Merge pull request #3910 from etrunko/agent_random

Agent: Unit tests for random.rs

src/agent/src/random.rs

@@ -3,7 +3,7 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 
-use anyhow::Result;
+use anyhow::{ensure, Result};
 use nix::errno::Errno;
 use nix::fcntl::{self, OFlag};
 use nix::sys::stat::Mode;
@@ -13,7 +13,7 @@ use tracing::instrument;
 
 pub const RNGDEV: &str = "/dev/random";
 pub const RNDADDTOENTCNT: libc::c_int = 0x40045201;
-pub const RNDRESEEDRNG: libc::c_int = 0x5207;
+pub const RNDRESEEDCRNG: libc::c_int = 0x5207;
 
 // Handle the differing ioctl(2) request types for different targets
 #[cfg(target_env = "musl")]
@@ -24,6 +24,9 @@ type IoctlRequestType = libc::c_ulong;
 #[instrument]
 pub fn reseed_rng(data: &[u8]) -> Result<()> {
     let len = data.len() as libc::c_long;
+
+    ensure!(len > 0, "missing entropy data");
+
     fs::write(RNGDEV, data)?;
 
     let f = {
@@ -41,8 +44,52 @@ pub fn reseed_rng(data: &[u8]) -> Result<()> {
     };
     Errno::result(ret).map(drop)?;
 
-    let ret = unsafe { libc::ioctl(f.as_raw_fd(), RNDRESEEDRNG as IoctlRequestType, 0) };
+    let ret = unsafe { libc::ioctl(f.as_raw_fd(), RNDRESEEDCRNG as IoctlRequestType, 0) };
     Errno::result(ret).map(drop)?;
 
     Ok(())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::skip_if_not_root;
+    use std::fs::File;
+    use std::io::prelude::*;
+
+    #[test]
+    fn test_reseed_rng() {
+        skip_if_not_root!();
+        const POOL_SIZE: usize = 512;
+        let mut f = File::open("/dev/urandom").unwrap();
+        let mut seed = [0; POOL_SIZE];
+        let n = f.read(&mut seed).unwrap();
+        // Ensure the buffer was filled.
+        assert!(n == POOL_SIZE);
+        let ret = reseed_rng(&seed);
+        assert!(ret.is_ok());
+    }
+
+    #[test]
+    fn test_reseed_rng_not_root() {
+        const POOL_SIZE: usize = 512;
+        let mut f = File::open("/dev/urandom").unwrap();
+        let mut seed = [0; POOL_SIZE];
+        let n = f.read(&mut seed).unwrap();
+        // Ensure the buffer was filled.
+        assert!(n == POOL_SIZE);
+        let ret = reseed_rng(&seed);
+        if nix::unistd::Uid::effective().is_root() {
+            assert!(ret.is_ok());
+        } else {
+            assert!(!ret.is_ok());
+        }
+    }
+
+    #[test]
+    fn test_reseed_rng_zero_data() {
+        let seed = [];
+        let ret = reseed_rng(&seed);
+        assert!(!ret.is_ok());
+    }
+}