/*
 *    Routine to provide information about the other side of a FD.
 *
 * Copyright (C) 2015 Peter Wu <peter@lekensteyn.nl>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 * DEALINGS IN THE SOFTWARE.
 *
 */

#define _GNU_SOURCE             /* for struct ucred on Linux */
#include "scope.h"

#include <unistd.h>
#include <stdio.h>
#include <sys/types.h>          /* for pid_t */

#ifdef HAVE_GETPEERUCRED	/* Solaris-derived systems */
#include <ucred.h>
#endif

#ifdef __sun
#include <procfs.h>
#endif

static pid_t
GetPidFromFd(FD fd)
{
#ifdef SO_PEERCRED
    struct ucred cred;
    socklen_t cred_len = sizeof(cred);

    if (getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &cred, &cred_len) == 0 &&
        cred_len == sizeof(cred)) {
        return cred.pid;
    }
#elif defined(HAVE_GETPEERUCRED)
    ucred_t *peercred = NULL;

    if (getpeerucred(fd, &peercred) == 0) {
        pid_t peerpid = ucred_getpid(peercred);
        ucred_free(peercred);
        if (peerpid != -1) {
            return peerpid;
        }
    }
#endif
    return 0;
}

static const char *
GetProcnameForPid(pid_t pid)
{
#ifdef __sun	/* Solaris-derived /proc */
    static char comm[PRARGSZ];
    char path[32];
    int totsize = 0;
    int fd = 0;
    psinfo_t psinfo = { 0 };
    char *sp;

    if (snprintf(path, sizeof(path), "/proc/%d/psinfo", pid) < 0)
        return NULL;
    fd = open(path, O_RDONLY);
    if (fd < 0)
        return NULL;

    totsize = read(fd, &psinfo, sizeof(psinfo_t));
    close(fd);
    if (totsize <= 0)
        return NULL;

    /* pr_psargs is the first PRARGSZ (80) characters of the command
     * line string - assume up to the first space is the command name,
     * since it's not delimited.   While there is also pr_fname, that's
     * more limited, giving only the first 16 chars of the basename of
     * the file that was exec'ed, thus cutting off many long gnome
     * command names, or returning "isapython2.6" for all python scripts.
     */
    psinfo.pr_psargs[PRARGSZ - 1] = '\0';
    sp = strchr(psinfo.pr_psargs, ' ');
    if (sp)
        *sp = '\0';

    strlcpy(comm, psinfo.pr_psargs, sizeof(comm));
    return comm;
#else  /* Linux-style /proc */
    /* comm is no longer than TASK_COMM_LEN (16) */
    static char comm[17];
    char comm_path[32];
    char comm_fd;
    unsigned comm_len = 0;

    snprintf(comm_path, sizeof(comm_path), "/proc/%d/comm", pid);
    comm_fd = open(comm_path, O_RDONLY);
    if (comm_fd != -1) {
        comm_len = read(comm_fd, comm, sizeof(comm) - 1);
        if (comm_len < 0)
            comm_len = 0;
        close(comm_fd);
    }

    if (comm_len > 0 && comm[comm_len - 1] == '\n')
        comm_len--;
    comm[comm_len] = '\0';
    return comm;
#endif
}

/*
   Retrieves additional information about the other side of the fd.
   For Unix domain sockets, this results in the process ID and name.
 */
char *
ReadPeerInfo(FD fd)
{
    /* should hold enough for "PID <number> <command name>" */
    char peer_info[40];
    unsigned pos;
    pid_t pid;
    const char *comm;

    pid = GetPidFromFd(fd);
    /* Use the fact that pid_t is the first field of struct ucred. */
    if (pid) {
        pos = snprintf(peer_info, sizeof(peer_info), "pid %d", pid);

        comm = GetProcnameForPid(pid);
        if (comm)
            pos += snprintf(peer_info + pos, sizeof(peer_info) - pos,
                            " %s", comm);

        return strdup(peer_info);
    }

    /* (Could add port number here for AF_INET if it helps.) */

    return NULL;
}
