pwd.cpp

/*
 * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this
 *    list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <AK/String.h>
#include <AK/Vector.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <unistd.h>

extern "C" {

#define PWDB_STR_MAX_LEN 256

struct passwd_with_strings : public passwd {
    char name_buffer[PWDB_STR_MAX_LEN];
    char passwd_buffer[PWDB_STR_MAX_LEN];
    char gecos_buffer[PWDB_STR_MAX_LEN];
    char dir_buffer[PWDB_STR_MAX_LEN];
    char shell_buffer[PWDB_STR_MAX_LEN];
};

static FILE* __pwdb_stream = nullptr;
static unsigned __pwdb_line_number = 0;
static struct passwd_with_strings* __pwdb_entry = nullptr;

void setpwent()
{
    __pwdb_line_number = 0;
    if (__pwdb_stream) {
        rewind(__pwdb_stream);
    } else {
        __pwdb_stream = fopen("/etc/passwd", "r");
        if (!__pwdb_stream) {
            perror("open /etc/passwd");
        }
        assert(__pwdb_stream);
        __pwdb_entry = (struct passwd_with_strings*)mmap_with_name(nullptr, getpagesize(), PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, 0, 0, "setpwent");
    }
}

void endpwent()
{
    __pwdb_line_number = 0;
    if (__pwdb_stream) {
        fclose(__pwdb_stream);
        __pwdb_stream = nullptr;
    }
    if (__pwdb_entry) {
        munmap(__pwdb_entry, getpagesize());
        __pwdb_entry = nullptr;
    }
}

struct passwd* getpwuid(uid_t uid)
{
    setpwent();
    while (auto* pw = getpwent()) {
        if (pw->pw_uid == uid)
            return pw;
    }
    return nullptr;
}

struct passwd* getpwnam(const char* name)
{
    setpwent();
    while (auto* pw = getpwent()) {
        if (!strcmp(pw->pw_name, name))
            return pw;
    }
    return nullptr;
}

struct passwd* getpwent()
{
    if (!__pwdb_stream)
        setpwent();

    assert(__pwdb_stream);
    if (feof(__pwdb_stream))
        return nullptr;

next_entry:
    char buffer[1024];
    ++__pwdb_line_number;
    char* s = fgets(buffer, sizeof(buffer), __pwdb_stream);
    if (!s)
        return nullptr;
    assert(__pwdb_stream);
    if (feof(__pwdb_stream))
        return nullptr;
    String line(s, Chomp);
    auto parts = line.split(':', true);
    if (parts.size() != 7) {
        fprintf(stderr, "getpwent(): Malformed entry on line %u\n", __pwdb_line_number);
        goto next_entry;
    }
    auto& e_name = parts[0];
    auto& e_passwd = parts[1];
    auto& e_uid_string = parts[2];
    auto& e_gid_string = parts[3];
    auto& e_gecos = parts[4];
    auto& e_dir = parts[5];
    auto& e_shell = parts[6];
    auto e_uid = e_uid_string.to_uint();
    if (!e_uid.has_value()) {
        fprintf(stderr, "getpwent(): Malformed UID on line %u\n", __pwdb_line_number);
        goto next_entry;
    }
    auto e_gid = e_gid_string.to_uint();
    if (!e_gid.has_value()) {
        fprintf(stderr, "getpwent(): Malformed GID on line %u\n", __pwdb_line_number);
        goto next_entry;
    }
    __pwdb_entry->pw_uid = e_uid.value();
    __pwdb_entry->pw_gid = e_gid.value();
    __pwdb_entry->pw_name = __pwdb_entry->name_buffer;
    __pwdb_entry->pw_passwd = __pwdb_entry->passwd_buffer;
    __pwdb_entry->pw_gecos = __pwdb_entry->gecos_buffer;
    __pwdb_entry->pw_dir = __pwdb_entry->dir_buffer;
    __pwdb_entry->pw_shell = __pwdb_entry->shell_buffer;

    strncpy(__pwdb_entry->name_buffer, e_name.characters(), PWDB_STR_MAX_LEN - 1);
    strncpy(__pwdb_entry->passwd_buffer, e_passwd.characters(), PWDB_STR_MAX_LEN - 1);
    strncpy(__pwdb_entry->gecos_buffer, e_gecos.characters(), PWDB_STR_MAX_LEN - 1);
    strncpy(__pwdb_entry->dir_buffer, e_dir.characters(), PWDB_STR_MAX_LEN - 1);
    strncpy(__pwdb_entry->shell_buffer, e_shell.characters(), PWDB_STR_MAX_LEN - 1);
    return __pwdb_entry;
}

int putpwent(const struct passwd* p, FILE* stream)
{
    if (!p || !stream || !p->pw_passwd || !p->pw_name || !p->pw_dir || !p->pw_gecos || !p->pw_shell) {
        errno = EINVAL;
        return -1;
    }

    auto is_valid_field = [](const char* str) {
        return str && !strpbrk(str, ":\n");
    };

    if (!is_valid_field(p->pw_name) || !is_valid_field(p->pw_dir) || !is_valid_field(p->pw_gecos) || !is_valid_field(p->pw_shell)) {
        errno = EINVAL;
        return -1;
    }

    int nwritten = fprintf(stream, "%s:%s:%u:%u:%s,,,:%s:%s\n", p->pw_name, p->pw_passwd, p->pw_uid, p->pw_gid, p->pw_gecos, p->pw_dir, p->pw_shell);
    if (!nwritten || nwritten < 0) {
        errno = ferror(stream);
        return -1;
    }

    return 0;
}
}