lean_ctx/core/

secret_detection.rs

use std::sync::OnceLock;

use regex::Regex;

use crate::core::config::{Config, SecretDetectionConfig};

macro_rules! static_regex {
    ($pattern:expr_2021) => {{
        static RE: OnceLock<Regex> = OnceLock::new();
        RE.get_or_init(|| Regex::new($pattern).expect(concat!("invalid regex: ", $pattern)))
    }};
}

#[derive(Debug, Clone)]
pub struct SecretMatch {
    pub pattern_name: &'static str,
    pub line_number: usize,
    pub redacted_preview: String,
}

fn aws_key_re() -> &'static Regex {
    static_regex!(r"(?:AKIA|ASIA)[0-9A-Z]{16}")
}

fn private_key_re() -> &'static Regex {
    static_regex!(r"-----BEGIN (?:RSA |EC |DSA |OPENSSH )?PRIVATE KEY-----")
}

fn github_token_re() -> &'static Regex {
    static_regex!(r"gh[ps]_[A-Za-z0-9_]{36,}")
}

pub(crate) fn anthropic_key_re() -> &'static Regex {
    static_regex!(r"sk-ant-[A-Za-z0-9_\-]{20,}")
}

pub(crate) fn openai_key_re() -> &'static Regex {
    static_regex!(r"\bsk-(?:(?:proj|svcacct)-[A-Za-z0-9_\-]{20,}|[A-Za-z0-9]{20,})")
}

// #718 word boundaries for the generic key/value patterns: the keyword must
// not be a camelCase subword (`superuserPassword`), while SNAKE_CASE env
// names (`MY_TOKEN=…`) keep matching — `_` stays a permitted predecessor.
// Group 1 = predecessor + key prefix (kept on redaction), group 2 = value
// (guarded: identifier references and placeholders are benign).
// #1830: blanks only around the separator — a valueless `token:` line must not
// take the next line for its value.
fn generic_api_key_re() -> &'static Regex {
    static_regex!(
        r#"(?im)((?:^|[^a-z0-9])(?:aws[_-]?secret[_-]?access[_-]?key|secret[_-]?access[_-]?key|api[_-]?key|secret[_-]?key|token|password|passwd|access[_-]?token|client[_-]?secret)(?:\\?["'])?[ \t]*[=:][ \t]*(?:\\?["'])?)([A-Za-z0-9_+/=\-]{20,})"#
    )
}

fn high_entropy_b64_re() -> &'static Regex {
    static_regex!(
        r#"(?im)((?:^|[^a-z0-9])(?:key|token|secret|password|credential|auth)(?:\\?["'])?[ \t]*[=:][ \t]*(?:\\?["'])?)([A-Za-z0-9+/=\-_]{40,})"#
    )
}

fn url_encoded_secret_re() -> &'static Regex {
    static_regex!(
        r#"(?im)((?:^|[^a-z0-9])(?:aws[_-]?secret[_-]?access[_-]?key|secret[_-]?access[_-]?key|api[_-]?key|secret[_-]?key|token|password|passwd|access[_-]?token|client[_-]?secret)(?:\\?["'])?[ \t]*[=:][ \t]*(?:\\?["'])?)((?:%[0-9a-f]{2}|[A-Za-z0-9_\-]){20,})"#
    )
}

fn authorization_header_re() -> &'static Regex {
    static_regex!(r"(?i)authorization[ \t]*:[ \t]*(?:bearer|basic)[ \t]+[A-Za-z0-9_+/=\-.]{4,}")
}

/// A bare `Bearer <token>` outside an `Authorization:` header (curl flags, logs).
/// Group 1 is filtered by `redaction::bearer_value_is_credential`, the same check
/// the core redactor applies, so prose ("Bearer authentication") stays clean and
/// the two layers cannot disagree.
fn bearer_token_re() -> &'static Regex {
    static_regex!(r"(?i)bearer[ \t]+([A-Za-z0-9_\-.]{8,})")
}

fn gitlab_pat_re() -> &'static Regex {
    static_regex!(r"glpat-[A-Za-z0-9_\-]{20,}")
}

fn jwt_re() -> &'static Regex {
    static_regex!(r"eyJ[A-Za-z0-9_\-]{10,}\.[A-Za-z0-9_\-]{10,}")
}

fn slack_token_re() -> &'static Regex {
    static_regex!(r"xox[bpas]-[0-9a-zA-Z\-]{10,}")
}

fn stripe_key_re() -> &'static Regex {
    static_regex!(r"[sr]k_live_[0-9a-zA-Z]{10,}")
}

/// A password in the userinfo of any other URL (`https://user:pw@host`).
fn url_credentials_re() -> &'static Regex {
    static_regex!(
        r"(?i)(?:https?|ftps?|sftp|ssh|amqps?|smtps?|ldaps?|wss?|git)://[^\s:/@]+:[^\s@/]+@"
    )
}

fn npm_token_re() -> &'static Regex {
    static_regex!(r"npm_[A-Za-z0-9]{10,}")
}

fn github_fine_grained_re() -> &'static Regex {
    static_regex!(r"github_pat_[A-Za-z0-9_]{20,}")
}

const BUILTIN_PATTERNS: &[(&str, fn() -> &'static Regex)] = &[
    ("aws_key", aws_key_re),
    ("authorization_header", authorization_header_re),
    ("private_key", private_key_re),
    ("github_token", github_token_re),
    ("github_fine_grained", github_fine_grained_re),
    ("anthropic_key", anthropic_key_re),
    ("openai_key", openai_key_re),
    ("gitlab_pat", gitlab_pat_re),
    ("jwt", jwt_re),
    ("slack_token", slack_token_re),
    ("stripe_key", stripe_key_re),
    ("url_credentials", url_credentials_re),
    ("npm_token", npm_token_re),
];

/// Key/value patterns with a kept prefix (group 1) and a guarded value
/// (group 2): identifier references, placeholders and language literals are
/// benign (#718) and neither reported nor redacted.
const GUARDED_PATTERNS: &[(&str, fn() -> &'static Regex)] = &[
    ("generic_api_key", generic_api_key_re),
    ("high_entropy_secret", high_entropy_b64_re),
    ("url_encoded_secret", url_encoded_secret_re),
];

/// True when a guarded-pattern match should be skipped: the value is benign
/// (#718) — shares the benign-value heuristics with `core::redaction` so the
/// two layers cannot drift.
fn guarded_match_is_benign(caps: &regex::Captures) -> bool {
    // A quoted value is a literal, never an identifier reference — same rule as
    // the core redactor, so the scanner cannot report "clean" for what it redacts.
    let quoted = caps
        .get(1)
        .is_some_and(|prefix| prefix.as_str().ends_with(['"', '\'']));
    caps.get(2).is_some_and(|value| {
        if quoted {
            crate::core::redaction::is_benign_quoted_value(value.as_str())
        } else {
            crate::core::redaction::is_benign_secret_value(value.as_str())
        }
    })
}

/// Compile the subtractive `exclude_patterns` from config (#718). Invalid
/// regexes are skipped — a broken exclude must never disable detection.
fn compile_excludes(patterns: &[String]) -> Vec<Regex> {
    patterns.iter().filter_map(|p| Regex::new(p).ok()).collect()
}

fn excluded(excludes: &[Regex], matched: &str) -> bool {
    excludes.iter().any(|ex| ex.is_match(matched))
}

fn make_redacted_preview(matched: &str) -> String {
    let chars: Vec<char> = matched.chars().collect();
    if chars.len() <= 6 {
        return "***".to_string();
    }
    let prefix: String = chars[..4].iter().collect();
    let suffix: String = chars[chars.len() - 2..].iter().collect();
    format!("{prefix}***{suffix}")
}

fn collect_matches(
    content: &str,
    custom_patterns: &[String],
    excludes: &[Regex],
) -> Vec<SecretMatch> {
    let mut matches = Vec::new();
    let normalized = crate::core::redaction::normalize_secret_text(content);

    // Built on the first match only: most content has none. Offsets index
    // the normalized text the patterns run on.
    let line_offsets: std::cell::OnceCell<Vec<usize>> = std::cell::OnceCell::new();

    let offset_to_line = |byte_offset: usize| -> usize {
        let line_offsets = line_offsets.get_or_init(|| {
            std::iter::once(0)
                .chain(normalized.match_indices('\n').map(|(i, _)| i + 1))
                .collect()
        });
        match line_offsets.binary_search(&byte_offset) {
            Ok(i) => i + 1,
            Err(i) => i,
        }
    };

    for &(name, regex_fn) in BUILTIN_PATTERNS {
        let re = regex_fn();
        for m in re.find_iter(&normalized) {
            if excluded(excludes, m.as_str()) {
                continue;
            }
            matches.push(SecretMatch {
                pattern_name: name,
                line_number: offset_to_line(m.start()),
                redacted_preview: make_redacted_preview(m.as_str()),
            });
        }
    }

    for caps in bearer_token_re().captures_iter(&normalized) {
        let Some(whole) = caps.get(0) else {
            continue;
        };
        let credential = caps.get(1).is_some_and(|value| {
            crate::core::redaction::bearer_value_is_credential(value.as_str())
        });
        if !credential || excluded(excludes, whole.as_str()) {
            continue;
        }
        matches.push(SecretMatch {
            pattern_name: "bearer_token",
            line_number: offset_to_line(whole.start()),
            redacted_preview: make_redacted_preview(whole.as_str()),
        });
    }

    // Same rule as the redactor: a placeholder password or an already
    // redacted URL is no credential, so redacted output never re-matches.
    for caps in crate::core::redaction::database_url_re().captures_iter(&normalized) {
        let Some(whole) = caps.get(0) else {
            continue;
        };
        if !crate::core::redaction::database_url_has_credential(&caps)
            || excluded(excludes, whole.as_str())
        {
            continue;
        }
        matches.push(SecretMatch {
            pattern_name: "db_url",
            line_number: offset_to_line(whole.start()),
            redacted_preview: make_redacted_preview(whole.as_str()),
        });
    }

    for &(name, regex_fn) in GUARDED_PATTERNS {
        let re = regex_fn();
        for caps in re.captures_iter(&normalized) {
            let whole = caps.get(0).map_or("", |m| m.as_str());
            if guarded_match_is_benign(&caps)
                || (name == "high_entropy_secret"
                    && caps.get(2).is_some_and(|value| {
                        caps.get(1).is_some_and(|prefix| {
                            crate::core::redaction::is_fact_key_slug(
                                prefix.as_str(),
                                value.as_str(),
                            )
                        })
                    }))
                || excluded(excludes, whole)
            {
                continue;
            }
            let start = caps.get(0).map_or(0, |m| m.start());
            matches.push(SecretMatch {
                pattern_name: name,
                line_number: offset_to_line(start),
                redacted_preview: make_redacted_preview(whole),
            });
        }
    }

    for pattern_str in custom_patterns {
        if let Ok(re) = Regex::new(pattern_str) {
            for m in re.find_iter(&normalized) {
                if excluded(excludes, m.as_str()) {
                    continue;
                }
                matches.push(SecretMatch {
                    pattern_name: "custom_pattern",
                    line_number: offset_to_line(m.start()),
                    redacted_preview: make_redacted_preview(m.as_str()),
                });
            }
        }
    }

    matches
}

/// How many matches the `custom_patterns` of `config` alone have in
/// `content` — no built-in pattern runs. The custom-pattern step of
/// `collect_matches` on its own: the same normalized text, the same
/// `exclude_patterns`, a pattern that does not compile is skipped. For a
/// caller that has counted the built-in patterns elsewhere (the gateway's
/// whole-text pass for custom patterns that can match across lines).
pub(crate) fn custom_pattern_hits(content: &str, config: &SecretDetectionConfig) -> usize {
    let excludes = compile_excludes(&config.exclude_patterns);
    let normalized = crate::core::redaction::normalize_secret_text(content);
    config
        .custom_patterns
        .iter()
        .filter_map(|pattern| Regex::new(pattern).ok())
        .map(|re| {
            re.find_iter(&normalized)
                .filter(|found| !excluded(&excludes, found.as_str()))
                .count()
        })
        .sum()
}

pub fn detect_secrets(content: &str) -> Vec<SecretMatch> {
    collect_matches(content, &[], &[])
}

pub fn detect_secrets_with_custom(content: &str, custom_patterns: &[String]) -> Vec<SecretMatch> {
    collect_matches(content, custom_patterns, &[])
}

pub fn scan_and_redact(
    content: &str,
    config: &SecretDetectionConfig,
) -> (String, Vec<SecretMatch>) {
    if !config.enabled {
        return (content.to_string(), Vec::new());
    }

    let excludes = compile_excludes(&config.exclude_patterns);
    let matches = collect_matches(content, &config.custom_patterns, &excludes);

    if matches.is_empty() || !config.redact {
        return (content.to_string(), matches);
    }

    // The same masker and the same labels as every other redaction pass
    // (`redaction::redact_counting`): one spelling per secret kind.
    let mut redacted = crate::core::redaction::redact_text_with_excludes(content, &excludes);

    for pattern_str in &config.custom_patterns {
        if let Ok(re) = Regex::new(pattern_str) {
            redacted = re
                .replace_all(&redacted, |caps: &regex::Captures| {
                    let whole = caps.get(0).map_or("", |m| m.as_str());
                    if excluded(&excludes, whole) {
                        return whole.to_string();
                    }
                    "[REDACTED:custom_pattern]".to_string()
                })
                .to_string();
        }
    }

    (redacted, matches)
}

pub fn scan_and_redact_from_config(content: &str) -> (String, Vec<SecretMatch>) {
    let cfg = Config::load();
    scan_and_redact(content, &cfg.secret_detection)
}

#[cfg(test)]
#[path = "security_corpus_tests.rs"]
mod security_corpus_tests;

#[cfg(test)]
pub mod tests {
    use super::*;

    #[test]
    fn detects_aws_key() {
        let input = concat!("aws_key = AK", "IAIOSFODNN7EXAMPLE");
        let matches = detect_secrets(input);
        assert!(matches.iter().any(|m| m.pattern_name == "aws_key"));
    }

    #[test]
    fn detects_private_key_header() {
        let input = concat!("-----BEGIN RSA PRIVATE", " KEY-----\nMIIEpAIB...");
        let matches = detect_secrets(input);
        assert!(matches.iter().any(|m| m.pattern_name == "private_key"));
    }

    #[test]
    fn detects_github_token() {
        let input = concat!(
            "export GITHUB_TOKEN=gh",
            "p_ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijk"
        );
        let matches = detect_secrets(input);
        assert!(matches.iter().any(|m| m.pattern_name == "github_token"));
    }

    #[test]
    fn detects_anthropic_key() {
        let input = concat!("ANTHROPIC_API_KEY=sk-ant-api03-", "abcdef1234567890ABCD");
        let matches = detect_secrets(input);
        assert!(matches.iter().any(|m| m.pattern_name == "anthropic_key"));
    }

    #[test]
    fn detects_openai_key() {
        let input = concat!("OPENAI_API_KEY=sk-", "abcdefghijklmnopqrstuvwx");
        let matches = detect_secrets(input);
        assert!(matches.iter().any(|m| m.pattern_name == "openai_key"));
    }

    #[test]
    fn detects_gitlab_pat() {
        let input = concat!("token = glpat-", "xxxxxxxxxxxxxxxxxxxx");
        let matches = detect_secrets(input);
        assert!(matches.iter().any(|m| m.pattern_name == "gitlab_pat"));
    }

    #[test]
    fn detects_generic_api_key() {
        let input = concat!("api_key = abcdefghijklmnop", "qrstuvwxyz1234567890");
        let matches = detect_secrets(input);
        assert!(matches.iter().any(
            |m| m.pattern_name == "generic_api_key" || m.pattern_name == "high_entropy_secret"
        ));
    }

    #[test]
    fn clean_content_returns_empty() {
        let input = "fn main() { println!(\"hello world\"); }";
        let matches = detect_secrets(input);
        assert!(matches.is_empty());
    }

    #[test]
    fn detects_jwt() {
        let input = concat!("token = eyJhbGciOiJIU", "zI1NiJ9.eyJzdWIiOiIxMjM0NTY3ODkw");
        let matches = detect_secrets(input);
        assert!(matches.iter().any(|m| m.pattern_name == "jwt"));
    }

    #[test]
    fn detects_slack_token() {
        let input = concat!("SLACK_TOKEN=xoxb-12345", "67890-abcdefghij");
        let matches = detect_secrets(input);
        assert!(matches.iter().any(|m| m.pattern_name == "slack_token"));
    }

    #[test]
    fn detects_stripe_key() {
        let input = concat!("stripe_key = sk_", "live_abcdefghij1234567890");
        let matches = detect_secrets(input);
        assert!(matches.iter().any(|m| m.pattern_name == "stripe_key"));
    }

    #[test]
    fn detects_db_url() {
        let input = concat!(
            "DATABASE_URL=postgres://user:pass",
            "word@localhost:5432/db"
        );
        let matches = detect_secrets(input);
        assert!(matches.iter().any(|m| m.pattern_name == "db_url"));
    }

    /// Ops telemetry (3.11.4): `ctx_read` withheld whole files with
    /// `(secret.redacted, redaction.incomplete)` — the redacted database URL
    /// `scheme://[REDACTED:db_url]@host` matched the detector's
    /// `user:password@` again. Redacted output must never re-match.
    #[test]
    fn redacted_database_urls_do_not_match_again() {
        let url = |scheme: &str, user: &str, pw: &str| {
            format!("{scheme}{}{user}:{pw}{}db.internal:5432/app", "://", "@")
        };
        let cases = [
            url("postgres", "app", "s3cretPassw0rd"),
            url("postgresql", "app", "Zq7Lm2Vx"),
            url("mysql", "root", "hunter2hunter2"),
            url("mongodb+srv", "admin", "Xy9pQ2rT"),
            url("redis", "", "Zk3mP9qL"),
            url("postgres", "app", "p@ss"),
        ];
        let report_only = SecretDetectionConfig {
            redact: false,
            ..SecretDetectionConfig::default()
        };
        for case in cases {
            let input = format!("DATABASE_URL={case}\nkeep after\n");
            assert!(
                detect_secrets(&input)
                    .iter()
                    .any(|m| m.pattern_name == "db_url"),
                "credential must be detected: {input}"
            );
            let (redacted, _) = scan_and_redact(&input, &SecretDetectionConfig::default());
            assert!(
                !redacted.contains("Passw0rd") && !redacted.contains("ss@db"),
                "{redacted}"
            );
            assert!(redacted.ends_with("keep after\n"), "{redacted}");
            let (_, residual) = scan_and_redact(&redacted, &report_only);
            assert!(
                residual.is_empty(),
                "re-scan of {redacted} found {residual:?}"
            );
        }
        // A documentation placeholder is neither reported nor rewritten.
        let doc = format!("DATABASE_URL={}\n", url("postgres", "user", "changeme"));
        assert!(detect_secrets(&doc).is_empty(), "{doc}");
    }

    #[test]
    fn detects_npm_token() {
        let input = concat!("NPM_TOKEN=npm_abcd", "efghij1234567890");
        let matches = detect_secrets(input);
        assert!(matches.iter().any(|m| m.pattern_name == "npm_token"));
    }

    #[test]
    fn detects_github_fine_grained() {
        let input = concat!("token = github_pat_ABC", "DEFGHIJKLMNOPQRSTuv");
        let matches = detect_secrets(input);
        assert!(
            matches
                .iter()
                .any(|m| m.pattern_name == "github_fine_grained")
        );
    }

    #[test]
    fn redacted_preview_format() {
        let preview = make_redacted_preview(concat!("AK", "IAIOSFODNN7EXAMPLE"));
        assert!(preview.starts_with("AKIA"));
        assert!(preview.ends_with("LE"));
        assert!(preview.contains("***"));
    }

    #[test]
    fn redacted_preview_short_string() {
        let preview = make_redacted_preview("short");
        assert_eq!(preview, "***");
    }

    #[test]
    fn scan_and_redact_replaces_secrets() {
        let cfg = SecretDetectionConfig {
            enabled: true,
            redact: true,
            ..Default::default()
        };
        let input = concat!("key = AK", "IAIOSFODNN7EXAMPLE");
        let (redacted, matches) = scan_and_redact(input, &cfg);
        assert!(!matches.is_empty());
        assert!(redacted.contains("[REDACTED:AWS key]"));
        assert!(!redacted.contains(concat!("AK", "IAIOSFODNN7EXAMPLE")));
    }

    #[test]
    fn scan_without_redact_preserves_content() {
        let cfg = SecretDetectionConfig {
            enabled: true,
            redact: false,
            ..Default::default()
        };
        let input = concat!("key = AK", "IAIOSFODNN7EXAMPLE");
        let (output, matches) = scan_and_redact(input, &cfg);
        assert!(!matches.is_empty());
        assert_eq!(output, input);
    }

    #[test]
    fn disabled_detection_returns_unchanged() {
        let cfg = SecretDetectionConfig {
            enabled: false,
            redact: true,
            ..Default::default()
        };
        let input = concat!("key = AK", "IAIOSFODNN7EXAMPLE");
        let (output, matches) = scan_and_redact(input, &cfg);
        assert!(matches.is_empty());
        assert_eq!(output, input);
    }

    #[test]
    fn custom_pattern_detected() {
        let cfg = SecretDetectionConfig {
            enabled: true,
            redact: true,
            custom_patterns: vec![r"MYCORP_[A-Z]{10,}".to_string()],
            ..Default::default()
        };
        let input = "value is MYCORP_ABCDEFGHIJKLMNO here";
        let (redacted, matches) = scan_and_redact(input, &cfg);
        assert!(matches.iter().any(|m| m.pattern_name == "custom_pattern"));
        assert!(redacted.contains("[REDACTED:custom_pattern]"));
    }

    #[test]
    fn line_numbers_are_correct() {
        let input = concat!("line1\nline2\nAK", "IAIOSFODNN7EXAMPLE\nline4");
        let matches = detect_secrets(input);
        assert!(!matches.is_empty());
        assert_eq!(matches[0].line_number, 3);
    }

    #[test]
    fn key_value_secret_patterns_do_not_cross_lines() {
        let input = [
            "token:",
            "\n",
            "ABCDEFGHIJKLMNOP",
            "QRSTUVWXYZabcdef",
            "012345",
        ]
        .concat();
        let matches = detect_secrets(&input);
        assert!(
            !matches
                .iter()
                .any(|m| matches!(m.pattern_name, "generic_api_key" | "high_entropy_secret")),
            "a valueless key must not consume the next line: {matches:?}"
        );

        let same_line_input =
            ["token: ", "ABCDEFGHIJKLMNOP", "QRSTUVWXYZabcdef", "012345"].concat();
        let matches = detect_secrets(&same_line_input);
        assert!(
            matches.iter().any(|m| m.pattern_name == "generic_api_key"),
            "same-line key/value secrets must still be detected: {matches:?}"
        );
    }

    #[test]
    fn multiple_secrets_on_different_lines() {
        let input = concat!(
            "AK",
            "IAIOSFODNN7EXAMPLE\nclean\nsk-abcdef",
            "ghijklmnopqrstuvwx"
        );
        let matches = detect_secrets(input);
        assert!(matches.len() >= 2);
        let aws = matches
            .iter()
            .find(|m| m.pattern_name == "aws_key")
            .unwrap();
        assert_eq!(aws.line_number, 1);
        let oai = matches
            .iter()
            .find(|m| m.pattern_name == "openai_key")
            .unwrap();
        assert_eq!(oai.line_number, 3);
    }

    #[test]
    fn ec_private_key_detected() {
        let input = concat!("-----BEGIN EC PRIVATE", " KEY-----");
        let matches = detect_secrets(input);
        assert!(matches.iter().any(|m| m.pattern_name == "private_key"));
    }

    #[test]
    fn openssh_private_key_detected() {
        let input = concat!("-----BEGIN OPENSSH PRIVATE", " KEY-----");
        let matches = detect_secrets(input);
        assert!(matches.iter().any(|m| m.pattern_name == "private_key"));
    }

    /// The context-gateway admission path relies on this contract: report-only mode
    /// returns the input untouched, custom/exclude patterns are honoured, and redacted
    /// output has no residual match (admission re-scans it and withholds on a hit).
    /// Normalization (zero-width, full-width) only affects matching, never the bytes
    /// outside a redacted span.
    #[test]
    fn scan_and_redact_keeps_the_gateway_contract() {
        let aws = format!("AK\u{200b}IA{}", "Q7".repeat(8));
        let key_block = [
            "-----BEGIN PRIVATE KEY",
            "-----\nbody-line-one\nbody-line-two\n-----END PRIVATE KEY",
            "-----",
        ]
        .concat();
        let excluded_key = concat!("AK", "IAIOSFODNN7EXAMPLE");
        let input = format!(
            "keep before\nAWS_ACCESS_KEY_ID={aws}\n{key_block}\nticket EMP-4711\nsample {excluded_key}\nkeep after\n"
        );
        let cfg = SecretDetectionConfig {
            custom_patterns: vec![r"EMP-\d{4}".into()],
            exclude_patterns: vec![excluded_key.into()],
            ..SecretDetectionConfig::default()
        };

        let report_only = SecretDetectionConfig {
            redact: false,
            ..cfg.clone()
        };
        let (unchanged, found) = scan_and_redact(&input, &report_only);
        assert_eq!(unchanged, input, "report-only mode must not touch the text");
        assert!(!found.is_empty());

        let (redacted, _) = scan_and_redact(&input, &cfg);
        assert!(redacted.starts_with("keep before\n"), "{redacted}");
        assert!(redacted.ends_with("keep after\n"), "{redacted}");
        assert!(
            redacted.contains(excluded_key),
            "excluded value kept verbatim"
        );
        assert!(!redacted.contains("EMP-4711"), "custom pattern redacted");
        assert!(!redacted.contains("body-line-one"), "{redacted}");
        let (_, residual) = scan_and_redact(&redacted, &report_only);
        assert!(
            residual.is_empty(),
            "redacted output must not match again: {residual:?}\n{redacted}"
        );
    }
}