From a3abfd6bfd399bd4f366f47b527d9cd68957c018 Mon Sep 17 00:00:00 2001
From: "Neal H. Walfield" <neal@pep.foundation>
Date: Wed, 11 Jul 2018 12:02:02 +0200
Subject: openpgp: Instead of using an ad-hoc parser, use a parser generator.

  - Instead of using an ad-hoc parser for recognizing OpenPGP
    messages, use lalrpop, an lr(1) parser generator, for recognizing
    OpenPGP messages.
---
 openpgp/src/message/lexer.rs | 125 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 125 insertions(+)
 create mode 100644 openpgp/src/message/lexer.rs

(limited to 'openpgp/src/message/lexer.rs')

diff --git a/openpgp/src/message/lexer.rs b/openpgp/src/message/lexer.rs
new file mode 100644
index 00000000..442399d4
--- /dev/null
+++ b/openpgp/src/message/lexer.rs
@@ -0,0 +1,125 @@
+use Error;
+use Result;
+
+use Packet;
+use PacketPile;
+
+// The type of the parser's input.
+//
+// The parser iterators over tuples consisting of the token's starting
+// position, the token itself, and the token's ending position.
+pub(crate) type LexerItem<Tok, Loc, Error>
+    = ::std::result::Result<(Loc, Tok, Loc), Error>;
+
+#[derive(Debug, Clone)]
+pub enum Token {
+    Literal,
+    CompressedData,
+
+    SKESK,
+    PKESK,
+    SEIP,
+
+    OPS,
+    SIG,
+
+    Pop,
+
+    // This represents the content of a container that is not parsed.
+    OpaqueContent,
+}
+
+#[derive(Debug)]
+pub enum LexicalError {
+    // There are no lexing errors.
+}
+
+pub(crate) enum Lexer<'input> {
+    Refed(Box<Iterator<Item=(usize, &'input Token)> + 'input>),
+    Owned(Box<Iterator<Item=(usize, Token)> + 'input>),
+}
+
+impl<'input> Iterator for Lexer<'input> {
+    type Item = LexerItem<Token, usize, LexicalError>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let n = match self {
+            Lexer::Refed(ref mut i) =>
+                i.next().map(|(pos, tok)| (pos, tok.clone())),
+            Lexer::Owned(ref mut i) => i.next(),
+        };
+
+        if let Some((pos, tok)) = n {
+            Some(Ok((pos, tok, pos)))
+        } else {
+            None
+        }
+    }
+}
+
+impl<'input> Lexer<'input> {
+    /// Uses a raw sequence of tokens as input to the parser.
+    // This is only used in the test code.  It would be better to use
+    // cfg(test), but then we have to do the same for the Lexer enum
+    // above and then we also have to specialize Lexer::next().  This
+    // is significantly less ugly.
+    #[allow(unused)]
+    pub(crate) fn from_tokens(raw: &'input [Token]) -> Self {
+        let iter = raw.iter().enumerate();
+        Lexer::Refed(Box::new(iter))
+    }
+
+    /// Uses a `PacketPile` as input to the parser.
+    pub(crate) fn from_packet_pile(pp: &'input PacketPile) -> Result<Self> {
+        let mut t = vec![];
+        let mut last_path = vec![0];
+
+        for (path, p) in pp.descendants().paths() {
+            if last_path.len() > path.len() {
+                // We popped one or more containers.
+                for _ in 1..last_path.len() - path.len() + 1 {
+                    t.push(Token::Pop);
+                }
+            }
+            last_path = path;
+
+            match p {
+                Packet::Literal(_) => t.push(Token::Literal),
+                Packet::CompressedData(_) => t.push(Token::CompressedData),
+                Packet::SKESK(_) => t.push(Token::SKESK),
+                Packet::PKESK(_) => t.push(Token::PKESK),
+                Packet::SEIP(_) => t.push(Token::SEIP),
+                Packet::OnePassSig(_) => t.push(Token::OPS),
+                Packet::Signature(_) => t.push(Token::SIG),
+
+                p =>
+                    return Err(Error::MalformedMessage(
+                        format!("Invalid OpenPGP message: \
+                                 unexpected packet: {:?}",
+                                p.tag()).into()).into()),
+            }
+
+            match p {
+                Packet::CompressedData(_) | Packet::SEIP(_) => {
+                    // If a container's content is not unpacked, then
+                    // we treat the content as an opaque message.
+
+                    if p.children.is_none() && p.body.is_some() {
+                        t.push(Token::OpaqueContent);
+                        t.push(Token::Pop);
+                    }
+                }
+                _ => {}
+            }
+        }
+
+        if last_path.len() > 1 {
+            // We popped one or more containers.
+            for _ in 1..last_path.len() {
+                t.push(Token::Pop);
+            }
+        }
+
+        Ok(Lexer::Owned(Box::new(t.into_iter().enumerate())))
+    }
+}
-- 
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