1 files changed, 181 insertions, 0 deletions
diff --git a/wpa-psk/src/lib.rs b/wpa-psk/src/lib.rs
new file mode 100644
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--- /dev/null
+++ b/wpa-psk/src/lib.rs
@@ -0,0 +1,181 @@
+//! Compute the WPA-PSK of a Wi-Fi SSID and passphrase.
+//!
+//! # Example
+//!
+//! Compute and print the WPA-PSK of a valid SSID and passphrase:
+//!
+//! ```
+//! # use wpa_psk::{Ssid, Passphrase, wpa_psk, bytes_to_hex};
+//! # fn main() -> Result<(), Box<dyn std::error::Error>> {
+//! let ssid = Ssid::try_from("home")?;
+//! let passphrase = Passphrase::try_from("0123-4567-89")?;
+//! let psk = wpa_psk(&ssid, &passphrase);
+//! assert_eq!(bytes_to_hex(&psk), "150c047b6fad724512a17fa431687048ee503d14c1ea87681d4f241beb04f5ee");
+//! # Ok(())
+//! # }
+//! ```
+//!
+//! Compute the WPA-PSK of possibly invalid raw bytes:
+//!
+//! ```
+//! # use wpa_psk::{wpa_psk_unchecked, bytes_to_hex};
+//! let ssid = "bar".as_bytes();
+//! let passphrase = "2short".as_bytes();
+//! let psk = wpa_psk_unchecked(&ssid, &passphrase);
+//! assert_eq!(bytes_to_hex(&psk), "cb5de4e4d23b2ab0bf5b9ba0fe8132c1e2af3bb52298ec801af8ad520cea3437");
+//! ```
+
+use std::{error::Error, fmt::Display};
+
+use hmac::Hmac;
+use pbkdf2::pbkdf2;
+use sha1::Sha1;
+
+/// An SSID consisting of 1 up to 32 arbitrary bytes.
+#[derive(Debug)]
+pub struct Ssid<'a>(&'a [u8]);
+
+impl<'a> TryFrom<&'a [u8]> for Ssid<'a> {
+    type Error = ValidateSsidError;
+
+    fn try_from(value: &'a [u8]) -> Result<Self, Self::Error> {
+        if value.is_empty() {
+            Err(ValidateSsidError::TooShort)
+        } else if value.len() > 32 {
+            Err(ValidateSsidError::TooLong)
+        } else {
+            Ok(Ssid(value))
+        }
+    }
+}
+
+impl<'a> TryFrom<&'a str> for Ssid<'a> {
+    type Error = ValidateSsidError;
+
+    fn try_from(value: &'a str) -> Result<Self, Self::Error> {
+        Self::try_from(value.as_bytes())
+    }
+}
+
+#[derive(Debug, PartialEq)]
+pub enum ValidateSsidError {
+    TooShort,
+    TooLong,
+}
+
+impl Error for ValidateSsidError {}
+
+impl Display for ValidateSsidError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let msg = match self {
+            ValidateSsidError::TooShort => "SSID must have at least one byte",
+            ValidateSsidError::TooLong => "SSID must have at most 32 bytes",
+        };
+        write!(f, "{msg}")
+    }
+}
+
+/// A passphrase consisting of 8 up to 63 printable ASCII characters.
+#[derive(Debug)]
+pub struct Passphrase<'a>(&'a [u8]);
+
+impl<'a> TryFrom<&'a [u8]> for Passphrase<'a> {
+    type Error = ValidatePassphraseError;
+
+    fn try_from(value: &'a [u8]) -> Result<Self, Self::Error> {
+        if value.len() < 8 {
+            Err(ValidatePassphraseError::TooShort)
+        } else if value.len() > 63 {
+            Err(ValidatePassphraseError::TooLong)
+        } else if value.iter().any(|i| !matches!(i, 32u8..=126)) {
+            Err(ValidatePassphraseError::InvalidByte)
+        } else {
+            Ok(Passphrase(value))
+        }
+    }
+}
+
+impl<'a> TryFrom<&'a str> for Passphrase<'a> {
+    type Error = ValidatePassphraseError;
+
+    fn try_from(value: &'a str) -> Result<Self, Self::Error> {
+        Self::try_from(value.as_bytes())
+    }
+}
+
+impl Display for Passphrase<'_> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}", std::str::from_utf8(self.0).unwrap())
+    }
+}
+
+#[derive(Debug, PartialEq)]
+pub enum ValidatePassphraseError {
+    TooShort,
+    TooLong,
+    InvalidByte,
+}
+
+impl Error for ValidatePassphraseError {}
+
+impl Display for ValidatePassphraseError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let msg = match self {
+            ValidatePassphraseError::TooShort => "passphrase must have at least 8 bytes",
+            ValidatePassphraseError::TooLong => "passphrase must have at most 63 bytes",
+            ValidatePassphraseError::InvalidByte => {
+                "passphrase must consist of printable ASCII characters"
+            }
+        };
+        write!(f, "{msg}")
+    }
+}
+
+/// Returns the WPA-PSK of the given SSID and passphrase.
+pub fn wpa_psk(ssid: &Ssid, passphrase: &Passphrase) -> [u8; 32] {
+    wpa_psk_unchecked(ssid.0, passphrase.0)
+}
+
+/// Unchecked WPA-PSK.
+/// See [`wpa_psk`].
+pub fn wpa_psk_unchecked(ssid: &[u8], passphrase: &[u8]) -> [u8; 32] {
+    let mut buf = [0u8; 32];
+    pbkdf2::<Hmac<Sha1>>(passphrase, ssid, 4096, &mut buf);
+    buf
+}
+
+/// Returns the hexdecimal representation of the given bytes.
+pub fn bytes_to_hex(bytes: &[u8]) -> String {
+    bytes.iter().map(|b| format!("{:02x}", b)).collect()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn special_characters() {
+        let ssid = Ssid::try_from("123abcABC.,-").unwrap();
+        let passphrase = Passphrase::try_from("456defDEF *<:D").unwrap();
+        assert_eq!(
+            bytes_to_hex(&wpa_psk(&ssid, &passphrase)),
+            "8a366e5bc51cd5d8fbbeffacc5f1af23fac30e3ac93cdcc368fafbbf63a1085c"
+        );
+    }
+
+    #[test]
+    fn passphrase_too_short() {
+        assert_eq!(
+            Passphrase::try_from("foobar").unwrap_err(),
+            ValidatePassphraseError::TooShort
+        );
+    }
+
+    #[test]
+    fn display_passphrase() {
+        assert_eq!(
+            format!("{}", Passphrase::try_from("foobarbuzz").unwrap()),
+            "foobarbuzz"
+        );
+    }
+}