Simple emulation of POSIX pty APIs posix_openpt(), ptsname(),

grantpt() and unlockpt() using /dev/ptm.  Man pages from FreeBSD.
OK kettenis@ deraadt@ beck@ ajacoutot@ naddy@

1 files changed, 119 insertions, 0 deletions

diff --git a/src/lib/libc/stdlib/posix_pty.c b/src/lib/libc/stdlib/posix_pty.c
new file mode 100644
index 0000000000..a2025ddbb6
--- /dev/null
+++ b/src/lib/libc/stdlib/posix_pty.c
@@ -0,0 +1,119 @@
+/*      $OpenBSD: posix_pty.c,v 1.1 2012/12/03 20:08:33 millert Exp $   */
+
+/*
+ * Copyright (c) 2012 Todd C. Miller <Todd.Miller@courtesan.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <sys/types.h>
+#include <sys/ioctl.h>
+#include <sys/stat.h>
+#include <sys/tty.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <paths.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+int
+posix_openpt(int oflag)
+{
+        struct ptmget ptm;
+        int fd, mfd = -1;
+
+        /* User must specify O_RDWR in oflag. */
+        if (!(oflag & O_RDWR)) {
+                errno = EINVAL;
+                return -1;
+        }
+
+        /* Get pty master and slave (this API only uses the master). */
+        fd = open(PATH_PTMDEV, O_RDWR);
+        if (fd != -1) {
+                if (ioctl(fd, PTMGET, &ptm) != -1) {
+                        close(ptm.sfd);
+                        mfd = ptm.cfd;
+                }
+                close(fd);
+        }
+
+        return mfd;
+}
+
+/*
+ * Look up the name of the specified pty master fd.
+ * Note that the name returned does *not* include the /dev/ prefix.
+ * Returns the name on success and NULL on error, setting errno.
+ */
+static const char *
+ptmname(int mfd)
+{
+        struct stat sb;
+        const char *name;
+
+        /* Make sure it is a pty master. */
+        if (fstat(mfd, &sb) != 0)
+                return NULL;
+        if (!S_ISCHR(sb.st_mode)) {
+                errno = EINVAL;
+                return NULL;
+        }
+        name = devname(sb.st_rdev, S_IFCHR);
+        if (strncmp(name, "pty", 3) != 0) {
+                errno = EINVAL;
+                return NULL;
+        }
+        return name;
+}
+
+/*
+ * The PTMGET ioctl handles the mode and owner for us.
+ */
+int
+grantpt(int mfd)
+{
+        return ptmname(mfd) ? 0 : -1;
+}
+
+/*
+ * The PTMGET ioctl unlocks the pty master and slave for us.
+ */
+int
+unlockpt(int mfd)
+{
+        return ptmname(mfd) ? 0 : -1;
+}
+
+/*
+ * Look up the path of the slave pty that corresponds to the master fd.
+ * Returns the path if successful or NULL on error.
+ */
+char *
+ptsname(int mfd)
+{
+        const char *master;
+        static char slave[sizeof(((struct ptmget *)NULL)->sn)];
+
+        if ((master = ptmname(mfd)) == NULL)
+                return NULL;
+
+        /* Add /dev/ prefix and convert "pty" to "tty". */
+        strlcpy(slave, _PATH_DEV, sizeof(slave));
+        strlcat(slave, master, sizeof(slave));
+        slave[sizeof(_PATH_DEV) - 1] = 't';
+
+        return slave;
+}