Port run and KeylimeTpmError to unique modules

This change ports the `run` function from `tpm.rs` into its own
file / module `cmd_exec.rs` - primary reason for this is that non
tpm functions also call on the `run` function, so its not
exclusive to tpm operations (for example secure_mount uses run)

For `KeylimeTpmError` - this has been ported into a module
`keylime_error`, so that we can group all errors into a single
module, as it makes sense that we will eventually have more
error types and have them neatly self contained in single module

Resolves: #81

src/cmd_exec.rs

@@ -0,0 +1,195 @@
+extern crate base64;
+
+use super::*;
+use keylime_error;
+use std::env;
+use std::process::Command;
+use std::process::Output;
+use std::str;
+use std::thread;
+use std::time::Duration;
+use std::time::SystemTime;
+
+const MAX_TRY: usize = 10;
+const RETRY_SLEEP: Duration = Duration::from_millis(50);
+const TPM_IO_ERROR: i32 = 5;
+const RETRY: usize = 4;
+static EMPTYMASK: &'static str = "1";
+
+/*
+ * Input:
+ *     command: command to be executed
+ *     output_path: file output location
+ * return:
+ *     execution return output and file output
+ *     KeylimeTpmError
+ *
+ * Set up execution envrionment to execute tpm command through shell commands
+ * and return the execution result in a tuple. Based on the latest update of
+ * python keylime this function implement the functionality of cmd_exec
+ * script in the python keylime repo. RaiseOnError, return code and lock are
+ * dropped due to different error handling in Rust. Returned output string are
+ * preprocessed to before returning for code efficient.
+ */
+pub fn run<'a>(
+    command: String,
+    output_path: Option<&str>,
+) -> Result<(String, String), keylime_error::KeylimeTpmError> {
+    let mut file_output = String::new();
+    let mut output: Output;
+
+    // tokenize input command
+    let words: Vec<&str> = command.split(" ").collect();
+    let mut number_tries = 0;
+    let args = &words[1..words.len()];
+    let cmd = &words[0];
+
+    // setup environment variable
+    let mut env_vars: HashMap<String, String> = HashMap::new();
+    for (key, value) in env::vars() {
+        env_vars.insert(key.to_string(), value.to_string());
+    }
+    env_vars.insert("TPM_SERVER_PORT".to_string(), "9998".to_string());
+    env_vars.insert("TPM_SERVER_NAME".to_string(), "localhost".to_string());
+    match env_vars.get_mut("PATH") {
+        Some(v) => v.push_str(common::TPM_TOOLS_PATH),
+        None => {
+            return Err(keylime_error::KeylimeTpmError::new_tpm_rust_error(
+                "PATH envrionment variable dosen't exist.",
+            ));
+        }
+    }
+
+    // main loop
+    'exec: loop {
+        // Start time stamp
+        let t0 = SystemTime::now();
+
+        output = Command::new(&cmd).args(args).envs(&env_vars).output()?;
+
+        // measure execution time
+        let t_diff = t0.duration_since(t0)?;
+        info!("Time cost: {}", t_diff.as_secs());
+
+        // assume the system is linux
+        println!("number tries: {:?}", number_tries);
+
+        match output.status.code() {
+            Some(TPM_IO_ERROR) => {
+                number_tries += 1;
+                if number_tries >= MAX_TRY {
+                    return Err(keylime_error::KeylimeTpmError::new_tpm_error(
+                        TPM_IO_ERROR,
+                        "TPM appears to be in use by another application. 
+                         Keylime is incompatible with other TPM TSS 
+                         applications like trousers/tpm-tools. Please 
+                         uninstall or disable.",
+                    ));
+                }
+
+                info!(
+                    "Failed to call TPM {}/{} times, trying again in {} secs.",
+                    number_tries,
+                    MAX_TRY,
+                    RETRY,
+                );
+
+                thread::sleep(RETRY_SLEEP);
+            }
+
+            _ => break 'exec,
+        }
+    }
+
+    let return_output = String::from_utf8(output.stdout)?;
+    match output.status.code() {
+        None => {
+            return Err(keylime_error::KeylimeTpmError::new_tpm_rust_error(
+                "Execution return code is None.",
+            ));
+        }
+        Some(0) => info!("Successfully executed TPM command."),
+        Some(c) => {
+            return Err(keylime_error::KeylimeTpmError::new_tpm_error(
+                c,
+                format!(
+                    "Command: {} returned {}, output {}",
+                    command, c, return_output,
+                )
+                .as_str(),
+            ));
+        }
+    }
+
+    // Retrive data from output path file
+    if let Some(p) = output_path {
+        file_output = read_file_output_path(p.to_string())?;
+    }
+
+    Ok((return_output, file_output))
+}
+
+/*
+ * Input: file name
+ * Return: the content of the file int Result<>
+ *
+ * run method helper method
+ * read in the file and  return the content of the file into a Result enum
+ */
+fn read_file_output_path(output_path: String) -> std::io::Result<String> {
+    let mut file = File::open(output_path)?;
+    let mut contents = String::new();
+    file.read_to_string(&mut contents)?;
+    Ok(contents)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::error::Error;
+    use std::fs;
+
+    #[test]
+    fn test_read_file_output_path() {
+        assert_eq!(
+            read_file_output_path("test-data/test_input.txt".to_string())
+                .unwrap(),
+            "Hello World!\n"
+        );
+    }
+
+    #[test]
+    fn test_run_command() {
+        match command_exist("getrandom") {
+            true => {
+                let command = "getrandom -size 8 -out foo.out".to_string();
+                cmd_exec::run(command, None);
+                let p = Path::new("foo.out");
+                assert_eq!(p.exists(), true);
+                match fs::remove_file("foo.out") {
+                    Ok(_) => {}
+                    Err(_) => {}
+                }
+            }
+            false => assert!(true),
+        }
+    }
+    /*
+     * Input: command name
+     * Output: checkout command result
+     *
+     * Look for the command in path, if command is there return true, if
+     * command is not exist return false.
+     */
+    fn command_exist(command: &str) -> bool {
+        if let Ok(path) = env::var("PATH") {
+            for pp in path.split(":") {
+                let command_path = format!("{}/{}", pp, command);
+                if fs::metadata(command_path).is_ok() {
+                    return true;
+                }
+            }
+        }
+        false
+    }
+}

src/keylime_error.rs

@@ -0,0 +1,92 @@
+use super::*;
+use std::error::Error;
+use std::fmt;
+
+/*
+ * Custom Error type for tpm execution error. It contains both error from the
+ * TPM command execution result or error cause by rust function. Potential
+ * rust error are map to this error by implemented From<> trait.
+ */
+#[derive(Debug)]
+pub enum KeylimeTpmError {
+    TpmRustError { details: String },
+    TpmError { code: i32, details: String },
+}
+
+impl KeylimeTpmError {
+    pub fn new_tpm_error(err_code: i32, err_msg: &str) -> KeylimeTpmError {
+        KeylimeTpmError::TpmError {
+            code: err_code,
+            details: err_msg.to_string(),
+        }
+    }
+
+    pub fn new_tpm_rust_error(err_msg: &str) -> KeylimeTpmError {
+        KeylimeTpmError::TpmRustError {
+            details: err_msg.to_string(),
+        }
+    }
+}
+
+impl Error for KeylimeTpmError {
+    fn description(&self) -> &str {
+        match &self {
+            KeylimeTpmError::TpmError {
+                ref details,
+                ref code,
+            } => details,
+            KeylimeTpmError::TpmRustError { ref details } => details,
+        }
+    }
+}
+
+impl fmt::Display for KeylimeTpmError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match *self {
+            KeylimeTpmError::TpmError {
+                ref code,
+                ref details,
+            } => write!(
+                f,
+                "Execute TPM command failed with Error Code: [{}] and 
+                Error Message [{}].",
+                code, details,
+            ),
+            KeylimeTpmError::TpmRustError { ref details } => write!(
+                f,
+                "Error occur in TPM rust interface with message [{}].",
+                details,
+            ),
+        }
+    }
+}
+
+impl From<std::io::Error> for KeylimeTpmError {
+    fn from(e: std::io::Error) -> KeylimeTpmError {
+        KeylimeTpmError::new_tpm_rust_error(e.description())
+    }
+}
+
+impl From<std::time::SystemTimeError> for KeylimeTpmError {
+    fn from(e: std::time::SystemTimeError) -> KeylimeTpmError {
+        KeylimeTpmError::new_tpm_rust_error(e.description())
+    }
+}
+
+impl From<std::string::FromUtf8Error> for KeylimeTpmError {
+    fn from(e: std::string::FromUtf8Error) -> KeylimeTpmError {
+        KeylimeTpmError::new_tpm_rust_error(e.description())
+    }
+}
+
+impl From<serde_json::error::Error> for KeylimeTpmError {
+    fn from(e: serde_json::error::Error) -> KeylimeTpmError {
+        KeylimeTpmError::new_tpm_rust_error(e.description())
+    }
+}
+
+impl From<std::num::ParseIntError> for KeylimeTpmError {
+    fn from(e: std::num::ParseIntError) -> KeylimeTpmError {
+        KeylimeTpmError::new_tpm_rust_error(e.description())
+    }
+}

src/main.rs

@@ -20,8 +20,10 @@ extern crate rustc_serialize;
 extern crate serde;
 extern crate tempfile;
 
+mod cmd_exec;
 mod common;
 mod crypto;
+mod keylime_error;
 mod secure_mount;
 mod tpm;
 

src/secure_mount.rs

@@ -125,7 +125,7 @@ fn mount() -> Result<String, Box<String>> {
                         })?;
 
                     // mount tmpfs with secure directory
-                    tpm::run(
+                    cmd_exec::run(
                         format!(
                             "mount -t tmpfs -o size={},mode=0700 tmpfs {}",
                             secure_size, s,