cargo/diagnostics/rules/
text_direction_codepoint_in_literal.rs

1use std::path::Path;
2
3use cargo_util_schemas::manifest::TomlToolLints;
4use cargo_util_terminal::report::AnnotationKind;
5use cargo_util_terminal::report::Group;
6use cargo_util_terminal::report::Level;
7use cargo_util_terminal::report::Patch;
8use cargo_util_terminal::report::Snippet;
9use toml_parser::Source;
10use toml_parser::Span;
11use toml_parser::decoder::Encoding;
12use toml_parser::parser::Event;
13use toml_parser::parser::EventKind;
14use toml_parser::parser::EventReceiver;
15use tracing::instrument;
16
17use super::CORRECTNESS;
18use crate::CargoResult;
19use crate::GlobalContext;
20use crate::core::MaybePackage;
21use crate::diagnostics::Lint;
22use crate::diagnostics::LintLevel;
23use crate::diagnostics::ManifestFor;
24use crate::diagnostics::rel_cwd_manifest_path;
25
26pub static LINT: &Lint = &Lint {
27    name: "text_direction_codepoint_in_literal",
28    desc: "unicode codepoint changing visible direction of text present in literal",
29    primary_group: &CORRECTNESS,
30    msrv: Some(super::CARGO_LINTS_MSRV),
31    feature_gate: None,
32    docs: Some(
33        r#"
34### What it does
35Detects Unicode codepoints in literals in manifests that change the visual representation of text on screen
36in a way that does not correspond to their on memory representation.
37
38### Why it is bad
39Unicode allows changing the visual flow of text on screen
40in order to support scripts that are written right-to-left,
41but a specially crafted literal can make code that will be compiled appear to be part of a literal,
42depending on the software used to read the code.
43To avoid potential problems or confusion,
44such as in CVE-2021-42574,
45by default we deny their use.
46"#,
47    ),
48};
49
50#[instrument(skip_all)]
51pub fn text_direction_codepoint_in_literal(
52    manifest: ManifestFor<'_>,
53    manifest_path: &Path,
54    cargo_lints: &TomlToolLints,
55    error_count: &mut usize,
56    gctx: &GlobalContext,
57) -> CargoResult<()> {
58    let (lint_level, source) = manifest.lint_level(cargo_lints, LINT);
59    if lint_level == LintLevel::Allow {
60        return Ok(());
61    }
62
63    if matches!(
64        &manifest,
65        ManifestFor::Workspace {
66            maybe_pkg: MaybePackage::Package { .. },
67            ..
68        }
69    ) {
70        // For real manifests, lint as a package, rather than a workspace
71        return Ok(());
72    }
73
74    let Some(contents) = manifest.contents() else {
75        return Ok(());
76    };
77
78    let bidi_spans = contents
79        .char_indices()
80        .filter(|(_i, c)| {
81            UNICODE_BIDI_CODEPOINTS
82                .iter()
83                .any(|(bidi, _, _name)| c == bidi)
84        })
85        .map(|(i, c)| (i, i + c.len_utf8()))
86        .collect::<Vec<_>>();
87    if bidi_spans.is_empty() {
88        return Ok(());
89    }
90
91    let toml_source = Source::new(contents);
92    let events = bidi_events(&toml_source, &bidi_spans);
93    let manifest_path = rel_cwd_manifest_path(manifest_path, gctx);
94    let mut emitted_source = None;
95    for event in events {
96        if lint_level.is_error() {
97            *error_count += 1;
98        }
99
100        let token_span = event.token.span();
101        let token_span = token_span.start()..token_span.end();
102        let mut snippet = Snippet::source(contents).path(&manifest_path).annotation(
103            AnnotationKind::Context
104                .span(token_span.clone())
105                .label("this literal contains an invisible unicode text flow control codepoint"),
106        );
107        for bidi_span in event.bidi_spans {
108            let bidi_span = bidi_span.0..bidi_span.1;
109            let escaped = format!("{:?}", &contents[bidi_span.clone()]);
110            snippet = snippet.annotation(AnnotationKind::Primary.span(bidi_span).label(escaped));
111        }
112        let mut help_snippet = Snippet::source(contents).path(&manifest_path);
113        if let Some(original_raw) = toml_source.get(&event.token) {
114            let mut decoded = String::new();
115            let replacement = match event.token.kind() {
116                toml_parser::parser::EventKind::SimpleKey => {
117                    use toml_writer::ToTomlKey as _;
118                    original_raw.decode_key(&mut decoded, &mut ());
119                    let builder = toml_writer::TomlKeyBuilder::new(&decoded);
120                    let replacement = builder.as_basic();
121                    Some(replacement.to_toml_key())
122                }
123                toml_parser::parser::EventKind::Scalar => {
124                    use toml_writer::ToTomlValue as _;
125                    let kind = original_raw.decode_scalar(&mut decoded, &mut ());
126                    if matches!(kind, toml_parser::decoder::ScalarKind::String) {
127                        let builder = toml_writer::TomlStringBuilder::new(&decoded);
128                        let replacement = match event.token.encoding() {
129                            Some(toml_parser::decoder::Encoding::BasicString)
130                            | Some(toml_parser::decoder::Encoding::LiteralString)
131                            | None => builder.as_basic(),
132                            Some(toml_parser::decoder::Encoding::MlBasicString)
133                            | Some(toml_parser::decoder::Encoding::MlLiteralString) => {
134                                builder.as_ml_basic()
135                            }
136                        };
137                        Some(replacement.to_toml_value())
138                    } else {
139                        None
140                    }
141                }
142                _ => None,
143            };
144            if let Some(mut replacement) = replacement {
145                for (bidi, escaped, _) in UNICODE_BIDI_CODEPOINTS {
146                    replacement = replacement.replace(*bidi, escaped);
147                }
148                help_snippet = help_snippet.patch(Patch::new(token_span.clone(), replacement));
149            }
150        }
151
152        let level = lint_level.to_diagnostic_level();
153        let mut primary = Group::with_title(level.primary_title(LINT.desc)).element(snippet);
154        if emitted_source.is_none() {
155            emitted_source = Some(LINT.emitted_source(lint_level, source));
156            primary = primary.element(Level::NOTE.message(emitted_source.as_ref().unwrap()));
157        }
158
159        let help = Group::with_title(Level::HELP.secondary_title("if you want to keep them but make them visible in your source code, you can escape them")).element(help_snippet);
160
161        let report = [primary, help];
162        gctx.shell().print_report(&report, lint_level.force())?;
163    }
164
165    Ok(())
166}
167
168const UNICODE_BIDI_CODEPOINTS: &[(char, &str, &str)] = &[
169    ('\u{202A}', r"\u{202A}", "LEFT-TO-RIGHT EMBEDDING"),
170    ('\u{202B}', r"\u{202B}", "RIGHT-TO-LEFT EMBEDDING"),
171    ('\u{202C}', r"\u{202C}", "POP DIRECTIONAL FORMATTING"),
172    ('\u{202D}', r"\u{202D}", "LEFT-TO-RIGHT OVERRIDE"),
173    ('\u{202E}', r"\u{202E}", "RIGHT-TO-LEFT OVERRIDE"),
174    ('\u{2066}', r"\u{2066}", "LEFT-TO-RIGHT ISOLATE"),
175    ('\u{2067}', r"\u{2067}", "RIGHT-TO-LEFT ISOLATE"),
176    ('\u{2068}', r"\u{2068}", "FIRST STRONG ISOLATE"),
177    ('\u{2069}', r"\u{2069}", "POP DIRECTIONAL ISOLATE"),
178];
179
180struct BiDiEvent {
181    token: Event,
182    bidi_spans: Vec<(usize, usize)>,
183}
184
185fn bidi_events(source: &Source<'_>, bidi_spans: &[(usize, usize)]) -> Vec<BiDiEvent> {
186    let mut bidi_spans = bidi_spans.iter();
187    let bidi_span = bidi_spans.next().copied();
188
189    let tokens = source.lex().into_vec();
190    let mut collector = BiDiCollector {
191        bidi_span,
192        bidi_spans,
193        events: Vec::new(),
194    };
195    let mut errors = ();
196    toml_parser::parser::parse_document(&tokens, &mut collector, &mut errors);
197
198    collector.events
199}
200
201struct BiDiCollector<'b> {
202    bidi_span: Option<(usize, usize)>,
203    bidi_spans: std::slice::Iter<'b, (usize, usize)>,
204    events: Vec<BiDiEvent>,
205}
206
207impl BiDiCollector<'_> {
208    fn process(&mut self, kind: EventKind, encoding: Option<Encoding>, span: Span) {
209        let mut event_bidi_spans = Vec::new();
210        while let Some(bidi_span) = self.bidi_span {
211            if bidi_span.0 < span.start() {
212                self.bidi_span = self.bidi_spans.next().copied();
213                continue;
214            } else if span.end() <= bidi_span.0 {
215                break;
216            }
217
218            event_bidi_spans.push(bidi_span);
219            self.bidi_span = self.bidi_spans.next().copied();
220        }
221
222        if !event_bidi_spans.is_empty() {
223            let token = Event::new_unchecked(kind, encoding, span);
224            self.events.push(BiDiEvent {
225                token,
226                bidi_spans: event_bidi_spans,
227            });
228        }
229    }
230}
231
232impl EventReceiver for BiDiCollector<'_> {
233    fn simple_key(
234        &mut self,
235        span: Span,
236        encoding: Option<Encoding>,
237        _error: &mut dyn toml_parser::ErrorSink,
238    ) {
239        self.process(EventKind::SimpleKey, encoding, span)
240    }
241    fn scalar(
242        &mut self,
243        span: Span,
244        encoding: Option<Encoding>,
245        _error: &mut dyn toml_parser::ErrorSink,
246    ) {
247        self.process(EventKind::Scalar, encoding, span)
248    }
249}
cargo/diagnostics/rules/text_direction_codepoint_in_literal.rs

cargo/diagnostics/rules/
text_direction_codepoint_in_literal.rs
