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| 1 | +//! Secure password buffer for garlock |
| 2 | +//! |
| 3 | +//! Implements a password buffer that securely clears memory on drop |
| 4 | +//! using the zeroize crate to prevent password remnants in memory. |
| 5 | + |
| 6 | +use zeroize::{Zeroize, ZeroizeOnDrop}; |
| 7 | + |
| 8 | +/// Default buffer capacity (should be enough for most passwords) |
| 9 | +const DEFAULT_CAPACITY: usize = 256; |
| 10 | + |
| 11 | +/// Secure password buffer |
| 12 | +/// |
| 13 | +/// This buffer automatically zeroes its contents when dropped, |
| 14 | +/// preventing password data from lingering in memory. |
| 15 | +#[derive(ZeroizeOnDrop)] |
| 16 | +pub struct Password { |
| 17 | + /// Raw UTF-8 bytes of the password |
| 18 | + buffer: Vec<u8>, |
| 19 | + /// Current length in bytes (not characters) |
| 20 | + len: usize, |
| 21 | +} |
| 22 | + |
| 23 | +impl Password { |
| 24 | + /// Create a new empty password buffer |
| 25 | + pub fn new() -> Self { |
| 26 | + Self { |
| 27 | + buffer: vec![0u8; DEFAULT_CAPACITY], |
| 28 | + len: 0, |
| 29 | + } |
| 30 | + } |
| 31 | + |
| 32 | + /// Create a password buffer with custom capacity |
| 33 | + pub fn with_capacity(capacity: usize) -> Self { |
| 34 | + Self { |
| 35 | + buffer: vec![0u8; capacity], |
| 36 | + len: 0, |
| 37 | + } |
| 38 | + } |
| 39 | + |
| 40 | + /// Push a character onto the password buffer |
| 41 | + /// |
| 42 | + /// Returns `true` if the character was added, `false` if buffer is full. |
| 43 | + pub fn push(&mut self, c: char) -> bool { |
| 44 | + let mut buf = [0u8; 4]; |
| 45 | + let encoded = c.encode_utf8(&mut buf); |
| 46 | + let bytes = encoded.as_bytes(); |
| 47 | + |
| 48 | + // Check if we have room |
| 49 | + if self.len + bytes.len() > self.buffer.len() { |
| 50 | + tracing::warn!("Password buffer full, cannot add character"); |
| 51 | + return false; |
| 52 | + } |
| 53 | + |
| 54 | + // Copy bytes into buffer |
| 55 | + self.buffer[self.len..self.len + bytes.len()].copy_from_slice(bytes); |
| 56 | + self.len += bytes.len(); |
| 57 | + |
| 58 | + tracing::trace!(len = self.len, "Character added to password buffer"); |
| 59 | + true |
| 60 | + } |
| 61 | + |
| 62 | + /// Remove the last character from the password buffer |
| 63 | + /// |
| 64 | + /// Returns `true` if a character was removed, `false` if buffer was empty. |
| 65 | + pub fn pop(&mut self) -> bool { |
| 66 | + if self.len == 0 { |
| 67 | + return false; |
| 68 | + } |
| 69 | + |
| 70 | + // Find the start of the last UTF-8 character |
| 71 | + // UTF-8 continuation bytes start with 10xxxxxx (0x80-0xBF) |
| 72 | + let mut char_start = self.len - 1; |
| 73 | + while char_start > 0 && (self.buffer[char_start] & 0xC0) == 0x80 { |
| 74 | + char_start -= 1; |
| 75 | + } |
| 76 | + |
| 77 | + // Zero out the removed bytes |
| 78 | + for i in char_start..self.len { |
| 79 | + self.buffer[i] = 0; |
| 80 | + } |
| 81 | + self.len = char_start; |
| 82 | + |
| 83 | + tracing::trace!(len = self.len, "Character removed from password buffer"); |
| 84 | + true |
| 85 | + } |
| 86 | + |
| 87 | + /// Clear the entire password buffer |
| 88 | + /// |
| 89 | + /// Securely zeros all data in the buffer. |
| 90 | + pub fn clear(&mut self) { |
| 91 | + self.buffer[..self.len].zeroize(); |
| 92 | + self.len = 0; |
| 93 | + tracing::trace!("Password buffer cleared"); |
| 94 | + } |
| 95 | + |
| 96 | + /// Check if the password buffer is empty |
| 97 | + pub fn is_empty(&self) -> bool { |
| 98 | + self.len == 0 |
| 99 | + } |
| 100 | + |
| 101 | + /// Get the current length in bytes |
| 102 | + pub fn len(&self) -> usize { |
| 103 | + self.len |
| 104 | + } |
| 105 | + |
| 106 | + /// Get the number of characters in the password |
| 107 | + pub fn char_count(&self) -> usize { |
| 108 | + self.as_str().chars().count() |
| 109 | + } |
| 110 | + |
| 111 | + /// Get the password as a string slice |
| 112 | + /// |
| 113 | + /// This is used when passing the password to PAM for authentication. |
| 114 | + pub fn as_str(&self) -> &str { |
| 115 | + // Safety: We only ever add valid UTF-8 characters via push() |
| 116 | + std::str::from_utf8(&self.buffer[..self.len]).unwrap_or("") |
| 117 | + } |
| 118 | +} |
| 119 | + |
| 120 | +impl Default for Password { |
| 121 | + fn default() -> Self { |
| 122 | + Self::new() |
| 123 | + } |
| 124 | +} |
| 125 | + |
| 126 | +// Manual Zeroize implementation for extra safety |
| 127 | +impl Zeroize for Password { |
| 128 | + fn zeroize(&mut self) { |
| 129 | + self.buffer.zeroize(); |
| 130 | + self.len = 0; |
| 131 | + } |
| 132 | +} |
| 133 | + |
| 134 | +#[cfg(test)] |
| 135 | +mod tests { |
| 136 | + use super::*; |
| 137 | + |
| 138 | + #[test] |
| 139 | + fn test_push_pop() { |
| 140 | + let mut pw = Password::new(); |
| 141 | + assert!(pw.is_empty()); |
| 142 | + |
| 143 | + pw.push('h'); |
| 144 | + pw.push('e'); |
| 145 | + pw.push('l'); |
| 146 | + pw.push('l'); |
| 147 | + pw.push('o'); |
| 148 | + |
| 149 | + assert_eq!(pw.as_str(), "hello"); |
| 150 | + assert_eq!(pw.char_count(), 5); |
| 151 | + |
| 152 | + pw.pop(); |
| 153 | + assert_eq!(pw.as_str(), "hell"); |
| 154 | + |
| 155 | + pw.clear(); |
| 156 | + assert!(pw.is_empty()); |
| 157 | + } |
| 158 | + |
| 159 | + #[test] |
| 160 | + fn test_unicode() { |
| 161 | + let mut pw = Password::new(); |
| 162 | + |
| 163 | + pw.push('日'); |
| 164 | + pw.push('本'); |
| 165 | + pw.push('語'); |
| 166 | + |
| 167 | + assert_eq!(pw.as_str(), "日本語"); |
| 168 | + assert_eq!(pw.char_count(), 3); |
| 169 | + assert_eq!(pw.len(), 9); // 3 bytes per character |
| 170 | + |
| 171 | + pw.pop(); |
| 172 | + assert_eq!(pw.as_str(), "日本"); |
| 173 | + } |
| 174 | + |
| 175 | + #[test] |
| 176 | + fn test_mixed_characters() { |
| 177 | + let mut pw = Password::new(); |
| 178 | + |
| 179 | + pw.push('a'); |
| 180 | + pw.push('é'); |
| 181 | + pw.push('日'); |
| 182 | + pw.push('!'); |
| 183 | + |
| 184 | + assert_eq!(pw.char_count(), 4); |
| 185 | + |
| 186 | + pw.pop(); // ! |
| 187 | + pw.pop(); // 日 |
| 188 | + assert_eq!(pw.as_str(), "aé"); |
| 189 | + } |
| 190 | +} |