1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
// Copyright 2018 Developers of the Rand project.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use core::{fmt, num::NonZeroU32};

/// A small and `no_std` compatible error type
///
/// The [`Error::raw_os_error()`] will indicate if the error is from the OS, and
/// if so, which error code the OS gave the application. If such an error is
/// encountered, please consult with your system documentation.
///
/// Internally this type is a NonZeroU32, with certain values reserved for
/// certain purposes, see [`Error::INTERNAL_START`] and [`Error::CUSTOM_START`].
///
/// *If this crate's `"std"` Cargo feature is enabled*, then:
/// - [`getrandom::Error`][Error] implements
///   [`std::error::Error`](https://doc.rust-lang.org/std/error/trait.Error.html)
/// - [`std::io::Error`](https://doc.rust-lang.org/std/io/struct.Error.html) implements
///   [`From<getrandom::Error>`](https://doc.rust-lang.org/std/convert/trait.From.html).
#[derive(Copy, Clone, Eq, PartialEq)]
pub struct Error(NonZeroU32);

const fn internal_error(n: u16) -> Error {
    // SAFETY: code > 0 as INTERNAL_START > 0 and adding n won't overflow a u32.
    let code = Error::INTERNAL_START + (n as u32);
    Error(unsafe { NonZeroU32::new_unchecked(code) })
}

impl Error {
    /// This target/platform is not supported by `getrandom`.
    pub const UNSUPPORTED: Error = internal_error(0);
    /// The platform-specific `errno` returned a non-positive value.
    pub const ERRNO_NOT_POSITIVE: Error = internal_error(1);
    /// Call to iOS [`SecRandomCopyBytes`](https://developer.apple.com/documentation/security/1399291-secrandomcopybytes) failed.
    pub const IOS_SEC_RANDOM: Error = internal_error(3);
    /// Call to Windows [`RtlGenRandom`](https://docs.microsoft.com/en-us/windows/win32/api/ntsecapi/nf-ntsecapi-rtlgenrandom) failed.
    pub const WINDOWS_RTL_GEN_RANDOM: Error = internal_error(4);
    /// RDRAND instruction failed due to a hardware issue.
    pub const FAILED_RDRAND: Error = internal_error(5);
    /// RDRAND instruction unsupported on this target.
    pub const NO_RDRAND: Error = internal_error(6);
    /// The browser does not have support for `self.crypto`.
    pub const WEB_CRYPTO: Error = internal_error(7);
    /// The browser does not have support for `crypto.getRandomValues`.
    pub const WEB_GET_RANDOM_VALUES: Error = internal_error(8);
    /// On VxWorks, call to `randSecure` failed (random number generator is not yet initialized).
    pub const VXWORKS_RAND_SECURE: Error = internal_error(11);
    /// NodeJS does not have support for the `crypto` module.
    pub const NODE_CRYPTO: Error = internal_error(12);
    /// NodeJS does not have support for `crypto.randomFillSync`.
    pub const NODE_RANDOM_FILL_SYNC: Error = internal_error(13);

    /// Codes below this point represent OS Errors (i.e. positive i32 values).
    /// Codes at or above this point, but below [`Error::CUSTOM_START`] are
    /// reserved for use by the `rand` and `getrandom` crates.
    pub const INTERNAL_START: u32 = 1 << 31;

    /// Codes at or above this point can be used by users to define their own
    /// custom errors.
    pub const CUSTOM_START: u32 = (1 << 31) + (1 << 30);

    /// Extract the raw OS error code (if this error came from the OS)
    ///
    /// This method is identical to [`std::io::Error::raw_os_error()`][1], except
    /// that it works in `no_std` contexts. If this method returns `None`, the
    /// error value can still be formatted via the `Display` implementation.
    ///
    /// [1]: https://doc.rust-lang.org/std/io/struct.Error.html#method.raw_os_error
    #[inline]
    pub fn raw_os_error(self) -> Option<i32> {
        if self.0.get() < Self::INTERNAL_START {
            Some(self.0.get() as i32)
        } else {
            None
        }
    }

    /// Extract the bare error code.
    ///
    /// This code can either come from the underlying OS, or be a custom error.
    /// Use [`Error::raw_os_error()`] to disambiguate.
    #[inline]
    pub const fn code(self) -> NonZeroU32 {
        self.0
    }
}

cfg_if! {
    if #[cfg(unix)] {
        fn os_err(errno: i32, buf: &mut [u8]) -> Option<&str> {
            let buf_ptr = buf.as_mut_ptr() as *mut libc::c_char;
            if unsafe { libc::strerror_r(errno, buf_ptr, buf.len()) } != 0 {
                return None;
            }

            // Take up to trailing null byte
            let n = buf.len();
            let idx = buf.iter().position(|&b| b == 0).unwrap_or(n);
            core::str::from_utf8(&buf[..idx]).ok()
        }
    } else if #[cfg(target_os = "wasi")] {
        fn os_err(errno: i32, _buf: &mut [u8]) -> Option<wasi::Error> {
            wasi::Error::from_raw_error(errno as _)
        }
    } else {
        fn os_err(_errno: i32, _buf: &mut [u8]) -> Option<&str> {
            None
        }
    }
}

impl fmt::Debug for Error {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        let mut dbg = f.debug_struct("Error");
        if let Some(errno) = self.raw_os_error() {
            dbg.field("os_error", &errno);
            let mut buf = [0u8; 128];
            if let Some(err) = os_err(errno, &mut buf) {
                dbg.field("description", &err);
            }
        } else if let Some(desc) = internal_desc(*self) {
            dbg.field("internal_code", &self.0.get());
            dbg.field("description", &desc);
        } else {
            dbg.field("unknown_code", &self.0.get());
        }
        dbg.finish()
    }
}

impl fmt::Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        if let Some(errno) = self.raw_os_error() {
            let mut buf = [0u8; 128];
            match os_err(errno, &mut buf) {
                Some(err) => err.fmt(f),
                None => write!(f, "OS Error: {}", errno),
            }
        } else if let Some(desc) = internal_desc(*self) {
            f.write_str(desc)
        } else {
            write!(f, "Unknown Error: {}", self.0.get())
        }
    }
}

impl From<NonZeroU32> for Error {
    fn from(code: NonZeroU32) -> Self {
        Self(code)
    }
}

fn internal_desc(error: Error) -> Option<&'static str> {
    match error {
        Error::UNSUPPORTED => Some("getrandom: this target is not supported"),
        Error::ERRNO_NOT_POSITIVE => Some("errno: did not return a positive value"),
        Error::IOS_SEC_RANDOM => Some("SecRandomCopyBytes: iOS Security framework failure"),
        Error::WINDOWS_RTL_GEN_RANDOM => Some("RtlGenRandom: Windows system function failure"),
        Error::FAILED_RDRAND => Some("RDRAND: failed multiple times: CPU issue likely"),
        Error::NO_RDRAND => Some("RDRAND: instruction not supported"),
        Error::WEB_CRYPTO => Some("Web Crypto API is unavailable"),
        Error::WEB_GET_RANDOM_VALUES => Some("Web API crypto.getRandomValues is unavailable"),
        Error::VXWORKS_RAND_SECURE => Some("randSecure: VxWorks RNG module is not initialized"),
        Error::NODE_CRYPTO => Some("Node.js crypto module is unavailable"),
        Error::NODE_RANDOM_FILL_SYNC => Some("Node.js API crypto.randomFillSync is unavailable"),
        _ => None,
    }
}

#[cfg(test)]
mod tests {
    use super::Error;
    use core::mem::size_of;

    #[test]
    fn test_size() {
        assert_eq!(size_of::<Error>(), 4);
        assert_eq!(size_of::<Result<(), Error>>(), 4);
    }
}