| 1 | package sandbox |
| 2 | |
| 3 | import ( |
| 4 | "context" |
| 5 | "fmt" |
| 6 | "io" |
| 7 | "os" |
| 8 | "os/exec" |
| 9 | "path/filepath" |
| 10 | "runtime" |
| 11 | "strings" |
| 12 | "time" |
| 13 | |
| 14 | "reasonix/internal/proc" |
| 15 | "reasonix/internal/secrets" |
| 16 | ) |
| 17 | |
| 18 | // psUTF8Prologue forces PowerShell to emit UTF-8 instead of the host's OEM code |
| 19 | // page (e.g. CP936 on a Chinese Windows), so non-ASCII command output and error |
| 20 | // text come back as valid UTF-8 rather than mojibake. |
| 21 | const psUTF8Prologue = "$OutputEncoding=[Console]::OutputEncoding=[System.Text.Encoding]::UTF8;" |
| 22 | |
| 23 | // PowerShellUTF8Script prepares a PowerShell script for captured execution. |
| 24 | // Setting both encodings keeps PowerShell's own output and native child-process |
| 25 | // output UTF-8 across Windows console code pages. |
| 26 | func PowerShellUTF8Script(command string) string { |
| 27 | return psUTF8Prologue + command |
| 28 | } |
| 29 | |
| 30 | // ShellKind is the interpreter a shell command runs under. |
| 31 | type ShellKind int |
| 32 | |
| 33 | const ( |
| 34 | ShellBash ShellKind = iota |
| 35 | ShellPowerShell |
| 36 | ) |
| 37 | |
| 38 | func (k ShellKind) String() string { |
| 39 | if k == ShellPowerShell { |
| 40 | return "powershell" |
| 41 | } |
| 42 | return "bash" |
| 43 | } |
| 44 | |
| 45 | // Shell is the resolved interpreter the bash tool executes commands with: a kind |
| 46 | // (so callers can adapt prompts) and the executable to invoke. |
| 47 | type Shell struct { |
| 48 | Kind ShellKind |
| 49 | Path string |
| 50 | } |
| 51 | |
| 52 | // ResolveShell picks the interpreter the shell tool runs commands under. With |
| 53 | // prefer "auto"/"" it favours a real bash so the model's POSIX habits work and |
| 54 | // only falls back to PowerShell on Windows when bash is absent. prefer "bash" or |
| 55 | // "powershell"/"pwsh" forces that interpreter (path overrides the PATH lookup), |
| 56 | // warning to warn and falling back to auto-detection if the forced one is |
| 57 | // missing — so a typo or an uninstalled shell can never leave the tool broken. |
| 58 | func ResolveShell(prefer, path string, warn io.Writer) Shell { |
| 59 | return resolveShell(prefer, path, warn, runtime.GOOS, exec.LookPath, fileExists, windowsBashCandidates(), windowsPowerShellCandidates(), probeBash, isWindowsWSLBash) |
| 60 | } |
| 61 | |
| 62 | // resolveShell is ResolveShell with its environment lookups injected — including |
| 63 | // the Git-for-Windows bash candidates, which derive from %ProgramFiles% and so |
| 64 | // are empty off Windows — so the decision table is deterministically testable on |
| 65 | // any host. |
| 66 | func resolveShell(prefer, path string, warn io.Writer, goos string, lookPath func(string) (string, error), exists func(string) bool, winBashCandidates []string, winPowerShellCandidates []string, probe func(string) bool, isWSL func(string) bool) Shell { |
| 67 | findBash := func() (Shell, bool) { |
| 68 | if p, err := lookPath("bash"); err == nil && !isWSL(p) && probe(p) { |
| 69 | return Shell{Kind: ShellBash, Path: p}, true |
| 70 | } |
| 71 | for _, p := range winBashCandidates { |
| 72 | if exists(p) && probe(p) { |
| 73 | return Shell{Kind: ShellBash, Path: p}, true |
| 74 | } |
| 75 | } |
| 76 | return Shell{}, false |
| 77 | } |
| 78 | findPowerShell := func(order []string) (Shell, bool) { |
| 79 | for _, name := range order { |
| 80 | for _, p := range winPowerShellCandidates { |
| 81 | base := strings.ToLower(pathBase(p)) |
| 82 | if base != strings.ToLower(name) && strings.TrimSuffix(base, ".exe") != strings.ToLower(name) { |
| 83 | continue |
| 84 | } |
| 85 | if exists(p) { |
| 86 | return Shell{Kind: ShellPowerShell, Path: p}, true |
| 87 | } |
| 88 | } |
| 89 | if p, err := lookPath(name); err == nil { |
| 90 | return Shell{Kind: ShellPowerShell, Path: p}, true |
| 91 | } |
| 92 | } |
| 93 | return Shell{}, false |
| 94 | } |
| 95 | auto := func() Shell { |
| 96 | if sh, ok := findBash(); ok { |
| 97 | return sh |
| 98 | } |
| 99 | if goos == "windows" { |
| 100 | if sh, ok := findPowerShell([]string{"pwsh", "powershell"}); ok { |
| 101 | return sh |
| 102 | } |
| 103 | } |
| 104 | return Shell{Kind: ShellBash, Path: "bash"} |
| 105 | } |
| 106 | |
| 107 | switch strings.ToLower(strings.TrimSpace(prefer)) { |
| 108 | case "", "auto": |
| 109 | return auto() |
| 110 | case "bash": |
| 111 | if path != "" && exists(path) && probe(path) { |
| 112 | return Shell{Kind: ShellBash, Path: path} |
| 113 | } |
| 114 | if sh, ok := findBash(); ok { |
| 115 | return sh |
| 116 | } |
| 117 | warnMissingShell(warn, prefer) |
| 118 | return auto() |
| 119 | case "powershell", "pwsh": |
| 120 | if path != "" && exists(path) { |
| 121 | return Shell{Kind: ShellPowerShell, Path: path} |
| 122 | } |
| 123 | order := []string{"pwsh", "powershell"} |
| 124 | if strings.EqualFold(strings.TrimSpace(prefer), "powershell") { |
| 125 | order = []string{"powershell", "pwsh"} |
| 126 | } |
| 127 | if sh, ok := findPowerShell(order); ok { |
| 128 | return sh |
| 129 | } |
| 130 | warnMissingShell(warn, prefer) |
| 131 | return auto() |
| 132 | default: |
| 133 | if warn != nil { |
| 134 | fmt.Fprintf(warn, "warning: [tools.shell] prefer=%q is not recognised (use auto/bash/powershell); using auto-detection\n", prefer) |
| 135 | } |
| 136 | return auto() |
| 137 | } |
| 138 | } |
| 139 | |
| 140 | func warnMissingShell(warn io.Writer, prefer string) { |
| 141 | if warn != nil { |
| 142 | fmt.Fprintf(warn, "warning: [tools.shell] prefer=%q but that shell was not found; using auto-detection\n", prefer) |
| 143 | } |
| 144 | } |
| 145 | |
| 146 | // isWindowsWSLBash reports whether a resolved bash path is the WSL launcher |
| 147 | // Windows ships under %SystemRoot% (e.g. C:\Windows\System32\bash.exe). With WSL |
| 148 | // installed it runs commands inside the Linux VM — where the Windows workspace is |
| 149 | // a /mnt/<drive> path — so it must never be chosen for a native Windows workspace; |
| 150 | // the only bash.exe Microsoft places under the Windows dir is that launcher. |
| 151 | func isWindowsWSLBash(path string) bool { |
| 152 | if runtime.GOOS != "windows" || path == "" { |
| 153 | return false |
| 154 | } |
| 155 | win := os.Getenv("SystemRoot") |
| 156 | if win == "" { |
| 157 | win = os.Getenv("windir") |
| 158 | } |
| 159 | if win == "" { |
| 160 | return false |
| 161 | } |
| 162 | p := strings.ToLower(filepath.Clean(path)) |
| 163 | root := strings.ToLower(filepath.Clean(win)) + string(filepath.Separator) |
| 164 | return strings.HasPrefix(p, root) |
| 165 | } |
| 166 | |
| 167 | // Windows ships a bash.exe launcher stub in %SystemRoot% that opens the WSL |
| 168 | // install prompt instead of running anything, so confirm bash actually works |
| 169 | // before trusting it. Timeout-bounded in case the stub blocks on that prompt. |
| 170 | func probeBash(path string) bool { |
| 171 | if runtime.GOOS != "windows" { |
| 172 | return true |
| 173 | } |
| 174 | ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second) |
| 175 | defer cancel() |
| 176 | cmd := exec.CommandContext(ctx, path, "-c", "true") |
| 177 | cmd.Env = secrets.ProcessEnv() |
| 178 | proc.HideWindow(cmd) |
| 179 | return cmd.Run() == nil |
| 180 | } |
| 181 | |
| 182 | func fileExists(p string) bool { |
| 183 | fi, err := os.Stat(p) |
| 184 | return err == nil && !fi.IsDir() |
| 185 | } |
| 186 | |
| 187 | func pathBase(p string) string { |
| 188 | if i := strings.LastIndexAny(p, `/\\`); i >= 0 { |
| 189 | return p[i+1:] |
| 190 | } |
| 191 | return p |
| 192 | } |
| 193 | |
| 194 | // windowsBashCandidates lists the bash.exe paths a Git-for-Windows install |
| 195 | // ships, across the usual program-files roots and a per-user install. |
| 196 | func windowsBashCandidates() []string { |
| 197 | var roots []string |
| 198 | for _, env := range []string{"ProgramFiles", "ProgramW6432", "ProgramFiles(x86)"} { |
| 199 | if v := os.Getenv(env); v != "" { |
| 200 | roots = append(roots, v) |
| 201 | } |
| 202 | } |
| 203 | if v := os.Getenv("LOCALAPPDATA"); v != "" { |
| 204 | roots = append(roots, filepath.Join(v, "Programs")) |
| 205 | } |
| 206 | var out []string |
| 207 | for _, r := range roots { |
| 208 | out = append(out, |
| 209 | filepath.Join(r, "Git", "bin", "bash.exe"), |
| 210 | filepath.Join(r, "Git", "usr", "bin", "bash.exe"), |
| 211 | ) |
| 212 | } |
| 213 | return out |
| 214 | } |
| 215 | |
| 216 | // windowsPowerShellCandidates lists common PowerShell executables that are not |
| 217 | // always present on PATH, especially PowerShell 7's default MSI install path. |
| 218 | func windowsPowerShellCandidates() []string { |
| 219 | var roots []string |
| 220 | for _, env := range []string{"ProgramFiles", "ProgramW6432", "ProgramFiles(x86)"} { |
| 221 | if v := os.Getenv(env); v != "" { |
| 222 | roots = append(roots, v) |
| 223 | } |
| 224 | } |
| 225 | var out []string |
| 226 | for _, r := range roots { |
| 227 | out = append(out, filepath.Join(r, "PowerShell", "7", "pwsh.exe")) |
| 228 | } |
| 229 | if v := os.Getenv("SystemRoot"); v != "" { |
| 230 | out = append(out, filepath.Join(v, "System32", "WindowsPowerShell", "v1.0", "powershell.exe")) |
| 231 | } else if v := os.Getenv("windir"); v != "" { |
| 232 | out = append(out, filepath.Join(v, "System32", "WindowsPowerShell", "v1.0", "powershell.exe")) |
| 233 | } |
| 234 | return out |
| 235 | } |
| 236 | |
| 237 | // normalizeNullRedirects rewrites null-device redirect aliases to sink |
| 238 | // ("/dev/null" for bash, "$null" for PowerShell), so permission-approved |
| 239 | // null-sink commands discard output under the resolved shell. It handles |
| 240 | // cmd.exe-style `nul`, PowerShell `$null`, and POSIX `/dev/null` while avoiding |
| 241 | // quoted/escaped text. |
| 242 | func normalizeNullRedirects(command, sink string) string { |
| 243 | var ( |
| 244 | out strings.Builder |
| 245 | quote byte |
| 246 | ) |
| 247 | write := func(c byte) { |
| 248 | out.WriteByte(c) |
| 249 | } |
| 250 | for i := 0; i < len(command); { |
| 251 | c := command[i] |
| 252 | if quote != 0 { |
| 253 | write(c) |
| 254 | i++ |
| 255 | if c == '\\' && quote == '"' && i < len(command) { |
| 256 | write(command[i]) |
| 257 | i++ |
| 258 | continue |
| 259 | } |
| 260 | if c == '`' && i < len(command) { |
| 261 | write(command[i]) |
| 262 | i++ |
| 263 | continue |
| 264 | } |
| 265 | if c == quote { |
| 266 | quote = 0 |
| 267 | } |
| 268 | continue |
| 269 | } |
| 270 | switch c { |
| 271 | case '\'', '"': |
| 272 | quote = c |
| 273 | write(c) |
| 274 | i++ |
| 275 | case '\\', '`': |
| 276 | write(c) |
| 277 | i++ |
| 278 | if i < len(command) { |
| 279 | write(command[i]) |
| 280 | i++ |
| 281 | } |
| 282 | default: |
| 283 | if replacement, next, ok := consumeNullRedirect(command, i, sink); ok { |
| 284 | out.WriteString(replacement) |
| 285 | i = next |
| 286 | continue |
| 287 | } |
| 288 | write(c) |
| 289 | i++ |
| 290 | } |
| 291 | } |
| 292 | return out.String() |
| 293 | } |
| 294 | |
| 295 | func consumeNullRedirect(s string, start int, sink string) (string, int, bool) { |
| 296 | i := start |
| 297 | if i >= len(s) { |
| 298 | return "", start, false |
| 299 | } |
| 300 | if s[i] == '&' { |
| 301 | i++ |
| 302 | if i < len(s) && s[i] == '>' { |
| 303 | i++ |
| 304 | if i < len(s) && s[i] == '>' { |
| 305 | i++ |
| 306 | } |
| 307 | } else { |
| 308 | return "", start, false |
| 309 | } |
| 310 | } else { |
| 311 | for i < len(s) && s[i] >= '0' && s[i] <= '9' { |
| 312 | i++ |
| 313 | } |
| 314 | if i >= len(s) || s[i] != '>' { |
| 315 | return "", start, false |
| 316 | } |
| 317 | i++ |
| 318 | if i < len(s) && s[i] == '>' { |
| 319 | i++ |
| 320 | } |
| 321 | } |
| 322 | opEnd := i |
| 323 | for i < len(s) && (s[i] == ' ' || s[i] == '\t') { |
| 324 | i++ |
| 325 | } |
| 326 | next, ok := consumeNullSink(s, i) |
| 327 | if !ok { |
| 328 | return "", start, false |
| 329 | } |
| 330 | return s[start:opEnd] + sink, next, true |
| 331 | } |
| 332 | |
| 333 | func consumeNullSink(s string, i int) (int, bool) { |
| 334 | for _, sink := range []string{"/dev/null", "$null", "nul"} { |
| 335 | if i+len(sink) > len(s) { |
| 336 | continue |
| 337 | } |
| 338 | got := s[i : i+len(sink)] |
| 339 | if sink == "/dev/null" { |
| 340 | if got != sink { |
| 341 | continue |
| 342 | } |
| 343 | } else if !strings.EqualFold(got, sink) { |
| 344 | continue |
| 345 | } |
| 346 | next := i + len(sink) |
| 347 | if next < len(s) && !isNullRedirectWordEnd(s[next]) { |
| 348 | return next, false |
| 349 | } |
| 350 | return next, true |
| 351 | } |
| 352 | return i, false |
| 353 | } |
| 354 | |
| 355 | func isNullRedirectWordEnd(c byte) bool { |
| 356 | return c == ' ' || c == '\t' || c == '\n' || c == '\r' || strings.ContainsRune(";&|<>)]", rune(c)) |
| 357 | } |
| 358 | |
| 359 | // argv builds the exec argv that runs command under this shell. |
| 360 | func (s Shell) argv(command string) []string { |
| 361 | path := s.Path |
| 362 | if path == "" { |
| 363 | path = s.Kind.String() |
| 364 | } |
| 365 | if s.Kind == ShellPowerShell { |
| 366 | return []string{path, "-NoProfile", "-NonInteractive", "-Command", PowerShellUTF8Script(normalizeNullRedirects(command, "$null"))} |
| 367 | } |
| 368 | return []string{path, "-c", normalizeNullRedirects(command, "/dev/null")} |
| 369 | } |
| 370 | |
| 371 | // SupportsChaining reports whether the shell parses '&&' / '||'. bash does; |
| 372 | // Windows PowerShell 5.1 (powershell.exe) does not — only PowerShell 7+ (pwsh). |
| 373 | func (s Shell) SupportsChaining() bool { |
| 374 | if s.Kind != ShellPowerShell { |
| 375 | return true |
| 376 | } |
| 377 | base := strings.ToLower(pathBase(s.Path)) |
| 378 | return base == "pwsh" || base == "pwsh.exe" |
| 379 | } |
| 380 |