| 1 | // SPDX-License-Identifier: AGPL-3.0-or-later |
| 2 | |
| 3 | // Package log builds the slog handler the rest of the binary uses. |
| 4 | // |
| 5 | // Output format: |
| 6 | // - "text" — human-friendly key=value lines (default in dev) |
| 7 | // - "json" — one JSON object per line (default in prod) |
| 8 | // |
| 9 | // Standard log fields contract (every line): |
| 10 | // - time, level, msg |
| 11 | // - request_id when a request is in flight |
| 12 | // - user_id when known (post-S05) |
| 13 | // - component set by the package emitting the line |
| 14 | // - error/stack on error-level lines |
| 15 | // |
| 16 | // Redaction: field values whose key matches a known secret pattern (token, |
| 17 | // password, key, dsn, authorization, otpauth) are rewritten to "***" before |
| 18 | // they hit the underlying handler. |
| 19 | package log |
| 20 | |
| 21 | import ( |
| 22 | "context" |
| 23 | "io" |
| 24 | "log/slog" |
| 25 | "regexp" |
| 26 | "strings" |
| 27 | ) |
| 28 | |
| 29 | // Options configures the handler. |
| 30 | type Options struct { |
| 31 | Level string // debug | info | warn | error |
| 32 | Format string // text | json |
| 33 | Writer io.Writer |
| 34 | } |
| 35 | |
| 36 | // New returns a slog.Logger configured per opts. The redacting handler |
| 37 | // wraps the chosen base handler so every record is sanitised before output. |
| 38 | func New(opts Options) *slog.Logger { |
| 39 | if opts.Writer == nil { |
| 40 | opts.Writer = io.Discard |
| 41 | } |
| 42 | level := parseLevel(opts.Level) |
| 43 | handlerOpts := &slog.HandlerOptions{Level: level} |
| 44 | |
| 45 | var base slog.Handler |
| 46 | switch strings.ToLower(opts.Format) { |
| 47 | case "json": |
| 48 | base = slog.NewJSONHandler(opts.Writer, handlerOpts) |
| 49 | default: |
| 50 | base = slog.NewTextHandler(opts.Writer, handlerOpts) |
| 51 | } |
| 52 | return slog.New(&redactHandler{base: base}) |
| 53 | } |
| 54 | |
| 55 | func parseLevel(s string) slog.Level { |
| 56 | switch strings.ToLower(s) { |
| 57 | case "debug": |
| 58 | return slog.LevelDebug |
| 59 | case "warn", "warning": |
| 60 | return slog.LevelWarn |
| 61 | case "error": |
| 62 | return slog.LevelError |
| 63 | default: |
| 64 | return slog.LevelInfo |
| 65 | } |
| 66 | } |
| 67 | |
| 68 | // secretAttrKeys are case-insensitive substrings that mark an attribute key |
| 69 | // as a secret value to redact. |
| 70 | var secretAttrKeys = []string{ |
| 71 | "password", "pass", |
| 72 | "secret", |
| 73 | "key", |
| 74 | "token", |
| 75 | "authorization", |
| 76 | "dsn", |
| 77 | "otpauth", |
| 78 | } |
| 79 | |
| 80 | // secretValueMarkers are substrings that, if found anywhere in a string |
| 81 | // value, signal the line is leaking a token / URL credential / secret URI |
| 82 | // even if the attribute key itself looks innocent. |
| 83 | var secretValueMarkers = []string{ |
| 84 | "shithub_pat_", |
| 85 | "otpauth://", |
| 86 | "Bearer ", |
| 87 | "Basic ", |
| 88 | } |
| 89 | |
| 90 | // redactHandler wraps another slog.Handler, scrubbing matched attributes. |
| 91 | type redactHandler struct { |
| 92 | base slog.Handler |
| 93 | attrs []slog.Attr |
| 94 | group string |
| 95 | } |
| 96 | |
| 97 | func (h *redactHandler) Enabled(ctx context.Context, level slog.Level) bool { |
| 98 | return h.base.Enabled(ctx, level) |
| 99 | } |
| 100 | |
| 101 | func (h *redactHandler) Handle(ctx context.Context, r slog.Record) error { |
| 102 | scrubbed := slog.Record{ |
| 103 | Time: r.Time, |
| 104 | Message: r.Message, |
| 105 | Level: r.Level, |
| 106 | PC: r.PC, |
| 107 | } |
| 108 | r.Attrs(func(a slog.Attr) bool { |
| 109 | scrubbed.AddAttrs(redactAttr(a)) |
| 110 | return true |
| 111 | }) |
| 112 | return h.base.Handle(ctx, scrubbed) |
| 113 | } |
| 114 | |
| 115 | func (h *redactHandler) WithAttrs(attrs []slog.Attr) slog.Handler { |
| 116 | scrubbed := make([]slog.Attr, len(attrs)) |
| 117 | for i, a := range attrs { |
| 118 | scrubbed[i] = redactAttr(a) |
| 119 | } |
| 120 | return &redactHandler{base: h.base.WithAttrs(scrubbed), attrs: append(append([]slog.Attr{}, h.attrs...), scrubbed...), group: h.group} |
| 121 | } |
| 122 | |
| 123 | func (h *redactHandler) WithGroup(name string) slog.Handler { |
| 124 | return &redactHandler{base: h.base.WithGroup(name), attrs: h.attrs, group: name} |
| 125 | } |
| 126 | |
| 127 | func redactAttr(a slog.Attr) slog.Attr { |
| 128 | if shouldRedactKey(a.Key) { |
| 129 | if a.Value.Kind() == slog.KindString { |
| 130 | return slog.String(a.Key, "***") |
| 131 | } |
| 132 | } |
| 133 | if a.Value.Kind() == slog.KindString { |
| 134 | if v := redactValueIfSensitive(a.Value.String()); v != a.Value.String() { |
| 135 | return slog.String(a.Key, v) |
| 136 | } |
| 137 | } |
| 138 | return a |
| 139 | } |
| 140 | |
| 141 | func shouldRedactKey(key string) bool { |
| 142 | lower := strings.ToLower(key) |
| 143 | for _, needle := range secretAttrKeys { |
| 144 | if strings.Contains(lower, needle) { |
| 145 | return true |
| 146 | } |
| 147 | } |
| 148 | return false |
| 149 | } |
| 150 | |
| 151 | func redactValueIfSensitive(v string) string { |
| 152 | for _, marker := range secretValueMarkers { |
| 153 | if strings.Contains(v, marker) { |
| 154 | return "***" |
| 155 | } |
| 156 | } |
| 157 | if u := stripURLUserinfo(v); u != v { |
| 158 | return u |
| 159 | } |
| 160 | return v |
| 161 | } |
| 162 | |
| 163 | // urlUserinfoRE matches the credentials portion of a URL of the form |
| 164 | // scheme://user:pass@host/path. We replace it with scheme://***@host/path |
| 165 | // so the host + path stay readable in logs (helps debugging) while the |
| 166 | // credentials are gone. |
| 167 | // |
| 168 | // The pattern is deliberately strict: scheme [a-z][a-z0-9+\-.]* / / a |
| 169 | // minimal user:pass containing no @ before the literal @host. Slack and |
| 170 | // other URL-detection regexes get this wrong all the time; we only need |
| 171 | // to handle URLs that come through Go's net/url emitter, which canonicalizes. |
| 172 | var urlUserinfoRE = regexp.MustCompile(`(?i)\b([a-z][a-z0-9+\-.]*)://[^\s/@:]+:[^\s/@]+@`) |
| 173 | |
| 174 | func stripURLUserinfo(s string) string { |
| 175 | if !strings.Contains(s, "://") || !strings.Contains(s, "@") { |
| 176 | return s |
| 177 | } |
| 178 | return urlUserinfoRE.ReplaceAllString(s, "$1://***@") |
| 179 | } |
| 180 |