utils.c

/*
 * MIT License
 *
 * Copyright (c) 2019 Jianhui Zhao <zhaojh329@gmail.com>
 *
 * 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 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.
 */

#include <sys/stat.h>
#include <mntent.h>
#include <stdio.h>
#include <stdint.h>
#include <string.h>
#include <ctype.h>
#include <unistd.h>

#include "utils.h"

int find_login(char *buf, int len)
{
    FILE *fp = popen("which login", "r");
    if (fp) {
        if (fgets(buf, len, fp))
            buf[strlen(buf) - 1] = 0;
        pclose(fp);

        if (!buf[0])
            return -1;
        return 0;
    }

    return -1;
}

bool valid_id(const char *id)
{
    while (*id) {
        if (!isalnum(*id) && *id != '-' && *id != '_')
            return false;
        id++;
    }

    return true;
}

/* reference from https://tools.ietf.org/html/rfc4648#section-4 */
int b64_encode(const void *src, size_t srclen, void *dest, size_t destsize)
{
    char *Base64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
    const uint8_t *input = src;
    char *output = dest;

    while (srclen > 0) {
        int skip = 1;
        int i0 = input[0] >> 2;
        int i1 = (input[0] & 0x3) << 4;
        int i2 = 64;
        int i3 = 64;

        if (destsize < 5)
            return -1;

        if (srclen > 1) {
            skip++;
            i1 += input[1] >> 4;
            i2 = (input[1] & 0xF) << 2;

            if (srclen > 2) {
                i2 += input[2] >> 6;
                i3 = input[2] & 0x3F;
                skip++;
            }
        }

        *output++ = Base64[i0];
        *output++ = Base64[i1];
        *output++ = Base64[i2];
        *output++ = Base64[i3];

        input += skip;
        srclen -= skip;
        destsize -= 4;
    }

    *output++ = 0;
    return output - (char *) dest - 1;
}

const char *format_size(size_t size)
{
    static char str[64];

    if (size < 1024)
        sprintf(str, "%zu B", size);
    else if (size < 1024 * 1024)
        sprintf(str, "%.2f KB", size / 1024.0);
    else
        sprintf(str, "%.2f MB", size / 1024.0 / 1024.0);

    return str;
}

/*
 * Given any file (or directory), find the mount table entry for its
 * filesystem.
 */
struct mntent *find_mount_point(const char *name)
{
    struct mntent *ment;
    dev_t devno_of_name;
    struct stat s;
    FILE *mtab_fp;

    if (stat(name, &s) < 0)
        return NULL;

    devno_of_name = s.st_dev;

    if (S_ISBLK(s.st_mode) || S_ISCHR(s.st_mode))
        return NULL;

    mtab_fp = setmntent("/etc/mtab", "r");
    if (!mtab_fp)
        return NULL;

    while ((ment = getmntent(mtab_fp))) {
        if (!strcmp(ment->mnt_fsname, "rootfs"))
            continue;

        /* string match */
        if (!strcmp(name, ment->mnt_dir))
            break;

        /* match the directory's mount point. */
        if (stat(ment->mnt_dir, &s) == 0 && s.st_dev == devno_of_name)
            break;
    }
    endmntent(mtab_fp);

    return ment;
}

/*
 *  getcwd_pid does not append a null byte to buf.  It will (silently) truncate the contents (to
 *  a length of bufsiz characters), in case the buffer is too small to hold all the contents.
 */
ssize_t getcwd_by_pid(pid_t pid, char *buf, size_t bufsiz)
{
    char link[128];

    sprintf(link, "/proc/%d/cwd", pid);

    return readlink(link, buf, bufsiz);
}

bool getuid_by_pid(pid_t pid, uid_t *uid)
{
    char status[128];
    char line[128];
    int i = 9;
    FILE *fp;

    sprintf(status, "/proc/%d/status", pid);

    fp = fopen(status, "r");
    if (!fp)
        return false;

    while (i-- > 0) {
        if (!fgets(line, sizeof(line), fp)) {
            fclose(fp);
            return false;
        }
    }

    fclose(fp);

    sscanf(line, "Uid:\t%u", uid);

    return true;
}

bool getgid_by_pid(pid_t pid, gid_t *gid)
{
    char status[128];
    char line[128];
    int i = 10;
    FILE *fp;

    sprintf(status, "/proc/%d/status", pid);

    fp = fopen(status, "r");
    if (!fp)
        return false;

    while (i-- > 0) {
        if (!fgets(line, sizeof(line), fp)) {
            fclose(fp);
            return false;
        }
    }

    fclose(fp);

    sscanf(line, "Gid:\t%u", gid);

    return true;
}