Add OSC 52 terminal clipboard fallback for -c

xclip requires an X11 display, so -c silently did nothing useful over
a plain SSH session into a headless box. Fall back to the OSC 52
terminal escape sequence (supported by Windows Terminal, PuTTY,
mintty, iTerm2, kitty, ...) when no X display is reachable, and report
which clipboard method was used in the output.

Author: isghe

pattern.c

@@ -554,7 +554,10 @@ vg_output_match_console(vg_context_t *vcp, EC_KEY *pkey, const char *pattern)
 	}
 
 	int clipped = vcp->vc_clip ?
-		vg_clipboard_copy_secret(privkey_buf, 45) : 0;
+		vg_clipboard_copy_secret(privkey_buf, 45) : VG_CLIPBOARD_NONE;
+	const char *clip_method =
+		(clipped == VG_CLIPBOARD_XCLIP) ? "xclip" :
+		(clipped == VG_CLIPBOARD_OSC52) ? "terminal (OSC 52)" : "";
 
 	if (!vcp->vc_result_file || (vcp->vc_verbose > 0)) {
 		printf("\r%79s\rPattern: %s\n", "", pattern);
@@ -568,8 +571,8 @@ vg_output_match_console(vg_context_t *vcp, EC_KEY *pkey, const char *pattern)
 			dumphex(key_buf, len);
 			if (clipped) {
 				printf("Privkey (hex): "
-				       "(copied to clipboard, "
-				       "clearing in 45s)\n");
+				       "(copied to clipboard via %s, "
+				       "clearing in 45s)\n", clip_method);
 			} else {
 				printf("Privkey (hex): ");
 				dumpbn(EC_KEY_get0_private_key(pkey));
@@ -587,8 +590,9 @@ vg_output_match_console(vg_context_t *vcp, EC_KEY *pkey, const char *pattern)
 			printf("P2SHAddress: %s\n", addr2_buf);
 		if (clipped) {
 			printf("Address: %s\n"
-			       "%s: (copied to clipboard, clearing in 45s)\n",
-			       addr_buf, keytype);
+			       "%s: (copied to clipboard via %s, "
+			       "clearing in 45s)\n",
+			       addr_buf, keytype, clip_method);
 		} else {
 			printf("Address: %s\n"
 			       "%s: %s\n",

util.c

@@ -1093,50 +1093,34 @@ vg_read_file(FILE *fp, char ***result, int *rescount)
 }
 
 
+#if !defined(_WIN32)
 /*
- * Copy a secret (e.g. a private key) to the X11 clipboard using xclip,
- * and schedule it to be cleared after timeout_secs -- but only if the
- * clipboard still holds exactly what we put there, so we don't clobber
- * something else the user copied in the meantime.  Modeled after the
- * clipboard handling in "pass" (passwordstore.org).
+ * Copy a secret to the X11 clipboard using xclip, and schedule it to be
+ * cleared after timeout_secs -- but only if the clipboard still holds
+ * exactly what we put there, so we don't clobber something else the user
+ * copied in the meantime.  Modeled after the clipboard handling in "pass"
+ * (passwordstore.org).
  *
- * Returns 1 if the secret was copied to the clipboard, 0 if no clipboard
- * tool was available (in which case the caller should fall back to
- * printing the secret).
+ * Returns 1 on success, 0 if xclip is unavailable or failed.
  */
-int
-vg_clipboard_copy_secret(const char *secret, int timeout_secs)
+static int
+vg_clipboard_copy_xclip(const char *secret, int timeout_secs)
 {
-#if defined(_WIN32)
-	return 0;
-#else
 	FILE *fp;
 	pid_t pid;
 	char cmd[256];
 	int status;
 
-	if (system("command -v xclip >/dev/null 2>&1") != 0) {
-		fprintf(stderr,
-			"vanitygen: xclip not found in PATH, "
-			"printing private key instead\n");
+	if (system("command -v xclip >/dev/null 2>&1") != 0)
 		return 0;
-	}
 
-	fp = popen("xclip -selection clipboard", "w");
-	if (!fp) {
-		fprintf(stderr,
-			"vanitygen: could not run xclip (%s), "
-			"printing private key instead\n", strerror(errno));
+	fp = popen("xclip -selection clipboard 2>/dev/null", "w");
+	if (!fp)
 		return 0;
-	}
 	fputs(secret, fp);
 	status = pclose(fp);
-	if (status != 0) {
-		fprintf(stderr,
-			"vanitygen: xclip exited with status %d, "
-			"printing private key instead\n", status);
+	if (status != 0)
 		return 0;
-	}
 
 	pid = fork();
 	if (pid < 0)
@@ -1167,5 +1151,103 @@ vg_clipboard_copy_secret(const char *secret, int timeout_secs)
 	/* Reap the intermediate child, which exits immediately */
 	waitpid(pid, NULL, 0);
 	return 1;
+}
+
+/*
+ * Copy a secret to the terminal's clipboard using the OSC 52 escape
+ * sequence, understood by most modern terminal emulators (Windows
+ * Terminal, iTerm2, kitty, xterm, mintty, ...) without requiring an X11
+ * server -- this is what makes it work over a plain SSH session into a
+ * headless box.  Scheduled clearing has no readback to compare against
+ * (OSC 52 has no reliable, portable query), so it unconditionally sends
+ * an empty payload after timeout_secs, which terminals interpret as
+ * "clear the clipboard".
+ *
+ * Returns 1 on success, 0 if no terminal is attached.
+ */
+static int
+vg_clipboard_copy_osc52(const char *secret, int timeout_secs)
+{
+	FILE *tty;
+	char *b64;
+	int b64_len;
+	pid_t pid;
+
+	tty = fopen("/dev/tty", "w");
+	if (!tty)
+		return 0;
+
+	b64_len = 4 * ((strlen(secret) + 2) / 3) + 1;
+	b64 = malloc(b64_len);
+	if (!b64) {
+		fclose(tty);
+		return 0;
+	}
+	EVP_EncodeBlock((unsigned char *)b64,
+			(const unsigned char *)secret, strlen(secret));
+
+	fprintf(tty, "\x1b]52;c;%s\x07", b64);
+	fflush(tty);
+	fclose(tty);
+	free(b64);
+
+	pid = fork();
+	if (pid < 0)
+		/* Copy succeeded even though we can't schedule the clear */
+		return 1;
+
+	if (pid == 0) {
+		/* Detach a grandchild so the parent doesn't have to wait */
+		if (fork() > 0)
+			_exit(0);
+		setsid();
+		close(0);
+		close(1);
+		close(2);
+
+		sleep(timeout_secs);
+		tty = fopen("/dev/tty", "w");
+		if (tty) {
+			fprintf(tty, "\x1b]52;c;\x07");
+			fflush(tty);
+			fclose(tty);
+		}
+		_exit(0);
+	}
+
+	/* Reap the intermediate child, which exits immediately */
+	waitpid(pid, NULL, 0);
+	return 1;
+}
+#endif /* !defined(_WIN32) */
+
+/*
+ * Copy a secret (e.g. a private key) to the clipboard, preferring the X11
+ * clipboard via xclip when a display is available, and falling back to
+ * the OSC 52 terminal escape sequence otherwise (e.g. over a plain SSH
+ * session with no X server).
+ *
+ * Returns VG_CLIPBOARD_XCLIP or VG_CLIPBOARD_OSC52 if the secret was
+ * copied to the clipboard, VG_CLIPBOARD_NONE if no clipboard mechanism
+ * was available (in which case the caller should fall back to printing
+ * the secret).
+ */
+int
+vg_clipboard_copy_secret(const char *secret, int timeout_secs)
+{
+#if defined(_WIN32)
+	return VG_CLIPBOARD_NONE;
+#else
+	if (getenv("DISPLAY") &&
+	    vg_clipboard_copy_xclip(secret, timeout_secs))
+		return VG_CLIPBOARD_XCLIP;
+
+	if (vg_clipboard_copy_osc52(secret, timeout_secs))
+		return VG_CLIPBOARD_OSC52;
+
+	fprintf(stderr,
+		"vanitygen: no clipboard available, "
+		"printing private key instead\n");
+	return VG_CLIPBOARD_NONE;
 #endif
 }

util.h

@@ -75,6 +75,10 @@ extern int vg_check_password_complexity(const char *pass, int verbose);
 
 extern int vg_read_file(FILE *fp, char ***result, int *rescount);
 
+#define VG_CLIPBOARD_NONE  0
+#define VG_CLIPBOARD_XCLIP 1
+#define VG_CLIPBOARD_OSC52 2
+
 extern int vg_clipboard_copy_secret(const char *secret, int timeout_secs);
 
 #endif /* !defined (__VG_UTIL_H__) */

vanitygen.c

@@ -312,7 +312,8 @@ usage(const char *name)
 "-k            Keep pattern and continue search after finding a match\n"
 "-1            Stop after first match\n"
 "-c            Copy private key to the clipboard instead of printing it\n"
-"              (cleared automatically after 45 seconds; requires xclip)\n"
+"              (cleared automatically after 45 seconds; uses xclip if an\n"
+"              X display is available, otherwise the terminal clipboard)\n"
 "-N            Generate namecoin address\n"
 "-T            Generate bitcoin testnet address\n"
 "-X <version>  Generate address with the given version\n"