CST-agent/src/clipboard.c

#include "cst_clipboard.h"
#include "cst_attach.h"
#include "os_compat.h"

#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#ifdef _WIN32
#include <windows.h>
#else
#include <unistd.h>
#endif

static void set_err(char *err, size_t err_sz, const char *msg) {
  if (err && err_sz)
    snprintf(err, err_sz, "%s", msg);
}

#ifndef _WIN32
/* PATH lookup without shelling out: cheap enough for a capability probe. */
static int on_path(const char *name) {
  const char *path = getenv("PATH");
  if (!path)
    return 0;
  for (const char *p = path;;) {
    const char *colon = strchr(p, ':');
    size_t len = colon ? (size_t)(colon - p) : strlen(p);
    char cand[4096];
    if (len + strlen(name) + 2 < sizeof(cand)) {
      if (len == 0)
        snprintf(cand, sizeof(cand), "./%s", name);
      else
        snprintf(cand, sizeof(cand), "%.*s/%s", (int)len, p, name);
      if (access(cand, X_OK) == 0)
        return 1;
    }
    if (!colon)
      break;
    p = colon + 1;
  }
  return 0;
}
#endif

int cst_clipboard_available(char *why, size_t why_sz) {
  if (why && why_sz)
    why[0] = 0;
#ifdef _WIN32
  return 0; /* the Win32 clipboard API is always there */
#elif defined(__APPLE__)
  return 0; /* pbpaste / pbcopy ship with the OS */
#else
  static const char *const helpers[] = {"wl-paste", "wl-copy", "xclip", NULL};
  for (int i = 0; helpers[i]; i++)
    if (on_path(helpers[i]))
      return 0;
  if (why && why_sz)
    snprintf(why, why_sz,
             "no clipboard helper on PATH (install wl-clipboard or xclip)");
  return -1;
#endif
}

static void put_le32(unsigned char *p, unsigned long v) {
  p[0] = (unsigned char)(v & 0xff);
  p[1] = (unsigned char)((v >> 8) & 0xff);
  p[2] = (unsigned char)((v >> 16) & 0xff);
  p[3] = (unsigned char)((v >> 24) & 0xff);
}

static void put_be32(unsigned char *p, unsigned long v) {
  p[0] = (unsigned char)((v >> 24) & 0xff);
  p[1] = (unsigned char)((v >> 16) & 0xff);
  p[2] = (unsigned char)((v >> 8) & 0xff);
  p[3] = (unsigned char)(v & 0xff);
}

static unsigned long get_le32(const unsigned char *p) {
  return (unsigned long)p[0] | (unsigned long)p[1] << 8 |
         (unsigned long)p[2] << 16 | (unsigned long)p[3] << 24;
}

static unsigned long crc32_update(unsigned long crc, const unsigned char *p,
                                  size_t n) {
  static unsigned long table[256];
  static int ready;
  if (!ready) {
    for (unsigned long i = 0; i < 256; i++) {
      unsigned long c = i;
      for (int k = 0; k < 8; k++)
        c = c & 1 ? 0xedb88320UL ^ (c >> 1) : c >> 1;
      table[i] = c;
    }
    ready = 1;
  }
  crc ^= 0xffffffffUL;
  for (size_t i = 0; i < n; i++)
    crc = table[(crc ^ p[i]) & 0xff] ^ (crc >> 8);
  return crc ^ 0xffffffffUL;
}

static unsigned char *png_chunk(unsigned char *o, const char *type,
                                const unsigned char *data, size_t n) {
  put_be32(o, (unsigned long)n);
  memcpy(o + 4, type, 4);
  if (n)
    memcpy(o + 8, data, n);
  put_be32(o + 8 + n, crc32_update(0, o + 4, n + 4));
  return o + 12 + n;
}

/* RGB rows (filter byte 0 each) in stored deflate blocks: no compressor in
 * the tree, and clipboard screenshots stay well under the attach cap. */
static char *png_from_raw(const unsigned char *raw, size_t raw_n, long w,
                          long h, size_t *n) {
  size_t blocks = raw_n / 65535 + 1;
  size_t z_n = 2 + raw_n + blocks * 5 + 4;
  size_t total = 8 + (12 + 13) + (12 + z_n) + 12;
  unsigned char *out = malloc(total);
  unsigned char *z = malloc(z_n);
  if (!out || !z) {
    free(out);
    free(z);
    return NULL;
  }
  unsigned char *q = z;
  *q++ = 0x78;
  *q++ = 0x01;
  unsigned long a = 1, b = 0;
  size_t left = raw_n, pos = 0;
  do {
    size_t len = left > 65535 ? 65535 : left;
    *q++ = left == len ? 1 : 0;
    q[0] = (unsigned char)(len & 0xff);
    q[1] = (unsigned char)(len >> 8);
    q[2] = (unsigned char)(~len & 0xff);
    q[3] = (unsigned char)((~len >> 8) & 0xff);
    q += 4;
    memcpy(q, raw + pos, len);
    for (size_t i = 0; i < len; i++) {
      a = (a + raw[pos + i]) % 65521;
      b = (b + a) % 65521;
    }
    q += len;
    pos += len;
    left -= len;
  } while (left);
  put_be32(q, b << 16 | a);
  q += 4;

  unsigned char ihdr[13];
  put_be32(ihdr, (unsigned long)w);
  put_be32(ihdr + 4, (unsigned long)h);
  ihdr[8] = 8; /* bit depth */
  ihdr[9] = 2; /* RGB */
  ihdr[10] = ihdr[11] = ihdr[12] = 0;
  unsigned char *o = out;
  memcpy(o, "\x89PNG\r\n\x1a\n", 8);
  o = png_chunk(o + 8, "IHDR", ihdr, sizeof(ihdr));
  o = png_chunk(o, "IDAT", z, (size_t)(q - z));
  o = png_chunk(o, "IEND", NULL, 0);
  free(z);
  *n = (size_t)(o - out);
  return (char *)out;
}

/* CF_DIB is a BMP without its 14-byte file header; the pixel offset depends
 * on the header size, BI_BITFIELDS masks and the color table. */
char *cst_dib_to_image(const void *dib_v, size_t sz, size_t *n) {
  const unsigned char *dib = dib_v;
  if (!dib || sz < 40)
    return NULL;
  unsigned long hsize = get_le32(dib);
  long w = (long)(int)get_le32(dib + 4);
  long hh = (long)(int)get_le32(dib + 8);
  unsigned bits = (unsigned)(dib[14] | dib[15] << 8);
  unsigned long comp = get_le32(dib + 16);
  unsigned long used = get_le32(dib + 32);
  if (hsize < 40 || hsize > sz)
    return NULL;
  size_t off = hsize;
  if (hsize == 40 && comp == 3 /* BI_BITFIELDS */)
    off += 12;
  size_t colors = used;
  if (!colors && bits <= 8)
    colors = (size_t)1 << bits;
  if (colors > 256)
    return NULL;
  off += colors * 4;
  if (off > sz)
    return NULL;

  long h = hh < 0 ? -hh : hh;
  if ((bits == 24 || bits == 32) && (comp == 0 || comp == 3) && w > 0 &&
      h > 0 && w <= 32768 && h <= 32768) {
    size_t stride = ((size_t)w * bits / 8 + 3) & ~(size_t)3;
    size_t raw_n = (size_t)h * (1 + (size_t)w * 3);
    if (stride * (size_t)h <= sz - off && raw_n < CST_ATTACH_MAX_BYTES) {
      unsigned char *raw = malloc(raw_n);
      if (!raw)
        return NULL;
      size_t bpp = bits / 8;
      for (long y = 0; y < h; y++) {
        long src_y = hh > 0 ? h - 1 - y : y; /* positive height = bottom-up */
        const unsigned char *s = dib + off + (size_t)src_y * stride;
        unsigned char *d = raw + (size_t)y * (1 + (size_t)w * 3);
        *d++ = 0;
        for (long x = 0; x < w; x++, s += bpp) {
          *d++ = s[2];
          *d++ = s[1];
          *d++ = s[0];
        }
      }
      char *png = png_from_raw(raw, raw_n, w, h, n);
      free(raw);
      return png;
    }
  }

  char *out = malloc(14 + sz);
  if (!out)
    return NULL;
  unsigned char *hd = (unsigned char *)out;
  hd[0] = 'B';
  hd[1] = 'M';
  put_le32(hd + 2, (unsigned long)(14 + sz));
  put_le32(hd + 6, 0);
  put_le32(hd + 10, (unsigned long)(14 + off));
  memcpy(out + 14, dib, sz);
  *n = 14 + sz;
  return out;
}

#ifdef _WIN32

int cst_clipboard_image(char **data, size_t *n, char *err, size_t err_sz) {
  *data = NULL;
  *n = 0;
  UINT png = RegisterClipboardFormatA("PNG");
  if (!OpenClipboard(NULL)) {
    set_err(err, err_sz, "could not open the clipboard");
    return -1;
  }
  HANDLE h = NULL;
  int is_png = 0;
  if (png && IsClipboardFormatAvailable(png)) {
    h = GetClipboardData(png);
    is_png = 1;
  } else if (IsClipboardFormatAvailable(CF_DIB)) {
    h = GetClipboardData(CF_DIB);
  }
  const unsigned char *p = h ? GlobalLock(h) : NULL;
  if (!p) {
    CloseClipboard();
    set_err(err, err_sz, "no image on the clipboard");
    return -1;
  }
  size_t sz = (size_t)GlobalSize(h);
  char *out = NULL;
  if (sz > CST_ATTACH_MAX_BYTES) {
    set_err(err, err_sz, "clipboard image is too large");
  } else if (is_png) {
    out = malloc(sz ? sz : 1);
    if (out) {
      memcpy(out, p, sz);
      *n = sz;
    }
  } else {
    out = cst_dib_to_image(p, sz, n);
    if (!out)
      set_err(err, err_sz, "clipboard bitmap is malformed");
  }
  GlobalUnlock(h);
  CloseClipboard();
  if (!out)
    return -1;
  *data = out;
  return 0;
}

#else

/* Runs cmd (stderr already redirected by the caller); 127 = not installed. */
static int run_bytes(const char *cmd, char **data, size_t *n) {
  os_run_result_t r;
  memset(&r, 0, sizeof(r));
  if (os_run_shell_c(NULL, cmd, CST_ATTACH_MAX_BYTES + 1, &r) != 0) {
    os_run_result_free(&r);
    return -1;
  }
  if (r.exit_code != 0 || r.out_len == 0) {
    int code = r.exit_code == 127 ? 127 : -1;
    os_run_result_free(&r);
    return code;
  }
  *data = r.out;
  *n = r.out_len;
  return 0;
}

static int type_ok(const char *s, size_t n) {
  if (n < 7 || n > 63 || strncmp(s, "image/", 6) != 0)
    return 0;
  for (size_t i = 0; i < n; i++)
    if (!isalnum((unsigned char)s[i]) && !strchr("/.+-", s[i]))
      return 0;
  return 1;
}

/* Best image MIME type from a newline-separated list: PNG first. */
static int pick_type(const char *list, size_t len, char *out, size_t out_sz) {
  out[0] = 0;
  size_t i = 0;
  while (i < len) {
    size_t j = i;
    while (j < len && list[j] != '\n' && list[j] != '\r')
      j++;
    if (type_ok(list + i, j - i)) {
      int is_png = j - i == 9 && strncmp(list + i, "image/png", 9) == 0;
      if (is_png || !out[0])
        snprintf(out, out_sz, "%.*s", (int)(j - i), list + i);
      if (is_png)
        break;
    }
    i = j + 1;
  }
  return out[0] ? 0 : -1;
}

static int via_lister(const char *list_cmd, const char *get_fmt,
                      const char *tool, char **data, size_t *n, char *err,
                      size_t err_sz) {
  char *types = NULL;
  size_t tn = 0;
  int rc = run_bytes(list_cmd, &types, &tn);
  if (rc == 127) {
    char msg[96];
    snprintf(msg, sizeof(msg), "reading the clipboard needs %s", tool);
    set_err(err, err_sz, msg);
    return -1;
  }
  char type[64];
  int ok = rc == 0 && pick_type(types, tn, type, sizeof(type)) == 0;
  free(types);
  if (!ok) {
    set_err(err, err_sz, "no image on the clipboard");
    return -1;
  }
  char cmd[256];
  snprintf(cmd, sizeof(cmd), get_fmt, type);
  if (run_bytes(cmd, data, n) != 0) {
    set_err(err, err_sz, "could not read the clipboard image");
    return -1;
  }
  return 0;
}

#ifdef __APPLE__
static int mac_image(char **data, size_t *n, char *err, size_t err_sz) {
  int rc = run_bytes("pngpaste - 2>/dev/null", data, n);
  if (rc == 0)
    return 0;
  char path[1024];
  int fd = os_mkstemp(path, sizeof(path), "cst-clip");
  if (fd < 0) {
    set_err(err, err_sz, "could not create a temp file");
    return -1;
  }
  close(fd);
  char cmd[1600];
  snprintf(cmd, sizeof(cmd),
           "osascript -e 'set f to open for access (POSIX file \"%s\") with "
           "write permission' -e 'set eof f to 0' -e 'write (the clipboard as "
           "\xc2\xabclass PNGf\xc2\xbb) to f' -e 'close access f' "
           ">/dev/null 2>&1",
           path);
  os_run_result_t r;
  memset(&r, 0, sizeof(r));
  int ran = os_run_shell_c(NULL, cmd, 4096, &r);
  int code = r.exit_code;
  os_run_result_free(&r);
  char *buf = NULL;
  size_t len = 0;
  if (ran == 0 && code == 0) {
    FILE *f = fopen(path, "rb");
    if (f) {
      char chunk[65536];
      size_t got;
      while ((got = fread(chunk, 1, sizeof(chunk), f)) > 0 &&
             len <= CST_ATTACH_MAX_BYTES) {
        char *nb = realloc(buf, len + got);
        if (!nb)
          break;
        buf = nb;
        memcpy(buf + len, chunk, got);
        len += got;
      }
      fclose(f);
    }
  }
  remove(path);
  if (!buf || !len) {
    free(buf);
    set_err(err, err_sz, "no image on the clipboard");
    return -1;
  }
  *data = buf;
  *n = len;
  return 0;
}
#endif

int cst_clipboard_image(char **data, size_t *n, char *err, size_t err_sz) {
  *data = NULL;
  *n = 0;
#ifdef __APPLE__
  return mac_image(data, n, err, err_sz);
#else
  const char *wl = getenv("WAYLAND_DISPLAY");
  if (wl && *wl)
    return via_lister("wl-paste --list-types 2>/dev/null",
                      "wl-paste --no-newline --type '%s' 2>/dev/null",
                      "wl-clipboard (wl-paste)", data, n, err, err_sz);
  const char *x = getenv("DISPLAY");
  if (x && *x)
    return via_lister("xclip -selection clipboard -t TARGETS -o 2>/dev/null",
                      "xclip -selection clipboard -t '%s' -o 2>/dev/null",
                      "xclip", data, n, err, err_sz);
  set_err(err, err_sz, "no clipboard here (no Wayland or X11 display)");
  return -1;
#endif
}

#endif

/* --- text clipboard ------------------------------------------------------ */

#ifdef _WIN32

int cst_clipboard_text(char **data, size_t *n, char *err, size_t err_sz) {
  *data = NULL;
  *n = 0;
  if (!IsClipboardFormatAvailable(CF_UNICODETEXT) || !OpenClipboard(NULL)) {
    set_err(err, err_sz, "no text on the clipboard");
    return -1;
  }
  HANDLE h = GetClipboardData(CF_UNICODETEXT);
  const wchar_t *w = h ? GlobalLock(h) : NULL;
  if (!w) {
    if (h)
      GlobalUnlock(h);
    CloseClipboard();
    set_err(err, err_sz, "no text on the clipboard");
    return -1;
  }
  char *utf8 = os_wide_to_utf8(w);
  size_t len = utf8 ? strlen(utf8) : 0;
  GlobalUnlock(h);
  CloseClipboard();
  if (!utf8 || !len) {
    free(utf8);
    set_err(err, err_sz, "no text on the clipboard");
    return -1;
  }
  if (len > CST_CLIPBOARD_TEXT_MAX) {
    free(utf8);
    set_err(err, err_sz, "clipboard text is too large");
    return -1;
  }
  *data = utf8;
  *n = len;
  return 0;
}

int cst_clipboard_set_text(const char *text, size_t n, char *err,
                           size_t err_sz) {
  if (!text || os_clipboard_set(text, n) != 0) {
    set_err(err, err_sz, "could not put text on the clipboard");
    return -1;
  }
  return 0;
}

#else

/* stdout of a clipboard reader, capped and NUL-terminated. */
static int clip_read(const char *cmd, const char *tool, char **data, size_t *n,
                     char *err, size_t err_sz) {
  os_run_result_t r;
  memset(&r, 0, sizeof(r));
  if (os_run_shell_c(NULL, cmd, CST_CLIPBOARD_TEXT_MAX + 1, &r) != 0) {
    os_run_result_free(&r);
    set_err(err, err_sz, "could not read the clipboard");
    return -1;
  }
  if (r.exit_code != 0 || r.out_len == 0) {
    int missing = r.exit_code == 127;
    os_run_result_free(&r);
    if (missing) {
      char msg[96];
      snprintf(msg, sizeof(msg), "reading the clipboard needs %s", tool);
      set_err(err, err_sz, msg);
    } else {
      set_err(err, err_sz, "no text on the clipboard");
    }
    return -1;
  }
  if (r.out_len > CST_CLIPBOARD_TEXT_MAX) {
    os_run_result_free(&r);
    set_err(err, err_sz, "clipboard text is too large");
    return -1;
  }
  char *copy = malloc(r.out_len + 1);
  if (!copy) {
    os_run_result_free(&r);
    set_err(err, err_sz, "out of memory");
    return -1;
  }
  memcpy(copy, r.out, r.out_len);
  copy[r.out_len] = 0;
  os_run_result_free(&r);
  *data = copy;
  *n = r.out_len;
  return 0;
}

int cst_clipboard_text(char **data, size_t *n, char *err, size_t err_sz) {
  *data = NULL;
  *n = 0;
#ifdef __APPLE__
  return clip_read("pbpaste 2>/dev/null", "pbpaste", data, n, err, err_sz);
#else
  const char *wl = getenv("WAYLAND_DISPLAY");
  if (wl && *wl)
    return clip_read("wl-paste --type text/plain --no-newline 2>/dev/null",
                     "wl-clipboard (wl-paste)", data, n, err, err_sz);
  const char *x = getenv("DISPLAY");
  if (x && *x)
    return clip_read("xclip -selection clipboard -o 2>/dev/null", "xclip",
                     data, n, err, err_sz);
  set_err(err, err_sz, "no clipboard here (no Wayland or X11 display)");
  return -1;
#endif
}

int cst_clipboard_set_text(const char *text, size_t n, char *err,
                           size_t err_sz) {
  if (!text)
    return -1;
  if (n > CST_CLIPBOARD_TEXT_MAX) {
    set_err(err, err_sz, "text is too large for the clipboard");
    return -1;
  }
  const char *fmt = NULL, *tool = NULL;
#ifdef __APPLE__
  fmt = "pbcopy < '%s'";
  tool = "pbcopy";
#else
  if (getenv("WAYLAND_DISPLAY")) {
    fmt = "wl-copy < '%s'";
    tool = "wl-clipboard (wl-copy)";
  } else if (getenv("DISPLAY")) {
    fmt = "xclip -selection clipboard -i < '%s'";
    tool = "xclip";
  }
#endif
  if (!fmt) {
    set_err(err, err_sz, "no clipboard here (no Wayland or X11 display)");
    return -1;
  }
  char tmp[OS_PATH_MAX];
  int fd = os_mkstemp(tmp, sizeof(tmp), "cst-clip");
  if (fd < 0) {
    set_err(err, err_sz, "could not create a temporary file");
    return -1;
  }
  FILE *fp = fdopen(fd, "wb");
  int ok = fp && fwrite(text, 1, n, fp) == n && fclose(fp) == 0;
  if (!ok) {
    if (fp)
      fclose(fp);
    remove(tmp);
    set_err(err, err_sz, "could not write the text");
    return -1;
  }
  char cmd[OS_PATH_MAX + 64];
  snprintf(cmd, sizeof(cmd), fmt, tmp);
  os_run_result_t r;
  memset(&r, 0, sizeof(r));
  int rc = os_run_shell_c(NULL, cmd, 4096, &r);
  int code = r.exit_code;
  os_run_result_free(&r);
  remove(tmp);
  if (rc != 0 || code != 0) {
    char msg[96];
    snprintf(msg, sizeof(msg), "writing the clipboard needs %s", tool);
    set_err(err, err_sz, msg);
    return -1;
  }
  return 0;
}

#endif

static int hexval(int c) {
  if (c >= '0' && c <= '9')
    return c - '0';
  if (c >= 'a' && c <= 'f')
    return c - 'a' + 10;
  if (c >= 'A' && c <= 'F')
    return c - 'A' + 10;
  return -1;
}

/* file://[host]/path -> /path, percent-decoded; 0 on success. */
static int from_file_uri(char *s) {
  const char *p = s + 7;
  const char *slash = strchr(p, '/');
  if (!slash)
    return -1;
  if (slash != p && !(slash - p == 9 && strncmp(p, "localhost", 9) == 0))
    return -1;
  char *o = s;
  for (const char *q = slash; *q; q++) {
    if (*q == '%' && hexval(q[1]) >= 0 && hexval(q[2]) >= 0) {
      *o++ = (char)(hexval(q[1]) * 16 + hexval(q[2]));
      q += 2;
    } else {
      *o++ = *q;
    }
  }
  *o = 0;
#ifdef _WIN32
  if (s[0] == '/' && isalpha((unsigned char)s[1]) && s[2] == ':')
    memmove(s, s + 1, strlen(s));
#endif
  return s[0] ? 0 : -1;
}

static int is_space(char c) {
  return c == ' ' || c == '\t' || c == '\r' || c == '\n';
}

int cst_paste_paths(const char *text, size_t len,
                    char out[][CST_PASTE_PATH_MAX], int max) {
  int n = 0;
  size_t i = 0;
  while (i < len) {
    while (i < len && is_space(text[i]))
      i++;
    if (i >= len)
      break;
    if (n >= max)
      return -1;
    char *tok = out[n];
    size_t k = 0;
    char q = 0;
    while (i < len) {
      char c = text[i];
      if (!c)
        return -1;
      if (q) {
        if (c == q) {
          q = 0;
          i++;
          continue;
        }
      } else {
        if (c == '\'' || c == '"') {
          q = c;
          i++;
          continue;
        }
        if (is_space(c))
          break;
#ifndef _WIN32
        if (c == '\\' && i + 1 < len)
          c = text[++i];
#endif
      }
      if (k + 1 >= CST_PASTE_PATH_MAX)
        return -1;
      tok[k++] = c;
      i++;
    }
    if (q || !k)
      return -1;
    tok[k] = 0;
    if (strncmp(tok, "file://", 7) == 0 && from_file_uri(tok) != 0)
      return -1;
    n++;
  }
  return n > 0 ? n : -1;
}