hooklib/dns.c: Add initial WinDNS hook

We'll probably need to intercept the more traditional
gethostbyname() API and friends at some point too.

hooklib/dns.c

@@ -0,0 +1,327 @@
+/* Might push this to capnhook, don't add any util dependencies. */
+
+#include <windows.h>
+#include <windns.h>
+
+#include <assert.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "hook/hr.h"
+#include "hook/table.h"
+
+#include "hooklib/dns.h"
+
+/* Latest w32headers does not include DnsQueryEx, so we'll have to "polyfill"
+   its associated data types here for the time being.
+
+   Results and cancel handle are passed through, so we'll just use void
+   pointers for those args. So are most of the fields in this structure, for
+   that matter. */
+
+typedef struct POLYFILL_DNS_QUERY_REQUEST {
+    ULONG Version;
+    PCWSTR QueryName;
+    WORD QueryType;
+    ULONG64 QueryOptions;
+    void* pDnsServerList;
+    ULONG InterfaceIndex;
+    void* pQueryCompletionCallback;
+    PVOID pQueryContext;
+} POLYFILL_DNS_QUERY_REQUEST;
+
+struct dns_hook_entry {
+    wchar_t *from;
+    wchar_t *to;
+};
+
+static DNS_STATUS WINAPI hook_DnsQuery_A(
+        const char *pszName,
+        WORD wType,
+        DWORD Options,
+        void *pExtra,
+        DNS_RECORD **ppQueryResults,
+        void *pReserved);
+
+static DNS_STATUS WINAPI hook_DnsQuery_W(
+        const wchar_t *pszName,
+        WORD wType,
+        DWORD Options,
+        void *pExtra,
+        DNS_RECORD **ppQueryResults,
+        void *pReserved);
+
+static DNS_STATUS WINAPI hook_DnsQueryEx(
+        POLYFILL_DNS_QUERY_REQUEST *pRequest,
+        void *pQueryResults,
+        void *pCancelHandle);
+
+static DNS_STATUS WINAPI (*next_DnsQuery_A)(
+        const char *pszName,
+        WORD wType,
+        DWORD Options,
+        void *pExtra,
+        DNS_RECORD **ppQueryResults,
+        void *pReserved);
+
+static DNS_STATUS WINAPI (*next_DnsQuery_W)(
+        const wchar_t *pszName,
+        WORD wType,
+        DWORD Options,
+        void *pExtra,
+        DNS_RECORD **ppQueryResults,
+        void *pReserved);
+
+static DNS_STATUS WINAPI (*next_DnsQueryEx)(
+        POLYFILL_DNS_QUERY_REQUEST *pRequest,
+        void *pQueryResults,
+        void *pCancelHandle);
+
+static const struct hook_symbol dns_hook_syms[] = {
+    {
+        .name       = "DnsQuery_A",
+        .patch      = hook_DnsQuery_A,
+        .link       = (void **) &next_DnsQuery_A,
+    }, {
+        .name       = "DnsQuery_W",
+        .patch      = hook_DnsQuery_W,
+        .link       = (void **) &next_DnsQuery_W,
+    }, {
+        .name       = "DnsQueryEx",
+        .patch      = hook_DnsQueryEx,
+        .link       = (void **) &next_DnsQueryEx,
+    }
+};
+
+static bool dns_hook_initted;
+static CRITICAL_SECTION dns_hook_lock;
+static struct dns_hook_entry *dns_hook_entries;
+static size_t dns_hook_nentries;
+
+static void dns_hook_init(void)
+{
+    if (dns_hook_initted) {
+        return;
+    }
+
+    dns_hook_initted = true;
+    InitializeCriticalSection(&dns_hook_lock);
+
+    hook_table_apply(
+            NULL,
+            "dnsapi.dll",
+            dns_hook_syms,
+            _countof(dns_hook_syms));
+}
+
+HRESULT dns_hook_push(const wchar_t *from_src, const wchar_t *to_src)
+{
+    HRESULT hr;
+    struct dns_hook_entry *newmem;
+    struct dns_hook_entry *newitem;
+    wchar_t *from;
+    wchar_t *to;
+
+    assert(from_src != NULL);
+    assert(to_src != NULL);
+
+    to = NULL;
+    from = NULL;
+    dns_hook_init();
+
+    EnterCriticalSection(&dns_hook_lock);
+
+    from = _wcsdup(from_src);
+
+    if (from == NULL) {
+        hr = E_OUTOFMEMORY;
+
+        goto end;
+    }
+
+    to = _wcsdup(to_src);
+
+    if (to == NULL) {
+        hr = E_OUTOFMEMORY;
+
+        goto end;
+    }
+
+    newmem = realloc(
+            dns_hook_entries,
+            (dns_hook_nentries + 1) * sizeof(struct dns_hook_entry));
+
+    if (newmem == NULL) {
+        hr = E_OUTOFMEMORY;
+
+        goto end;
+    }
+
+    dns_hook_entries = newmem;
+    newitem = &newmem[dns_hook_nentries++];
+    newitem->from = from;
+    newitem->to = to;
+
+    from = NULL;
+    to = NULL;
+    hr = S_OK;
+
+end:
+    LeaveCriticalSection(&dns_hook_lock);
+
+    free(to);
+    free(from);
+
+    return hr;
+}
+
+static DNS_STATUS WINAPI hook_DnsQuery_A(
+        const char *pszName,
+        WORD wType,
+        DWORD Options,
+        void *pExtra,
+        DNS_RECORD **ppQueryResults,
+        void *pReserved)
+{
+    const struct dns_hook_entry *pos;
+    size_t i;
+    size_t wstr_c;
+    wchar_t *wstr;
+    size_t str_c;
+    char *str;
+    DNS_STATUS code;
+    HRESULT hr;
+
+    wstr = NULL;
+    str = NULL;
+
+    if (pszName == NULL) {
+        hr = HRESULT_FROM_WIN32(ERROR_INVALID_PARAMETER);
+
+        goto end;
+    }
+
+    mbstowcs_s(&wstr_c, NULL, 0, pszName, 0);
+    wstr = malloc(wstr_c * sizeof(wchar_t));
+
+    if (wstr == NULL) {
+        hr = HRESULT_FROM_WIN32(ERROR_OUTOFMEMORY);
+
+        goto end;
+    }
+
+    mbstowcs_s(NULL, wstr, wstr_c, pszName, wstr_c - 1);
+
+    for (i = 0 ; i < dns_hook_nentries ; i++) {
+        pos = &dns_hook_entries[i];
+
+        if (_wcsicmp(wstr, pos->from) == 0) {
+            wcstombs_s(&str_c, NULL, 0, pos->to, 0);
+            str = malloc(str_c * sizeof(char));
+
+            if (str == NULL) {
+                hr = HRESULT_FROM_WIN32(ERROR_OUTOFMEMORY);
+
+                goto end;
+            }
+
+            wcstombs_s(NULL, str, str_c, pos->to, str_c - 1);
+            pszName = str;
+
+            break;
+        }
+    }
+
+    code = next_DnsQuery_A(
+            pszName,
+            wType,
+            Options,
+            pExtra,
+            ppQueryResults,
+            pReserved);
+
+    hr = HRESULT_FROM_WIN32(code);
+
+end:
+    free(str);
+    free(wstr);
+
+    return hr_to_win32_error(hr);
+}
+
+static DNS_STATUS WINAPI hook_DnsQuery_W(
+        const wchar_t *pszName,
+        WORD wType,
+        DWORD Options,
+        void *pExtra,
+        DNS_RECORD **ppQueryResults,
+        void *pReserved)
+{
+    const struct dns_hook_entry *pos;
+    size_t i;
+
+    if (pszName == NULL) {
+        return ERROR_INVALID_PARAMETER;
+    }
+
+    for (i = 0 ; i < dns_hook_nentries ; i++) {
+        pos = &dns_hook_entries[i];
+
+        if (_wcsicmp(pszName, pos->from) == 0) {
+            pszName = pos->to;
+
+            break;
+        }
+    }
+
+    return next_DnsQuery_W(
+            pszName,
+            wType,
+            Options,
+            pExtra,
+            ppQueryResults,
+            pReserved);
+
+}
+
+static DNS_STATUS WINAPI hook_DnsQueryEx(
+        POLYFILL_DNS_QUERY_REQUEST *pRequest,
+        void *pQueryResults,
+        void *pCancelHandle)
+{
+    const wchar_t *orig;
+    const struct dns_hook_entry *pos;
+    DNS_STATUS code;
+    size_t i;
+
+    if (pRequest == NULL) {
+        return ERROR_INVALID_PARAMETER;
+    }
+
+    orig = pRequest->QueryName;
+
+    for (i = 0 ; i < dns_hook_nentries ; i++) {
+        pos = &dns_hook_entries[i];
+
+        if (_wcsicmp(pRequest->QueryName, pos->from) == 0) {
+            pRequest->QueryName = pos->to;
+
+            break;
+        }
+    }
+
+    code = next_DnsQueryEx(pRequest, pQueryResults, pCancelHandle);
+
+    /* Caller might not appreciate QueryName changing under its feet. It is
+       strongly implied by MSDN that a copy of *pRequest is taken by WINAPI,
+       so we can change it back after the call has been issued with no ill
+       effect... we hope.
+
+       Hopefully the completion callback is issued from an APC or something
+       (or otherwise happens after this returns) or we're in trouble. */
+
+    pRequest->QueryName = orig;
+
+    return code;
+}

hooklib/dns.h

@@ -0,0 +1,8 @@
+#pragma once
+
+#include <windows.h>
+
+#include <stddef.h>
+
+HRESULT dns_hook_push(const wchar_t *from_src, const wchar_t *to_src);
+

hooklib/meson.build

@@ -11,6 +11,8 @@ hooklib_lib = static_library(
         'clock.h',
         'dll.c',
         'dll.h',
+        'dns.c',
+        'dns.h',
         'fdshark.c',
         'fdshark.h',
         'gfx.c',

precompiled.h

@@ -10,6 +10,7 @@
 #include <winternl.h>
 #include <setupapi.h>
 #include <unknwn.h>
+#include <windns.h>
 #include <dinput.h>
 #include <xinput.h>
 #include <d3d9.h>