Fast path for CrevIDs with empty string as the passphrase

#385

cargo-crev/src/main.rs

@@ -6,6 +6,7 @@
     doc = "See [user documentation module](./doc/user/index.html)."
 )]
 #![cfg_attr(feature = "documentation", feature(external_doc))]
+use crev_data::UnlockedId;
 use crev_data::proof::ContentExt;
 use crate::prelude::*;
 use crev_lib::id::LockedId;
@@ -214,6 +215,7 @@ fn run_command(command: opts::Command) -> Result<CommandExitStatus> {
 
                 fn read_new_passphrase() -> io::Result<String> {
                     println!("CrevID will be protected by a passphrase.");
+                    println!("You can change it later with `cargo crev id passwd`.");
                     println!(
                         "There's no way to recover your CrevID if you forget your passphrase."
                     );
@@ -226,9 +228,11 @@ fn run_command(command: opts::Command) -> Result<CommandExitStatus> {
                         print_crev_proof_repo_fork_help();
                         e
                     })?;
-                println!("Your CrevID was created and will be printed below in an encrypted form.");
-                println!("Make sure to back it up on another device, to prevent losing it.");
-                println!("{}", res);
+                if !res.has_no_passphrase() {
+                    println!("Your CrevID was created and will be printed below in an encrypted form.");
+                    println!("Make sure to back it up on another device, to prevent losing it.");
+                    println!("{}", res);
+                }
 
                 let local = crev_lib::Local::auto_open()?;
                 let _ = ensure_known_owners_list_exists(&local);
@@ -238,10 +242,7 @@ fn run_command(command: opts::Command) -> Result<CommandExitStatus> {
                 local.switch_id(&args.id)?
             }
             opts::Id::Passwd => {
-                let res = current_id_change_passphrase()?;
-                println!("Your CrevID has been updated and will be printed below in the reencrypted form.");
-                println!("Make sure to back it up on another device, to prevent losing it.");
-                println!("{}", res);
+                current_id_change_passphrase()?;
             }
             opts::Id::Current => {
                 let local = Local::auto_open()?;
@@ -687,12 +688,21 @@ fn current_id_change_passphrase() -> Result<LockedId> {
     eprintln!("Please enter the OLD passphrase. If you don't know it, you will need to create a new Id.");
     let unlocked_id = local.read_current_unlocked_id(&term::read_passphrase)?;
     eprintln!("Now please enter the NEW passphrase.");
+    change_passphrase(&local, &unlocked_id)
+}
+
+fn change_passphrase(local: &Local, unlocked_id: &UnlockedId) -> Result<LockedId> {
     let passphrase = term::read_new_passphrase()?;
     let locked_id = LockedId::from_unlocked_id(&unlocked_id, &passphrase)?;
 
     local.save_locked_id(&locked_id)?;
     local.save_current_id(unlocked_id.as_ref())?;
     eprintln!("Passphrase changed successfully.");
+    if !locked_id.has_no_passphrase() {
+        println!("Your CrevID has been updated and will be printed below in the reencrypted form.");
+        println!("Make sure to back it up on another device, to prevent losing it.");
+        println!("{}", locked_id);
+    }
     Ok(locked_id)
 }
 

crev-lib/src/id.rs

@@ -63,19 +63,23 @@ impl LockedId {
     pub fn from_unlocked_id(unlocked_id: &UnlockedId, passphrase: &str) -> Result<LockedId> {
         use miscreant::aead::Aead;
 
-        let config = Config {
-            variant: argon2::Variant::Argon2id,
-            version: argon2::Version::Version13,
+        let config = if passphrase != "" {
+            Config {
+                variant: argon2::Variant::Argon2id,
+                version: argon2::Version::Version13,
 
-            hash_length: 64,
-            mem_cost: 4096,
-            time_cost: 192,
+                hash_length: 64,
+                mem_cost: 4096,
+                time_cost: 192,
 
-            lanes: num_cpus::get() as u32,
-            thread_mode: argon2::ThreadMode::Parallel,
+                lanes: num_cpus::get() as u32,
+                thread_mode: argon2::ThreadMode::Parallel,
 
-            ad: &[],
-            secret: &[],
+                ad: &[],
+                secret: &[],
+            }
+        } else {
+            Self::weak_passphrase_config()
         };
 
         let pwsalt = random_vec(32);
@@ -182,4 +186,26 @@ impl LockedId {
             Ok(result)
         }
     }
+
+    pub fn has_no_passphrase(&self) -> bool {
+        self.passphrase_config.iterations == 1 && self.to_unlocked("").is_ok()
+    }
+
+    /// Config for empty passphrase. User chose no security, so they're getting none.
+    fn weak_passphrase_config() -> Config<'static> {
+        Config {
+            variant: argon2::Variant::Argon2id,
+            version: argon2::Version::Version13,
+
+            hash_length: 64,
+            mem_cost: 16,
+            time_cost: 1,
+
+            lanes: 1,
+            thread_mode: argon2::ThreadMode::Parallel,
+
+            ad: &[],
+            secret: &[],
+        }
+    }
 }

crev-lib/src/local.rs

@@ -416,7 +416,7 @@ impl Local {
         let locked = self.read_locked_id(id)?;
         let mut i = 0;
         loop {
-            let passphrase = passphrase_callback()?;
+            let passphrase = if locked.has_no_passphrase() { String::new() } else { passphrase_callback()? };
             match locked.to_unlocked(&passphrase) {
                 Ok(o) => return Ok(o),
                 Err(e) => {