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comparison libpam-sys/libpam-sys-impls/build.rs @ 176:0730f5f2ee2a

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Turn `libpam-sys-consts` back into `libpam-sys-impls`. This moves the constants into `libpam-sys` and makes `libpam-sys-impls` responsible solely for detecting the current PAM implementation.
author Paul Fisher <paul@pfish.zone>
date Wed, 30 Jul 2025 17:53:31 -0400
parents libpam-sys/libpam-sys-consts/build.rs@46e8ce5cd5d1
children
comparison
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175:e30775c80b49 176:0730f5f2ee2a
1 #![allow(unexpected_cfgs)]
2
3 use std::ffi::{c_void, CString};
4 use std::ptr::NonNull;
5 use std::{env, fs};
6
7 include!("src/pam_impl.rs");
8
9 /// The strategy to use to detect PAM.
10 enum Detect {
11 /// Use the default PAM implementation based on the OS,
12 /// or the currently-installed version if the OS is not recognized.
13 TargetDefault,
14 /// Detect the installed implementation.
15 Installed,
16 /// Use the named version of PAM.
17 Specified(PamImpl),
18 }
19
20 const INSTALLED: &str = "__installed__";
21
22 fn main() {
23 let detection = match option_env!("LIBPAMSYS_IMPL") {
24 Some("") | None => Detect::TargetDefault,
25 Some(INSTALLED) => Detect::Installed,
26 Some(val) => Detect::Specified(PamImpl::try_from(val).unwrap_or_else(|_| {
27 panic!(
28 "unknown PAM implementation {val:?}. \
29 valid LIBPAMSYS_IMPLs are {:?}, \
30 {INSTALLED:?} to use the currently-installed version, \
31 or unset to use the OS default",
32 PamImpl::items()
33 )
34 })),
35 };
36 let pam_impl = match detection {
37 Detect::TargetDefault => LibPam::target_default(),
38 Detect::Installed => LibPam::probe_detect(),
39 Detect::Specified(other) => other,
40 };
41 let impl_str = format!("{pam_impl:?}");
42 println!("{}", generate_cfg(&impl_str));
43 // We set this environment variable to substitute into docstrings.
44 println!("cargo:rustc-env=LIBPAMSYS_IMPL={impl_str}");
45 fs::write(
46 format!("{}/pam_impl_const.rs", env::var("OUT_DIR").unwrap()),
47 generate_consts(&impl_str),
48 )
49 .unwrap();
50 }
51
52 fn generate_consts(impl_str: &str) -> String {
53 format!(
54 "\
55 impl PamImpl {{
56 /// The implementation of libpam this was built for (`{impl_str}`).
57 pub const CURRENT: Self = Self::{impl_str};
58 }}
59
60 /// String name of [`PamImpl::CURRENT`], for substituting into docs.
61 #[macro_export]
62 macro_rules! pam_impl_name {{ () => ({impl_str:?}) }}
63 "
64 )
65 }
66
67 struct LibPam(NonNull<c_void>);
68
69 impl LibPam {
70 /// Guess the PAM implementation based on the current OS.
71 fn target_default() -> PamImpl {
72 if cfg!(target_os = "linux") {
73 PamImpl::LinuxPam
74 } else if cfg!(any(
75 target_os = "macos",
76 target_os = "freebsd",
77 target_os = "netbsd",
78 target_os = "dragonfly",
79 target_os = "openbsd",
80 )) {
81 PamImpl::OpenPam
82 } else if cfg!(any(target_os = "illumos", target_os = "solaris")) {
83 PamImpl::Sun
84 } else {
85 Self::probe_detect()
86 }
87 }
88
89 /// Look at the currently-installed LibPAM.
90 fn probe_detect() -> PamImpl {
91 if let Some(lib) = Self::open() {
92 if lib.has("pam_syslog") {
93 return PamImpl::LinuxPam;
94 } else if lib.has("_openpam_log") {
95 return PamImpl::OpenPam;
96 } else if lib.has("__pam_get_authtok") {
97 return PamImpl::Sun;
98 }
99 }
100 // idk
101 PamImpl::XSso
102 }
103
104 fn open() -> Option<Self> {
105 let dlopen = |s: &[u8]| unsafe { libc::dlopen(s.as_ptr().cast(), libc::RTLD_LAZY) };
106 NonNull::new(dlopen(b"libpam.so\0"))
107 .or_else(|| NonNull::new(dlopen(b"libpam.dylib\0")))
108 .map(Self)
109 }
110
111 fn has(&self, name: &str) -> bool {
112 let name = CString::new(name).unwrap();
113 let symbol = unsafe { libc::dlsym(self.0.as_ptr(), name.as_ptr()) };
114 !symbol.is_null()
115 }
116 }
117
118 impl Drop for LibPam {
119 fn drop(&mut self) {
120 unsafe {
121 libc::dlclose(self.0.as_ptr());
122 }
123 }
124 }