const-oid: handle repeated dot characters in input (#1595)

Adds an `Error::RepeatedDot` case and handles it within the parser

Author: tarcieri

const-oid/src/error.rs

@@ -37,6 +37,9 @@ pub enum Error {
     /// OID length is invalid (too short or too long).
     Length,
 
+    /// Repeated `..` characters in input data.
+    RepeatedDot,
+
     /// Trailing `.` character at end of input.
     TrailingDot,
 }
@@ -53,6 +56,7 @@ impl Error {
             Error::DigitExpected { .. } => panic!("OID expected to start with digit"),
             Error::Empty => panic!("OID value is empty"),
             Error::Length => panic!("OID length invalid"),
+            Error::RepeatedDot => panic!("repeated consecutive '..' characters in OID"),
             Error::TrailingDot => panic!("OID ends with invalid trailing '.'"),
         }
     }
@@ -69,6 +73,7 @@ impl fmt::Display for Error {
             }
             Error::Empty => f.write_str("OID value is empty"),
             Error::Length => f.write_str("OID length invalid"),
+            Error::RepeatedDot => f.write_str("repeated consecutive '..' characters in OID"),
             Error::TrailingDot => f.write_str("OID ends with invalid trailing '.'"),
         }
     }

const-oid/src/parser.rs

@@ -8,7 +8,7 @@ use crate::{encoder::Encoder, Arc, Error, ObjectIdentifier, Result};
 #[derive(Debug)]
 pub(crate) struct Parser {
     /// Current arc in progress
-    current_arc: Arc,
+    current_arc: Option<Arc>,
 
     /// BER/DER encoder
     encoder: Encoder<{ ObjectIdentifier::MAX_SIZE }>,
@@ -25,7 +25,7 @@ impl Parser {
 
         match bytes[0] {
             b'0'..=b'9' => Self {
-                current_arc: 0,
+                current_arc: None,
                 encoder: Encoder::new(),
             }
             .parse_bytes(bytes),
@@ -42,37 +42,50 @@ impl Parser {
     const fn parse_bytes(mut self, bytes: &[u8]) -> Result<Self> {
         match bytes {
             // TODO(tarcieri): use `?` when stable in `const fn`
-            [] => match self.encoder.arc(self.current_arc) {
-                Ok(encoder) => {
-                    self.encoder = encoder;
-                    Ok(self)
-                }
-                Err(err) => Err(err),
+            [] => match self.current_arc {
+                Some(arc) => match self.encoder.arc(arc) {
+                    Ok(encoder) => {
+                        self.encoder = encoder;
+                        Ok(self)
+                    }
+                    Err(err) => Err(err),
+                },
+                None => Err(Error::TrailingDot),
             },
             [byte @ b'0'..=b'9', remaining @ ..] => {
                 let digit = byte.saturating_sub(b'0');
-                self.current_arc = match self.current_arc.checked_mul(10) {
+                let arc = match self.current_arc {
+                    Some(arc) => arc,
+                    None => 0,
+                };
+
+                self.current_arc = match arc.checked_mul(10) {
                     Some(arc) => match arc.checked_add(digit as Arc) {
-                        Some(arc) => arc,
                         None => return Err(Error::ArcTooBig),
+                        arc => arc,
                     },
                     None => return Err(Error::ArcTooBig),
                 };
                 self.parse_bytes(remaining)
             }
             [b'.', remaining @ ..] => {
-                if remaining.is_empty() {
-                    return Err(Error::TrailingDot);
-                }
+                match self.current_arc {
+                    Some(arc) => {
+                        if remaining.is_empty() {
+                            return Err(Error::TrailingDot);
+                        }
 
-                // TODO(tarcieri): use `?` when stable in `const fn`
-                match self.encoder.arc(self.current_arc) {
-                    Ok(encoder) => {
-                        self.encoder = encoder;
-                        self.current_arc = 0;
-                        self.parse_bytes(remaining)
+                        // TODO(tarcieri): use `?` when stable in `const fn`
+                        match self.encoder.arc(arc) {
+                            Ok(encoder) => {
+                                self.encoder = encoder;
+                                self.current_arc = None;
+                                self.parse_bytes(remaining)
+                            }
+                            Err(err) => Err(err),
+                        }
                     }
-                    Err(err) => Err(err),
+                    None => Err(Error::RepeatedDot),
                 }
             }
             [byte, ..] => Err(Error::DigitExpected { actual: *byte }),

const-oid/tests/oid.rs

@@ -241,6 +241,11 @@ fn parse_invalid_second_arc() {
     );
 }
 
+#[test]
+fn parse_invalid_repeat_dots() {
+    assert_eq!(ObjectIdentifier::new("1.2..3.4"), Err(Error::RepeatedDot))
+}
+
 #[test]
 fn parent() {
     let child = oid("1.2.3.4");