cargo/diagnostics/rules/
text_direction_codepoint_in_literal.rs

1use std::path::Path;
2
3use cargo_util_terminal::report::AnnotationKind;
4use cargo_util_terminal::report::Group;
5use cargo_util_terminal::report::Level;
6use cargo_util_terminal::report::Patch;
7use cargo_util_terminal::report::Snippet;
8use toml_parser::Source;
9use toml_parser::Span;
10use toml_parser::decoder::Encoding;
11use toml_parser::parser::Event;
12use toml_parser::parser::EventKind;
13use toml_parser::parser::EventReceiver;
14use tracing::instrument;
15
16use super::CORRECTNESS;
17use crate::CargoResult;
18use crate::GlobalContext;
19use crate::core::MaybePackage;
20use crate::core::Workspace;
21use crate::diagnostics::Lint;
22use crate::diagnostics::LintLevelProduct;
23use crate::diagnostics::ManifestFor;
24use crate::diagnostics::ScopedDiagnosticStats;
25use crate::diagnostics::workspace_rel_path;
26
27pub static LINT: &Lint = &Lint {
28    name: "text_direction_codepoint_in_literal",
29    desc: "unicode codepoint changing visible direction of text present in literal",
30    primary_group: &CORRECTNESS,
31    msrv: Some(super::CARGO_LINTS_MSRV),
32    feature_gate: None,
33    docs: Some(
34        r#"
35### What it does
36Detects Unicode codepoints in literals in manifests that change the visual representation of text on screen
37in a way that does not correspond to their on memory representation.
38
39### Why it is bad
40Unicode allows changing the visual flow of text on screen
41in order to support scripts that are written right-to-left,
42but a specially crafted literal can make code that will be compiled appear to be part of a literal,
43depending on the software used to read the code.
44To avoid potential problems or confusion,
45such as in CVE-2021-42574,
46by default we deny their use.
47"#,
48    ),
49};
50
51#[instrument(skip_all)]
52pub(crate) fn lint_manifest(
53    ws: &Workspace<'_>,
54    manifest: ManifestFor<'_>,
55    manifest_path: &Path,
56    level: LintLevelProduct,
57    pkg_stats: &mut ScopedDiagnosticStats<'_>,
58    gctx: &GlobalContext,
59) -> CargoResult<()> {
60    let LintLevelProduct {
61        level: lint_level,
62        source,
63    } = level;
64
65    if matches!(
66        &manifest,
67        ManifestFor::Workspace {
68            maybe_pkg: MaybePackage::Package { .. },
69            ..
70        }
71    ) {
72        // For real manifests, lint as a package, rather than a workspace
73        return Ok(());
74    }
75
76    let Some(contents) = manifest.contents() else {
77        return Ok(());
78    };
79
80    let bidi_spans = contents
81        .char_indices()
82        .filter(|(_i, c)| {
83            UNICODE_BIDI_CODEPOINTS
84                .iter()
85                .any(|(bidi, _, _name)| c == bidi)
86        })
87        .map(|(i, c)| (i, i + c.len_utf8()))
88        .collect::<Vec<_>>();
89    if bidi_spans.is_empty() {
90        return Ok(());
91    }
92
93    let toml_source = Source::new(contents);
94    let events = bidi_events(&toml_source, &bidi_spans);
95    let manifest_path = workspace_rel_path(ws, manifest_path);
96    let mut emitted_source = None;
97    for event in events {
98        let token_span = event.token.span();
99        let token_span = token_span.start()..token_span.end();
100        let mut snippet = Snippet::source(contents).path(&manifest_path).annotation(
101            AnnotationKind::Context
102                .span(token_span.clone())
103                .label("this literal contains an invisible unicode text flow control codepoint"),
104        );
105        for bidi_span in event.bidi_spans {
106            let bidi_span = bidi_span.0..bidi_span.1;
107            let escaped = format!("{:?}", &contents[bidi_span.clone()]);
108            snippet = snippet.annotation(AnnotationKind::Primary.span(bidi_span).label(escaped));
109        }
110        let mut help_snippet = Snippet::source(contents).path(&manifest_path);
111        if let Some(original_raw) = toml_source.get(&event.token) {
112            let mut decoded = String::new();
113            let replacement = match event.token.kind() {
114                toml_parser::parser::EventKind::SimpleKey => {
115                    use toml_writer::ToTomlKey as _;
116                    original_raw.decode_key(&mut decoded, &mut ());
117                    let builder = toml_writer::TomlKeyBuilder::new(&decoded);
118                    let replacement = builder.as_basic();
119                    Some(replacement.to_toml_key())
120                }
121                toml_parser::parser::EventKind::Scalar => {
122                    use toml_writer::ToTomlValue as _;
123                    let kind = original_raw.decode_scalar(&mut decoded, &mut ());
124                    if matches!(kind, toml_parser::decoder::ScalarKind::String) {
125                        let builder = toml_writer::TomlStringBuilder::new(&decoded);
126                        let replacement = match event.token.encoding() {
127                            Some(toml_parser::decoder::Encoding::BasicString)
128                            | Some(toml_parser::decoder::Encoding::LiteralString)
129                            | None => builder.as_basic(),
130                            Some(toml_parser::decoder::Encoding::MlBasicString)
131                            | Some(toml_parser::decoder::Encoding::MlLiteralString) => {
132                                builder.as_ml_basic()
133                            }
134                        };
135                        Some(replacement.to_toml_value())
136                    } else {
137                        None
138                    }
139                }
140                _ => None,
141            };
142            if let Some(mut replacement) = replacement {
143                for (bidi, escaped, _) in UNICODE_BIDI_CODEPOINTS {
144                    replacement = replacement.replace(*bidi, escaped);
145                }
146                help_snippet = help_snippet.patch(Patch::new(token_span.clone(), replacement));
147            }
148        }
149
150        let level = lint_level.to_diagnostic_level();
151        let mut primary = Group::with_title(level.primary_title(LINT.desc)).element(snippet);
152        if emitted_source.is_none() {
153            emitted_source = Some(LINT.emitted_source(lint_level, source));
154            primary = primary.element(Level::NOTE.message(emitted_source.as_ref().unwrap()));
155        }
156
157        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);
158
159        let report = [primary, help];
160
161        pkg_stats.record_lint(lint_level);
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
