rustls_pki_types/
pem.rs

1use alloc::borrow::ToOwned;
2use alloc::format;
3use alloc::string::String;
4use alloc::vec;
5use alloc::vec::Vec;
6use core::fmt;
7use core::marker::PhantomData;
8use core::ops::ControlFlow;
9#[cfg(feature = "std")]
10use std::fs::File;
11#[cfg(feature = "std")]
12use std::io::{self, ErrorKind};
13
14use crate::base64;
15
16/// Items that can be decoded from PEM data.
17pub trait PemObject: Sized {
18    /// Decode the first section of this type from PEM contained in
19    /// a byte slice.
20    ///
21    /// [`Error::NoItemsFound`] is returned if no such items are found.
22    fn from_pem_slice(pem: &[u8]) -> Result<Self, Error> {
23        Self::pem_slice_iter(pem)
24            .next()
25            .unwrap_or(Err(Error::NoItemsFound))
26    }
27
28    /// Iterate over all sections of this type from PEM contained in
29    /// a byte slice.
30    fn pem_slice_iter(pem: &[u8]) -> SliceIter<'_, Self> {
31        SliceIter {
32            current: pem,
33            _ty: PhantomData,
34        }
35    }
36
37    /// Decode the first section of this type from the PEM contents of the named file.
38    ///
39    /// [`Error::NoItemsFound`] is returned if no such items are found.
40    #[cfg(feature = "std")]
41    fn from_pem_file(file_name: impl AsRef<std::path::Path>) -> Result<Self, Error> {
42        Self::pem_file_iter(file_name)?
43            .next()
44            .unwrap_or(Err(Error::NoItemsFound))
45    }
46
47    /// Iterate over all sections of this type from the PEM contents of the named file.
48    ///
49    /// This reports errors in two phases:
50    ///
51    /// - errors opening the file are reported from this function directly,
52    /// - errors reading from the file are reported from the returned iterator,
53    #[cfg(feature = "std")]
54    fn pem_file_iter(
55        file_name: impl AsRef<std::path::Path>,
56    ) -> Result<ReadIter<io::BufReader<File>, Self>, Error> {
57        Ok(ReadIter::<_, Self> {
58            rd: io::BufReader::new(File::open(file_name).map_err(Error::Io)?),
59            _ty: PhantomData,
60        })
61    }
62
63    /// Decode the first section of this type from PEM read from an [`io::Read`].
64    #[cfg(feature = "std")]
65    fn from_pem_reader(rd: impl std::io::Read) -> Result<Self, Error> {
66        Self::pem_reader_iter(rd)
67            .next()
68            .unwrap_or(Err(Error::NoItemsFound))
69    }
70
71    /// Iterate over all sections of this type from PEM present in an [`io::Read`].
72    #[cfg(feature = "std")]
73    fn pem_reader_iter<R: std::io::Read>(rd: R) -> ReadIter<io::BufReader<R>, Self> {
74        ReadIter::<_, Self> {
75            rd: io::BufReader::new(rd),
76            _ty: PhantomData,
77        }
78    }
79
80    /// Conversion from a PEM [`SectionKind`] and body data.
81    ///
82    /// This inspects `kind`, and if it matches this type's PEM section kind,
83    /// converts `der` into this type.
84    fn from_pem(kind: SectionKind, der: Vec<u8>) -> Option<Self>;
85}
86
87pub(crate) trait PemObjectFilter: PemObject + From<Vec<u8>> {
88    const KIND: SectionKind;
89}
90
91impl<T: PemObjectFilter + From<Vec<u8>>> PemObject for T {
92    fn from_pem(kind: SectionKind, der: Vec<u8>) -> Option<Self> {
93        match Self::KIND == kind {
94            true => Some(Self::from(der)),
95            false => None,
96        }
97    }
98}
99
100/// Extract and return all PEM sections by reading `rd`.
101#[cfg(feature = "std")]
102pub struct ReadIter<R, T> {
103    rd: R,
104    _ty: PhantomData<T>,
105}
106
107#[cfg(feature = "std")]
108impl<R: io::BufRead, T: PemObject> ReadIter<R, T> {
109    /// Create a new iterator.
110    pub fn new(rd: R) -> Self {
111        Self {
112            rd,
113            _ty: PhantomData,
114        }
115    }
116}
117
118#[cfg(feature = "std")]
119impl<R: io::BufRead, T: PemObject> Iterator for ReadIter<R, T> {
120    type Item = Result<T, Error>;
121
122    fn next(&mut self) -> Option<Self::Item> {
123        loop {
124            return match from_buf(&mut self.rd) {
125                Ok(Some((sec, item))) => match T::from_pem(sec, item) {
126                    Some(res) => Some(Ok(res)),
127                    None => continue,
128                },
129                Ok(None) => return None,
130                Err(err) => Some(Err(err)),
131            };
132        }
133    }
134}
135
136/// Iterator over all PEM sections in a `&[u8]` slice.
137pub struct SliceIter<'a, T> {
138    current: &'a [u8],
139    _ty: PhantomData<T>,
140}
141
142impl<'a, T: PemObject> SliceIter<'a, T> {
143    /// Create a new iterator.
144    pub fn new(current: &'a [u8]) -> Self {
145        Self {
146            current,
147            _ty: PhantomData,
148        }
149    }
150
151    /// Returns the rest of the unparsed data.
152    ///
153    /// This is the slice immediately following the most
154    /// recently returned item from `next()`.
155    #[doc(hidden)]
156    pub fn remainder(&self) -> &'a [u8] {
157        self.current
158    }
159}
160
161impl<T: PemObject> Iterator for SliceIter<'_, T> {
162    type Item = Result<T, Error>;
163
164    fn next(&mut self) -> Option<Self::Item> {
165        loop {
166            return match from_slice(self.current) {
167                Ok(Some(((sec, item), rest))) => {
168                    self.current = rest;
169                    match T::from_pem(sec, item) {
170                        Some(res) => Some(Ok(res)),
171                        None => continue,
172                    }
173                }
174                Ok(None) => return None,
175                Err(err) => Some(Err(err)),
176            };
177        }
178    }
179}
180
181impl PemObject for (SectionKind, Vec<u8>) {
182    fn from_pem(kind: SectionKind, der: Vec<u8>) -> Option<Self> {
183        Some((kind, der))
184    }
185}
186
187/// Extract and decode the next supported PEM section from `input`
188///
189/// - `Ok(None)` is returned if there is no PEM section to read from `input`
190/// - Syntax errors and decoding errors produce a `Err(...)`
191/// - Otherwise each decoded section is returned with a `Ok(Some((..., remainder)))` where
192///   `remainder` is the part of the `input` that follows the returned section
193#[allow(clippy::type_complexity)]
194fn from_slice(mut input: &[u8]) -> Result<Option<((SectionKind, Vec<u8>), &[u8])>, Error> {
195    let mut b64buf = Vec::with_capacity(1024);
196    let mut section = None::<(Vec<_>, Vec<_>)>;
197
198    loop {
199        let next_line = if let Some(index) = input
200            .iter()
201            .position(|byte| *byte == b'\n' || *byte == b'\r')
202        {
203            let (line, newline_plus_remainder) = input.split_at(index);
204            input = &newline_plus_remainder[1..];
205            Some(line)
206        } else if !input.is_empty() {
207            let next_line = input;
208            input = &[];
209            Some(next_line)
210        } else {
211            None
212        };
213
214        match read(next_line, &mut section, &mut b64buf)? {
215            ControlFlow::Continue(()) => continue,
216            ControlFlow::Break(item) => return Ok(item.map(|item| (item, input))),
217        }
218    }
219}
220
221/// Extract and decode the next supported PEM section from `rd`.
222///
223/// - Ok(None) is returned if there is no PEM section read from `rd`.
224/// - Underlying IO errors produce a `Err(...)`
225/// - Otherwise each decoded section is returned with a `Ok(Some(...))`
226#[cfg(feature = "std")]
227pub fn from_buf(rd: &mut dyn io::BufRead) -> Result<Option<(SectionKind, Vec<u8>)>, Error> {
228    let mut b64buf = Vec::with_capacity(1024);
229    let mut section = None::<(Vec<_>, Vec<_>)>;
230    let mut line = Vec::with_capacity(80);
231
232    loop {
233        line.clear();
234        let len = read_until_newline(rd, &mut line).map_err(Error::Io)?;
235
236        let next_line = if len == 0 {
237            None
238        } else {
239            Some(line.as_slice())
240        };
241
242        match read(next_line, &mut section, &mut b64buf) {
243            Ok(ControlFlow::Break(opt)) => return Ok(opt),
244            Ok(ControlFlow::Continue(())) => continue,
245            Err(e) => return Err(e),
246        }
247    }
248}
249
250#[allow(clippy::type_complexity)]
251fn read(
252    next_line: Option<&[u8]>,
253    section: &mut Option<(Vec<u8>, Vec<u8>)>,
254    b64buf: &mut Vec<u8>,
255) -> Result<ControlFlow<Option<(SectionKind, Vec<u8>)>, ()>, Error> {
256    let line = if let Some(line) = next_line {
257        line
258    } else {
259        // EOF
260        return match section.take() {
261            Some((_, end_marker)) => Err(Error::MissingSectionEnd { end_marker }),
262            None => Ok(ControlFlow::Break(None)),
263        };
264    };
265
266    if line.starts_with(b"-----BEGIN ") {
267        let (mut trailer, mut pos) = (0, line.len());
268        for (i, &b) in line.iter().enumerate().rev() {
269            match b {
270                b'-' => {
271                    trailer += 1;
272                    pos = i;
273                }
274                b'\n' | b'\r' | b' ' => continue,
275                _ => break,
276            }
277        }
278
279        if trailer != 5 {
280            return Err(Error::IllegalSectionStart {
281                line: line.to_vec(),
282            });
283        }
284
285        let ty = &line[11..pos];
286        let mut end = Vec::with_capacity(10 + 4 + ty.len());
287        end.extend_from_slice(b"-----END ");
288        end.extend_from_slice(ty);
289        end.extend_from_slice(b"-----");
290        *section = Some((ty.to_owned(), end));
291        return Ok(ControlFlow::Continue(()));
292    }
293
294    if let Some((section_label, end_marker)) = section.as_ref() {
295        if line.starts_with(end_marker) {
296            let kind = match SectionKind::try_from(&section_label[..]) {
297                Ok(kind) => kind,
298                // unhandled section: have caller try again
299                Err(()) => {
300                    *section = None;
301                    b64buf.clear();
302                    return Ok(ControlFlow::Continue(()));
303                }
304            };
305
306            let mut der = vec![0u8; base64::decoded_length(b64buf.len())];
307            let der_len = match kind.secret() {
308                true => base64::decode_secret(b64buf, &mut der),
309                false => base64::decode_public(b64buf, &mut der),
310            }
311            .map_err(|err| Error::Base64Decode(format!("{err:?}")))?
312            .len();
313
314            der.truncate(der_len);
315
316            return Ok(ControlFlow::Break(Some((kind, der))));
317        }
318    }
319
320    if section.is_some() {
321        b64buf.extend(line);
322    }
323
324    Ok(ControlFlow::Continue(()))
325}
326
327/// A single recognised section in a PEM file.
328#[non_exhaustive]
329#[derive(Clone, Copy, Debug, PartialEq)]
330pub enum SectionKind {
331    /// A DER-encoded x509 certificate.
332    ///
333    /// Appears as "CERTIFICATE" in PEM files.
334    Certificate,
335
336    /// A DER-encoded Subject Public Key Info; as specified in RFC 7468.
337    ///
338    /// Appears as "PUBLIC KEY" in PEM files.
339    PublicKey,
340
341    /// A DER-encoded plaintext RSA private key; as specified in PKCS #1/RFC 3447
342    ///
343    /// Appears as "RSA PRIVATE KEY" in PEM files.
344    RsaPrivateKey,
345
346    /// A DER-encoded plaintext private key; as specified in PKCS #8/RFC 5958
347    ///
348    /// Appears as "PRIVATE KEY" in PEM files.
349    PrivateKey,
350
351    /// A Sec1-encoded plaintext private key; as specified in RFC 5915
352    ///
353    /// Appears as "EC PRIVATE KEY" in PEM files.
354    EcPrivateKey,
355
356    /// A Certificate Revocation List; as specified in RFC 5280
357    ///
358    /// Appears as "X509 CRL" in PEM files.
359    Crl,
360
361    /// A Certificate Signing Request; as specified in RFC 2986
362    ///
363    /// Appears as "CERTIFICATE REQUEST" in PEM files.
364    Csr,
365
366    /// An EchConfigList structure, as specified in
367    /// <https://www.ietf.org/archive/id/draft-farrell-tls-pemesni-05.html>.
368    ///
369    /// Appears as "ECHCONFIG" in PEM files.
370    EchConfigList,
371}
372
373impl SectionKind {
374    fn secret(&self) -> bool {
375        match self {
376            Self::RsaPrivateKey | Self::PrivateKey | Self::EcPrivateKey => true,
377            Self::Certificate | Self::PublicKey | Self::Crl | Self::Csr | Self::EchConfigList => {
378                false
379            }
380        }
381    }
382}
383
384impl TryFrom<&[u8]> for SectionKind {
385    type Error = ();
386
387    fn try_from(value: &[u8]) -> Result<Self, Self::Error> {
388        Ok(match value {
389            b"CERTIFICATE" => Self::Certificate,
390            b"PUBLIC KEY" => Self::PublicKey,
391            b"RSA PRIVATE KEY" => Self::RsaPrivateKey,
392            b"PRIVATE KEY" => Self::PrivateKey,
393            b"EC PRIVATE KEY" => Self::EcPrivateKey,
394            b"X509 CRL" => Self::Crl,
395            b"CERTIFICATE REQUEST" => Self::Csr,
396            b"ECHCONFIG" => Self::EchConfigList,
397            _ => return Err(()),
398        })
399    }
400}
401
402/// Errors that may arise when parsing the contents of a PEM file
403#[non_exhaustive]
404#[derive(Debug)]
405pub enum Error {
406    /// a section is missing its "END marker" line
407    MissingSectionEnd {
408        /// the expected "END marker" line that was not found
409        end_marker: Vec<u8>,
410    },
411
412    /// syntax error found in the line that starts a new section
413    IllegalSectionStart {
414        /// line that contains the syntax error
415        line: Vec<u8>,
416    },
417
418    /// base64 decode error
419    Base64Decode(String),
420
421    /// I/O errors, from APIs that accept `std::io` types.
422    #[cfg(feature = "std")]
423    Io(io::Error),
424
425    /// No items found of desired type
426    NoItemsFound,
427}
428
429impl fmt::Display for Error {
430    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
431        match self {
432            Self::MissingSectionEnd { end_marker } => {
433                write!(f, "missing section end marker: {end_marker:?}")
434            }
435            Self::IllegalSectionStart { line } => {
436                write!(f, "illegal section start: {line:?}")
437            }
438            Self::Base64Decode(e) => write!(f, "base64 decode error: {e}"),
439            #[cfg(feature = "std")]
440            Self::Io(e) => write!(f, "I/O error: {e}"),
441            Self::NoItemsFound => write!(f, "no items found"),
442        }
443    }
444}
445
446#[cfg(feature = "std")]
447impl std::error::Error for Error {}
448
449// Ported from https://github.com/rust-lang/rust/blob/91cfcb021935853caa06698b759c293c09d1e96a/library/std/src/io/mod.rs#L1990 and
450// modified to look for our accepted newlines.
451#[cfg(feature = "std")]
452fn read_until_newline<R: io::BufRead + ?Sized>(r: &mut R, buf: &mut Vec<u8>) -> io::Result<usize> {
453    let mut read = 0;
454    loop {
455        let (done, used) = {
456            let available = match r.fill_buf() {
457                Ok(n) => n,
458                Err(ref e) if e.kind() == ErrorKind::Interrupted => continue,
459                Err(e) => return Err(e),
460            };
461            match available
462                .iter()
463                .copied()
464                .position(|b| b == b'\n' || b == b'\r')
465            {
466                Some(i) => {
467                    buf.extend_from_slice(&available[..=i]);
468                    (true, i + 1)
469                }
470                None => {
471                    buf.extend_from_slice(available);
472                    (false, available.len())
473                }
474            }
475        };
476        r.consume(used);
477        read += used;
478        if done || used == 0 {
479            return Ok(read);
480        }
481    }
482}
rustls_pki_types/pem.rs

rustls_pki_types/
pem.rs
