105 lines
3.7 KiB
Zig
105 lines
3.7 KiB
Zig
const builtin = @import("builtin");
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const Os = builtin.Os;
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const os = @import("../os.zig");
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const io = @import("../io.zig");
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pub const UserInfo = struct {
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uid: u32,
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gid: u32,
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};
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/// POSIX function which gets a uid from username.
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pub fn getUserInfo(name: []const u8) !UserInfo {
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return switch (builtin.os) {
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Os.linux, Os.macosx, Os.ios, Os.freebsd, Os.netbsd => posixGetUserInfo(name),
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else => @compileError("Unsupported OS"),
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};
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}
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const State = enum {
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Start,
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WaitForNextLine,
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SkipPassword,
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ReadUserId,
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ReadGroupId,
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};
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// TODO this reads /etc/passwd. But sometimes the user/id mapping is in something else
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// like NIS, AD, etc. See `man nss` or look at an strace for `id myuser`.
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pub fn posixGetUserInfo(name: []const u8) !UserInfo {
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var in_stream = try io.InStream.open("/etc/passwd", null);
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defer in_stream.close();
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var buf: [os.page_size]u8 = undefined;
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var name_index: usize = 0;
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var state = State.Start;
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var uid: u32 = 0;
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var gid: u32 = 0;
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while (true) {
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const amt_read = try in_stream.read(buf[0..]);
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for (buf[0..amt_read]) |byte| {
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switch (state) {
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State.Start => switch (byte) {
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':' => {
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state = if (name_index == name.len) State.SkipPassword else State.WaitForNextLine;
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},
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'\n' => return error.CorruptPasswordFile,
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else => {
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if (name_index == name.len or name[name_index] != byte) {
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state = State.WaitForNextLine;
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}
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name_index += 1;
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},
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},
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State.WaitForNextLine => switch (byte) {
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'\n' => {
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name_index = 0;
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state = State.Start;
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},
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else => continue,
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},
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State.SkipPassword => switch (byte) {
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'\n' => return error.CorruptPasswordFile,
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':' => {
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state = State.ReadUserId;
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},
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else => continue,
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},
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State.ReadUserId => switch (byte) {
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':' => {
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state = State.ReadGroupId;
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},
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'\n' => return error.CorruptPasswordFile,
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else => {
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const digit = switch (byte) {
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'0'...'9' => byte - '0',
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else => return error.CorruptPasswordFile,
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};
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if (@mulWithOverflow(u32, uid, 10, *uid)) return error.CorruptPasswordFile;
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if (@addWithOverflow(u32, uid, digit, *uid)) return error.CorruptPasswordFile;
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},
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},
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State.ReadGroupId => switch (byte) {
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'\n', ':' => {
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return UserInfo{
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.uid = uid,
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.gid = gid,
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};
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},
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else => {
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const digit = switch (byte) {
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'0'...'9' => byte - '0',
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else => return error.CorruptPasswordFile,
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};
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if (@mulWithOverflow(u32, gid, 10, *gid)) return error.CorruptPasswordFile;
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if (@addWithOverflow(u32, gid, digit, *gid)) return error.CorruptPasswordFile;
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},
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},
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}
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}
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if (amt_read < buf.len) return error.UserNotFound;
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}
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}
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