getrandom/error.rs
1#[cfg(feature = "std")]
2extern crate std;
3
4use core::fmt;
5
6cfg_if::cfg_if!(
7 if #[cfg(target_os = "uefi")] {
8 // See the UEFI spec for more information:
9 // https://uefi.org/specs/UEFI/2.10/Apx_D_Status_Codes.html
10
11 /// Raw error code.
12 ///
13 /// This alias mirrors unstable [`std::io::RawOsError`].
14 ///
15 /// [`std::io::RawOsError`]: https://doc.rust-lang.org/std/io/type.RawOsError.html
16 pub type RawOsError = usize;
17 type NonZeroRawOsError = core::num::NonZeroUsize;
18 const UEFI_ERROR_FLAG: RawOsError = 1 << (RawOsError::BITS - 1);
19 } else {
20 /// Raw error code.
21 ///
22 /// This alias mirrors unstable [`std::io::RawOsError`].
23 ///
24 /// [`std::io::RawOsError`]: https://doc.rust-lang.org/std/io/type.RawOsError.html
25 pub type RawOsError = i32;
26 type NonZeroRawOsError = core::num::NonZeroI32;
27 }
28);
29
30/// A small and `no_std` compatible error type
31///
32/// The [`Error::raw_os_error()`] will indicate if the error is from the OS, and
33/// if so, which error code the OS gave the application. If such an error is
34/// encountered, please consult with your system documentation.
35///
36/// *If this crate's `"std"` Cargo feature is enabled*, then:
37/// - [`getrandom::Error`][Error] implements
38/// [`std::error::Error`](https://doc.rust-lang.org/std/error/trait.Error.html)
39/// - [`std::io::Error`](https://doc.rust-lang.org/std/io/struct.Error.html) implements
40/// [`From<getrandom::Error>`](https://doc.rust-lang.org/std/convert/trait.From.html).
41
42// note: on non-UEFI targets OS errors are represented as negative integers,
43// while on UEFI targets OS errors have the highest bit set to 1.
44#[derive(Copy, Clone, Eq, PartialEq)]
45pub struct Error(NonZeroRawOsError);
46
47impl Error {
48 /// This target/platform is not supported by `getrandom`.
49 pub const UNSUPPORTED: Error = Self::new_internal(0);
50 /// The platform-specific `errno` returned a non-positive value.
51 pub const ERRNO_NOT_POSITIVE: Error = Self::new_internal(1);
52 /// Encountered an unexpected situation which should not happen in practice.
53 pub const UNEXPECTED: Error = Self::new_internal(2);
54
55 /// Internal errors can be in the range of 2^16..2^17
56 const INTERNAL_START: RawOsError = 1 << 16;
57 /// Custom errors can be in the range of 2^17..(2^17 + 2^16)
58 const CUSTOM_START: RawOsError = 1 << 17;
59
60 /// Creates a new `Error` instance from a positive error code.
61 ///
62 /// Returns [`Error::ERRNO_NOT_POSITIVE`] for zero and negative error codes.
63 #[cfg(not(target_os = "uefi"))]
64 #[allow(dead_code)]
65 pub(super) fn from_errno(errno: i32) -> Self {
66 if errno > 0 {
67 let code = errno
68 .checked_neg()
69 .expect("Positive number can be always negated");
70 Error::from_neg_error_code(code)
71 } else {
72 Error::ERRNO_NOT_POSITIVE
73 }
74 }
75
76 /// Creates a new `Error` instance from a negative error code.
77 ///
78 /// Returns [`Error::UNEXPECTED`] for zero and positive error codes.
79 #[cfg(not(target_os = "uefi"))]
80 #[allow(dead_code)]
81 pub(super) fn from_neg_error_code(code: RawOsError) -> Self {
82 if code < 0 {
83 let code = NonZeroRawOsError::new(code).expect("`code` is negative");
84 Self(code)
85 } else {
86 Error::UNEXPECTED
87 }
88 }
89
90 /// Creates a new instance of an `Error` from an UEFI error code.
91 #[cfg(target_os = "uefi")]
92 #[allow(dead_code)]
93 pub(super) fn from_uefi_code(code: RawOsError) -> Self {
94 if code & UEFI_ERROR_FLAG != 0 {
95 let code = NonZeroRawOsError::new(code).expect("The highest bit of `code` is set to 1");
96 Self(code)
97 } else {
98 Self::UNEXPECTED
99 }
100 }
101
102 /// Extract the raw OS error code (if this error came from the OS)
103 ///
104 /// This method is identical to [`std::io::Error::raw_os_error()`][1], except
105 /// that it works in `no_std` contexts. On most targets this method returns
106 /// `Option<i32>`, but some platforms (e.g. UEFI) may use a different primitive
107 /// type like `usize`. Consult with the [`RawOsError`] docs for more information.
108 ///
109 /// If this method returns `None`, the error value can still be formatted via
110 /// the `Display` implementation.
111 ///
112 /// [1]: https://doc.rust-lang.org/std/io/struct.Error.html#method.raw_os_error
113 /// [`RawOsError`]: https://doc.rust-lang.org/std/io/type.RawOsError.html
114 #[inline]
115 pub fn raw_os_error(self) -> Option<RawOsError> {
116 let code = self.0.get();
117
118 // note: in this method we need to cover only backends which rely on
119 // `Error::{from_error_code, from_errno, from_uefi_code}` methods,
120 // on all other backends this method always returns `None`.
121
122 #[cfg(target_os = "uefi")]
123 {
124 if code & UEFI_ERROR_FLAG != 0 {
125 Some(code)
126 } else {
127 None
128 }
129 }
130
131 #[cfg(not(target_os = "uefi"))]
132 {
133 // On most targets `std` expects positive error codes while retrieving error strings:
134 // - `libc`-based targets use `strerror_r` which expects positive error codes.
135 // - Hermit relies on the `hermit-abi` crate, which expects positive error codes:
136 // https://docs.rs/hermit-abi/0.4.0/src/hermit_abi/errno.rs.html#400-532
137 // - WASIp1 uses the same conventions as `libc`:
138 // https://github.com/rust-lang/rust/blob/1.85.0/library/std/src/sys/pal/wasi/os.rs#L57-L67
139 //
140 // The only exception is Solid, `std` expects negative system error codes, see:
141 // https://github.com/rust-lang/rust/blob/1.85.0/library/std/src/sys/pal/solid/error.rs#L5-L31
142 if code >= 0 {
143 None
144 } else if cfg!(not(target_os = "solid_asp3")) {
145 code.checked_neg()
146 } else {
147 Some(code)
148 }
149 }
150 }
151
152 /// Creates a new instance of an `Error` from a particular custom error code.
153 pub const fn new_custom(n: u16) -> Error {
154 // SAFETY: code > 0 as CUSTOM_START > 0 and adding `n` won't overflow `RawOsError`.
155 let code = Error::CUSTOM_START + (n as RawOsError);
156 Error(unsafe { NonZeroRawOsError::new_unchecked(code) })
157 }
158
159 /// Creates a new instance of an `Error` from a particular internal error code.
160 pub(crate) const fn new_internal(n: u16) -> Error {
161 // SAFETY: code > 0 as INTERNAL_START > 0 and adding `n` won't overflow `RawOsError`.
162 let code = Error::INTERNAL_START + (n as RawOsError);
163 Error(unsafe { NonZeroRawOsError::new_unchecked(code) })
164 }
165
166 fn internal_desc(&self) -> Option<&'static str> {
167 let desc = match *self {
168 Error::UNSUPPORTED => "getrandom: this target is not supported",
169 Error::ERRNO_NOT_POSITIVE => "errno: did not return a positive value",
170 Error::UNEXPECTED => "unexpected situation",
171 #[cfg(any(
172 target_os = "ios",
173 target_os = "visionos",
174 target_os = "watchos",
175 target_os = "tvos",
176 ))]
177 Error::IOS_RANDOM_GEN => "SecRandomCopyBytes: iOS Security framework failure",
178 #[cfg(all(windows, target_vendor = "win7"))]
179 Error::WINDOWS_RTL_GEN_RANDOM => "RtlGenRandom: Windows system function failure",
180 #[cfg(all(
181 feature = "wasm_js",
182 target_arch = "wasm32",
183 any(target_os = "unknown", target_os = "none")
184 ))]
185 Error::WEB_CRYPTO => "Web Crypto API is unavailable",
186 #[cfg(target_os = "vxworks")]
187 Error::VXWORKS_RAND_SECURE => "randSecure: VxWorks RNG module is not initialized",
188
189 #[cfg(any(
190 getrandom_backend = "rdrand",
191 all(target_arch = "x86_64", target_env = "sgx")
192 ))]
193 Error::FAILED_RDRAND => "RDRAND: failed multiple times: CPU issue likely",
194 #[cfg(any(
195 getrandom_backend = "rdrand",
196 all(target_arch = "x86_64", target_env = "sgx")
197 ))]
198 Error::NO_RDRAND => "RDRAND: instruction not supported",
199
200 #[cfg(getrandom_backend = "rndr")]
201 Error::RNDR_FAILURE => "RNDR: Could not generate a random number",
202 #[cfg(getrandom_backend = "rndr")]
203 Error::RNDR_NOT_AVAILABLE => "RNDR: Register not supported",
204 _ => return None,
205 };
206 Some(desc)
207 }
208}
209
210impl core::error::Error for Error {}
211
212impl fmt::Debug for Error {
213 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
214 let mut dbg = f.debug_struct("Error");
215 if let Some(errno) = self.raw_os_error() {
216 dbg.field("os_error", &errno);
217 #[cfg(feature = "std")]
218 dbg.field("description", &std::io::Error::from_raw_os_error(errno));
219 } else if let Some(desc) = self.internal_desc() {
220 dbg.field("internal_code", &self.0.get());
221 dbg.field("description", &desc);
222 } else {
223 dbg.field("unknown_code", &self.0.get());
224 }
225 dbg.finish()
226 }
227}
228
229impl fmt::Display for Error {
230 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
231 if let Some(errno) = self.raw_os_error() {
232 cfg_if! {
233 if #[cfg(feature = "std")] {
234 std::io::Error::from_raw_os_error(errno).fmt(f)
235 } else {
236 write!(f, "OS Error: {errno}")
237 }
238 }
239 } else if let Some(desc) = self.internal_desc() {
240 f.write_str(desc)
241 } else {
242 write!(f, "Unknown Error: {}", self.0.get())
243 }
244 }
245}