rand.rs.html -- source
Description: Source to the Rust file `src/libstd/sys/unix/rand.rs`.
Keywords: rust, rustlang, rust-lang

      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
    185
    186
    187
    188
    189
    190
    191
    192
    193
    194
    195
    196
    197
    198
    199
    200
    201
    202
    203
    204
    205
    206
    207
    208
    209
    210
    211
    212
    213
    214
    215
    216
    217
    218
    219
    220
    221
    222
    223
    224
    225
    226
    227
    228
    229
    230

    use crate::mem;
    use crate::slice;

    pub fn hashmap_random_keys() -> (u64, u64) {
        let mut v = (0, 0);
        unsafe {
            let view = slice::from_raw_parts_mut(&mut v as *mut _ as *mut u8, mem::size_of_val(&v));
            imp::fill_bytes(view);
        }
        v
    }

    #[cfg(all(
        unix,
        not(target_os = "macos"),
        not(target_os = "ios"),
        not(target_os = "openbsd"),
        not(target_os = "freebsd"),
        not(target_os = "netbsd"),
        not(target_os = "fuchsia"),
        not(target_os = "redox")
    ))]
    mod imp {
        use crate::fs::File;
        use crate::io::Read;

        #[cfg(any(target_os = "linux", target_os = "android"))]
        fn getrandom(buf: &mut [u8]) -> libc::c_long {
            unsafe {
                libc::syscall(libc::SYS_getrandom, buf.as_mut_ptr(), buf.len(), libc::GRND_NONBLOCK)
            }
        }

        #[cfg(not(any(target_os = "linux", target_os = "android")))]
        fn getrandom_fill_bytes(_buf: &mut [u8]) -> bool {
            false
        }

        #[cfg(any(target_os = "linux", target_os = "android"))]
        fn getrandom_fill_bytes(v: &mut [u8]) -> bool {
            use crate::sync::atomic::{AtomicBool, Ordering};
            use crate::sys::os::errno;

            static GETRANDOM_UNAVAILABLE: AtomicBool = AtomicBool::new(false);
            if GETRANDOM_UNAVAILABLE.load(Ordering::Relaxed) {
                return false;
            }

            let mut read = 0;
            while read < v.len() {
                let result = getrandom(&mut v[read..]);
                if result == -1 {
                    let err = errno() as libc::c_int;
                    if err == libc::EINTR {
                        continue;
                    } else if err == libc::ENOSYS || err == libc::EPERM {
                        // Fall back to reading /dev/urandom if `getrandom` is not
                        // supported on the current kernel.
                        //
                        // Also fall back in case it is disabled by something like
                        // seccomp or inside of virtual machines.
                        GETRANDOM_UNAVAILABLE.store(true, Ordering::Relaxed);
                        return false;
                    } else if err == libc::EAGAIN {
                        return false;
                    } else {
                        panic!("unexpected getrandom error: {}", err);
                    }
                } else {
                    read += result as usize;
                }
            }
            true
        }

        pub fn fill_bytes(v: &mut [u8]) {
            // getrandom_fill_bytes here can fail if getrandom() returns EAGAIN,
            // meaning it would have blocked because the non-blocking pool (urandom)
            // has not initialized in the kernel yet due to a lack of entropy. The
            // fallback we do here is to avoid blocking applications which could
            // depend on this call without ever knowing they do and don't have a
            // work around. The PRNG of /dev/urandom will still be used but over a
            // possibly predictable entropy pool.
            if getrandom_fill_bytes(v) {
                return;
            }

            // getrandom failed because it is permanently or temporarily (because
            // of missing entropy) unavailable. Open /dev/urandom, read from it,
            // and close it again.
            let mut file = File::open("/dev/urandom").expect("failed to open /dev/urandom");
            file.read_exact(v).expect("failed to read /dev/urandom")
        }
    }

    #[cfg(target_os = "macos")]
    mod imp {
        use crate::fs::File;
        use crate::io::Read;
        use crate::sys::os::errno;
        use libc::{c_int, c_void, size_t};

        fn getentropy_fill_bytes(v: &mut [u8]) -> bool {
            weak!(fn getentropy(*mut c_void, size_t) -> c_int);

            getentropy
                .get()
                .map(|f| {
                    // getentropy(2) permits a maximum buffer size of 256 bytes
                    for s in v.chunks_mut(256) {
                        let ret = unsafe { f(s.as_mut_ptr() as *mut c_void, s.len()) };
                        if ret == -1 {
                            panic!("unexpected getentropy error: {}", errno());
                        }
                    }
                    true
                })
                .unwrap_or(false)
        }

        pub fn fill_bytes(v: &mut [u8]) {
            if getentropy_fill_bytes(v) {
                return;
            }

            // for older macos which doesn't support getentropy
            let mut file = File::open("/dev/urandom").expect("failed to open /dev/urandom");
            file.read_exact(v).expect("failed to read /dev/urandom")
        }
    }

    #[cfg(target_os = "openbsd")]
    mod imp {
        use crate::sys::os::errno;

        pub fn fill_bytes(v: &mut [u8]) {
            // getentropy(2) permits a maximum buffer size of 256 bytes
            for s in v.chunks_mut(256) {
                let ret = unsafe { libc::getentropy(s.as_mut_ptr() as *mut libc::c_void, s.len()) };
                if ret == -1 {
                    panic!("unexpected getentropy error: {}", errno());
                }
            }
        }
    }

    // On iOS and MacOS `SecRandomCopyBytes` calls `CCRandomCopyBytes` with
    // `kCCRandomDefault`. `CCRandomCopyBytes` manages a CSPRNG which is seeded
    // from `/dev/random` and which runs on its own thread accessed via GCD.
    // This seems needlessly heavyweight for the purposes of generating two u64s
    // once per thread in `hashmap_random_keys`. Therefore `SecRandomCopyBytes` is
    // only used on iOS where direct access to `/dev/urandom` is blocked by the
    // sandbox.
    #[cfg(target_os = "ios")]
    mod imp {
        use crate::io;
        use crate::ptr;
        use libc::{c_int, size_t};

        enum SecRandom {}

        #[allow(non_upper_case_globals)]
        const kSecRandomDefault: *const SecRandom = ptr::null();

        extern "C" {
            fn SecRandomCopyBytes(rnd: *const SecRandom, count: size_t, bytes: *mut u8) -> c_int;
        }

        pub fn fill_bytes(v: &mut [u8]) {
            let ret = unsafe { SecRandomCopyBytes(kSecRandomDefault, v.len(), v.as_mut_ptr()) };
            if ret == -1 {
                panic!("couldn't generate random bytes: {}", io::Error::last_os_error());
            }
        }
    }

    #[cfg(any(target_os = "freebsd", target_os = "netbsd"))]
    mod imp {
        use crate::ptr;

        pub fn fill_bytes(v: &mut [u8]) {
            let mib = [libc::CTL_KERN, libc::KERN_ARND];
            // kern.arandom permits a maximum buffer size of 256 bytes
            for s in v.chunks_mut(256) {
                let mut s_len = s.len();
                let ret = unsafe {
                    libc::sysctl(
                        mib.as_ptr(),
                        mib.len() as libc::c_uint,
                        s.as_mut_ptr() as *mut _,
                        &mut s_len,
                        ptr::null(),
                        0,
                    )
                };
                if ret == -1 || s_len != s.len() {
                    panic!(
                        "kern.arandom sysctl failed! (returned {}, s.len() {}, oldlenp {})",
                        ret,
                        s.len(),
                        s_len
                    );
                }
            }
        }
    }

    #[cfg(target_os = "fuchsia")]
    mod imp {
        #[link(name = "zircon")]
        extern "C" {
            fn zx_cprng_draw(buffer: *mut u8, len: usize);
        }

        pub fn fill_bytes(v: &mut [u8]) {
            unsafe { zx_cprng_draw(v.as_mut_ptr(), v.len()) }
        }
    }

    #[cfg(target_os = "redox")]
    mod imp {
        use crate::fs::File;
        use crate::io::Read;

        pub fn fill_bytes(v: &mut [u8]) {
            // Open rand:, read from it, and close it again.
            let mut file = File::open("rand:").expect("failed to open rand:");
            file.read_exact(v).expect("failed to read rand:")
        }
    }