chore(csprng): no longer check macOS version

We checked the macOS version to be sure that the
SecRandomCopyBytes was available.

Since rust 1.74 (which is older than our current msrv)
rust only supports macOS >= 10.12, thus we can expect
SecRandomCopyBytes to always be available and can remove the check

concrete-csprng/src/seeders/implem/apple_secure_enclave_seeder.rs

@@ -51,80 +51,21 @@ pub struct AppleSecureEnclaveSeeder;
 
 impl Seeder for AppleSecureEnclaveSeeder {
     fn seed(&mut self) -> Seed {
-        // 16 bytes == 128 bits
-        let mut bytes = [0u8; 16];
+        let mut bytes = [0u8; std::mem::size_of::<u128>() / std::mem::size_of::<u8>()];
         secure_enclave::generate_random_bytes(&mut bytes)
             .expect("Failure while using Apple secure enclave: {err:?}");
 
         Seed(u128::from_le_bytes(bytes))
     }
 
     fn is_available() -> bool {
-        let os_version_sysctl_name = match std::ffi::CString::new("kern.osproductversion") {
-            Ok(c_str) => c_str,
-            _ => return false,
-        };
-
-        // Big enough buffer to get a version output as an ASCII string
-        const OUTPUT_BUFFER_SIZE: usize = 64;
-        let mut output_buffer_size = OUTPUT_BUFFER_SIZE;
-        let mut output_buffer = [0u8; OUTPUT_BUFFER_SIZE];
-        let res = unsafe {
-            libc::sysctlbyname(
-                os_version_sysctl_name.as_ptr() as *const _ as *const _,
-                &mut output_buffer as *mut _ as *mut _,
-                &mut output_buffer_size as *mut _ as *mut _,
-                std::ptr::null_mut(),
-                0,
-            )
-        };
-
-        if res != 0 {
-            return false;
-        }
-
-        let result_c_str =
-            match std::ffi::CStr::from_bytes_with_nul(&output_buffer[..output_buffer_size]) {
-                Ok(c_str) => c_str,
-                _ => return false,
-            };
-
-        let result_string = match result_c_str.to_str() {
-            Ok(str) => str,
-            _ => return false,
-        };
-
-        // Normally we get a major version and minor version
-        let split_string: Vec<&str> = result_string.split('.').collect();
-
-        let mut major = -1;
-        let mut minor = -1;
-
-        // Major part of the version string
-        if !split_string.is_empty() {
-            major = match split_string[0].parse() {
-                Ok(major_from_str) => major_from_str,
-                _ => return false,
-            };
-        }
-
-        // SecRandomCopyBytes is available starting with mac OS 10.7
+        // SecRandomCopyBytes is available starting with macOS 10.7
         // https://developer.apple.com/documentation/security/1399291-secrandomcopybytes?language=objc
-        // This match pattern is recommended by clippy, so we oblige here
-        match major.cmp(&10) {
-            Ordering::Greater => true,
-            Ordering::Equal => {
-                // Minor part of the version string
-                if split_string.len() >= 2 {
-                    minor = match split_string[1].parse() {
-                        Ok(minor_from_str) => minor_from_str,
-                        _ => return false,
-                    };
-                }
-                minor >= 7
-            }
-            Ordering::Less => false,
-        }
+        //
+        // Since Rust 1.74, rust supports macOS >= 10.12
+        // https://blog.rust-lang.org/2023/09/25/Increasing-Apple-Version-Requirements.html
+        // Thus SecRandomCopyBytes is always expected to be available
+        true
     }
 }