1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163

#[cfg(feature = "logging")]
use crate::log::warn;
use crate::KeyLog;

use alloc::vec::Vec;
use core::fmt::{Debug, Formatter};
use std::env;
use std::ffi::OsString;
use std::fs::{File, OpenOptions};
use std::io;
use std::io::Write;
use std::sync::Mutex;

// Internal mutable state for KeyLogFile
struct KeyLogFileInner {
    file: Option<File>,
    buf: Vec<u8>,
}

impl KeyLogFileInner {
    fn new(var: Option<OsString>) -> Self {
        let path = match &var {
            Some(path) => path,
            None => {
                return Self {
                    file: None,
                    buf: Vec::new(),
                };
            }
        };

        #[cfg_attr(not(feature = "logging"), allow(unused_variables))]
        let file = match OpenOptions::new()
            .append(true)
            .create(true)
            .open(path)
        {
            Ok(f) => Some(f),
            Err(e) => {
                warn!("unable to create key log file {:?}: {}", path, e);
                None
            }
        };

        Self {
            file,
            buf: Vec::new(),
        }
    }

    fn try_write(&mut self, label: &str, client_random: &[u8], secret: &[u8]) -> io::Result<()> {
        let mut file = match self.file {
            None => {
                return Ok(());
            }
            Some(ref f) => f,
        };

        self.buf.truncate(0);
        write!(self.buf, "{} ", label)?;
        for b in client_random.iter() {
            write!(self.buf, "{:02x}", b)?;
        }
        write!(self.buf, " ")?;
        for b in secret.iter() {
            write!(self.buf, "{:02x}", b)?;
        }
        writeln!(self.buf)?;
        file.write_all(&self.buf)
    }
}

impl Debug for KeyLogFileInner {
    fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
        f.debug_struct("KeyLogFileInner")
            // Note: we omit self.buf deliberately as it may contain key data.
            .field("file", &self.file)
            .finish()
    }
}

/// [`KeyLog`] implementation that opens a file whose name is
/// given by the `SSLKEYLOGFILE` environment variable, and writes
/// keys into it.
///
/// If `SSLKEYLOGFILE` is not set, this does nothing.
///
/// If such a file cannot be opened, or cannot be written then
/// this does nothing but logs errors at warning-level.
pub struct KeyLogFile(Mutex<KeyLogFileInner>);

impl KeyLogFile {
    /// Makes a new `KeyLogFile`.  The environment variable is
    /// inspected and the named file is opened during this call.
    pub fn new() -> Self {
        let var = env::var_os("SSLKEYLOGFILE");
        Self(Mutex::new(KeyLogFileInner::new(var)))
    }
}

impl KeyLog for KeyLogFile {
    fn log(&self, label: &str, client_random: &[u8], secret: &[u8]) {
        #[cfg_attr(not(feature = "logging"), allow(unused_variables))]
        match self
            .0
            .lock()
            .unwrap()
            .try_write(label, client_random, secret)
        {
            Ok(()) => {}
            Err(e) => {
                warn!("error writing to key log file: {}", e);
            }
        }
    }
}

impl Debug for KeyLogFile {
    fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
        match self.0.try_lock() {
            Ok(key_log_file) => write!(f, "{:?}", key_log_file),
            Err(_) => write!(f, "KeyLogFile {{ <locked> }}"),
        }
    }
}

#[cfg(all(test, target_os = "linux"))]
mod tests {
    use super::*;

    fn init() {
        let _ = env_logger::builder()
            .is_test(true)
            .try_init();
    }

    #[test]
    fn test_env_var_is_not_set() {
        init();
        let mut inner = KeyLogFileInner::new(None);
        assert!(inner
            .try_write("label", b"random", b"secret")
            .is_ok());
    }

    #[test]
    fn test_env_var_cannot_be_opened() {
        init();
        let mut inner = KeyLogFileInner::new(Some("/dev/does-not-exist".into()));
        assert!(inner
            .try_write("label", b"random", b"secret")
            .is_ok());
    }

    #[test]
    fn test_env_var_cannot_be_written() {
        init();
        let mut inner = KeyLogFileInner::new(Some("/dev/full".into()));
        assert!(inner
            .try_write("label", b"random", b"secret")
            .is_err());
    }
}