1 files changed, 212 insertions, 0 deletions
diff --git a/src/lib/fdpass.c b/src/lib/fdpass.c
new file mode 100644
index 0000000..bd54443
--- /dev/null
+++ b/src/lib/fdpass.c
@@ -0,0 +1,212 @@
+/* Copyright (c) 2002-2018 Dovecot authors, see the included COPYING file */
+
+/*
+   fdpass.c - File descriptor passing between processes via UNIX sockets
+
+   This isn't fully portable, but pretty much all UNIXes nowadays should
+   support this. If you're having runtime problems with fd_read(), check the
+   end of fd_read() and play with the if condition. If you're having problems
+   with fd_send(), try defining BUGGY_CMSG_MACROS.
+
+   If this file doesn't compile at all, you should check if this is supported
+   in your system at all. It may require some extra #define to enable it.
+   If not, you're pretty much out of luck. Cygwin didn't last I checked.
+*/
+
+#define _XPG4_2
+
+#if defined(irix) || defined (__irix__) || defined(sgi) || defined (__sgi__)
+#  define _XOPEN_SOURCE 4 /* for IRIX */
+#endif
+
+#if !defined(_AIX) && !defined(_XOPEN_SOURCE_EXTENDED)
+#  define _XOPEN_SOURCE_EXTENDED /* for Tru64, breaks AIX */
+#endif
+
+#ifdef HAVE_CONFIG_H
+#  include "lib.h"
+#else
+#  define i_assert(x)
+#endif
+
+#include <string.h>
+#include <limits.h>
+#include <sys/types.h>
+
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <sys/uio.h>
+
+#include "fdpass.h"
+
+#ifndef HAVE_CONFIG_H
+struct const_iovec {
+	const void *iov_base;
+	size_t iov_len;
+};
+#endif
+
+/* RFC 2292 defines CMSG_*() macros, but some operating systems don't have them
+   so we'll define our own if they don't exist.
+
+   CMSG_LEN(data) is used to calculate size of sizeof(struct cmsghdr) +
+   sizeof(data) and padding between them.
+
+   CMSG_SPACE(data) also calculates the padding needed after the data, in case
+   multiple objects are sent.
+
+   cmsghdr contains cmsg_len field and two integers. cmsg_len is sometimes
+   defined as sockaddr_t and sometimes size_t, so it can be either 32bit or
+   64bit. This padding is added by compiler in sizeof(struct cmsghdr).
+
+   Padding required by CMSG_DATA() can vary. Usually it wants size_t or 32bit.
+   With Solaris it's in _CMSG_DATA_ALIGNMENT (32bit), we assume others want
+   size_t.
+
+   We don't really need CMSG_SPACE() to be exactly correct, because currently
+   we send only one object at a time. But anyway I'm trying to keep that
+   correct in case it's sometimes needed..
+*/
+
+#ifdef BUGGY_CMSG_MACROS
+/* Some OSes have broken CMSG macros in 64bit systems. The macros use 64bit
+   alignment while kernel uses 32bit alignment. */
+#  undef CMSG_SPACE
+#  undef CMSG_LEN
+#  undef CMSG_DATA
+#  define CMSG_DATA(cmsg) ((char *)((cmsg) + 1))
+#  define _CMSG_DATA_ALIGNMENT 4
+#  define _CMSG_HDR_ALIGNMENT 4
+#endif
+
+#ifndef CMSG_SPACE
+#  define MY_ALIGN(len, align) \
+	(((len) + align - 1) & ~(align - 1))
+
+/* Alignment between cmsghdr and data */
+#  ifndef _CMSG_DATA_ALIGNMENT
+#    define _CMSG_DATA_ALIGNMENT sizeof(size_t)
+#  endif
+/* Alignment between data and next cmsghdr */
+#  ifndef _CMSG_HDR_ALIGNMENT
+#    define _CMSG_HDR_ALIGNMENT sizeof(size_t)
+#  endif
+
+#  define CMSG_SPACE(len) \
+	(MY_ALIGN(sizeof(struct cmsghdr), _CMSG_DATA_ALIGNMENT) + \
+	 MY_ALIGN(len, _CMSG_HDR_ALIGNMENT))
+#  define CMSG_LEN(len) \
+	(MY_ALIGN(sizeof(struct cmsghdr), _CMSG_DATA_ALIGNMENT) + (len))
+#endif
+
+#ifdef SCM_RIGHTS
+
+ssize_t fd_send(int handle, int send_fd, const void *data, size_t size)
+{
+        struct msghdr msg;
+        struct const_iovec iov;
+        struct cmsghdr *cmsg;
+	char buf[CMSG_SPACE(sizeof(int))];
+
+	/* at least one byte is required to be sent with fd passing */
+	i_assert(size > 0 && size < INT_MAX);
+
+	memset(&msg, 0, sizeof(struct msghdr));
+
+        iov.iov_base = data;
+        iov.iov_len = size;
+
+        msg.msg_iov = (void *)&iov;
+	msg.msg_iovlen = 1;
+
+	if (send_fd != -1) {
+		/* set the control and controllen before CMSG_FIRSTHDR(). */
+		memset(buf, 0, sizeof(buf));
+		msg.msg_control = buf;
+		msg.msg_controllen = sizeof(buf);
+
+		cmsg = CMSG_FIRSTHDR(&msg);
+		cmsg->cmsg_level = SOL_SOCKET;
+		cmsg->cmsg_type = SCM_RIGHTS;
+		cmsg->cmsg_len = CMSG_LEN(sizeof(int));
+		memcpy(CMSG_DATA(cmsg), &send_fd, sizeof(send_fd));
+
+		/* set the real length we want to use. Do it after all is
+		   set just in case CMSG macros required the extra padding
+		   in the end. */
+		msg.msg_controllen = cmsg->cmsg_len;
+	}
+
+	return sendmsg(handle, &msg, 0);
+}
+
+#ifdef LINUX20
+/* Linux 2.0.x doesn't set any cmsg fields. Note that this might make some
+   attacks possible so don't do it unless you really have to. */
+#  define CHECK_CMSG(cmsg) ((cmsg) != NULL)
+#else
+#  define CHECK_CMSG(cmsg) \
+	((cmsg) != NULL && \
+	 (size_t)(cmsg)->cmsg_len >= (size_t)CMSG_LEN(sizeof(int)) && \
+	 (cmsg)->cmsg_level == SOL_SOCKET && (cmsg)->cmsg_type == SCM_RIGHTS)
+#endif
+
+ssize_t fd_read(int handle, void *data, size_t size, int *fd)
+{
+	struct msghdr msg;
+	struct iovec iov;
+	struct cmsghdr *cmsg;
+	ssize_t ret;
+	char buf[CMSG_SPACE(sizeof(int))];
+
+	i_assert(size > 0 && size < INT_MAX);
+
+	memset(&msg, 0, sizeof (struct msghdr));
+
+	iov.iov_base = data;
+	iov.iov_len = size;
+
+	msg.msg_iov = &iov;
+	msg.msg_iovlen = 1;
+
+	memset(buf, 0, sizeof(buf));
+	msg.msg_control = buf;
+	msg.msg_controllen = sizeof(buf);
+
+	ret = recvmsg(handle, &msg, 0);
+	if (ret <= 0) {
+		*fd = -1;
+		return ret;
+	}
+
+	/* at least one byte transferred - we should have the fd now.
+	   do extra checks to make sure it really is an fd that is being
+	   transferred to avoid potential DoS conditions. some systems don't
+	   set all these values correctly however so CHECK_CMSG() is somewhat
+	   system dependent */
+	cmsg = CMSG_FIRSTHDR(&msg);
+	if (!CHECK_CMSG(cmsg))
+		*fd = -1;
+	else
+		memcpy(fd, CMSG_DATA(cmsg), sizeof(*fd));
+	return ret;
+}
+
+#else
+#  ifdef __GNUC__
+#    warning SCM_RIGHTS not supported, privilege separation not possible
+#  endif
+ssize_t fd_send(int handle ATTR_UNUSED, int send_fd ATTR_UNUSED,
+		const void *data ATTR_UNUSED, size_t size ATTR_UNUSED)
+{
+	errno = ENOSYS;
+	return -1;
+}
+
+ssize_t fd_read(int handle ATTR_UNUSED, void *data ATTR_UNUSED,
+		size_t size ATTR_UNUSED, int *fd ATTR_UNUSED)
+{
+	errno = ENOSYS;
+	return -1;
+}
+#endif