBUG("Failed executing program");
 
        return ret;
}
 
/** Cleans up an exec'd process on error
 *
 * This function is intended to be called at any point after a successful
 * #fr_exec_oneshot call in order to release resources and cleanup
 * zombie processes.
 *
 * @param[in] exec      state to cleanup.
 * @param[in] signal    If non-zero, and we think the process is still
 *                      running, send it a signal to cause it to exit.
 *                      The PID reaper we insert here will cleanup its
 *                      state so it doesn't become a zombie.
 *
 */
void fr_exec_oneshot_cleanup(fr_exec_state_t *exec, int signal)
{
        request_t       *request = exec->request;
        fr_event_list_t *el = unlang_interpret_event_list(request);
 
        if (exec->pid >= 0) {
                RDEBUG3("Cleaning up exec state for PID %u", exec->pid);
 
        } else if (exec->failed != FR_EXEC_FAIL_NONE) {
                RDEBUG3("Cleaning up failed exec");
        }
 
        /*
         *      There's still an EV_PROC event installed
         *      for the PID remove it (there's a destructor).
         */
        if (exec->ev_pid) {
                talloc_const_free(exec->ev_pid);
                fr_assert(!exec->ev_pid);       /* Should be NULLified by destructor */
        }
 
        if (exec->stdout_fd >= 0) {
                if (fr_event_fd_delete(el, exec->stdout_fd, FR_EVENT_FILTER_IO) < 0){
                        RPERROR("Failed removing stdout handler");
                }
                close(exec->stdout_fd);
                exec->stdout_fd = -1;
        }
 
        if (exec->stderr_fd >= 0) {
                if (fr_event_fd_delete(el, exec->stderr_fd, FR_EVENT_FILTER_IO) < 0) {
                        RPERROR("Failed removing stderr handler");
                }
                close(exec->stderr_fd);
                exec->stderr_fd = -1;
        }
 
        if (exec->pid >= 0) {
                if (signal > 0) kill(exec->pid, signal);
 
                if (unlikely(fr_event_pid_reap(el, exec->pid, NULL, NULL) < 0)) {
                        int status;
 
                        RPERROR("Failed setting up async PID reaper, PID %u may now be a zombie", exec->pid);
 
                        /*
                         *      Try and cleanup... really we have
                         *      no idea what state things are in.
                         */
                        kill(exec->pid, SIGKILL);
                        waitpid(exec->pid, &status, WNOHANG);
                }
                exec->pid = -1;
        }
 
        FR_TIMER_DELETE(&exec->ev);
}
 
/*
 *      Callback when exec has completed.  Record the status and tidy up.
 */
static void exec_reap(fr_event_list_t *el, pid_t pid, int status, void *uctx)
{
        fr_exec_state_t *exec = uctx;   /* may not be talloced */
        request_t       *request = exec->request;
        int             wait_status = 0;
        int             ret;
 
        if (!fr_cond_assert(pid == exec->pid)) RWDEBUG("Event PID %u and exec->pid %u do not match", pid, exec->pid);
 
        /*
         *      Reap the process.  This is needed so the processes
         *      don't stick around indefinitely.  libkqueue/kqueue
         *      does not do this for us!
         */
        ret = waitpid(exec->pid, &wait_status, WNOHANG);
        if (ret < 0) {
                RWDEBUG("Failed reaping PID %i: %s", exec->pid, fr_syserror(errno));
        /*
         *      Either something cleaned up the process before us
         *      (bad!), or the notification system is broken
         *      (also bad!)
         *
         *      This could be caused by 3rd party libraries.
         */
        } else if (ret == 0) {
                RWDEBUG("Something reaped PID %d before us!", exec->pid);
                wait_status = status;
        }
 
        /*
         *      kevent should be returning an identical status value
         *      to waitpid.
         */
        if (wait_status != status) RWDEBUG("Exit status from waitpid (%d) and kevent (%d) disagree",
                                           wait_status, status);
 
        if (WIFEXITED(wait_status)) {
                RDEBUG("Program exited with status code %d", WEXITSTATUS(wait_status));
                exec->status = WEXITSTATUS(wait_status);
        } else if (WIFSIGNALED(wait_status)) {
                RDEBUG("Program exited due to signal with status code %d", WTERMSIG(wait_status));
                exec->status = -WTERMSIG(wait_status);
        } else {
                RDEBUG("Program exited due to unknown status %d", wait_status);
                exec->status = -wait_status;
        }
        exec->pid = -1; /* pid_t is signed */
 
        FR_TIMER_DELETE(&exec->ev);
 
        /*
         *      Process exit notifications (EV_PROC) and file
         *      descriptor read events (EV_READ) can race.
         *
         *      So... If the process has exited, trigger the IO
         *      handlers manually.
         *
         *      This is icky, but the only other option is to
         *      enhance our event loop so we can look for
         *      pending events associated with file
         *      descriptors...
         *
         *      Even then we might get the file readable
         *      notification and the process exited notification
         *      in different kevent() calls on busy systems.
         */
        if (exec->stdout_fd >= 0) {
                fr_event_fd_t           *ef;
                fr_event_fd_cb_t        cb;
 
                ef = fr_event_fd_handle(el, exec->stdout_fd, FR_EVENT_FILTER_IO);
                if (!fr_cond_assert_msg(ef, "no event associated with processes's stdout fd (%i)",
                                        exec->stdout_fd)) goto close_stdout;
 
                cb = fr_event_fd_cb(ef, EVFILT_READ, 0);
                if (!fr_cond_assert_msg(cb, "no read callback associated with processes's stdout_fd (%i)",
                                        exec->stdout_fd)) goto close_stdout;
 
                /*
                 *      Call the original read callback that
                 *      was setup here to ensure that there's
                 *      no pending data.
                 */
                cb(el, exec->stdout_fd, 0, fr_event_fd_uctx(ef));
 
                /*
                 *      ...and delete the event from the event
                 *      loop.  This should also suppress the
                 *      EVFILT_READ event if there was one.
                 */
                (void) fr_event_fd_delete(el, exec->stdout_fd, FR_EVENT_FILTER_IO);
        close_stdout:
                close(exec->stdout_fd);
                exec->stdout_fd = -1;
        }
 
        if (exec->stderr_fd >= 0) {
                fr_event_fd_t           *ef;
                fr_event_fd_cb_t        cb;
 
                ef = fr_event_fd_handle(el, exec->stderr_fd, FR_EVENT_FILTER_IO);
                if (!fr_cond_assert_msg(ef, "no event associated with processes's stderr fd (%i)",
                                        exec->stderr_fd)) goto close_stderr;
 
                cb = fr_event_fd_cb(ef, EVFILT_READ, 0);
                if (!fr_cond_assert_msg(cb, "no read callback associated with processes's stderr_fd (%i)",
                                        exec->stderr_fd)) goto close_stderr;
 
                cb(el, exec->stderr_fd, 0, fr_event_fd_uctx(ef));
                (void) fr_event_fd_delete(el, exec->stderr_fd, FR_EVENT_FILTER_IO);
        close_stderr:
                close(exec->stderr_fd);
                exec->stderr_fd = -1;
        }
 
        unlang_interpret_mark_runnable(exec->request);
}
 
/*
 *      Callback when an exec times out.
 */
static void exec_timeout(UNUSED fr_timer_list_t *tl, UNUSED fr_time_t now, void *uctx)
{
        fr_exec_state_t *exec = uctx; /* may not be talloced */
        bool            exit_timeout;
 
        /*
         *      Some race conditions cause fr_exec_oneshot_cleanup to insert
         *      a new event, which calls fr_strerror_clear(), resulting in
         *      inconsistent error messages.
         *      Recording the condition to drive the error message here and
         *      then setting after tidying up keeps things consistent.
         */
        exit_timeout = (exec->stdout_fd < 0);
 
        exec->failed = FR_EXEC_FAIL_TIMEOUT;
        fr_exec_oneshot_cleanup(exec, SIGKILL);
 
        if (exit_timeout) {
                fr_strerror_const("Timeout waiting for program to exit");
        } else {
                fr_strerror_const("Timeout running program");
        }
 
        unlang_interpret_mark_runnable(exec->request);
}
 
/*
 *      Callback to read stdout from an exec into the pre-prepared extensible sbuff
 */
static void exec_stdout_read(UNUSED fr_event_list_t *el, int fd, int flags, void *uctx) {
        fr_exec_state_t         *exec = uctx;
        request_t               *request = exec->request;
        ssize_t                 data_len, remaining;
        fr_sbuff_marker_t       start_m;
 
        fr_sbuff_marker(&start_m, &exec->stdout_buff);
 
        do {
                /*
                 *      Read in 128 byte chunks
                 */
                remaining = fr_sbuff_extend_lowat(NULL, &exec->stdout_buff, 128);
 
                /*
                 *      Ran out of buffer space.
                 */
                if (unlikely(!remaining)) {
                        REDEBUG("Too much output from program - killing it and failing the request");
 
                error:
                        exec->failed = FR_EXEC_FAIL_TOO_MUCH_DATA;
                        fr_exec_oneshot_cleanup(exec, SIGKILL);
                        break;
                }
 
                data_len = read(fd, fr_sbuff_current(&exec->stdout_buff), remaining);
                if (data_len < 0) {
                        if (errno == EINTR) continue;
 
                        /*
                         *      This can happen when the callback is called
                         *      manually when we're reaping the process.
                         *
                         *      It's pretty much an identical condition to
                         *      data_len == 0.
                         */
                        if (errno == EWOULDBLOCK) break;
 
                        REDEBUG("Error reading from child program - %s", fr_syserror(errno));
                        goto error;
                }
 
                /*
                 *      Even if we get 0 now the process may write more data later
                 *      before it completes, so we leave the fd handlers in place.
                 */
                if (data_len == 0) break;
 
                fr_sbuff_advance(&exec->stdout_buff, data_len);
        } while (remaining == data_len);        /* If process returned maximum output, loop again */
 
        if (flags & EV_EOF) {
                /*
                 *      We've received EOF - so the process has finished writing
                 *      Remove event and tidy up
                 */
                (void) fr_event_fd_delete(unlang_interpret_event_list(exec->request), fd, FR_EVENT_FILTER_IO);
                close(fd);
                exec->stdout_fd = -1;
 
                if (exec->pid < 0) {
                        /*
                         *      Child has already exited - unlang can resume
                         */
                        FR_TIMER_DELETE(&exec->ev);
                        unlang_interpret_mark_runnable(exec->request);
                }
        }
 
        /*
         *      Only print if we got additional data
         */
        if (RDEBUG_ENABLED2 && fr_sbuff_behind(&start_m)) {
                RDEBUG2("pid %u (stdout) - %pV", exec->pid,
                        fr_box_strvalue_len(fr_sbuff_current(&start_m), fr_sbuff_behind(&start_m)));
        }
 
        fr_sbuff_marker_release(&start_m);
}
 
/** Call an child program, optionally reading it's output
 *
 * @note If the caller set need_stdin = true, it is the caller's
 *       responsibility to close exec->std_in and remove it from any event loops
 *       if this function returns 0 (success).
 *
 * @param[in] ctx               to allocate events in.
 * @param[in,out] exec          structure holding the state of the external call.
 * @param[in] request           currently being processed, may be NULL.
 * @param[in] args              to call as a fr_value_box_list_t.  Program will
 *                              be the first box and arguments in the subsequent boxes.
 * @param[in] env_pairs         list of pairs to be presented as environment variables
 *                              to the child.
 * @param[in] env_escape        Wrap string values in double quotes, and apply doublequote
 *                              escaping to all environmental variable values.
 * @param[in] env_inherit       Inherit the environment from the current process.
 *                              This will be merged with any variables from env_pairs.
 * @param[in] need_stdin        If true, allocate a pipe that will allow us to send data to the
 *                              process.
 * @param[in] store_stdout      if true keep a copy of stdout in addition to logging
 *                              it if RDEBUG_ENABLED2.
 * @param[in] stdout_ctx        ctx to alloc stdout data in.
 * @param[in] timeout           to wait for child to complete.
 * @return
 *      - 0 on success
 *      - -1 on failure
 */
int fr_exec_oneshot(TALLOC_CTX *ctx, fr_exec_state_t *exec, request_t *request,
                    fr_value_box_list_t *args,
                    fr_pair_list_t *env_pairs, bool env_escape, bool env_inherit,
                    bool need_stdin,
                    bool store_stdout, TALLOC_CTX *stdout_ctx,
                    fr_time_delta_t timeout)
{
        int             *stdout_fd = (store_stdout || RDEBUG_ENABLED2) ? &exec->stdout_fd : NULL;
        fr_event_list_t *el = unlang_interpret_event_list(request);
        char            **env = NULL;
        char            **argv;
        int             ret;
 
        if (unlikely(fr_exec_value_box_list_to_argv(unlang_interpret_frame_talloc_ctx(request), &argv, args) < 0)) {
                RPEDEBUG("Failed converting boxes to argument strings");
                return -1;
        }
 
        if (env_pairs) {
                env = fr_exec_pair_to_env(request, env_pairs, env_escape);
                if (unlikely(!env)) {
                        RPEDEBUG("Failed creating environment pairs");
                        return -1;
                }
        }
 
        if (RDEBUG_ENABLED3) exec_debug(request, argv, env, env_inherit);
        *exec = (fr_exec_state_t){
                .request = request,
                .env_pairs = env_pairs,
                .pid = -1,
                .stdout_fd = -1,
                .stderr_fd = -1,
                .stdin_fd = -1,
                .status = -1,                           /* default to program didn't work */
                .stdin_used = need_stdin,
                .stdout_used = store_stdout,
                .stdout_ctx = stdout_ctx
        };
        ret = fr_exec_fork_wait(&exec->pid,
                              exec->stdin_used ? &exec->stdin_fd : NULL,
                              stdout_fd, &exec->stderr_fd,
                              argv, env,
                              env_inherit, ROPTIONAL_ENABLED(RDEBUG_ENABLED2, DEBUG_ENABLED2));
        talloc_free(argv);
        if (ret < 0) {
        fail:
                RPEDEBUG("Failed executing program");
 
                /*
                 *      Not done in fr_exec_oneshot_cleanup as it's
                 *      usually the caller's responsibility.
                 */
                if (exec->stdin_fd >= 0) {
                        close(exec->stdin_fd);
                        exec->stdin_fd = -1;
                }
                fr_exec_oneshot_cleanup(exec, 0);
                return -1;
        }
 
        /*
         *      First setup I/O events for the child process. This needs
         *      to be done before we call fr_event_pid_wait, as it may
         *      immediately trigger the PID callback if there's a race
         *      between kevent and the child exiting, and that callback
         *      will expect file descriptor events to have been created.
         */
 
        /*
         *      If we need to parse stdout, insert a special IO handler that
         *      aggregates all stdout data into an expandable buffer.
         */
        if (exec->stdout_used) {
                /*
                 *      Accept a maximum of 32k of data from the process.
                 */
                fr_sbuff_init_talloc(exec->stdout_ctx, &exec->stdout_buff, &exec->stdout_tctx, 128, 32 * 1024);
                if (fr_event_fd_insert(ctx, NULL, el, exec->stdout_fd, exec_stdout_read, NULL, NULL, exec) < 0) {
                        RPEDEBUG("Failed adding event listening to stdout");
                        goto fail_and_close;
                }
 
        /*
         *      If the caller doesn't want the output box, we still want to copy stdout
         *      into the request log if we're logging at a high enough level of verbosity.
         */
        } else if (RDEBUG_ENABLED2) {
                snprintf(exec->stdout_prefix, sizeof(exec->stdout_prefix), "pid %u (stdout)", exec->pid);
                exec->stdout_uctx = (log_fd_event_ctx_t) {
                        .type = L_DBG,
                        .lvl = L_DBG_LVL_2,
                        .request = request,
                        .prefix = exec->stdout_prefix
                };
 
                if (fr_event_fd_insert(ctx, NULL, el, exec->stdout_fd, log_request_fd_event,
                                       NULL, NULL, &exec->stdout_uctx) < 0){
                        RPEDEBUG("Failed adding event listening to stdout");
                        goto fail_and_close;
                }
        }
 
        /*
         *      Send stderr to the request log as error messages with a custom prefix
         */
        snprintf(exec->stderr_prefix, sizeof(exec->stderr_prefix), "pid %u (stderr)", exec->pid);
        exec->stderr_uctx = (log_fd_event_ctx_t) {
                .type = L_DBG_ERR,
                .lvl = L_DBG_LVL_1,
                .request = request,
                .prefix = exec->stderr_prefix
        };
 
        if (fr_event_fd_insert(ctx, NULL, el, exec->stderr_fd, log_request_fd_event,
                               NULL, NULL, &exec->stderr_uctx) < 0) {
                RPEDEBUG("Failed adding event listening to stderr");
                close(exec->stderr_fd);
                exec->stderr_fd = -1;
                goto fail;
        }
 
        /*
         *      Tell the event loop that it needs to wait for this PID
         */
        if (fr_event_pid_wait(ctx, el, &exec->ev_pid, exec->pid, exec_reap, exec) < 0) {
                exec->pid = -1;
                RPEDEBUG("Failed adding watcher for child process");
 
        fail_and_close:
                /*
                 *      Avoid spurious errors in fr_exec_oneshot_cleanup
                 *      when it tries to remove FDs from the
                 *      event loop that were never added.
                 */
                if (exec->stdout_fd >= 0) {
                        close(exec->stdout_fd);
                        exec->stdout_fd = -1;
                }
 
                if (exec->stderr_fd >= 0) {
                        close(exec->stderr_fd);
                        exec->stderr_fd = -1;
                }
 
                goto fail;
        }
 
        /*
         *      Setup event to kill the child process after a period of time.
         */
        if (fr_time_delta_ispos(timeout) &&
                (fr_timer_in(ctx, el->tl, &exec->ev, timeout, true, exec_timeout, exec) < 0)) goto fail_and_close;
 
        return 0;
}