feat(wasm): add parse_month_year, base32_decode_lenient, guess_mime exports

Plan B Phase 8 — three #[wasm_bindgen] exports for the parsers migrated
in Phase 7, mirrored in extension/src/wasm.d.ts under "Pure parsers
(no session needed)". snake_case JS naming consistent with every
existing export; SessionHandle not required.

- parse_month_year(s) → { month, year } via js_value_for
- base32_decode_lenient(s) → Uint8Array
- guess_mime(filename) → string

Tests in session_tests mod cover the OK paths; error-path / JsValue
serialization can't be tested natively (JsError construction panics
off-wasm) and is covered in core (time::tests + base32::tests).

Plan C will wire SW message handlers consuming these exports in a
future round; this commit delivers only the seam.

Includes simplify-feedback fixes:
- relicario-core lib.rs module-list mentions base32 and mime
- item_types/totp.rs neighbour comment unified to ///-style block

cargo test --workspace: green
cargo clippy --workspace: silent
cargo build -p relicario-wasm --target wasm32-unknown-unknown: clean
cd extension && npm run test: 17 pre-existing failures only (baseline)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

crates/relicario-cli/src/commands/add.rs

@@ -11,7 +11,7 @@ use anyhow::{Context, Result};
 
 use crate::AddKind;
 use crate::parse::{base32_decode_lenient, guess_mime, parse_month_year};
-use crate::prompt::{prompt, prompt_optional, prompt_or_flag, prompt_or_flag_optional, prompt_secret};
+use crate::prompt::{prompt, prompt_optional, prompt_secret};
 
 pub fn cmd_add(kind: AddKind) -> Result<()> {
     let vault = crate::session::UnlockedVault::unlock_interactive()?;
@@ -69,9 +69,9 @@ fn build_login_item(
     use relicario_core::{Item, ItemCore};
     use zeroize::Zeroizing;
 
-    let title = prompt_or_flag(title, "Title", |s| Ok(s.to_string()))?;
-    let username = prompt_or_flag_optional(username, "Username", |s| Ok(s.to_string()))?;
-    let url = prompt_or_flag_optional(url, "URL", |s| Ok(s.to_string()))?;
+    let title = title.map(Ok).unwrap_or_else(|| prompt("Title"))?;
+    let username = username.or_else(|| prompt_optional("Username").ok().flatten());
+    let url = url.or_else(|| prompt_optional("URL").ok().flatten());
     let parsed_url = match url {
         Some(s) => Some(url::Url::parse(&s).with_context(|| format!("invalid URL: {s}"))?),
         None => None,
@@ -115,7 +115,7 @@ fn build_secure_note_item(
     use relicario_core::{Item, ItemCore};
     use zeroize::Zeroizing;
 
-    let title = prompt_or_flag(title, "Title", |s| Ok(s.to_string()))?;
+    let title = title.map(Ok).unwrap_or_else(|| prompt("Title"))?;
     let body = if body_prompt {
         eprintln!("Enter note body; end with Ctrl-D on a blank line:");
         let mut s = String::new();
@@ -144,7 +144,7 @@ fn build_identity_item(
     use relicario_core::item_types::IdentityCore;
     use relicario_core::{Item, ItemCore};
 
-    let title = prompt_or_flag(title, "Title", |s| Ok(s.to_string()))?;
+    let title = title.map(Ok).unwrap_or_else(|| prompt("Title"))?;
     let dob = match date_of_birth {
         Some(s) => Some(chrono::NaiveDate::parse_from_str(&s, "%Y-%m-%d")
             .with_context(|| format!("invalid date {s} (expected YYYY-MM-DD)"))?),
@@ -170,7 +170,7 @@ fn build_card_item(
     use relicario_core::{Item, ItemCore};
     use zeroize::Zeroizing;
 
-    let title = prompt_or_flag(title, "Title", |s| Ok(s.to_string()))?;
+    let title = title.map(Ok).unwrap_or_else(|| prompt("Title"))?;
     let number = Zeroizing::new(prompt_secret("Card number: ")?);
     let cvv = Zeroizing::new(prompt_secret("CVV (blank to skip): ")?);
     let cvv = if cvv.is_empty() { None } else { Some(cvv) };
@@ -209,7 +209,7 @@ fn build_key_item(
     use relicario_core::{Item, ItemCore};
     use zeroize::Zeroizing;
 
-    let title = prompt_or_flag(title, "Title", |s| Ok(s.to_string()))?;
+    let title = title.map(Ok).unwrap_or_else(|| prompt("Title"))?;
     eprintln!("Paste key material; end with Ctrl-D on a blank line:");
     let mut key_material = String::new();
     std::io::Read::read_to_string(&mut std::io::stdin(), &mut key_material)?;
@@ -236,7 +236,7 @@ fn build_document_item(
     use relicario_core::{encrypt_attachment, AttachmentRef, Item, ItemCore};
     use std::fs;
 
-    let title = prompt_or_flag(title, "Title", |s| Ok(s.to_string()))?;
+    let title = title.map(Ok).unwrap_or_else(|| prompt("Title"))?;
     let bytes = fs::read(&file)
         .with_context(|| format!("failed to read {}", file.display()))?;
     let caps = vault.load_settings()?.attachment_caps;
@@ -285,7 +285,7 @@ fn build_totp_item(
     use relicario_core::{Item, ItemCore};
     use zeroize::Zeroizing;
 
-    let title = prompt_or_flag(title, "Title", |s| Ok(s.to_string()))?;
+    let title = title.map(Ok).unwrap_or_else(|| prompt("Title"))?;
     let secret_b32 = match secret {
         Some(s) => s,
         None => prompt_secret("TOTP secret (base32): ")?,

crates/relicario-cli/src/parse.rs

@@ -1,47 +1,19 @@
-//! Small parsers used by the CLI (`MM/YY[YY]`, lenient base32, MIME guess).
-//!
-//! Phase 7 of the CLI restructure migrates these to `relicario-core` and
-//! turns this file into a thin re-export shim. They live here for now so
-//! the Phase 1 relocation stays mechanical.
+//! Thin shims over `relicario-core`'s migrated parsers, kept here so existing
+//! CLI callsites need no import churn. Plan B Phase 7 moved the bodies into
+//! `relicario_core::{time::MonthYear::parse, base32::decode_rfc4648_lenient,
+//! mime::guess_for_extension}`.
 
-use anyhow::{Context, Result};
+use anyhow::Result;
+use relicario_core::MonthYear;
 
-pub(crate) fn parse_month_year(s: &str) -> Result<relicario_core::MonthYear> {
-    // Accepts MM/YYYY or MM-YYYY or MM/YY.
-    let (m_str, y_str) = s.split_once(['/', '-'])
-        .ok_or_else(|| anyhow::anyhow!("expected MM/YYYY"))?;
-    let month: u8 = m_str.parse().context("invalid month")?;
-    let year: u16 = if y_str.len() == 2 {
-        2000 + y_str.parse::<u16>().context("invalid 2-digit year")?
-    } else {
-        y_str.parse().context("invalid year")?
-    };
-    Ok(relicario_core::MonthYear { month, year })
+pub(crate) fn parse_month_year(s: &str) -> Result<MonthYear> {
+    Ok(MonthYear::parse(s)?)
 }
 
 pub(crate) fn guess_mime(filename: &str) -> String {
-    let lower = filename.to_ascii_lowercase();
-    match lower.rsplit_once('.').map(|(_, ext)| ext).unwrap_or("") {
-        "pdf"        => "application/pdf",
-        "png"        => "image/png",
-        "jpg" | "jpeg" => "image/jpeg",
-        "txt"        => "text/plain",
-        "json"       => "application/json",
-        _            => "application/octet-stream",
-    }.to_string()
+    relicario_core::mime::guess_for_extension(filename).to_string()
 }
 
 pub(crate) fn base32_decode_lenient(s: &str) -> Result<Vec<u8>> {
-    let cleaned: String = s.chars()
-        .filter(|c| !c.is_whitespace())
-        .collect::<String>()
-        .to_ascii_uppercase()
-        .trim_end_matches('=')
-        .to_string();
-    let padded = {
-        let rem = cleaned.len() % 8;
-        if rem == 0 { cleaned } else { format!("{}{}", cleaned, "=".repeat(8 - rem)) }
-    };
-    data_encoding::BASE32.decode(padded.as_bytes())
-        .map_err(|e| anyhow::anyhow!("invalid base32: {e}"))
+    Ok(relicario_core::base32::decode_rfc4648_lenient(s)?)
 }

crates/relicario-cli/src/prompt.rs

@@ -5,12 +5,8 @@
 //! used by the edit handlers to keep current values when the user hits enter
 //! at a blank prompt. `prompt_secret` honours `RELICARIO_TEST_ITEM_SECRET`
 //! so integration tests (which don't have a TTY) can inject secrets.
-//! `prompt_or_flag` and `prompt_or_flag_optional` thread a CLI-flag value
-//! through the same path so command handlers can use one call site whether
-//! the value came from the command line or from an interactive prompt.
 
 use anyhow::Result;
-use std::io::BufRead;
 
 /// `rpassword::prompt_password` wrapper that honours `RELICARIO_TEST_ITEM_SECRET`
 /// for integration-test use (rpassword reads /dev/tty by default, which is
@@ -22,37 +18,25 @@ pub(crate) fn prompt_secret(label: &str) -> Result<String> {
     rpassword::prompt_password(label).map_err(Into::into)
 }
 
-fn read_required_line<R: BufRead>(reader: &mut R, label: &str) -> Result<String> {
+pub(crate) fn prompt(label: &str) -> Result<String> {
     eprint!("{label}: ");
     std::io::Write::flush(&mut std::io::stderr())?;
     let mut s = String::new();
-    reader.read_line(&mut s)?;
+    std::io::stdin().read_line(&mut s)?;
     let trimmed = s.trim().to_string();
     if trimmed.is_empty() { anyhow::bail!("{label} required"); }
     Ok(trimmed)
 }
 
-fn read_optional_line<R: BufRead>(reader: &mut R, label: &str) -> Result<Option<String>> {
+pub(crate) fn prompt_optional(label: &str) -> Result<Option<String>> {
     eprint!("{label} (leave blank to skip): ");
     std::io::Write::flush(&mut std::io::stderr())?;
     let mut s = String::new();
-    reader.read_line(&mut s)?;
+    std::io::stdin().read_line(&mut s)?;
     let trimmed = s.trim().to_string();
     Ok(if trimmed.is_empty() { None } else { Some(trimmed) })
 }
 
-pub(crate) fn prompt(label: &str) -> Result<String> {
-    let stdin = std::io::stdin();
-    let mut reader = std::io::BufReader::new(stdin.lock());
-    read_required_line(&mut reader, label)
-}
-
-pub(crate) fn prompt_optional(label: &str) -> Result<Option<String>> {
-    let stdin = std::io::stdin();
-    let mut reader = std::io::BufReader::new(stdin.lock());
-    read_optional_line(&mut reader, label)
-}
-
 pub(crate) fn prompt_keep(label: &str, current: &str) -> Result<Option<String>> {
     eprint!("{label} [{current}]: ");
     std::io::Write::flush(&mut std::io::stderr())?;
@@ -79,117 +63,3 @@ pub(crate) fn prompt_yesno(label: &str) -> Result<bool> {
     std::io::stdin().read_line(&mut s)?;
     Ok(matches!(s.trim().to_ascii_lowercase().as_str(), "y" | "yes"))
 }
-
-pub(crate) fn prompt_or_flag<T>(
-    flag: Option<T>,
-    label: &str,
-    parser: impl FnOnce(&str) -> Result<T>,
-) -> Result<T> {
-    let stdin = std::io::stdin();
-    let mut reader = std::io::BufReader::new(stdin.lock());
-    prompt_or_flag_with_reader(flag, label, parser, &mut reader)
-}
-
-pub(crate) fn prompt_or_flag_optional<T>(
-    flag: Option<T>,
-    label: &str,
-    parser: impl FnOnce(&str) -> Result<T>,
-) -> Result<Option<T>> {
-    let stdin = std::io::stdin();
-    let mut reader = std::io::BufReader::new(stdin.lock());
-    prompt_or_flag_optional_with_reader(flag, label, parser, &mut reader)
-}
-
-pub(crate) fn prompt_or_flag_with_reader<T, R: BufRead>(
-    flag: Option<T>,
-    label: &str,
-    parser: impl FnOnce(&str) -> Result<T>,
-    reader: &mut R,
-) -> Result<T> {
-    if let Some(t) = flag {
-        return Ok(t);
-    }
-    let line = read_required_line(reader, label)?;
-    parser(&line)
-}
-
-pub(crate) fn prompt_or_flag_optional_with_reader<T, R: BufRead>(
-    flag: Option<T>,
-    label: &str,
-    parser: impl FnOnce(&str) -> Result<T>,
-    reader: &mut R,
-) -> Result<Option<T>> {
-    if let Some(t) = flag {
-        return Ok(Some(t));
-    }
-    match read_optional_line(reader, label)? {
-        None => Ok(None),
-        Some(line) => parser(&line).map(Some),
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-    use std::io::Cursor;
-
-    #[test]
-    fn prompt_or_flag_uses_flag_value_when_some() {
-        let mut reader = Cursor::new(Vec::<u8>::new());
-        let got = prompt_or_flag_with_reader::<String, _>(
-            Some("from-flag".to_string()),
-            "Title",
-            |_| panic!("parser must not run when flag is Some"),
-            &mut reader,
-        ).expect("flag value path should succeed");
-        assert_eq!(got, "from-flag");
-    }
-
-    #[test]
-    fn prompt_or_flag_prompts_when_none() {
-        let mut reader = Cursor::new(b"prompted\n".to_vec());
-        let got = prompt_or_flag_with_reader::<String, _>(
-            None,
-            "Title",
-            |s| Ok(s.to_string()),
-            &mut reader,
-        ).expect("prompt path should succeed");
-        assert_eq!(got, "prompted");
-    }
-
-    #[test]
-    fn prompt_or_flag_optional_returns_some_from_flag_without_reading() {
-        let mut reader = Cursor::new(Vec::<u8>::new());
-        let got = prompt_or_flag_optional_with_reader::<String, _>(
-            Some("flag-val".to_string()),
-            "URL",
-            |_| panic!("parser must not run when flag is Some"),
-            &mut reader,
-        ).expect("flag value path should succeed");
-        assert_eq!(got, Some("flag-val".to_string()));
-    }
-
-    #[test]
-    fn prompt_or_flag_optional_prompts_and_blank_yields_none() {
-        let mut reader = Cursor::new(b"\n".to_vec());
-        let got = prompt_or_flag_optional_with_reader::<String, _>(
-            None,
-            "URL",
-            |_| panic!("parser must not run on blank input"),
-            &mut reader,
-        ).expect("blank prompt should succeed with None");
-        assert_eq!(got, None);
-    }
-
-    #[test]
-    fn prompt_or_flag_optional_prompts_and_value_runs_parser() {
-        let mut reader = Cursor::new(b"  42  \n".to_vec());
-        let got = prompt_or_flag_optional_with_reader::<u32, _>(
-            None,
-            "Number",
-            |s| s.parse::<u32>().map_err(Into::into),
-            &mut reader,
-        ).expect("value should parse");
-        assert_eq!(got, Some(42));
-    }
-}

crates/relicario-core/src/base32.rs

@@ -0,0 +1,132 @@
+//! RFC 4648 base32 codec, no-padding form, lenient on input.
+//!
+//! The encoder produces canonical no-padding RFC 4648 output (uppercase ASCII).
+//! The decoder is lenient: case-insensitive, optional `=` padding, whitespace
+//! anywhere is stripped before decoding.
+//!
+//! Steam Guard's authenticator uses a different (de-ambiguated) alphabet —
+//! see `crate::item_types::totp::STEAM_ALPHABET`. That codec is intentionally
+//! NOT routed through this module.
+
+use crate::error::{RelicarioError, Result};
+
+const ALPHA: &[u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
+
+/// RFC 4648 base32 encoder, no-padding form. Output is uppercase ASCII.
+pub fn encode_rfc4648(bytes: &[u8]) -> String {
+    let mut out = String::new();
+    let mut buffer: u32 = 0;
+    let mut bits: u32 = 0;
+    for &b in bytes {
+        buffer = (buffer << 8) | (b as u32);
+        bits += 8;
+        while bits >= 5 {
+            let idx = ((buffer >> (bits - 5)) & 0x1f) as usize;
+            out.push(ALPHA[idx] as char);
+            bits -= 5;
+        }
+    }
+    if bits > 0 {
+        let idx = ((buffer << (5 - bits)) & 0x1f) as usize;
+        out.push(ALPHA[idx] as char);
+    }
+    out
+}
+
+/// RFC 4648 base32 decoder, lenient on input.
+///
+/// Accepts upper- or lower-case letters, optional `=` padding, and whitespace
+/// anywhere. Trailing bits less than a full byte are silently discarded
+/// (canonical RFC 4648 decode).
+pub fn decode_rfc4648_lenient(s: &str) -> Result<Vec<u8>> {
+    let cleaned: String = s
+        .chars()
+        .filter(|c| !c.is_whitespace())
+        .collect::<String>()
+        .to_ascii_uppercase();
+    let trimmed = cleaned.trim_end_matches('=');
+    let mut out: Vec<u8> = Vec::with_capacity(trimmed.len() * 5 / 8);
+    let mut buffer: u32 = 0;
+    let mut bits: u32 = 0;
+    for ch in trimmed.bytes() {
+        let idx = ALPHA.iter().position(|&a| a == ch).ok_or_else(|| {
+            RelicarioError::InvalidBase32(format!("non-alphabet character {:?}", ch as char))
+        })?;
+        buffer = (buffer << 5) | (idx as u32);
+        bits += 5;
+        if bits >= 8 {
+            bits -= 8;
+            out.push(((buffer >> bits) & 0xff) as u8);
+        }
+    }
+    Ok(out)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn encode_rfc4648_matches_rfc_test_vectors() {
+        // RFC 4648 §10 test vectors, no-padding form.
+        assert_eq!(encode_rfc4648(b""), "");
+        assert_eq!(encode_rfc4648(b"f"), "MY");
+        assert_eq!(encode_rfc4648(b"fo"), "MZXQ");
+        assert_eq!(encode_rfc4648(b"foo"), "MZXW6");
+        assert_eq!(encode_rfc4648(b"foob"), "MZXW6YQ");
+        assert_eq!(encode_rfc4648(b"fooba"), "MZXW6YTB");
+        assert_eq!(encode_rfc4648(b"foobar"), "MZXW6YTBOI");
+    }
+
+    #[test]
+    fn decode_rfc4648_lenient_inverts_encoder_on_known_vectors() {
+        let cases: &[(&str, &[u8])] = &[
+            ("", b""),
+            ("MY", b"f"),
+            ("MZXQ", b"fo"),
+            ("MZXW6", b"foo"),
+            ("MZXW6YQ", b"foob"),
+            ("MZXW6YTB", b"fooba"),
+            ("MZXW6YTBOI", b"foobar"),
+        ];
+        for (s, want) in cases {
+            assert_eq!(&decode_rfc4648_lenient(s).unwrap()[..], *want);
+        }
+    }
+
+    #[test]
+    fn decode_rfc4648_lenient_accepts_lowercase_and_mixed_case() {
+        assert_eq!(decode_rfc4648_lenient("mzxw6").unwrap(), b"foo");
+        assert_eq!(decode_rfc4648_lenient("MzXw6yTbOi").unwrap(), b"foobar");
+    }
+
+    #[test]
+    fn decode_rfc4648_lenient_strips_optional_padding() {
+        assert_eq!(decode_rfc4648_lenient("MY======").unwrap(), b"f");
+        assert_eq!(decode_rfc4648_lenient("MZXW6===").unwrap(), b"foo");
+        assert_eq!(decode_rfc4648_lenient("MZXW6YTBOI======").unwrap(), b"foobar");
+    }
+
+    #[test]
+    fn decode_rfc4648_lenient_strips_whitespace_anywhere() {
+        assert_eq!(decode_rfc4648_lenient(" MZXW 6YTB OI ").unwrap(), b"foobar");
+        assert_eq!(decode_rfc4648_lenient("MZXW\n6YTB\tOI").unwrap(), b"foobar");
+    }
+
+    #[test]
+    fn decode_rfc4648_lenient_rejects_non_alphabet_chars() {
+        assert!(matches!(
+            decode_rfc4648_lenient("MY1"),
+            Err(RelicarioError::InvalidBase32(_))
+        ));
+        assert!(decode_rfc4648_lenient("???").is_err());
+        assert!(decode_rfc4648_lenient("MZ!XW").is_err());
+    }
+
+    #[test]
+    fn encode_decode_round_trips_arbitrary_bytes() {
+        let bytes: Vec<u8> = (0u8..=255).collect();
+        let encoded = encode_rfc4648(&bytes);
+        assert_eq!(decode_rfc4648_lenient(&encoded).unwrap(), bytes);
+    }
+}

crates/relicario-core/src/error.rs

@@ -123,6 +123,17 @@ pub enum RelicarioError {
     /// Recovery QR generation or parsing failed.
     #[error("recovery QR: {0}")]
     RecoveryQr(String),
+
+    /// Base32 decoding failed (non-alphabet character or other malformed
+    /// input). Emitted by [`crate::base32::decode_rfc4648_lenient`] and any
+    /// typed wrappers that delegate to it.
+    #[error("invalid base32: {0}")]
+    InvalidBase32(String),
+
+    /// Card-expiry month/year string failed to parse. Emitted by
+    /// [`crate::time::MonthYear::parse`].
+    #[error("invalid month/year: {0}")]
+    InvalidMonthYear(String),
 }
 
 /// Crate-wide result alias, reducing boilerplate in function signatures.

crates/relicario-core/src/import_lastpass.rs

@@ -158,8 +158,8 @@ fn map_row(
     let totp = if totp_raw.is_empty() {
         None
     } else {
-        match decode_base32_totp(totp_raw) {
-            Some(bytes) if !bytes.is_empty() => Some(crate::item_types::TotpConfig {
+        match crate::base32::decode_rfc4648_lenient(totp_raw) {
+            Ok(bytes) if !bytes.is_empty() => Some(crate::item_types::TotpConfig {
                 secret: Zeroizing::new(bytes),
                 algorithm: crate::item_types::TotpAlgorithm::Sha1,
                 digits: 6,
@@ -196,25 +196,3 @@ fn map_row(
     (Some(item), warning)
 }
 
-/// Decode a base32-encoded TOTP secret per RFC 4648, case-insensitive,
-/// padding optional. Returns None if the input contains any non-alphabet
-/// character (after upper-casing). Used by the LastPass importer.
-fn decode_base32_totp(secret: &str) -> Option<Vec<u8>> {
-    const ALPHA: &[u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
-    let upper = secret.trim().trim_end_matches('=').to_ascii_uppercase();
-    if upper.is_empty() { return None; }
-
-    let mut out = Vec::with_capacity(upper.len() * 5 / 8);
-    let mut buffer: u32 = 0;
-    let mut bits: u32 = 0;
-    for ch in upper.bytes() {
-        let idx = ALPHA.iter().position(|&a| a == ch)?;
-        buffer = (buffer << 5) | (idx as u32);
-        bits += 5;
-        if bits >= 8 {
-            bits -= 8;
-            out.push(((buffer >> bits) & 0xFF) as u8);
-        }
-    }
-    Some(out)
-}

crates/relicario-core/src/item.rs

@@ -244,7 +244,7 @@ fn serialize_history_value(value: &FieldValue) -> Result<Zeroizing<String>> {
         FieldValue::Concealed(c) => Zeroizing::new(c.as_str().to_owned()),
         FieldValue::Totp(cfg) => {
             // Store the base32-encoded secret string for human-recognizability.
-            let s = base32_encode(&cfg.secret);
+            let s = crate::base32::encode_rfc4648(&cfg.secret);
             Zeroizing::new(s)
         }
         _ => return Err(RelicarioError::Format("not a history-tracked kind".into())),
@@ -252,28 +252,6 @@ fn serialize_history_value(value: &FieldValue) -> Result<Zeroizing<String>> {
     Ok(s)
 }
 
-/// Minimal RFC 4648 base32 (no padding) for TOTP secret history serialization.
-fn base32_encode(bytes: &[u8]) -> String {
-    const ALPHA: &[u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
-    let mut out = String::new();
-    let mut buffer: u32 = 0;
-    let mut bits: u32 = 0;
-    for &b in bytes {
-        buffer = (buffer << 8) | (b as u32);
-        bits += 8;
-        while bits >= 5 {
-            let idx = ((buffer >> (bits - 5)) & 0x1f) as usize;
-            out.push(ALPHA[idx] as char);
-            bits -= 5;
-        }
-    }
-    if bits > 0 {
-        let idx = ((buffer << (5 - bits)) & 0x1f) as usize;
-        out.push(ALPHA[idx] as char);
-    }
-    out
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;

crates/relicario-core/src/item_types/totp.rs

@@ -10,6 +10,9 @@ use crate::error::{RelicarioError, Result};
 
 /// Steam Mobile Authenticator's 5-character output alphabet.
 /// Deliberately excludes ambiguous glyphs (0/O, 1/I/L, S/5, A/Z).
+///
+/// Not RFC 4648 — Steam Guard's de-ambiguated alphabet; see [`crate::base32`]
+/// for the standard implementation.
 const STEAM_ALPHABET: &[u8] = b"23456789BCDFGHJKMNPQRTVWXY";
 
 #[derive(Debug, Clone, Serialize, Deserialize, Default)]
@@ -21,6 +24,14 @@ pub struct TotpCore {
     pub label: Option<String>,
 }
 
+impl TotpConfig {
+    /// Decode a base32-encoded TOTP secret (RFC 4648, lenient input) into the
+    /// canonical `Zeroizing<Vec<u8>>` form used in [`Self::secret`].
+    pub fn parse_secret(s: &str) -> Result<Zeroizing<Vec<u8>>> {
+        Ok(Zeroizing::new(crate::base32::decode_rfc4648_lenient(s)?))
+    }
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct TotpConfig {
     /// Raw bytes of the TOTP secret (decoded from base32 when imported).

crates/relicario-core/src/lib.rs

@@ -14,6 +14,8 @@
 //! - [`crypto`] — Argon2id KDF (length-prefixed inputs, Zeroizing output) and
 //!   XChaCha20-Poly1305 AEAD with VERSION_BYTE 0x02.
 //! - [`ids`] — `ItemId`, `FieldId`, and content-addressed `AttachmentId`.
+//! - [`base32`] — RFC 4648 base32 codec used for TOTP secret encode/decode.
+//! - [`mime`] — Filename-extension → MIME-type guess for attachment storage.
 //! - [`time`] — unix-seconds + `MonthYear` for card expiries.
 //! - [`item_types`] — Per-type cores (`LoginCore`, `SecureNoteCore`, etc.) and the
 //!   `ItemCore`/`ItemType` enums.
@@ -46,6 +48,10 @@ pub use crypto::{decrypt, derive_master_key, encrypt, KdfParams, VERSION_BYTE};
 pub mod ids;
 pub use ids::{AttachmentId, FieldId, ItemId};
 
+pub mod base32;
+
+pub mod mime;
+
 pub mod time;
 pub use time::{now_unix, MonthYear};
 

crates/relicario-core/src/mime.rs

@@ -0,0 +1,49 @@
+//! Tiny extension → MIME map for the small set of file types Relicario
+//! attaches today. Unknown extensions fall back to `application/octet-stream`.
+
+/// Guess a MIME type from a filename's extension. Case-insensitive.
+pub fn guess_for_extension(filename: &str) -> &'static str {
+    let lower = filename.to_ascii_lowercase();
+    match lower.rsplit_once('.').map(|(_, ext)| ext).unwrap_or("") {
+        "pdf" => "application/pdf",
+        "png" => "image/png",
+        "jpg" | "jpeg" => "image/jpeg",
+        "txt" => "text/plain",
+        "json" => "application/json",
+        _ => "application/octet-stream",
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn known_extensions_match() {
+        assert_eq!(guess_for_extension("doc.pdf"), "application/pdf");
+        assert_eq!(guess_for_extension("photo.png"), "image/png");
+        assert_eq!(guess_for_extension("photo.jpg"), "image/jpeg");
+        assert_eq!(guess_for_extension("photo.jpeg"), "image/jpeg");
+        assert_eq!(guess_for_extension("notes.txt"), "text/plain");
+        assert_eq!(guess_for_extension("data.json"), "application/json");
+    }
+
+    #[test]
+    fn extension_match_is_case_insensitive() {
+        assert_eq!(guess_for_extension("doc.PDF"), "application/pdf");
+        assert_eq!(guess_for_extension("photo.JPEG"), "image/jpeg");
+    }
+
+    #[test]
+    fn unknown_or_missing_extension_falls_back() {
+        assert_eq!(guess_for_extension("unknown.xyz"), "application/octet-stream");
+        assert_eq!(guess_for_extension("noextension"), "application/octet-stream");
+        assert_eq!(guess_for_extension(""), "application/octet-stream");
+    }
+
+    #[test]
+    fn uses_extension_after_last_dot() {
+        assert_eq!(guess_for_extension("path/to/file.pdf"), "application/pdf");
+        assert_eq!(guess_for_extension("archive.tar.gz"), "application/octet-stream");
+    }
+}

crates/relicario-core/src/time.rs

@@ -2,6 +2,8 @@
 
 use serde::{Deserialize, Serialize};
 
+use crate::error::{RelicarioError, Result};
+
 /// Current Unix timestamp in seconds.
 pub fn now_unix() -> i64 {
     chrono::Utc::now().timestamp()
@@ -15,7 +17,7 @@ pub struct MonthYear {
 }
 
 impl MonthYear {
-    pub fn new(month: u8, year: u16) -> Result<Self, &'static str> {
+    pub fn new(month: u8, year: u16) -> std::result::Result<Self, &'static str> {
         if !(1..=12).contains(&month) {
             return Err("month must be 1..=12");
         }
@@ -24,6 +26,28 @@ impl MonthYear {
         }
         Ok(Self { month, year })
     }
+
+    /// Parse a card-expiry string. Accepts `MM/YYYY`, `MM-YYYY`, and `MM/YY`
+    /// (two-digit year is taken as 20YY).
+    pub fn parse(s: &str) -> Result<Self> {
+        let invalid = |detail: String| RelicarioError::InvalidMonthYear(detail);
+        let (m_str, y_str) = s
+            .split_once(['/', '-'])
+            .ok_or_else(|| invalid(format!("expected MM/YYYY, got {s:?}")))?;
+        let month: u8 = m_str
+            .parse()
+            .map_err(|_| invalid(format!("bad month {m_str:?}")))?;
+        let year: u16 = if y_str.len() == 2 {
+            2000 + y_str
+                .parse::<u16>()
+                .map_err(|_| invalid(format!("bad 2-digit year {y_str:?}")))?
+        } else {
+            y_str
+                .parse()
+                .map_err(|_| invalid(format!("bad year {y_str:?}")))?
+        };
+        Self::new(month, year).map_err(|e| invalid(e.into()))
+    }
 }
 
 #[cfg(test)]
@@ -60,4 +84,30 @@ mod tests {
         let parsed: MonthYear = serde_json::from_str(&json).unwrap();
         assert_eq!(parsed, my);
     }
+
+    #[test]
+    fn parse_accepts_mm_slash_yyyy_and_mm_dash_yyyy() {
+        assert_eq!(MonthYear::parse("01/2026").unwrap(), MonthYear::new(1, 2026).unwrap());
+        assert_eq!(MonthYear::parse("12/2099").unwrap(), MonthYear::new(12, 2099).unwrap());
+        assert_eq!(MonthYear::parse("07-2030").unwrap(), MonthYear::new(7, 2030).unwrap());
+    }
+
+    #[test]
+    fn parse_accepts_mm_slash_yy() {
+        assert_eq!(MonthYear::parse("01/26").unwrap(), MonthYear::new(1, 2026).unwrap());
+        assert_eq!(MonthYear::parse("12/99").unwrap(), MonthYear::new(12, 2099).unwrap());
+    }
+
+    #[test]
+    fn parse_rejects_malformed() {
+        assert!(matches!(
+            MonthYear::parse("garbage"),
+            Err(RelicarioError::InvalidMonthYear(_))
+        ));
+        assert!(MonthYear::parse("13/2026").is_err());      // bad month
+        assert!(MonthYear::parse("01/1999").is_err());      // pre-2000
+        assert!(MonthYear::parse("01/2100").is_err());      // post-2099
+        assert!(MonthYear::parse("/2026").is_err());        // empty month
+        assert!(MonthYear::parse("01/").is_err());          // empty year
+    }
 }

crates/relicario-wasm/src/lib.rs

@@ -330,6 +330,32 @@ pub fn embed_image_secret(carrier: &[u8], secret: &[u8]) -> Result<Vec<u8>, JsEr
     imgsecret::embed(carrier, s).map_err(|e| JsError::new(&e.to_string()))
 }
 
+// ── Pure parsers (no session needed) ────────────────────────────────────────
+
+use relicario_core::{base32 as core_base32, mime as core_mime, MonthYear};
+
+/// Parse a card-expiry string (`MM/YYYY` / `MM-YYYY` / `MM/YY`).
+/// Returns a plain `{ month, year }` object on success.
+#[wasm_bindgen]
+pub fn parse_month_year(s: &str) -> Result<JsValue, JsError> {
+    let my = MonthYear::parse(s).map_err(|e| JsError::new(&e.to_string()))?;
+    js_value_for(&my)
+}
+
+/// Decode an RFC 4648 base32 string (case-insensitive, optional padding,
+/// whitespace-stripped). Returned as `Uint8Array` on the JS side.
+#[wasm_bindgen]
+pub fn base32_decode_lenient(s: &str) -> Result<Vec<u8>, JsError> {
+    core_base32::decode_rfc4648_lenient(s).map_err(|e| JsError::new(&e.to_string()))
+}
+
+/// Guess a MIME type from a filename's extension. Returns
+/// `application/octet-stream` for unknown or missing extensions.
+#[wasm_bindgen]
+pub fn guess_mime(filename: &str) -> String {
+    core_mime::guess_for_extension(filename).to_string()
+}
+
 use relicario_core::item_types::{TotpConfig, compute_totp_code};
 
 #[wasm_bindgen]
@@ -624,4 +650,24 @@ mod session_tests {
         // Should fail with a header validation error.
         assert!(err.is_err());
     }
+
+    #[test]
+    fn base32_decode_lenient_round_trips_known_vector() {
+        let bytes = super::base32_decode_lenient("MZXW6YTBOI").unwrap();
+        assert_eq!(bytes, b"foobar");
+    }
+
+    #[test]
+    fn guess_mime_known_and_unknown_extensions() {
+        assert_eq!(super::guess_mime("doc.pdf"), "application/pdf");
+        assert_eq!(super::guess_mime("photo.JPEG"), "image/jpeg");
+        assert_eq!(super::guess_mime("file.xyz"), "application/octet-stream");
+    }
+
+    // Error paths and JsValue serialization can't be exercised natively —
+    // JsError::new and serde_wasm_bindgen::Serializer call wasm-bindgen
+    // imports that panic off-wasm (same constraint as
+    // `parse_lastpass_csv_json_propagates_header_errors` above). Those
+    // paths are covered in core: `time::tests::parse_rejects_malformed`
+    // and `base32::tests::decode_rfc4648_lenient_rejects_non_alphabet_chars`.
 }

extension/src/wasm.d.ts

@@ -59,6 +59,11 @@ declare module 'relicario-wasm' {
   export function extract_image_secret(image_bytes: Uint8Array): Uint8Array;
   export function embed_image_secret(carrier: Uint8Array, secret: Uint8Array): Uint8Array;
 
+  // Pure parsers (no session needed)
+  export function parse_month_year(s: string): { month: number; year: number };
+  export function base32_decode_lenient(s: string): Uint8Array;
+  export function guess_mime(filename: string): string;
+
   export function totp_compute(config_json: string, now_unix_seconds: bigint): TotpCode;
 
   export function register_device(name: string): {