keyfork-prompt: add validator system

keyfork-prompt/src/lib.rs

@@ -20,6 +20,8 @@ mod raw_mode;
 use alternate_screen::AlternateScreen;
 use raw_mode::RawMode;
 
+pub mod validators;
+
 #[cfg(feature = "qrencode")]
 pub mod qrencode;
 
@@ -28,6 +30,9 @@ pub enum Error {
     #[error("The given handler is not a TTY")]
     NotATTY,
 
+    #[error("Validation of the input failed after {0} retries (last error: {1})")]
+    Validation(u8, String),
+
     #[error("IO Error: {0}")]
     IO(#[from] std::io::Error),
 }
@@ -80,6 +85,37 @@ where
         Ok(line)
     }
 
+    #[cfg(feature = "mnemonic")]
+    pub fn prompt_validated_wordlist<V, F, E>(
+        &mut self,
+        prompt: &str,
+        wordlist: &Wordlist,
+        retries: u8,
+        validator_fn: F,
+    ) -> Result<V, Error>
+    where
+        F: Fn(String) -> Result<V, E>,
+        E: std::error::Error,
+    {
+        let mut last_error = None;
+        for _ in 0..retries {
+            let s = self.prompt_wordlist(prompt, wordlist)?;
+            match validator_fn(s) {
+                Ok(v) => return Ok(v),
+                Err(e) => {
+                    self.prompt_message(&Message::Text(format!("Error validating wordlist: {e}")))?;
+                    let _ = last_error.insert(e);
+                }
+            }
+        }
+        Err(Error::Validation(
+            retries,
+            last_error
+                .map(|e| e.to_string())
+                .unwrap_or_else(|| "Unknown".to_string()),
+        ))
+    }
+
     // TODO: create a wrapper for bracketed paste similar to RawMode
     #[cfg(feature = "mnemonic")]
     #[allow(clippy::too_many_lines)]
@@ -204,6 +240,36 @@ where
         Ok(input)
     }
 
+    #[cfg(feature = "mnemonic")]
+    pub fn prompt_validated_passphrase<V, F, E>(
+        &mut self,
+        prompt: &str,
+        retries: u8,
+        validator_fn: F,
+    ) -> Result<V, Error>
+    where
+        F: Fn(String) -> Result<V, E>,
+        E: std::error::Error,
+    {
+        let mut last_error = None;
+        for _ in 0..retries {
+            let s = self.prompt_passphrase(prompt)?;
+            match validator_fn(s) {
+                Ok(v) => return Ok(v),
+                Err(e) => {
+                    self.prompt_message(&Message::Text(format!("Error validating passphrase: {e}")))?;
+                    let _ = last_error.insert(e);
+                }
+            }
+        }
+        Err(Error::Validation(
+            retries,
+            last_error
+                .map(|e| e.to_string())
+                .unwrap_or_else(|| "Unknown".to_string()),
+        ))
+    }
+
     // TODO: return secrecy::Secret<String>
     pub fn prompt_passphrase(&mut self, prompt: &str) -> Result<String> {
         let mut terminal = AlternateScreen::new(&mut self.write)?;

keyfork-prompt/src/validators.rs

@@ -0,0 +1,54 @@
+#![allow(clippy::type_complexity)]
+
+pub trait Validator {
+    type Output;
+    type Error;
+
+    fn to_fn(&self) -> Box<dyn Fn(String) -> Result<Self::Output, Self::Error>>;
+}
+
+#[derive(thiserror::Error, Debug)]
+pub enum PinError {
+    #[error("PIN too short: {0} < {1}")]
+    TooShort(usize, usize),
+
+    #[error("PIN too long: {0} > {1}")]
+    TooLong(usize, usize),
+
+    #[error("PIN contained invalid characters (found {0} at position {1})")]
+    InvalidCharacters(char, usize),
+}
+
+#[derive(Default, Clone)]
+pub struct PinValidator {
+    pub min_length: Option<usize>,
+    pub max_length: Option<usize>,
+    pub range: Option<std::ops::RangeInclusive<char>>,
+}
+
+impl Validator for PinValidator {
+    type Output = String;
+    type Error = PinError;
+
+    fn to_fn(&self) -> Box<dyn Fn(String) -> Result<String, PinError>> {
+        let min_len = self.min_length.unwrap_or(usize::MIN);
+        let max_len = self.max_length.unwrap_or(usize::MAX);
+        let range = self.range.clone().unwrap_or('0'..='9');
+        Box::new(move |mut s: String| {
+            s.truncate(s.trim_end().len());
+            let len = s.len();
+            if len < min_len {
+                return Err(PinError::TooShort(len, min_len));
+            }
+            if len > max_len {
+                return Err(PinError::TooLong(len, max_len));
+            }
+            for (index, ch) in s.chars().enumerate() {
+                if !range.contains(&ch) {
+                    return Err(PinError::InvalidCharacters(ch, index));
+                }
+            }
+            Ok(s)
+        })
+    }
+}

keyfork-shard/src/openpgp/smartcard.rs

@@ -1,6 +1,10 @@
 use std::collections::{HashMap, HashSet};
 
-use keyfork_prompt::{default_prompt_manager, DefaultPromptManager, Error as PromptError, Message};
+use keyfork_prompt::{
+    default_prompt_manager,
+    validators::{PinValidator, Validator},
+    DefaultPromptManager, Error as PromptError, Message,
+};
 
 use super::openpgp::{
     self,
@@ -222,6 +226,11 @@ impl DecryptionHelper for &mut SmartcardManager {
             .context("Could not load application identifier")?
             .ident();
         let mut pin = self.pin_cache.get(&fp).cloned();
+        let pin_validator = PinValidator {
+            min_length: Some(6),
+            ..Default::default()
+        }
+        .to_fn();
         while transaction
             .pw_status_bytes()
             .map_err(Error::PwStatusBytes)?
@@ -240,7 +249,9 @@ impl DecryptionHelper for &mut SmartcardManager {
             } else {
                 format!("Unlock card {card_id} ({cardholder_name})\n{rpea}: {attempts}\n\nPIN: ")
             };
-            let temp_pin = self.pm.prompt_passphrase(&message)?;
+            let temp_pin = self
+                .pm
+                .prompt_validated_passphrase(&message, 3, &pin_validator)?;
             let verification_status = transaction.verify_user_pin(temp_pin.as_str().trim());
             match verification_status {
                 #[allow(clippy::ignored_unit_patterns)]
@@ -248,8 +259,11 @@ impl DecryptionHelper for &mut SmartcardManager {
                     self.pin_cache.insert(fp.clone(), temp_pin.clone());
                     pin.replace(temp_pin);
                 }
+                // NOTE: This should not be hit, because of the above validator.
                 Err(CardError::CardStatus(StatusBytes::IncorrectParametersCommandDataField)) => {
-                    self.pm.prompt_message(&Message::Text("Invalid PIN length entered.".to_string()))?;
+                    self.pm.prompt_message(&Message::Text(
+                        "Invalid PIN length entered.".to_string(),
+                    ))?;
                 }
                 Err(_) => {}
             }

keyfork/src/cli/wizard.rs

@@ -10,7 +10,14 @@ use keyfork_derive_util::{
     request::{DerivationAlgorithm, DerivationRequest},
     DerivationIndex, DerivationPath,
 };
-use keyfork_prompt::{Message, PromptManager};
+use keyfork_prompt::{
+    validators::{PinValidator, Validator},
+    Message, PromptManager,
+};
+
+#[derive(thiserror::Error, Debug)]
+#[error("Invalid PIN length: {0}")]
+pub struct PinLength(usize);
 
 type Result<T, E = Box<dyn std::error::Error>> = std::result::Result<T, E>;
 
@@ -105,6 +112,17 @@ fn generate_shard_secret(threshold: u8, max: u8, keys_per_shard: u8) -> Result<(
         "not printing shard to terminal, redirect output"
     );
 
+    let user_pin_validator = PinValidator {
+        min_length: Some(6),
+        ..Default::default()
+    }
+    .to_fn();
+    let admin_pin_validator = PinValidator {
+        min_length: Some(8),
+        ..Default::default()
+    }
+    .to_fn();
+
     for index in 0..max {
         let cert = derive_key(&seed, index)?;
         for i in 0..keys_per_shard {
@@ -113,10 +131,16 @@ fn generate_shard_secret(threshold: u8, max: u8, keys_per_shard: u8) -> Result<(
                 i + 1,
                 index + 1,
             )))?;
-            // TODO: add a second prompt for verification, perhaps as an argument to
-            // prompt_passphrase
-            let user_pin = pm.prompt_passphrase("Please enter the new smartcard User PIN: ")?;
-            let admin_pin = pm.prompt_passphrase("Please enter the new smartcard Admin PIN: ")?;
+            let user_pin = pm.prompt_validated_passphrase(
+                "Please enter the new smartcard User PIN: ",
+                3,
+                &user_pin_validator,
+            )?;
+            let admin_pin = pm.prompt_validated_passphrase(
+                "Please enter the new smartcard Admin PIN: ",
+                3,
+                &admin_pin_validator,
+            )?;
             factory_reset_current_card(&mut seen_cards, user_pin.trim(), admin_pin.trim(), &cert)?;
         }
         certs.push(cert);