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