src/lib/process-title.c

/* Copyright (c) 2002-2018 Dovecot authors, see the included COPYING file */

#include "lib.h"
#include "env-util.h"
#include "process-title.h"

#ifdef HAVE_LIBBSD
#include <bsd/unistd.h>
#else
#include <unistd.h> /* FreeBSD */
#endif

static char *process_name = NULL;
static char *current_process_title;

#ifdef HAVE_SETPROCTITLE
#  undef PROCTITLE_HACK
#endif

#ifdef PROCTITLE_HACK

#define PROCTITLE_CLEAR_CHAR 0xab

static char *process_title;
static size_t process_title_len, process_title_clean_pos;
static void *argv_memblock, *environ_memblock;

static void proctitle_hack_init(char *argv[], char *env[])
{
    char *last;
    unsigned int i;
    bool clear_env;

    i_assert(argv[0] != NULL);

    /* find the last argv or environment string. it should always be the
       last string in environ, but don't rely on it. this is what openssh
       does, so hopefully it's safe enough. */
    last = argv[0] + strlen(argv[0]) + 1;
    for (i = 1; argv[i] != NULL; i++) {
        if (argv[i] == last)
            last = argv[i] + strlen(argv[i]) + 1;
    }
    if (env[0] == NULL)
        clear_env = FALSE;
    else {
        clear_env = last == env[0];
        for (i = 0; env[i] != NULL; i++) {
            if (env[i] == last)
                last = env[i] + strlen(env[i]) + 1;
        }
    }

    process_title = argv[0];
    process_title_len = last - argv[0];

    /* if there are problems with this approach, try to make sure we
       notice it */
    if (clear_env) {
        memset(env[0], PROCTITLE_CLEAR_CHAR, last - env[0]);
        process_title_clean_pos = env[0] - process_title;
    } else {
        process_title_clean_pos = 0;
    }
}

static char **argv_dup(char *old_argv[], void **memblock_r)
{
    /* @UNSAFE */
    void *memblock, *memblock_end;
    char **new_argv;
    unsigned int i, count;
    size_t len, memblock_len = 0;

    for (count = 0; old_argv[count] != NULL; count++)
        memblock_len += strlen(old_argv[count]) + 1;
    memblock_len += sizeof(char *) * (count + 1);

    memblock = malloc(memblock_len);
    if (memblock == NULL)
        i_fatal_status(FATAL_OUTOFMEM, "malloc() failed: %m");
    *memblock_r = memblock;
    memblock_end = PTR_OFFSET(memblock, memblock_len);

    new_argv = memblock;
    memblock = PTR_OFFSET(memblock, sizeof(char *) * (count + 1));

    for (i = 0; i < count; i++) {
        new_argv[i] = memblock;
        len = strlen(old_argv[i]) + 1;
        memcpy(memblock, old_argv[i], len);
        memblock = PTR_OFFSET(memblock, len);
    }
    i_assert(memblock == memblock_end);
    new_argv[i] = NULL;
    return new_argv;
}

static void proctitle_hack_set(const char *title)
{
    size_t len = strlen(title);

    /* OS X wants two NULs */
    if (len >= process_title_len-1)
        len = process_title_len - 2;

    memcpy(process_title, title, len);
    process_title[len++] = '\0';
    process_title[len++] = '\0';

    if (len < process_title_clean_pos) {
        memset(process_title + len, PROCTITLE_CLEAR_CHAR,
               process_title_clean_pos - len);
        process_title_clean_pos = len;
    } else if (process_title_clean_pos != 0) {
        process_title_clean_pos = len;
    }
}

#endif

void process_title_init(int argc ATTR_UNUSED, char **argv[])
{
#ifdef PROCTITLE_HACK
    char ***environ_p = env_get_environ_p();
    char **orig_argv = *argv;
    char **orig_environ = *environ_p;

    *argv = argv_dup(orig_argv, &argv_memblock);
    *environ_p = argv_dup(orig_environ, &environ_memblock);
    proctitle_hack_init(orig_argv, orig_environ);
#endif
#ifdef HAVE_LIBBSD
    setproctitle_init(argc, *argv, *env_get_environ_p());
#endif
    process_name = (*argv)[0];
}

void process_title_set(const char *title)
{
    i_assert(process_name != NULL);

    i_free(current_process_title);
    current_process_title = i_strdup(title);
#ifdef HAVE_SETPROCTITLE
    if (title == NULL)
        setproctitle(NULL);
    else
        setproctitle("%s", title);
#elif defined(PROCTITLE_HACK)
    T_BEGIN {
        proctitle_hack_set(t_strconcat(process_name, " ", title, NULL));
    } T_END;
#endif
}

const char *process_title_get(void)
{
    return current_process_title;
}

void process_title_deinit(void)
{
#ifdef PROCTITLE_HACK
    char ***environ_p = env_get_environ_p();

    free(argv_memblock);
    free(environ_memblock);

    /* Environment is no longer usable. Make sure we won't crash in case
       some library's deinit function still calls getenv(). This code was
       mainly added because of GNUTLS where we don't really care about the
       getenv() call.

       Alternatively we could remove the free() calls above, but that would
       annoy memory leak checking tools. Also we could attempt to restore
       the environ_p to its original state, but that's a bit complicated. */
    *environ_p = NULL;
#endif
    i_free(current_process_title);
}