feat(login) password login using encrypted nsec

Enables the user to only handle the nsec upon first use of the tool
by encrypting it with a password and storing it on disk in an
application cache.

The approach to encryption draws heavily from that used by the gossip
nostr client.
 - unencrypted nsec is zeroed from memory
 - a salt is used to defend against rainbow tables
 - computationally expensive key stretching defends against
   brute-force attacks of passwords with low entropy.

There is UX trade-off between decryption speed and key-stretching
computation. This UX challenge is exacerbated in a cli tool as
decryption must take place more regularly. Thought was put into the
selected n_log and a heavily reduced value is provided for long
passwords where security benefits are smaller.

A more granular reducing in computation was also considered by
rejected to avoided to revealing just how weak a password is as most
weak passwords are reused.

1 files changed, 29 insertions, 2 deletions

diff --git a/src/cli_interactor.rs b/src/cli_interactor.rs
index 2f28aee..d7de087 100644
--- a/src/cli_interactor.rs
+++ b/src/cli_interactor.rs
@@ -1,5 +1,5 @@
-use anyhow::{bail, Result};
-use dialoguer::{theme::ColorfulTheme, Input};
+use anyhow::Result;
+use dialoguer::{theme::ColorfulTheme, Input, Password};
 #[cfg(test)]
 use mockall::*;
 
@@ -11,6 +11,7 @@ pub struct Interactor {
 #[cfg_attr(test, automock)]
 pub trait InteractorPrompt {
     fn input(&self, parms: PromptInputParms) -> Result<String>;
+    fn password(&self, parms: PromptPasswordParms) -> Result<String>;
 }
 impl InteractorPrompt for Interactor {
     fn input(&self, parms: PromptInputParms) -> Result<String> {
@@ -19,6 +20,15 @@ impl InteractorPrompt for Interactor {
             .interact_text()?;
         Ok(input)
     }
+    fn password(&self, parms: PromptPasswordParms) -> Result<String> {
+        let mut p = Password::with_theme(&self.theme);
+        p.with_prompt(parms.prompt);
+        if parms.confirm {
+            p.with_confirmation("confirm password", "passwords didnt match...");
+        }
+        let pass: String = p.interact()?;
+        Ok(pass)
+    }
 }
 
 #[derive(Default)]
@@ -32,3 +42,20 @@ impl PromptInputParms {
         self
     }
 }
+
+#[derive(Default)]
+pub struct PromptPasswordParms {
+    pub prompt: String,
+    pub confirm: bool,
+}
+
+impl PromptPasswordParms {
+    pub fn with_prompt<S: Into<String>>(mut self, prompt: S) -> Self {
+        self.prompt = prompt.into();
+        self
+    }
+    pub const fn with_confirm(mut self) -> Self {
+        self.confirm = true;
+        self
+    }
+}