fix: 2FA secret QR code for Bitwarden/KeePassXC needs to be Base32 encoded instead Base64

src/commands/qr.rs

@@ -1,6 +1,5 @@
 use std::sync::{Arc, Mutex};
 
-use base64::Engine;
 use log::*;
 use qrcode::QrCode;
 use secrecy::ExposeSecret;
@@ -34,6 +33,24 @@ pub struct QrCommand {
 	pub format: QrFormat,
 }
 
+impl QrCommand {
+	pub(crate) fn qr_content(&self, account: &SteamGuardAccount) -> String {
+		let secret_b32 = base32_encode_unpadded(account.shared_secret.expose_secret());
+
+		match self.format {
+			QrFormat::Steam => account.uri.expose_secret().to_owned(),
+			QrFormat::Bitwarden => format!("steam://{}", secret_b32),
+			QrFormat::KeePassXc => {
+				let username = percent_encode_username(&account.account_name);
+				format!(
+					"otpauth://totp/Steam:{}?secret={}&period=30&digits=5&issuer=Steam&encoder=steam",
+					username, secret_b32
+				)
+			}
+		}
+	}
+}
+
 impl<T> AccountCommand<T> for QrCommand
 where
 	T: Transport,
@@ -51,20 +68,7 @@ where
 
 		for account in accounts {
 			let account = account.lock().unwrap();
-			let secret_b64 = base64::engine::general_purpose::STANDARD
-				.encode(account.shared_secret.expose_secret());
-
-			let qr_content: String = match self.format {
-				QrFormat::Steam => account.uri.expose_secret().to_owned(),
-				QrFormat::Bitwarden => format!("steam://{}", secret_b64),
-				QrFormat::KeePassXc => {
-					let username = percent_encode_username(&account.account_name);
-					format!(
-						"otpauth://totp/Steam:{}?secret={}&period=30&digits=5&issuer=Steam&encoder=steam",
-						username, secret_b64
-					)
-				}
-			};
+			let qr_content = self.qr_content(&account);
 
 			let qr = QrCode::new(qr_content.as_bytes())
 				.context(format!("generating qr code for {}", account.account_name))?;
@@ -90,6 +94,31 @@ where
 	}
 }
 
+/// Encode raw bytes to an unpadded Base32 string (RFC 3548 / RFC 4648).
+fn base32_encode_unpadded(data: &[u8]) -> String {
+	const ALPHABET: &[u8; 32] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
+	let mut out = String::new();
+	let mut buffer: u32 = 0;
+	let mut bits: u32 = 0;
+
+	for &byte in data {
+		buffer = (buffer << 8) | (byte as u32);
+		bits += 8;
+		while bits >= 5 {
+			bits -= 5;
+			let index = ((buffer >> bits) & 0x1F) as usize;
+			out.push(ALPHABET[index] as char);
+		}
+	}
+
+	if bits > 0 {
+		let index = ((buffer << (5 - bits)) & 0x1F) as usize;
+		out.push(ALPHABET[index] as char);
+	}
+
+	out
+}
+
 /// Percent-encode characters that are unsafe in a URI path component.
 ///
 /// Only encodes characters that would structurally break a URI (delimiters,
@@ -139,4 +168,78 @@ mod tests {
 	fn percent_encode_username_encodes_non_ascii() {
 		assert_eq!(percent_encode_username("usér"), "us%C3%A9r");
 	}
+
+	#[test]
+	fn test_base32_encode_unpadded() {
+		assert_eq!(base32_encode_unpadded(b"f"), "MY");
+		assert_eq!(base32_encode_unpadded(b"fo"), "MZXQ");
+		assert_eq!(base32_encode_unpadded(b"foo"), "MZXW6");
+		assert_eq!(base32_encode_unpadded(b"foob"), "MZXW6YQ");
+		assert_eq!(base32_encode_unpadded(b"fooba"), "MZXW6YTB");
+		assert_eq!(base32_encode_unpadded(b"foobar"), "MZXW6YTBOI");
+	}
+
+	#[test]
+	fn test_qr_format_secret_base32_check() {
+		let account = SteamGuardAccount {
+			account_name: "test_user".to_string(),
+			shared_secret: steamguard::token::TwoFactorSecret::parse_shared_secret(
+				"zvIayp3JPvtvX/QGHqsqKBk/44s=".to_string(),
+			)
+			.unwrap(),
+			uri: secrecy::SecretString::from(
+				"otpauth://totp/Steam:test_user?secret=ASDF&issuer=Steam".to_string(),
+			),
+			..Default::default()
+		};
+
+		// Bitwarden format check
+		let bw_cmd = QrCommand {
+			ascii: false,
+			format: QrFormat::Bitwarden,
+		};
+		let bw_content = bw_cmd.qr_content(&account);
+		let bw_secret = bw_content
+			.strip_prefix("steam://")
+			.expect("should start with steam://");
+		let bw_is_unpadded_base32 = bw_secret
+			.chars()
+			.all(|c| matches!(c, 'A'..='Z' | '2'..='7'))
+			&& !bw_secret.contains('=');
+		assert!(
+			bw_is_unpadded_base32,
+			"Bitwarden QR format secret should be unpadded base32 encoded, but got: {}",
+			bw_secret
+		);
+
+		// KeePassXC format check
+		let keepass_cmd = QrCommand {
+			ascii: false,
+			format: QrFormat::KeePassXc,
+		};
+		let keepass_content = keepass_cmd.qr_content(&account);
+		let keepass_secret = keepass_content
+			.split('?')
+			.nth(1)
+			.and_then(|query| {
+				query.split('&').find_map(|pair| {
+					let mut parts = pair.split('=');
+					if parts.next()? == "secret" {
+						parts.next().map(ToString::to_string)
+					} else {
+						None
+					}
+				})
+			})
+			.expect("secret parameter should be present");
+		let keepass_is_unpadded_base32 = keepass_secret
+			.chars()
+			.all(|c| matches!(c, 'A'..='Z' | '2'..='7'))
+			&& !keepass_secret.contains('=');
+		assert!(
+			keepass_is_unpadded_base32,
+			"KeePassXC QR format secret should be unpadded base32 encoded, but got: {}",
+			keepass_secret
+		);
+	}
 }