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
164
165
166
167
168
169
170
171
172
173
174

//! Rust wrapper around the BCrypt hashing algorithm implementation [written in C
//! by Solar Designer][src].
//!
//! The C code is embedded into this crate and compiled using build script.
//!
//! [src]: http://www.openwall.com/crypt/
//!

extern crate libc;
extern crate rand;

use std::str::from_utf8_unchecked;
use std::ffi::{CString, CStr};
use std::error::Error;
use std::fmt;
use libc::{c_int, strerror};
use rand::Rng;
use rand::os::OsRng;

extern "C" {
    // result is a 30-byte C string of base64 code
    fn c_gen_salt(cost: u8, random16: *const u8, result: *mut u8) -> c_int;

    // result is a 61-byte C string of base64 code
    fn c_hash(key: *const u8, salt: *const u8, result: *mut u8) -> c_int;
}

/// Generate salt for a BCrypt hash.
///
/// 
pub fn gen_salt(cost: u8) -> Result<[u8; 30], CryptError> {
    let mut salt: [u8; 30] = [0; 30];
    let mut random: [u8; 16] = [0; 16];

    fill_random(&mut random);

    unsafe {
        match c_gen_salt(cost, random.as_ptr(), salt.as_mut_ptr()) {
            0 => Ok(salt),
            errno => Err(CryptError::new(errno, None)),
        }
    }
}

// NOTE: password longer than 72 characters are truncated
/// Compute BCrypt hash from a password and salt.
///
///
pub fn hash(password: &str, salt: &[u8]) -> Result<[u8; 61], CryptError> {
    if password.len() == 0 {
        return Err(CryptError::invalid_arg("password cannot be empty".into()));
    }
    if password.len() > 72 {
        return Err(CryptError::invalid_arg("password length must not exceed 72".into()));
    }
    if salt.len() < 30 {
        return Err(CryptError::invalid_arg("salt must be at least 30 bytes long".into()));
    }

    let c_password = if let Ok(c) = CString::new(password) {
        c
    } else {
        return Err(CryptError::invalid_arg("password must not contain NULL characters".into()));
    };

    unsafe {
        let mut result: [u8; 61] = [0; 61];
        match c_hash(c_password.as_bytes().as_ptr(),
                     salt.as_ptr(),
                     result.as_mut_ptr()) {
            0 => Ok(result),
            errno => Err(CryptError::new(errno, None)),
        }
    }
}

/// Convert a nul-terminated byte slice into a borrowed string.
pub fn to_str<'a>(bytes: &'a [u8]) -> Result<&'a str, CryptError> {
    match CStr::from_bytes_with_nul(bytes) {
        Ok(c_str) => {
            match c_str.to_str() {
                Ok(s) => Ok(s),
                Err(e) => Err(CryptError::invalid_arg(e.to_string())),
            }
        }
        Err(e) => Err(CryptError::invalid_arg(e.to_string())),
    }
}


/// BCrypt hashing error.
///
/// 
#[derive(Debug)]
pub struct CryptError {
    /// C error code
    errno: c_int,

    /// optional message
    desc: Option<String>,
}

impl CryptError {
    pub fn new(errno: c_int, desc: Option<String>) -> CryptError {
        CryptError { errno, desc }
    }

    pub fn invalid_arg(desc: String) -> CryptError {
        CryptError {
            errno: libc::EINVAL,
            desc: Some(desc),
        }
    }

    pub fn errno(&self) -> c_int {
        self.errno
    }
}

impl Error for CryptError {
    fn description(&self) -> &str {
        "bcrypt error"
    }
}

impl fmt::Display for CryptError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let desc = if let Some(ref desc) = self.desc {
            desc.clone()
        } else {
            unsafe { errno_to_string(self.errno) }
        };

        write!(f, "bcrypt error: {} ({})", desc, self.errno)
    }
}

fn fill_random(random: &mut [u8]) {
    let mut rng = OsRng::new().unwrap();
    rng.fill_bytes(random);
}

unsafe fn errno_to_string(errno: c_int) -> String {
    from_utf8_unchecked(CStr::from_ptr(strerror(errno)).to_bytes()).into()
}


#[cfg(test)]
mod tests {
    use super::{to_str, gen_salt, hash};

    #[test]
    fn test_to_str() {
        assert_eq!(to_str(&[114, 117, 115, 116, 097, 099, 101, 097, 110, 0]).unwrap(),
                   "rustacean");
        assert!(to_str(&[114, 117, 115, 116, 097, 099, 101, 097, 110]).is_err());
        assert!(to_str(&[114, 117, 115, 116, 097, 099, 101, 097, 0, 110, 0]).is_err());
    }

    #[test]
    fn test_gen_salt() {
        let salt = gen_salt(4).unwrap();
        assert_eq!(to_str(&salt).unwrap().len(), 29);
    }

    #[test]
    fn test_hash() {
        let pwhash = hash("Password", &gen_salt(4).unwrap()).unwrap();
        assert_eq!(to_str(&pwhash).unwrap().len(), 60);

        assert!(hash("Password", &[0; 15]).is_err());
        assert!(hash("", &gen_salt(4).unwrap()).is_err());
    }
}