init password generator

src/main.rs

@@ -0,0 +1,68 @@
+use rand::Rng;
+use rand::rngs::OsRng;
+use std::fs;
+
+// enum variant (i keep forgetting the terminology)
+// enum PasswordType {
+//     RandomChars(usize),
+//     Passphrase(usize, usize),
+// }
+
+// non-CTRL chars
+fn random_ascii() -> u8 {
+    // we definitely want to use the OS for randomness
+    // doesn't require seeding because it is backed by CSPRNG, backed by OS
+    // the OS maintains it's own entropy from mouse movement, hardware noise,etc
+    let mut rng = OsRng;
+
+    // NOT IDEAL FOR CRYPTO/password generation 
+    // let range_max = 122; // 125 - 33
+    // let n = rng.next_u32() % range_max; // slightly modulo biased
+    // (n + 33) as u8
+
+    // this function under the hood creates a zone that divides evenly
+    // into the range so we don't encounter modulo bias
+    rng.gen_range(33..125) as u8
+}
+
+fn generate_random_chars(len: usize) -> String {
+    // String is a thin wrapper around Vec<u8> so we can expect re-allocation
+    // and copy only when we exceed the capacity of the vector
+    let mut res = String::new();
+    for _ in 0..len {
+        res.push(random_ascii() as char);
+    }
+    res
+}
+
+fn generate_passphrase(phrases: usize, len: usize, words: &Vec<&str>) -> String {
+    let mut res = String::new();
+    let mut count = 0;
+    while count < phrases {
+        let word = random_word(words);
+        if word.is_ascii() { // only add ascii words
+            res.push_str(random_word(words));
+            count += 1;
+        }
+    }
+    res.truncate(len); // only works on ascii
+    res
+}
+
+fn random_word<'a>(words: &'a Vec<&'a str>) -> &'a str {
+    let mut rng = OsRng;
+    words[rng.gen_range(0..words.len())]
+}
+
+
+fn main() {
+    let content = fs::read_to_string("/usr/share/dict/words")
+        .expect("could not read dictionary");
+    let words: Vec<&str> = content.lines().collect();
+
+    let chars = generate_random_chars(20);
+    println!("generated random chars: {}", chars.as_str());
+
+    let phrase = generate_passphrase(3, 20, &words);
+    println!("generated passphrase: {}", phrase.as_str());
+}