From f79bca42ee00f73b7831c0400a7e935eadc5ee15 Mon Sep 17 00:00:00 2001
From: Elliot Saba <staticfloat@gmail.com>
Date: Fri, 10 Jun 2022 18:33:33 +0000
Subject: [PATCH] Throw `ArgumentError` if `unsafe_SecretBuffer!()` is passed
 NULL

Previously, if given a NULL `Cstring` we would blithely call `strlen()`
on it, which resulted in a segfault.  It is better if we throw an
exception instead.
---
 base/secretbuffer.jl | 8 +++++++-
 test/secretbuffer.jl | 4 ++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/base/secretbuffer.jl b/base/secretbuffer.jl
index 02a133be088f03..29e11faf41ebf8 100644
--- a/base/secretbuffer.jl
+++ b/base/secretbuffer.jl
@@ -79,7 +79,13 @@ function SecretBuffer!(d::Vector{UInt8})
     s
 end
 
-unsafe_SecretBuffer!(s::Cstring) = unsafe_SecretBuffer!(convert(Ptr{UInt8}, s), Int(ccall(:strlen, Csize_t, (Cstring,), s)))
+function unsafe_SecretBuffer!(s::Cstring)
+    if s == C_NULL
+        throw(ArgumentError("cannot convert NULL to SecretBuffer"))
+    end
+    len = Int(ccall(:strlen, Csize_t, (Cstring,), s))
+    unsafe_SecretBuffer!(convert(Ptr{UInt8}, s), len)
+end
 function unsafe_SecretBuffer!(p::Ptr{UInt8}, len=1)
     s = SecretBuffer(sizehint=len)
     for i in 1:len
diff --git a/test/secretbuffer.jl b/test/secretbuffer.jl
index df67204dd63baa..9f0b79932539cf 100644
--- a/test/secretbuffer.jl
+++ b/test/secretbuffer.jl
@@ -122,4 +122,8 @@ using Test
         @test hash(sb1, UInt(5)) === hash(sb2, UInt(5))
         shred!(sb1); shred!(sb2)
     end
+    @testset "NULL initialization" begin
+        null_ptr = Cstring(C_NULL)
+        @test_throws ArgumentError Base.unsafe_SecretBuffer!(null_ptr)
+    end
 end