Add support for API keys

This is mainly useful for CLI-based login automation.

src/crypto.rs

@@ -51,6 +51,28 @@ pub fn get_random(mut array: Vec<u8>) -> Vec<u8> {
     array
 }
 
+/// Generates a random string over a specified alphabet.
+pub fn get_random_string(alphabet: &[u8], num_chars: usize) -> String {
+    // Ref: https://rust-lang-nursery.github.io/rust-cookbook/algorithms/randomness.html
+    use rand::Rng;
+    let mut rng = rand::thread_rng();
+
+    (0..num_chars)
+        .map(|_| {
+            let i = rng.gen_range(0..alphabet.len());
+            alphabet[i] as char
+        })
+        .collect()
+}
+
+/// Generates a random alphanumeric string.
+pub fn get_random_string_alphanum(num_chars: usize) -> String {
+    const ALPHABET: &[u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZ\
+                              abcdefghijklmnopqrstuvwxyz\
+                              0123456789";
+    get_random_string(ALPHABET, num_chars)
+}
+
 pub fn generate_id(num_bytes: usize) -> String {
     HEXLOWER.encode(&get_random(vec![0; num_bytes]))
 }
@@ -84,6 +106,12 @@ pub fn generate_token(token_size: u32) -> Result<String, Error> {
     Ok(token)
 }
 
+/// Generates a personal API key.
+/// Upstream uses 30 chars, which is ~178 bits of entropy.
+pub fn generate_api_key() -> String {
+    get_random_string_alphanum(30)
+}
+
 //
 // Constant time compare
 //