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use super::error::{Error, ErrorKind, Result};
use byteorder::{BigEndian, ByteOrder};
/// A `Reader` is used for reading from a byte sequence
/// representing an encoded OpenSSH public key or certificate.
#[derive(Debug)]
pub struct Reader<'a> {
inner: &'a [u8],
offset: usize,
}
impl<'a> Reader<'a> {
/// Creates a new `Reader` instance from the given byte sequence.
///
/// # Example
/// ```rust
/// # use sshkeys;
/// let data = vec![0, 0, 0, 42];
/// let mut reader = sshkeys::Reader::new(&data);
/// let num = reader.read_u32().unwrap();
/// assert_eq!(num, 42);
/// ```
pub fn new<T: ?Sized + AsRef<[u8]>>(inner: &T) -> Reader<'_> {
Reader {
inner: inner.as_ref(),
offset: 0,
}
}
/// Sets the `Reader` current offset to a given position.
///
/// # Example
/// ```rust
/// # use sshkeys;
/// let data = vec![0, 0, 0, 42];
/// let mut reader = sshkeys::Reader::new(&data);
/// let num = reader.read_u32().unwrap();
/// assert_eq!(num, 42);
/// reader.set_offset(0);
/// let num_42_again = reader.read_u32().unwrap();
/// assert_eq!(num_42_again, 42);
/// ```
pub fn set_offset(&mut self, offset: usize) -> Result<()> {
self.offset = offset;
Ok(())
}
/// Reads a byte buffer from the wrapped byte sequence and
/// returns it as a `Vec<u8>`.
/// The buffer is represented by it's length as `u32` value
/// followed by the actual bytes to read.
///
/// # Example
/// ```rust
/// # use sshkeys;
/// let data = vec![0, 0, 0, 13, 97, 32, 116, 101, 115, 116, 32, 115, 116, 114, 105, 110, 103];
/// let mut reader = sshkeys::Reader::new(&data);
/// let bytes = reader.read_bytes().unwrap();
/// assert_eq!(bytes, [97, 32, 116, 101, 115, 116, 32, 115, 116, 114, 105, 110, 103]);
/// ```
pub fn read_bytes(&mut self) -> Result<Vec<u8>> {
if self.offset >= self.inner.len() {
return Err(Error::with_kind(ErrorKind::UnexpectedEof));
}
let slice = &self.inner[self.offset..];
if slice.len() < 4 {
return Err(Error::with_kind(ErrorKind::InvalidFormat));
}
let size = BigEndian::read_u32(&slice[..4]) as usize;
if slice.len() < size + 4 {
return Err(Error::with_kind(ErrorKind::InvalidFormat));
}
self.offset += size + 4;
let result = slice[4..size + 4].to_vec();
Ok(result)
}
/// Reads an `mpint` value from the wrapped byte sequence.
///
/// Drops the leading byte if it's value is zero according to the RFC 4251, section 5.
///
/// # Example
/// ```rust
/// # use sshkeys;
/// let data = vec![0, 0, 0, 3, 1, 0, 1];
/// let mut reader = sshkeys::Reader::new(&data);
/// let mpint = reader.read_mpint().unwrap();
/// assert_eq!(mpint, [1, 0, 1]);
/// ```
pub fn read_mpint(&mut self) -> Result<Vec<u8>> {
let bytes = self.read_bytes()?;
if bytes[0] == 0 {
return Ok(bytes[1..].to_vec());
}
Ok(bytes)
}
/// Reads a `string` value from the wrapped byte sequence and
/// returns it as a `String`. The value that we read should be a valid UTF-8.
///
/// # Example
/// ```rust
/// # use sshkeys;
/// let data = vec![0, 0, 0, 13, 97, 32, 116, 101, 115, 116, 32, 115, 116, 114, 105, 110, 103];
/// let mut reader = sshkeys::Reader::new(&data);
/// let result = reader.read_string().unwrap();
/// assert_eq!(result, "a test string");
/// ```
pub fn read_string(&mut self) -> Result<String> {
let bytes = self.read_bytes()?;
let result = String::from_utf8(bytes)?;
Ok(result)
}
/// Reads an `u32` value from the wrapped byte sequence and returns it.
///
/// # Example
/// ```rust
/// # use sshkeys;
/// let data = vec![0, 0, 0, 42];
/// let mut reader = sshkeys::Reader::new(&data);
/// let num = reader.read_u32().unwrap();
/// assert_eq!(num, 42);
/// ```
pub fn read_u32(&mut self) -> Result<u32> {
if self.offset >= self.inner.len() {
return Err(Error::with_kind(ErrorKind::UnexpectedEof));
}
let slice = &self.inner[self.offset..];
if slice.len() < 4 {
return Err(Error::with_kind(ErrorKind::InvalidFormat));
}
self.offset += 4;
let value = BigEndian::read_u32(&slice[..4]);
Ok(value)
}
/// Reads an `u64` value from the wrapped byte sequence and returns it.
///
/// # Example
/// ```rust
/// # use sshkeys;
/// let data = vec![0, 0, 0, 0, 0, 0, 0, 42];
/// let mut reader = sshkeys::Reader::new(&data);
/// let num = reader.read_u64().unwrap();
/// assert_eq!(num, 42);
/// ```
pub fn read_u64(&mut self) -> Result<u64> {
if self.offset >= self.inner.len() {
return Err(Error::with_kind(ErrorKind::UnexpectedEof));
}
let slice = &self.inner[self.offset..];
if slice.len() < 8 {
return Err(Error::with_kind(ErrorKind::InvalidFormat));
}
self.offset += 8;
let value = BigEndian::read_u64(&slice[..8]);
Ok(value)
}
}