Hi,
I was reluctant to review this as I do not understand
the event processing in OpenVPN well enough. Now that Stefann
has reviewed those bits and given an Ack, here are some
comments on the rest of the code.
TLDR:
(i) stealing SYSTEM access from winlogon.exe is not a good thing to do
(ii) with a small change we can support multiple tunnels and provide better
diagnostics when there are no free wintun adapters -- but this could also
be a follow up patch.
On Fri, Dec 13, 2019 at 2:20 PM Lev Stipakov <lstipa...@gmail.com> wrote:
>
> From: Lev Stipakov <l...@openvpn.net>
>
> Implemented according to Wintun documentation
> and reference client code.
>
> Wintun uses ring buffers to communicate between
> kernel driver and user process. Client allocates
> send and receive ring buffers, creates events
> and passes it to kernel driver under LocalSystem
> privileges.
>
> When data is available for read, wintun modifies
> "tail" pointer of send ring and signals via event.
> User process reads data from "head" to "tail" and
> updates "head" pointer.
>
> When user process is ready to write, it writes
> to receive ring, updates "tail" pointer and signals
> to kernel via event.
>
> In openvpn code we add send ring's event to event loop.
> Before performing io wait, we compare "head" and "tail"
> pointers of send ring and if they're different, we skip
> io wait and perform read.
>
> This also adds ring buffers support to tcp and udp
> server code.
>
> Signed-off-by: Lev Stipakov <l...@openvpn.net>
> ---
> v6:
> - added a sanity check to write_wintun() to avoid
> writing malformed IPv4/6 packet, which causes
> "ring buffer is out of capacity" error.
>
> v5:
> - fix crash at ring buffer registration on Win7
> (passing NULL to DeviceIOControl, reported by kitsune1)
>
> v4:
> - added helper function tuntap_ring_empty()
> - refactored event handling, got rid of separate
> event_ctl() call for wintun and send/receive_tail_moved
> members
> - added wintun_ prefix for ring buffer variables
> - added a comment explaining the size of wintun-specific buffers
>
> v3:
> - simplified convoluted #ifdefs
> - replaced "greater than" with "greater or equal than"
>
> v2;
> - rebased on top of master
>
> src/openvpn/forward.c | 25 ++++++-
> src/openvpn/forward.h | 38 +++++++++-
> src/openvpn/mtcp.c | 19 ++++-
> src/openvpn/mudp.c | 7 +-
> src/openvpn/options.c | 4 +-
> src/openvpn/syshead.h | 1 +
> src/openvpn/tun.c | 62 +++++++++++++++-
> src/openvpn/tun.h | 169 +++++++++++++++++++++++++++++++++++++++++-
> src/openvpn/win32.c | 122 ++++++++++++++++++++++++++++++
> src/openvpn/win32.h | 51 +++++++++++++
> 10 files changed, 487 insertions(+), 11 deletions(-)
>
> diff --git a/src/openvpn/forward.c b/src/openvpn/forward.c
> index 8451706b..3dc04a40 100644
> --- a/src/openvpn/forward.c
> +++ b/src/openvpn/forward.c
> @@ -1256,8 +1256,24 @@ read_incoming_tun(struct context *c)
> perf_push(PERF_READ_IN_TUN);
>
> c->c2.buf = c->c2.buffers->read_tun_buf;
> +
> #ifdef _WIN32
> - read_tun_buffered(c->c1.tuntap, &c->c2.buf);
> + if (c->c1.tuntap->wintun)
> + {
> + read_wintun(c->c1.tuntap, &c->c2.buf);
> + if (c->c2.buf.len == -1)
> + {
> + register_signal(c, SIGHUP, "tun-abort");
> + c->persist.restart_sleep_seconds = 1;
> + msg(M_INFO, "Wintun read error, restarting");
> + perf_pop();
> + return;
> + }
> + }
> + else
> + {
> + read_tun_buffered(c->c1.tuntap, &c->c2.buf);
> + }
> #else
> ASSERT(buf_init(&c->c2.buf, FRAME_HEADROOM(&c->c2.frame)));
> ASSERT(buf_safe(&c->c2.buf, MAX_RW_SIZE_TUN(&c->c2.frame)));
> @@ -2099,6 +2115,13 @@ io_wait_dowork(struct context *c, const unsigned int
> flags)
> tuntap |= EVENT_READ;
> }
>
> +#ifdef _WIN32
> + if (tuntap_is_wintun(c->c1.tuntap))
> + {
> + tuntap = EVENT_READ;
> + }
> +#endif
> +
> /*
> * Configure event wait based on socket, tuntap flags.
> */
> diff --git a/src/openvpn/forward.h b/src/openvpn/forward.h
> index 48202c07..b711ff00 100644
> --- a/src/openvpn/forward.h
> +++ b/src/openvpn/forward.h
> @@ -375,6 +375,12 @@ p2p_iow_flags(const struct context *c)
> {
> flags |= IOW_TO_TUN;
> }
> +#ifdef _WIN32
> + if (tuntap_ring_empty(c->c1.tuntap))
> + {
> + flags &= ~IOW_READ_TUN;
> + }
> +#endif
> return flags;
> }
>
> @@ -403,8 +409,36 @@ io_wait(struct context *c, const unsigned int flags)
> }
> else
> {
> - /* slow path */
> - io_wait_dowork(c, flags);
> +#ifdef _WIN32
> + bool skip_iowait = flags & IOW_TO_TUN;
> + if (flags & IOW_READ_TUN)
> + {
> + /*
> + * don't read from tun if we have pending write to link,
> + * since every tun read overwrites to_link buffer filled
> + * by previous tun read
> + */
> + skip_iowait = !(flags & IOW_TO_LINK);
> + }
> + if (tuntap_is_wintun(c->c1.tuntap) && skip_iowait)
> + {
> + unsigned int ret = 0;
> + if (flags & IOW_TO_TUN)
> + {
> + ret |= TUN_WRITE;
> + }
> + if (flags & IOW_READ_TUN)
> + {
> + ret |= TUN_READ;
> + }
> + c->c2.event_set_status = ret;
> + }
> + else
> +#endif
> + {
> + /* slow path */
> + io_wait_dowork(c, flags);
> + }
> }
> }
>
> diff --git a/src/openvpn/mtcp.c b/src/openvpn/mtcp.c
> index abe20593..30a13f73 100644
> --- a/src/openvpn/mtcp.c
> +++ b/src/openvpn/mtcp.c
> @@ -269,8 +269,25 @@ multi_tcp_wait(const struct context *c,
> struct multi_tcp *mtcp)
> {
> int status;
> + unsigned int *persistent = &mtcp->tun_rwflags;
> socket_set_listen_persistent(c->c2.link_socket, mtcp->es, MTCP_SOCKET);
> - tun_set(c->c1.tuntap, mtcp->es, EVENT_READ, MTCP_TUN,
> &mtcp->tun_rwflags);
> +
> +#ifdef _WIN32
> + if (tuntap_is_wintun(c->c1.tuntap))
> + {
> + if (!tuntap_ring_empty(c->c1.tuntap))
> + {
> + /* there is a data in wintun ring buffer, read it immediately */
> + mtcp->esr[0].arg = MTCP_TUN;
> + mtcp->esr[0].rwflags = EVENT_READ;
> + mtcp->n_esr = 1;
> + return 1;
> + }
> + persistent = NULL;
> + }
> +#endif
> + tun_set(c->c1.tuntap, mtcp->es, EVENT_READ, MTCP_TUN, persistent);
> +
> #ifdef ENABLE_MANAGEMENT
> if (management)
> {
> diff --git a/src/openvpn/mudp.c b/src/openvpn/mudp.c
> index b7f061a2..6a29ccc8 100644
> --- a/src/openvpn/mudp.c
> +++ b/src/openvpn/mudp.c
> @@ -278,7 +278,12 @@ p2mp_iow_flags(const struct multi_context *m)
> {
> flags |= IOW_READ;
> }
> -
> +#ifdef _WIN32
> + if (tuntap_ring_empty(m->top.c1.tuntap))
> + {
> + flags &= ~IOW_READ_TUN;
> + }
> +#endif
> return flags;
> }
>
> diff --git a/src/openvpn/options.c b/src/openvpn/options.c
> index 49affc29..cebcbb07 100644
> --- a/src/openvpn/options.c
> +++ b/src/openvpn/options.c
> @@ -3016,10 +3016,10 @@ options_postprocess_mutate_invariant(struct options
> *options)
> options->ifconfig_noexec = false;
> }
>
> - /* for wintun kernel doesn't send DHCP requests, so use ipapi to set IP
> address and netmask */
> + /* for wintun kernel doesn't send DHCP requests, so use netsh to set IP
> address and netmask */
> if (options->wintun)
> {
> - options->tuntap_options.ip_win32_type = IPW32_SET_IPAPI;
> + options->tuntap_options.ip_win32_type = IPW32_SET_NETSH;
This shouldn't be required. I would prefer to not use netsh
for tasks where API calls are available. We know IPAPI works
as we use it in the service.
> }
>
> remap_redirect_gateway_flags(options);
> diff --git a/src/openvpn/syshead.h b/src/openvpn/syshead.h
> index 899aa59e..e9accb52 100644
> --- a/src/openvpn/syshead.h
> +++ b/src/openvpn/syshead.h
> @@ -39,6 +39,7 @@
> #ifdef _WIN32
> #include <windows.h>
> #include <winsock2.h>
> +#include <tlhelp32.h>
> #define sleep(x) Sleep((x)*1000)
> #define random rand
> #define srandom srand
> diff --git a/src/openvpn/tun.c b/src/openvpn/tun.c
> index 599fd817..3f66b216 100644
> --- a/src/openvpn/tun.c
> +++ b/src/openvpn/tun.c
> @@ -775,9 +775,27 @@ init_tun_post(struct tuntap *tt,
> #ifdef _WIN32
> overlapped_io_init(&tt->reads, frame, FALSE, true);
> overlapped_io_init(&tt->writes, frame, TRUE, true);
> - tt->rw_handle.read = tt->reads.overlapped.hEvent;
> - tt->rw_handle.write = tt->writes.overlapped.hEvent;
> tt->adapter_index = TUN_ADAPTER_INDEX_INVALID;
> +
> + if (tt->wintun)
> + {
> + tt->wintun_send_ring = malloc(sizeof(struct tun_ring));
> + tt->wintun_receive_ring = malloc(sizeof(struct tun_ring));
> + if ((tt->wintun_send_ring == NULL) || (tt->wintun_receive_ring ==
> NULL))
> + {
> + msg(M_FATAL, "Cannot allocate memory for ring buffer");
> + }
> + ZeroMemory(tt->wintun_send_ring, sizeof(struct tun_ring));
> + ZeroMemory(tt->wintun_receive_ring, sizeof(struct tun_ring));
> +
> + tt->rw_handle.read = CreateEvent(NULL, FALSE, FALSE, NULL);
> + tt->rw_handle.write = CreateEvent(NULL, FALSE, FALSE, NULL);
> + }
> + else
> + {
> + tt->rw_handle.read = tt->reads.overlapped.hEvent;
> + tt->rw_handle.write = tt->writes.overlapped.hEvent;
> + }
> #endif
> }
>
> @@ -6177,6 +6195,34 @@ open_tun(const char *dev, const char *dev_type, const
> char *dev_node, struct tun
> tt->ipapi_context_defined = true;
> }
> }
> +
> + if (tt->wintun)
> + {
> + if (tt->options.msg_channel)
> + {
> + /* TODO */
> + }
> + else
> + {
> + if (!impersonate_as_system())
> + {
> + msg(M_FATAL, "ERROR: Failed to impersonate as SYSTEM, make
> sure process is running under privileged account");
> + }
> + if (!register_ring_buffers(tt->hand,
> + tt->wintun_send_ring,
> + tt->wintun_receive_ring,
> + tt->rw_handle.read,
> + tt->rw_handle.write))
> + {
> + msg(M_FATAL, "ERROR: Failed to register ring buffers: %lu",
> GetLastError());
The correct error here is, very likely, the adapter is
already in use. To trigger that, why not do register_ring_buffers
soon after opening the device and on failure move on to the
next device (if any).
That will also allow running multiple tunnels with no further changes
provided the user manually creates wintum adapters.
> + }
> + if (!RevertToSelf())
> + {
> + msg(M_FATAL, "ERROR: RevertToSelf error: %lu",
> GetLastError());
> + }
> + }
> + }
> +
> /*netcmd_semaphore_release ();*/
> gc_free(&gc);
> }
> @@ -6315,6 +6361,18 @@ close_tun(struct tuntap *tt, openvpn_net_ctx_t *ctx)
> free(tt->actual_name);
> }
>
> + if (tt->wintun)
> + {
> + CloseHandle(tt->rw_handle.read);
> + CloseHandle(tt->rw_handle.write);
> + }
> +
> + free(tt->wintun_receive_ring);
> + free(tt->wintun_send_ring);
> +
> + tt->wintun_receive_ring = NULL;
> + tt->wintun_send_ring = NULL;
> +
> clear_tuntap(tt);
> free(tt);
> gc_free(&gc);
> diff --git a/src/openvpn/tun.h b/src/openvpn/tun.h
> index 66b75d93..10f687c5 100644
> --- a/src/openvpn/tun.h
> +++ b/src/openvpn/tun.h
> @@ -182,6 +182,9 @@ struct tuntap
>
> bool wintun; /* true if wintun is used instead of tap-windows6 */
> int standby_iter;
> +
> + struct tun_ring *wintun_send_ring;
> + struct tun_ring *wintun_receive_ring;
> #else /* ifdef _WIN32 */
> int fd; /* file descriptor for TUN/TAP dev */
> #endif
> @@ -211,6 +214,20 @@ tuntap_defined(const struct tuntap *tt)
> #endif
> }
>
> +#ifdef _WIN32
> +inline bool
> +tuntap_is_wintun(struct tuntap *tt)
> +{
> + return tt && tt->wintun;
> +}
> +
> +inline bool
> +tuntap_ring_empty(struct tuntap *tt)
> +{
> + return tuntap_is_wintun(tt) && (tt->wintun_send_ring->head ==
> tt->wintun_send_ring->tail);
> +}
> +#endif
> +
> /*
> * Function prototypes
> */
> @@ -478,10 +495,158 @@ read_tun_buffered(struct tuntap *tt, struct buffer
> *buf)
> return tun_finalize(tt->hand, &tt->reads, buf);
> }
>
> +static inline ULONG
> +wintun_ring_packet_align(ULONG size)
> +{
> + return (size + (WINTUN_PACKET_ALIGN - 1)) & ~(WINTUN_PACKET_ALIGN - 1);
> +}
> +
> +static inline ULONG
> +wintun_ring_wrap(ULONG value)
> +{
> + return value & (WINTUN_RING_CAPACITY - 1);
> +}
> +
> +static inline void
> +read_wintun(struct tuntap *tt, struct buffer* buf)
> +{
> + struct tun_ring *ring = tt->wintun_send_ring;
> + ULONG head = ring->head;
> + ULONG tail = ring->tail;
> + ULONG content_len;
> + struct TUN_PACKET *packet;
> + ULONG aligned_packet_size;
> +
> + *buf = tt->reads.buf_init;
> + buf->len = 0;
> +
> + if ((head >= WINTUN_RING_CAPACITY) || (tail >= WINTUN_RING_CAPACITY))
> + {
> + msg(M_INFO, "Wintun: ring capacity exceeded");
> + buf->len = -1;
> + return;
> + }
> +
> + if (head == tail)
> + {
> + /* nothing to read */
> + return;
> + }
> +
> + content_len = wintun_ring_wrap(tail - head);
> + if (content_len < sizeof(struct TUN_PACKET_HEADER))
> + {
> + msg(M_INFO, "Wintun: incomplete packet header in send ring");
> + buf->len = -1;
> + return;
> + }
> +
> + packet = (struct TUN_PACKET *) &ring->data[head];
> + if (packet->size > WINTUN_MAX_PACKET_SIZE)
> + {
> + msg(M_INFO, "Wintun: packet too big in send ring");
> + buf->len = -1;
> + return;
> + }
> +
> + aligned_packet_size = wintun_ring_packet_align(sizeof(struct
> TUN_PACKET_HEADER) + packet->size);
> + if (aligned_packet_size > content_len)
> + {
> + msg(M_INFO, "Wintun: incomplete packet in send ring");
> + buf->len = -1;
> + return;
> + }
> +
> + buf_write(buf, packet->data, packet->size);
> +
> + head = wintun_ring_wrap(head + aligned_packet_size);
> + ring->head = head;
> +}
> +
> +static inline bool
> +is_ip_packet_valid(const struct buffer *buf)
> +{
> + const struct openvpn_iphdr* ih = (const struct openvpn_iphdr *)BPTR(buf);
> +
> + if (OPENVPN_IPH_GET_VER(ih->version_len) == 4)
> + {
> + if (BLEN(buf) < sizeof(struct openvpn_iphdr))
> + {
> + return false;
> + }
> + }
> + else if (OPENVPN_IPH_GET_VER(ih->version_len) == 6)
> + {
> + if (BLEN(buf) < sizeof(struct openvpn_ipv6hdr))
> + {
> + return false;
> + }
> + }
> + else
> + {
> + return false;
> + }
> +
> + return true;
> +}
> +
> +static inline int
> +write_wintun(struct tuntap *tt, struct buffer *buf)
> +{
> + struct tun_ring *ring = tt->wintun_receive_ring;
> + ULONG head = ring->head;
> + ULONG tail = ring->tail;
> + ULONG aligned_packet_size;
> + ULONG buf_space;
> + struct TUN_PACKET *packet;
> +
> + /* wintun marks ring as corrupted (overcapacity) if it receives invalid
> IP packet */
> + if (!is_ip_packet_valid(buf))
> + {
> + msg(D_LOW, "write_wintun(): drop invalid IP packet");
> + return 0;
> + }
> +
> + if ((head >= WINTUN_RING_CAPACITY) || (tail >= WINTUN_RING_CAPACITY))
> + {
> + msg(M_INFO, "write_wintun(): head/tail value is over capacity");
> + return -1;
> + }
> +
> + aligned_packet_size = wintun_ring_packet_align(sizeof(struct
> TUN_PACKET_HEADER) + BLEN(buf));
> + buf_space = wintun_ring_wrap(head - tail - WINTUN_PACKET_ALIGN);
> + if (aligned_packet_size > buf_space)
> + {
> + msg(M_INFO, "write_wintun(): ring is full");
> + return 0;
> + }
> +
> + /* copy packet size and data into ring */
> + packet = (struct TUN_PACKET* )&ring->data[tail];
> + packet->size = BLEN(buf);
> + memcpy(packet->data, BPTR(buf), BLEN(buf));
> +
> + /* move ring tail */
> + ring->tail = wintun_ring_wrap(tail + aligned_packet_size);
> + if (ring->alertable != 0)
> + {
> + SetEvent(tt->rw_handle.write);
> + }
> +
> + return BLEN(buf);
> +}
> +
> static inline int
> write_tun_buffered(struct tuntap *tt, struct buffer *buf)
> {
> - return tun_write_win32(tt, buf);
> + if (tt->wintun)
> + {
> + return write_wintun(tt, buf);
> + }
> + else
> + {
> + return tun_write_win32(tt, buf);
> + }
> }
>
> #else /* ifdef _WIN32 */
> @@ -544,7 +709,7 @@ tun_set(struct tuntap *tt,
> }
> }
> #ifdef _WIN32
> - if (rwflags & EVENT_READ)
> + if (!tt->wintun && (rwflags & EVENT_READ))
> {
> tun_read_queue(tt, 0);
> }
> diff --git a/src/openvpn/win32.c b/src/openvpn/win32.c
> index eb4c0307..5c168b3b 100644
> --- a/src/openvpn/win32.c
> +++ b/src/openvpn/win32.c
> @@ -1493,4 +1493,126 @@ send_msg_iservice(HANDLE pipe, const void *data,
> size_t size,
> return ret;
> }
>
> +bool
> +impersonate_as_system()
> +{
This is implemented by stealing the access token from
winlogon.exe. I don't think such tricks belong to OpenVPN.
It may also trip some anti-virus software.
That said, probably there are no "legitimate" ways of getting
LOCAL SYSTEM rights on Windows without running a service.
Why does wintun require SYSTEM for using it? If there is a
good reason for that, we should not let every admin
user bypass it.
I would suggest to not elevate to system as the code will still
work in two important cases
(i) started by automatic service
(ii) started using interactive service (e.g., through the GUI)
Those who really need to test OpenVPN with wintun from
command prompt can use diagnostic tools available to get
a cmd prompt as system (e.g., psexec). That also makes
it explicit that SYSTEM privilege is required.
In the longer run, we could provide a script to launch
openvpn.exe using the interactive service. Modifying the
automatic service to use interactive service for launching
looks easy to do as well. Then, all privileged operations could
be removed from openvpn core.
> + HANDLE thread_token, process_snapshot, winlogon_process, winlogon_token,
> duplicated_token;
> + PROCESSENTRY32 entry;
> + BOOL ret;
> + DWORD pid = 0;
> + TOKEN_PRIVILEGES privileges;
> +
> + CLEAR(entry);
> + CLEAR(privileges);
> +
> + entry.dwSize = sizeof(PROCESSENTRY32);
> +
> + privileges.PrivilegeCount = 1;
> + privileges.Privileges->Attributes = SE_PRIVILEGE_ENABLED;
> +
> + if (!LookupPrivilegeValue(NULL, SE_DEBUG_NAME,
> &privileges.Privileges[0].Luid))
> + {
> + return false;
In case we keep this function, please log such
errors. Here and several such cases below.
> + }
> +
> + if (!ImpersonateSelf(SecurityImpersonation))
> + {
> + return false;
> + }
> +
> + if (!OpenThreadToken(GetCurrentThread(), TOKEN_ADJUST_PRIVILEGES, FALSE,
> &thread_token))
> + {
> + RevertToSelf();
> + return false;
> + }
> + if (!AdjustTokenPrivileges(thread_token, FALSE, &privileges,
> sizeof(privileges), NULL, NULL))
> + {
> + CloseHandle(thread_token);
> + RevertToSelf();
> + return false;
> + }
> + CloseHandle(thread_token);
> +
> + process_snapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
> + if (process_snapshot == INVALID_HANDLE_VALUE)
> + {
> + RevertToSelf();
> + return false;
> + }
> + for (ret = Process32First(process_snapshot, &entry); ret; ret =
> Process32Next(process_snapshot, &entry))
> + {
> + if (!_stricmp(entry.szExeFile, "winlogon.exe"))
> + {
> + pid = entry.th32ProcessID;
> + break;
> + }
> + }
> + CloseHandle(process_snapshot);
> + if (!pid)
> + {
> + RevertToSelf();
> + return false;
> + }
> +
> + winlogon_process = OpenProcess(PROCESS_QUERY_INFORMATION, FALSE, pid);
> + if (!winlogon_process)
> + {
> + RevertToSelf();
> + return false;
> + }
> +
> + if (!OpenProcessToken(winlogon_process, TOKEN_IMPERSONATE |
> TOKEN_DUPLICATE, &winlogon_token))
> + {
> + CloseHandle(winlogon_process);
> + RevertToSelf();
> + return false;
> + }
> + CloseHandle(winlogon_process);
> +
> + if (!DuplicateToken(winlogon_token, SecurityImpersonation,
> &duplicated_token))
> + {
> + CloseHandle(winlogon_token);
> + RevertToSelf();
> + return false;
> + }
> + CloseHandle(winlogon_token);
> +
> + if (!SetThreadToken(NULL, duplicated_token))
> + {
> + CloseHandle(duplicated_token);
> + RevertToSelf();
> + return false;
> + }
> + CloseHandle(duplicated_token);
> +
> + return true;
> +}
> +
> +bool
> +register_ring_buffers(HANDLE device,
> + struct tun_ring* send_ring,
> + struct tun_ring* receive_ring,
> + HANDLE send_tail_moved,
> + HANDLE receive_tail_moved)
> +{
> + struct tun_register_rings rr;
> + BOOL res;
> + DWORD bytes_returned;
> +
> + ZeroMemory(&rr, sizeof(rr));
> +
> + rr.send.ring = send_ring;
> + rr.send.ring_size = sizeof(send_ring->data);
> + rr.send.tail_moved = send_tail_moved;
> +
> + rr.receive.ring = receive_ring;
> + rr.receive.ring_size = sizeof(receive_ring->data);
> + rr.receive.tail_moved = receive_tail_moved;
> +
> + res = DeviceIoControl(device, TUN_IOCTL_REGISTER_RINGS, &rr, sizeof(rr),
> + NULL, 0, &bytes_returned, NULL);
> +
> + return res == TRUE;
> +}
> +
> #endif /* ifdef _WIN32 */
> diff --git a/src/openvpn/win32.h b/src/openvpn/win32.h
> index 4814bbc5..f6d45bdc 100644
> --- a/src/openvpn/win32.h
> +++ b/src/openvpn/win32.h
> @@ -25,6 +25,8 @@
> #ifndef OPENVPN_WIN32_H
> #define OPENVPN_WIN32_H
>
> +#include <winioctl.h>
> +
> #include "mtu.h"
> #include "openvpn-msg.h"
> #include "argv.h"
> @@ -323,5 +325,54 @@ bool send_msg_iservice(HANDLE pipe, const void *data,
> size_t size,
> int
> openvpn_execve(const struct argv *a, const struct env_set *es, const
> unsigned int flags);
>
> +/*
> + * Values below are taken from Wireguard Windows client
> + *
> https://github.com/WireGuard/wireguard-go/blob/master/tun/wintun/ring_windows.go#L14
> + */
> +#define WINTUN_RING_CAPACITY 0x800000
> +#define WINTUN_RING_TRAILING_BYTES 0x10000
> +#define WINTUN_RING_FRAMING_SIZE 12
> +#define WINTUN_MAX_PACKET_SIZE 0xffff
> +#define WINTUN_PACKET_ALIGN 4
> +
> +struct tun_ring
> +{
> + volatile ULONG head;
> + volatile ULONG tail;
> + volatile LONG alertable;
> + UCHAR data[WINTUN_RING_CAPACITY + WINTUN_RING_TRAILING_BYTES +
> WINTUN_RING_FRAMING_SIZE];
> +};
> +
> +struct tun_register_rings
> +{
> + struct
> + {
> + ULONG ring_size;
> + struct tun_ring *ring;
> + HANDLE tail_moved;
> + } send, receive;
> +};
> +
> +struct TUN_PACKET_HEADER
> +{
> + uint32_t size;
> +};
> +
> +struct TUN_PACKET
> +{
> + uint32_t size;
> + UCHAR data[WINTUN_MAX_PACKET_SIZE];
> +};
> +
> +#define TUN_IOCTL_REGISTER_RINGS CTL_CODE(51820U, 0x970U, METHOD_BUFFERED,
> FILE_READ_DATA | FILE_WRITE_DATA)
> +
> +bool impersonate_as_system();
> +
> +bool register_ring_buffers(HANDLE device,
> + struct tun_ring *send_ring,
> + struct tun_ring *receive_ring,
> + HANDLE send_tail_moved,
> + HANDLE receive_tail_moved);
> +
> #endif /* ifndef OPENVPN_WIN32_H */
> #endif /* ifdef _WIN32 */
> --
Selva
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