/*
    abrt-hook-ccpp.cpp - the hook for C/C++ crashing program

    Copyright (C) 2009	Zdenek Prikryl (zprikryl@redhat.com)
    Copyright (C) 2009	RedHat inc.

    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 "abrtlib.h"
#include "hooklib.h"
#include "DebugDump.h"
#include "CrashTypes.h"
#include "ABRTException.h"
#include <syslog.h>

using namespace std;

static char* malloc_readlink(const char *linkname)
{
    char buf[PATH_MAX + 1];
    int len;

    len = readlink(linkname, buf, sizeof(buf)-1);
    if (len >= 0)
    {
        buf[len] = '\0';
        return xstrdup(buf);
    }
    return NULL;
}

static char* get_executable(pid_t pid)
{
    char buf[sizeof("/proc/%lu/exe") + sizeof(long)*3];

    sprintf(buf, "/proc/%lu/exe", (long)pid);
    return malloc_readlink(buf);
}

static char* get_cwd(pid_t pid)
{
    char buf[sizeof("/proc/%lu/cwd") + sizeof(long)*3];

    sprintf(buf, "/proc/%lu/cwd", (long)pid);
    return malloc_readlink(buf);
}

int main(int argc, char** argv)
{
    int fd;
    struct stat sb;

    if (argc < 5)
    {
        const char* program_name = argv[0];
        error_msg_and_die("Usage: %s: DUMPDIR PID SIGNO UID CORE_SIZE_LIMIT", program_name);
    }
    openlog("abrt", LOG_PID, LOG_DAEMON);
    logmode = LOGMODE_SYSLOG;

    errno = 0;
    const char* dddir = argv[1];
    pid_t pid = xatoi_u(argv[2]);
    const char* signal_str = argv[3];
    int signal_no = xatoi_u(argv[3]);
    uid_t uid = xatoi_u(argv[4]);
    off_t ulimit_c = strtoull(argv[5], NULL, 10);
    if (ulimit_c < 0) /* unlimited? */
    {
        /* set to max possible >0 value */
        ulimit_c = ~((off_t)1 << (sizeof(off_t)*8-1));
    }
    off_t core_size = 0;

    if (errno || pid <= 0)
    {
        error_msg_and_die("pid '%s' or limit '%s' is bogus", argv[2], argv[5]);
    }

    const char *signame = NULL;
    /* Tried to use array for this but C++ does not support v[] = { [IDX] = "str" } */
    switch (signal_no)
    {
        case SIGQUIT: signame = "QUIT"; break;
        case SIGILL : signame = "ILL" ; break;
        case SIGABRT: signame = "ABRT"; break;
        case SIGFPE : signame = "FPE" ; break;
        case SIGSEGV: signame = "SEGV"; break;
    }
    if (signame == NULL) {
        /* not a signal we care about, exit silently */
        return 0;
    }

    char *user_pwd = get_cwd(pid); /* may be NULL on error */
    int core_fd = STDIN_FILENO;

    if (!daemon_is_ok())
    {
        /* not an error, exit with exitcode 0 */
        log("abrt daemon is not running. If it crashed, "
            "/proc/sys/kernel/core_pattern contains a stale value, "
            "consider resetting it to 'core'"
        );
        goto create_user_core;
    }

    try
    {
        char* executable = get_executable(pid);
        if (executable == NULL)
        {
            error_msg_and_die("can't read /proc/%lu/exe link", (long)pid);
        }
        if (strstr(executable, "/abrt-hook-ccpp"))
        {
            error_msg_and_die("pid %lu is '%s', not dumping it to avoid recursion",
                            (long)pid, executable);
        }

        /* Parse abrt.conf and plugins/CCpp.conf */
        unsigned setting_MaxCrashReportsSize = 0;
        bool setting_MakeCompatCore = false;
        parse_conf(CONF_DIR"/plugins/CCpp.conf", &setting_MaxCrashReportsSize, &setting_MakeCompatCore);

        if (setting_MaxCrashReportsSize > 0)
        {
            check_free_space(setting_MaxCrashReportsSize);
        }

        char path[PATH_MAX];

        /* Check /var/cache/abrt/last-ccpp marker, do not dump repeated crashes
         * if they happen too often. Else, write new marker value.
         */
        snprintf(path, sizeof(path), "%s/last-ccpp", dddir);
        fd = open(path, O_RDWR | O_CREAT, 0600);
        if (fd >= 0)
        {
            int sz;
            fstat(fd, &sb); /* !paranoia. this can't fail. */

            if (sb.st_size != 0 /* if it wasn't created by us just now... */
	     && (unsigned)(time(NULL) - sb.st_mtime) < 20 /* and is relatively new [is 20 sec ok?] */
            ) {
                sz = read(fd, path, sizeof(path)-1); /* (ab)using path as scratch buf */
                if (sz > 0)
                {
                    path[sz] = '\0';
                    if (strcmp(executable, path) == 0)
                    {
                        error_msg("not dumping repeating crash in '%s'", executable);
                        if (setting_MakeCompatCore)
                            goto create_user_core;
                        return 1;
                    }
                }
                lseek(fd, 0, SEEK_SET);
            }
            sz = write(fd, executable, strlen(executable));
            if (sz >= 0)
                ftruncate(fd, sz);
            close(fd);
        }

        if (strstr(executable, "/abrtd"))
        {
            /* If abrtd crashes, we don't want to create a _directory_,
             * since that can make new copy of abrtd to process it,
             * and maybe crash again...
             * Unlike dirs, mere files are ignored by abrtd.
             */
            snprintf(path, sizeof(path), "%s/abrtd-coredump", dddir);
            core_fd = xopen3(path, O_WRONLY | O_CREAT | O_TRUNC, 0644);
            core_size = copyfd_eof(STDIN_FILENO, core_fd);
            if (core_size < 0 || close(core_fd) != 0)
            {
                unlink(path);
                /* copyfd_eof logs the error including errno string,
                 * but it does not log file name */
                error_msg_and_die("error saving coredump to %s", path);
            }
            log("saved core dump of pid %lu (%s) to %s (%llu bytes)", (long)pid, executable, path, (long long)core_size);
            return 0;
        }

        char* cmdline = get_cmdline(pid); /* never NULL */
        char *reason = xasprintf("Process %s was killed by signal %s (SIG%s)", executable, signal_str, signame ? signame : signal_str);

        unsigned path_len = snprintf(path, sizeof(path), "%s/ccpp-%ld-%lu.new",
                dddir, (long)time(NULL), (long)pid);
        if (path_len >= sizeof(path))
            exit(1);

        CDebugDump dd;
        dd.Create(path, uid);
        dd.SaveText(FILENAME_ANALYZER, "CCpp");
        dd.SaveText(FILENAME_EXECUTABLE, executable);
        dd.SaveText(FILENAME_CMDLINE, cmdline);
        dd.SaveText(FILENAME_REASON, reason);

        int len = strlen(path);
        snprintf(path + len, sizeof(path) - len, "/"FILENAME_COREDUMP);

        /* We need coredumps to be readable by all, because
         * when abrt daemon processes coredump,
         * process producing backtrace is run under the same UID
         * as the crashed process.
         * Thus 644, not 600 */
        core_fd = open(path, O_RDWR | O_CREAT | O_TRUNC, 0644);
        if (core_fd < 0)
        {
            int sv_errno = errno;
            dd.Delete();
            dd.Close();
            errno = sv_errno;
            perror_msg_and_die("can't open '%s'", path);
        }
//TODO: chown to uid:abrt?
//Currently it is owned by 0:0 but is readable by anyone, so the owner
//of the crashed binary still can access it, as he has
//r-x access to the dump dir.
        core_size = copyfd_eof(STDIN_FILENO, core_fd);
        if (core_size < 0 || fsync(core_fd) != 0)
        {
            unlink(path);
            dd.Delete();
            dd.Close();
            /* copyfd_eof logs the error including errno string,
             * but it does not log file name */
            error_msg_and_die("error saving coredump to %s", path);
        }
        lseek(core_fd, 0, SEEK_SET);
        /* note: core_fd is still open, we may use it later to copy core to user's dir */
        log("saved core dump of pid %lu (%s) to %s (%llu bytes)", (long)pid, executable, path, (long long)core_size);
        free(executable);
        free(cmdline);
        path[len] = '\0'; /* path now contains directory name */

        /* We close dumpdir before we start catering for crash storm case.
         * Otherwise, delete_debug_dump_dir's from other concurrent
         * CCpp's won't be able to delete our dump (their delete_debug_dump_dir
         * will wait for us), and we won't be able to delete their dumps.
         * Classic deadlock.
         */
        dd.Close();
        char *newpath = xstrndup(path, path_len - (sizeof(".new")-1));
        if (rename(path, newpath) != 0)
            strcpy(path, newpath);
        free(newpath);

        /* rhbz#539551: "abrt going crazy when crashing process is respawned" */
        if (setting_MaxCrashReportsSize > 0)
        {
            trim_debug_dumps(setting_MaxCrashReportsSize, path);
        }

        if (!setting_MakeCompatCore)
            return 0;
        /* fall through to creating user core */
    }
    catch (CABRTException& e)
    {
        error_msg_and_die("%s", e.what());
    }
    catch (std::exception& e)
    {
        error_msg_and_die("%s", e.what());
    }


 create_user_core:
    /* note: core_size may be == 0 ("unknown") */
    if (core_size > ulimit_c || ulimit_c == 0)
        return 0;

    /* Write a core file for user */

    struct passwd* pw = getpwuid(uid);
    gid_t gid = pw ? pw->pw_gid : uid;
    setgroups(1, &gid);
    xsetregid(gid, gid);
    xsetreuid(uid, uid);

    errno = 0;
    if (user_pwd == NULL
     || chdir(user_pwd) != 0
    ) {
        perror_msg_and_die("can't cd to %s", user_pwd);
    }

    /* Mimic "core.PID" if requested */
    char core_basename[sizeof("core.%lu") + sizeof(long)*3] = "core";
    char buf[] = "0\n";
    fd = open("/proc/sys/kernel/core_uses_pid", O_RDONLY);
    if (fd >= 0)
    {
        read(fd, buf, sizeof(buf));
        close(fd);
    }
    if (strcmp(buf, "1\n") == 0)
    {
        sprintf(core_basename, "core.%lu", (long)pid);
    }

    /* man core:
     * There are various circumstances in which a core dump file
     * is not produced:
     *
     * [skipped obvious ones]
     * The process does not have permission to write the core file.
     * ...if a file with the same name exists and is not writable
     * or is not a regular file (e.g., it is a directory or a symbolic link).
     *
     * A file with the same name already exists, but there is more
     * than one hard link to that file.
     *
     * The file system where the core dump file would be created is full;
     * or has run out of inodes; or is mounted read-only;
     * or the user has reached their quota for the file system.
     *
     * The RLIMIT_CORE or RLIMIT_FSIZE resource limits for the process
     * are set to zero.
     * [shouldn't it be checked by kernel? 2.6.30.9-96 doesn't, still
     * calls us even if "ulimit -c 0"]
     *
     * The binary being executed by the process does not have
     * read permission enabled. [how we can check it here?]
     *
     * The process is executing a set-user-ID (set-group-ID) program
     * that is owned by a user (group) other than the real
     * user (group) ID of the process. [TODO?]
     * (However, see the description of the prctl(2) PR_SET_DUMPABLE operation,
     * and the description of the /proc/sys/fs/suid_dumpable file in proc(5).)
     */

    /* Do not O_TRUNC: if later checks fail, we do not want to have file already modified here */
    errno = 0;
    int usercore_fd = open(core_basename, O_WRONLY | O_CREAT | O_NOFOLLOW, 0600); /* kernel makes 0600 too */
    if (usercore_fd < 0
     || fstat(usercore_fd, &sb) != 0
     || !S_ISREG(sb.st_mode)
     || sb.st_nlink != 1
    /* kernel internal dumper checks this too: if (inode->i_uid != current->fsuid) <fail>, need to mimic? */
    ) {
        perror_msg_and_die("%s/%s is not a regular file with link count 1", user_pwd, core_basename);
    }

    /* Note: we do not copy more than ulimit_c */
    off_t size;
    if (ftruncate(usercore_fd, 0) != 0
     || (size = copyfd_size(core_fd, usercore_fd, ulimit_c)) < 0
     || close(usercore_fd) != 0
    ) {
        /* perror first, otherwise unlink may trash errno */
        perror_msg("write error writing %s/%s", user_pwd, core_basename);
        unlink(core_basename);
        return 1;
    }
    if (size == ulimit_c && size != core_size)
    {
        /* We copied exactly ulimit_c bytes (and it doesn't accidentally match
         * core_size (imagine exactly 1MB coredump with "ulimit -c 1M" - that'd be ok)),
         * it means that core is larger than ulimit_c. Abort and delete the dump.
         */
        unlink(core_basename);
        return 1;
    }
    log("saved core dump of pid %lu to %s/%s (%llu bytes)", (long)pid, user_pwd, core_basename, (long long)size);

    return 0;
}