Windows: official port -- UCRT static build, UTF-8 throughout, Low IL sandbox, ncurses TUI, installer; v0.6.0

Build
  * cross build switches to pkgsCross.ucrt64 (shell-win.nix); curl (Schannel),
    winpthreads and ncurses 6.6 are linked statically, so the release is
    cst-agent.exe + busybox.exe (busybox-w32 Unicode) with no extra DLLs
  * windres embeds a manifest with activeCodePage=UTF-8 and a version resource
  * ncurses 6.6 Windows console driver patches (mouse button state, A_DIM,
    wide-char declarations): scripts/patches/
  * scripts/bootstrap_msys2.sh builds the same release natively in MSYS2
    UCRT64; PR #1's MINGW64 notes now point there
  * vendor/tre-regex (musl's TRE) provides <regex.h> on MinGW

UTF-8
  * paths cross the system call boundary as UTF-16 (*W APIs); console code
    pages set to 65001 and restored on exit; files are read and written in
    binary mode
  * child output that is not valid UTF-8 is decoded from the console, OEM or
    ANSI system code page
  * read_file hides CR; edit_file, apply_patch and write_file keep CRLF line
    endings and a UTF-8 BOM

OS layer and processes
  * os_dir_* and cst_fnmatch replace the POSIX-only directory walks in
    subagent, plugins, skills, undo and fs_tools; realpath / path_under and
    symlink rejection work on Windows
  * every child goes through CreateProcessW with its own environment block
    inside a Job Object, so timeouts and Esc end the whole process tree

Sandbox (auto mode, "auto · lowil")
  * run_shell runs with a restricted Low integrity token; the workspace gets
    an inheritable Low label once, the sandbox TEMP is labeled Low, and the
    credentials file gets a no-read-up label
  * drive roots, the profile and system folders are never labeled
  * network commands still ask, since Low IL does not block the network;
    Access denied and MSYS2's 0xc0000142 offer a rerun outside the sandbox
  * /sandbox lists labeled folders, /sandbox reset-labels restores them

TUI
  * raster console fonts are switched to Consolas / NSimSun while running
  * the home logo falls back to text when the console font lacks U+2580
  * mouse drag copy goes to the Windows clipboard

Distribution
  * scripts/install_windows.ps1 installs a Gitea release into
    %LOCALAPPDATA%\Programs\cst-agent and adds it to the user PATH;
    cst-agent-update.cmd reruns it; scripts/release_windows.sh uploads the
    zip with the token taken from the environment
  * scripts/run_windows.bat is gone; docs/README-windows.md is rewritten

Tests
  * new test_lowil, test_win_utf8 and test_os_dir; tests made portable
    (cst_test_util.h)
  * scripts/win_test.sh and scripts/winvm/ run the suite on English and
    Chinese Windows Server VMs as Administrator, a standard user and a
    Chinese user name: 29/29 on all six

src/sandbox_exec.c

@@ -19,6 +19,9 @@
 #elif defined(__APPLE__)
 #define CST_HAVE_SEATBELT 1
 #include <stdint.h>
+#elif defined(_WIN32)
+#include <windows.h>
+#include <sddl.h>
 #endif
 
 #if defined(__linux__) && (defined(__x86_64__) || defined(__aarch64__))
@@ -864,6 +867,341 @@ static int sc_probe(void) {
 
 #endif /* CST_HAVE_SECCOMP */
 
+/* --- Windows: Low integrity level ----------------------------------------- */
+#ifdef _WIN32
+
+#define LW_LABEL "S:(ML;OICI;NW;;;LW)"
+#define LW_RECORD "sandbox-labels"
+
+/* Same user, no admin privileges, Low IL. No LUA_TOKEN: a deny-only
+ * Administrators group cannot open an admin's (SSH) window station and the
+ * child fails in DLL init; the integrity check does not need it. */
+static HANDLE lw_token(void) {
+  HANDLE self = NULL, tok = NULL;
+  if (!OpenProcessToken(GetCurrentProcess(),
+                        TOKEN_DUPLICATE | TOKEN_QUERY | TOKEN_ADJUST_DEFAULT |
+                            TOKEN_ASSIGN_PRIMARY,
+                        &self))
+    return NULL;
+  BOOL ok = CreateRestrictedToken(self, DISABLE_MAX_PRIVILEGE, 0, NULL, 0,
+                                  NULL, 0, NULL, &tok);
+  CloseHandle(self);
+  if (!ok)
+    return NULL;
+  PSID low = NULL;
+  if (!ConvertStringSidToSidW(L"S-1-16-4096", &low)) {
+    CloseHandle(tok);
+    return NULL;
+  }
+  TOKEN_MANDATORY_LABEL tml;
+  memset(&tml, 0, sizeof(tml));
+  tml.Label.Sid = low;
+  tml.Label.Attributes = SE_GROUP_INTEGRITY;
+  ok = SetTokenInformation(tok, TokenIntegrityLevel, &tml,
+                           (DWORD)(sizeof(tml) + GetLengthSid(low)));
+  LocalFree(low);
+  if (!ok) {
+    CloseHandle(tok);
+    return NULL;
+  }
+  return tok;
+}
+
+static int lw_record_path(char *out, size_t n) {
+  char dir[OS_PATH_MAX];
+  if (os_config_dir(dir, sizeof(dir)) != 0)
+    return -1;
+  return snprintf(out, n, "%s/%s", dir, LW_RECORD) < (int)n ? 0 : -1;
+}
+
+static char *lw_read_record(void) {
+  char path[OS_PATH_MAX];
+  if (lw_record_path(path, sizeof(path)) != 0)
+    return NULL;
+  FILE *f = fopen(path, "rb");
+  if (!f)
+    return NULL;
+  size_t cap = 4096, len = 0;
+  char *s = malloc(cap);
+  size_t k;
+  while (s && (k = fread(s + len, 1, cap - len - 1, f)) > 0) {
+    len += k;
+    if (cap - len < 2) {
+      char *g = realloc(s, cap * 2);
+      if (!g) {
+        free(s);
+        s = NULL;
+        break;
+      }
+      s = g;
+      cap *= 2;
+    }
+  }
+  fclose(f);
+  if (s)
+    s[len] = 0;
+  return s;
+}
+
+/* dir is a recorded directory or inside one (the label is inherited). */
+static int lw_recorded(const char *dir) {
+  char *s = lw_read_record();
+  int found = 0;
+  for (char *line = s; line && *line && !found;) {
+    char *nl = strchr(line, '\n');
+    if (nl)
+      *nl = 0;
+    char *tab = strchr(line, '\t');
+    if (tab)
+      *tab = 0;
+    found = line[0] && os_path_under(line, dir);
+    line = nl ? nl + 1 : NULL;
+  }
+  free(s);
+  return found;
+}
+
+static int lw_record_add(const char *dir, const char *old_sddl) {
+  char path[OS_PATH_MAX];
+  if (lw_record_path(path, sizeof(path)) != 0)
+    return -1;
+  FILE *f = fopen(path, "ab");
+  if (!f)
+    return -1;
+  fprintf(f, "%s\t%s\n", dir, old_sddl);
+  return fclose(f) == 0 ? 0 : -1;
+}
+
+static int lw_same_dir(const char *a, const char *b) {
+  return a && b && a[0] && b[0] && os_path_under(a, b) && os_path_under(b, a);
+}
+
+/* An environment directory in the form os_realpath gives the workspace
+ * (long names, '/'), or NULL. */
+static const char *lw_env_dir(const char *name, char *buf, size_t n) {
+  const char *v = getenv(name);
+  if (!v || !v[0] || os_realpath(v, buf, n) != 0)
+    return NULL;
+  os_path_norm_slashes(buf);
+  return buf;
+}
+
+/* Labeling a whole drive, the profile or system folders would open far more
+ * than a project to every sandboxed command. */
+static int lw_refused(const char *dir) {
+  size_t n = strlen(dir);
+  while (n > 0 && (dir[n - 1] == '/' || dir[n - 1] == '\\'))
+    n--;
+  if (n <= 2)
+    return 1;
+  static const char *const SELF[] = {"USERPROFILE", "APPDATA",
+                                     "LOCALAPPDATA", "TEMP"};
+  static const char *const TREE[] = {"SystemRoot", "ProgramFiles",
+                                     "ProgramFiles(x86)", "ProgramData"};
+  char buf[OS_PATH_MAX];
+  for (size_t i = 0; i < sizeof(SELF) / sizeof(SELF[0]); i++)
+    if (lw_same_dir(lw_env_dir(SELF[i], buf, sizeof(buf)), dir))
+      return 1;
+  for (size_t i = 0; i < sizeof(TREE) / sizeof(TREE[0]); i++) {
+    const char *v = lw_env_dir(TREE[i], buf, sizeof(buf));
+    if (v && os_path_under(v, dir))
+      return 1;
+  }
+  return 0;
+}
+
+static int lw_prepare(const char *ws, cst_sandbox_plan_t *p) {
+  static int creds_done, tmp_done;
+  char buf[OS_PATH_MAX + 256];
+  if (!ws || !ws[0])
+    return -1;
+  if (!creds_done) {
+    /* files saved by older versions have no no-read-up label yet */
+    char dir[OS_PATH_MAX];
+    if (os_config_dir(dir, sizeof(dir)) == 0 &&
+        snprintf(buf, sizeof(buf), "%s/credentials", dir) < (int)sizeof(buf)) {
+      os_stat_t st;
+      if (os_lstat(buf, &st) != 0 || os_chmod_private(buf) == 0)
+        creds_done = 1;
+    }
+  }
+  char tmp[OS_PATH_MAX];
+  if (os_temp_dir(tmp, sizeof(tmp)) != 0 ||
+      snprintf(buf, sizeof(buf), "%s/cst-agent-sandbox", tmp) >=
+          (int)sizeof(tmp))
+    return -1;
+  memcpy(tmp, buf, strlen(buf) + 1);
+  if (!tmp_done) {
+    os_mkdir_p(tmp, 0700);
+    if (os_win_set_label(tmp, LW_LABEL) != 0)
+      return -1;
+    tmp_done = 1;
+  }
+  if (!lw_recorded(ws)) {
+    char old[512];
+    if (lw_refused(ws) || os_win_get_label(ws, old, sizeof(old)) != 0 ||
+        os_win_set_label(ws, LW_LABEL) != 0)
+      return -1;
+    lw_record_add(ws, old);
+    snprintf(buf, sizeof(buf),
+             "[cst: sandbox: labeled %s Low integrity so sandboxed commands "
+             "can write there; /sandbox reset-labels undoes it]\n",
+             ws);
+    p->note = strdup(buf);
+  }
+  HANDLE tok = lw_token();
+  if (!tok) {
+    free(p->note);
+    p->note = NULL;
+    return -1;
+  }
+  p->token = tok;
+  for (char *c = tmp; *c; c++)
+    if (*c == '/')
+      *c = '\\';
+  p->tmpdir = strdup(tmp);
+  return p->tmpdir ? 0 : -1;
+}
+
+static int lw_run(const char *ws, const char *cmd, size_t max_out,
+                  const cst_sandbox_plan_t *p, os_run_result_t *r) {
+  size_t tl = strlen(p->tmpdir) + 8;
+  char *te = malloc(tl), *tm = malloc(tl);
+  int rc = -1;
+  if (te && tm) {
+    snprintf(te, tl, "TEMP=%s", p->tmpdir);
+    snprintf(tm, tl, "TMP=%s", p->tmpdir);
+    const char *env[] = {te, tm, NULL};
+    rc = os_run_shell_token(ws, cmd, max_out, r, p->token, env);
+  }
+  free(te);
+  free(tm);
+  if (rc == 0 && p->note) {
+    size_t nl = strlen(p->note);
+    char *o = malloc(nl + r->out_len + 1);
+    if (o) {
+      memcpy(o, p->note, nl);
+      if (r->out)
+        memcpy(o + nl, r->out, r->out_len);
+      o[nl + r->out_len] = 0;
+      free(r->out);
+      r->out = o;
+      r->out_len += nl;
+    }
+  }
+  return rc;
+}
+
+#endif /* _WIN32 */
+
+char *cst_sandbox_labels(void) {
+#ifdef _WIN32
+  char *s = lw_read_record();
+  if (!s)
+    return NULL;
+  size_t o = 0;
+  for (char *line = s; *line;) {
+    char *nl = strchr(line, '\n');
+    size_t len = nl ? (size_t)(nl - line) : strlen(line);
+    size_t path = strcspn(line, "\t\n");
+    if (path) {
+      memmove(s + o, line, path);
+      o += path;
+      s[o++] = '\n';
+    }
+    line += len + (nl ? 1 : 0);
+  }
+  s[o] = 0;
+  if (!o) {
+    free(s);
+    return NULL;
+  }
+  return s;
+#else
+  return NULL;
+#endif
+}
+
+int cst_sandbox_reset_labels(char **report) {
+  if (report)
+    *report = NULL;
+#ifdef _WIN32
+  char *s = lw_read_record();
+  size_t cap = 256, len = 0;
+  char *rep = malloc(cap), *keep = NULL;
+  size_t kcap = 0, klen = 0;
+  int ok = 0, bad = 0;
+  if (rep)
+    rep[0] = 0;
+  for (char *line = s; line && *line;) {
+    char *nl = strchr(line, '\n');
+    if (nl)
+      *nl = 0;
+    char *tab = strchr(line, '\t');
+    const char *old = tab ? tab + 1 : "S:";
+    if (tab)
+      *tab = 0;
+    if (line[0]) {
+      os_stat_t st;
+      int gone = os_lstat(line, &st) != 0;
+      int done = gone || os_win_set_label(line, old[0] ? old : "S:") == 0;
+      char msg[OS_PATH_MAX + 64];
+      int m = snprintf(msg, sizeof(msg), "%s %s\n",
+                       gone ? "gone    " : done ? "restored" : "FAILED  ",
+                       line);
+      if (m > 0 && rep) {
+        while (len + (size_t)m + 1 > cap) {
+          char *g = realloc(rep, cap *= 2);
+          if (!g)
+            break;
+          rep = g;
+        }
+        if (len + (size_t)m + 1 <= cap) {
+          memcpy(rep + len, msg, (size_t)m + 1);
+          len += (size_t)m;
+        }
+      }
+      if (done) {
+        ok++;
+      } else {
+        bad++;
+        size_t need = strlen(line) + strlen(old) + 3;
+        if (klen + need + 1 > kcap) {
+          char *g = realloc(keep, kcap = (klen + need + 1) * 2);
+          if (g)
+            keep = g;
+        }
+        if (keep && klen + need + 1 <= kcap)
+          klen += (size_t)snprintf(keep + klen, kcap - klen, "%s\t%s\n",
+                                   line, old);
+      }
+    }
+    line = nl ? nl + 1 : NULL;
+  }
+  free(s);
+  char path[OS_PATH_MAX];
+  if (lw_record_path(path, sizeof(path)) == 0) {
+    if (klen) {
+      FILE *f = fopen(path, "wb");
+      if (f) {
+        fwrite(keep, 1, klen, f);
+        fclose(f);
+      }
+    } else {
+      remove(path);
+    }
+  }
+  free(keep);
+  if (report)
+    *report = rep;
+  else
+    free(rep);
+  return bad ? -1 : ok;
+#else
+  return 0;
+#endif
+}
+
 /* --- common --------------------------------------------------------------- */
 
 int cst_sandbox_probe(void) {
@@ -891,6 +1229,15 @@ int cst_sandbox_probe(void) {
 #endif
 #ifdef CST_HAVE_SEATBELT
   kind = CST_SANDBOX_SEATBELT;
+#endif
+#ifdef _WIN32
+  if (!e || strcmp(e, "lowil") == 0) {
+    HANDLE tok = lw_token();
+    if (tok) {
+      CloseHandle(tok);
+      kind = CST_SANDBOX_LOWIL;
+    }
+  }
 #endif
   (void)want_ll;
   (void)want_sc;
@@ -917,6 +1264,8 @@ const char *cst_sandbox_name(int kind) {
     return "seatbelt";
   case CST_SANDBOX_SECCOMP:
     return "seccomp";
+  case CST_SANDBOX_LOWIL:
+    return "lowil";
   default:
     return "none";
   }
@@ -939,6 +1288,10 @@ int cst_sandbox_prepare(const char *workspace, const char *tmpdir,
 #ifdef CST_HAVE_SECCOMP
   if (kind == CST_SANDBOX_SECCOMP)
     rc = sc_prepare(workspace, tmpdir, plan);
+#endif
+#ifdef _WIN32
+  if (kind == CST_SANDBOX_LOWIL && (rc = lw_prepare(workspace, plan)) != 0)
+    cst_sandbox_release(plan);
 #endif
   (void)workspace;
   (void)tmpdir;
@@ -988,6 +1341,15 @@ void cst_sandbox_release(cst_sandbox_plan_t *plan) {
 #ifdef CST_HAVE_SECCOMP
   sc_free(plan->sc);
 #endif
+#ifdef _WIN32
+  if (plan->token)
+    CloseHandle(plan->token);
+#endif
+  plan->token = NULL;
+  free(plan->tmpdir);
+  plan->tmpdir = NULL;
+  free(plan->note);
+  plan->note = NULL;
   plan->sc = NULL;
   free(plan->profile);
   plan->profile = NULL;
@@ -1004,6 +1366,12 @@ int cst_sandbox_run_shell(const char *workspace, const char *cmd,
   if (cst_sandbox_prepare(workspace, tmp, &plan) != 0) {
     memset(r, 0, sizeof(*r));
     const char *msg = "[cst: sandbox unavailable; command not run]\n";
+#ifdef _WIN32
+    if (workspace && !lw_recorded(workspace) && lw_refused(workspace))
+      msg = "[cst: sandbox: will not label a drive root, the profile or a "
+            "system folder writable; command not run. Start cst-agent in a "
+            "project folder]\n";
+#endif
     r->out = malloc(strlen(msg) + 1);
     if (r->out) {
       memcpy(r->out, msg, strlen(msg) + 1);
@@ -1012,8 +1380,12 @@ int cst_sandbox_run_shell(const char *workspace, const char *cmd,
     r->exit_code = 126;
     return 0;
   }
+#ifdef _WIN32
+  int rc = lw_run(workspace, cmd, max_out, &plan, r);
+#else
   int rc = os_run_shell_ex(workspace, cmd, max_out, r, cst_sandbox_enter,
                            &plan);
+#endif
   cst_sandbox_release(&plan);
   return rc;
 }
@@ -1039,6 +1411,11 @@ int cst_sandbox_blocked(const char *out, size_t n, int exit_code) {
       "权限不够", "不允许的操作", "只读文件系统", "權限不足",
       "拒絕不符權限的操作", "許可がありません", "Keine Berechtigung",
       "Permission non accord", "Permiso denegado", "Отказано в доступе",
+      /* Windows ERROR_ACCESS_DENIED from cmd, PowerShell and Win32 tools */
+      "Access is denied", "Access to the path", "UnauthorizedAccess",
+      "拒绝访问", "存取被拒", "Zugriff verweigert", "Accès refusé",
+      /* Cygwin/MSYS2 programs cannot initialize at Low IL */
+      "DLL initialization routine failed", "0xc0000142",
   };
   for (size_t i = 0; i < sizeof(SIGNS) / sizeof(SIGNS[0]); i++)
     if (has(out, n, SIGNS[i]))