add functions to create random numbers #64
Conversation
stlankes
changed the title
| /// Create a cryptographicly secure 32bit random number with the support of | ||
| /// the underlying hardware. If the required hardware isn't available, | ||
| /// the function returns `None`. | ||
| #[inline(always)] | ||
| pub unsafe fn secure_rand32() -> Option<u32> { | ||
| sys_secure_rand32() | ||
| } | ||
|
|
||
| /// Create a cryptographicly secure 64bit random number with the support of | ||
| /// the underlying hardware. If the required hardware isn't available, | ||
| /// the function returns `None`. | ||
| #[inline(always)] | ||
| pub unsafe fn secure_rand64() -> Option<u64> { | ||
| sys_secure_rand64() | ||
| } |
There was a problem hiding this comment.
Is there a reason these functions are unsafe? Will asking for random number ever invoke UB?
There was a problem hiding this comment.
I will answer the question in the comment below.
| extern "Rust" { | ||
| fn sys_secure_rand64() -> Option<u64>; | ||
| fn sys_secure_rand32() -> Option<u32>; | ||
| } |
There was a problem hiding this comment.
So having extern "Rust" here means that the version of rustc used to compile hermit-abi must be exactly the same version used to compile the kernel (rusty-hermit/libhermit-rs). Is this a problem? (I don't know much about HermitCore).
If it is, you could just have a returned value of 0 represent failure (I realize this is technically a valid random number, but it's extremely unlikely that it gets returned). Alternatively, you could take a *mut u64 as input and return 0/-ENOSYS on success/failure.
There was a problem hiding this comment.
In principle, the unikernel is completely written in Rust. Technical it could be possible that the Rust standard library call directly the Rust function of the unikernel. However, the unikernel depends on too many crates. The Rust community will not permit that rustc depends on all these crates. The workaround is a small system interface hermit-abi, which provides a similar interface like the crate libc. The unikernel itself will be provided as common static library. To guarantee that the unikernel and the application are build by the same compiler, we provide the crate hermit-sys. This crate builds the unikernel and link the library to the application. This is the reason that we suggest to add following line to Cargo.toml:
[target.'cfg(target_os = "hermit")'.dependencies]
hermit-sys = "0.1.*"
Unfortunately, every jump into a static library is unsafe because the compiler is not able to check the function. But we are able to use "real" Rust functions and to use Option as return value.
|
bors ping |
|
pong |
|
bors try |
tryBuild failed: |
|
bors r+ |
|
Merge conflict. |
rand creates pseudo-random numbers, while secure_rand32/64 produce cryptographicly secure random numbers
|
bors r+ |
|
I assume that @josephlr like the patch an accept it |
|
Does this patch actually generate random numbers? |
|
It should generate random numbers. The function calls implicitly generate_random_number64, which uses Intel's |
|
okay great I have |
|
Currently not, but we are working on it. |
|
Okay so my patch to Thanks for your assistance! |
randcreates pseudo-random numbers, whilesecure_rand32/64produce cryptographicly secure random numbers