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Seed Libc rng from system entropy (JuliaLang#43606)
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We're seeing lots of CI failures that look like collisions in the
names of temporary variables. Currently we're seeding the libc
rng from a low entropy clock, which is somewhat likely to have
collisions particular if (as we are), you launch all your processes
at exactly the right time. Try to fix that by seeding the libc using
system entropy. Of course that still leaves the potential for birthday
problems, but hopfully this will tide us over until JuliaLang#43597 gets fixed.
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Keno authored and LilithHafner committed Feb 22, 2022
1 parent 76c0be8 commit 53ba2d9
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Showing 4 changed files with 85 additions and 38 deletions.
3 changes: 3 additions & 0 deletions base/Base.jl
Original file line number Diff line number Diff line change
Expand Up @@ -290,6 +290,9 @@ include("process.jl")
include("ttyhascolor.jl")
include("secretbuffer.jl")

# RandomDevice support
include("randomdevice.jl")

# core math functions
include("floatfuncs.jl")
include("math.jl")
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2 changes: 1 addition & 1 deletion base/libc.jl
Original file line number Diff line number Diff line change
Expand Up @@ -400,7 +400,7 @@ rand(::Type{Float64}) = rand(UInt32) * 2.0^-32
Interface to the C `srand(seed)` function.
"""
srand(seed=floor(Int, time()) % Cuint) = ccall(:srand, Cvoid, (Cuint,), seed)
srand(seed=Base._make_uint_seed()) = ccall(:srand, Cvoid, (Cuint,), seed)

struct Cpasswd
username::Cstring
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77 changes: 77 additions & 0 deletions base/randomdevice.jl
Original file line number Diff line number Diff line change
@@ -0,0 +1,77 @@
# This file is a part of Julia. License is MIT: https://julialang.org/license

# This file contains the minimal support of RandomDevice for Base's own usage.
# The actual RandomDevice type that makes use of this infrastructure is defined
# in the Random stdlib.

module DevRandomState
if !Sys.iswindows()
mutable struct FileRef
@atomic file::Union{IOStream, Nothing}
end
const DEV_RANDOM = FileRef(nothing)
const DEV_URANDOM = FileRef(nothing)
end
function __init__()
if !Sys.iswindows()
@atomic DEV_RANDOM.file = nothing
@atomic DEV_URANDOM.file = nothing
end
end
end

if Sys.iswindows()
function RtlGenRandom!(A::Union{Array, Ref})
Base.windowserror("SystemFunction036 (RtlGenRandom)", 0 == ccall(
(:SystemFunction036, :Advapi32), stdcall, UInt8, (Ptr{Cvoid}, UInt32),
A, sizeof(A)))
end

# Manually implemented to work without the Random machinery
function _rand_uint()
r = Ref{Cuint}()
RtlGenRandom!(r)
return r[]
end
else # !windows
function _get_dev_random_fd(unlimited::Bool)
ref = unlimited ? DevRandomState.DEV_URANDOM : DevRandomState.DEV_RANDOM
fd = ref.file
if fd === nothing
fd = open(unlimited ? "/dev/urandom" : "/dev/random")
old, ok = @atomicreplace ref.file nothing => fd
if !ok
close(fd)
fd = old::IOStream
end
end
return fd
end

# Manually implemented to work without the Random machinery
function _rand_uint()
return read(_get_dev_random_fd(true), Cuint)
end
end # os-test

function _ad_hoc_entropy()
println(stderr,
"Entropy pool not available to seed RNG; using ad-hoc entropy sources.")
seed = reinterpret(UInt64, time())
seed = hash(seed, getpid() % UInt)
try
seed = hash(seed, parse(UInt64,
read(pipeline(`ifconfig`, `sha1sum`), String)[1:40],
base = 16) % UInt)
catch
end
return seed
end

function _make_uint_seed()
try
_rand_uint()
catch
return _ad_hoc_entropy() % Cuint
end
end
41 changes: 4 additions & 37 deletions stdlib/Random/src/RNGs.jl
Original file line number Diff line number Diff line change
Expand Up @@ -23,42 +23,20 @@ else # !windows
RandomDevice(; unlimited::Bool=true) = new(unlimited)
end

getfile(rd::RandomDevice) = Base._get_dev_random_fd(rd.unlimited)

rand(rd::RandomDevice, sp::SamplerBoolBitInteger) = read(getfile(rd), sp[])
rand(rd::RandomDevice, ::SamplerType{Bool}) = read(getfile(rd), UInt8) % Bool

mutable struct FileRef
@atomic file::Union{IOStream, Nothing}
end

const DEV_RANDOM = FileRef(nothing)
const DEV_URANDOM = FileRef(nothing)

function getfile(rd::RandomDevice)
ref = rd.unlimited ? DEV_URANDOM : DEV_RANDOM
fd = ref.file
if fd === nothing
fd = open(rd.unlimited ? "/dev/urandom" : "/dev/random")
old, ok = @atomicreplace ref.file nothing => fd
if !ok
close(fd)
fd = old::IOStream
end
end
return fd
end

show(io::IO, rd::RandomDevice) =
print(io, RandomDevice, rd.unlimited ? "()" : "(unlimited=false)")

end # os-test

# NOTE: this can't be put within the if-else block above
for T in (Bool, BitInteger_types...)
if Sys.iswindows()
@eval function rand!(rd::RandomDevice, A::Array{$T}, ::SamplerType{$T})
Base.windowserror("SystemFunction036 (RtlGenRandom)", 0 == ccall(
(:SystemFunction036, :Advapi32), stdcall, UInt8, (Ptr{Cvoid}, UInt32),
A, sizeof(A)))
Base.RtlGenRandom!(A)
A
end
else
Expand Down Expand Up @@ -332,14 +310,7 @@ function make_seed()
catch
println(stderr,
"Entropy pool not available to seed RNG; using ad-hoc entropy sources.")
seed = reinterpret(UInt64, time())
seed = hash(seed, getpid() % UInt)
try
seed = hash(seed, parse(UInt64,
read(pipeline(`ifconfig`, `sha1sum`), String)[1:40],
base = 16) % UInt)
catch
end
Base._ad_hoc_entropy_source()
return make_seed(seed)
end
end
Expand Down Expand Up @@ -428,10 +399,6 @@ for T in BitInteger_types
end

function __init__()
@static if !Sys.iswindows()
@atomic DEV_RANDOM.file = nothing
@atomic DEV_URANDOM.file = nothing
end
seed!(GLOBAL_RNG)
end

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