java-topology/src/java.base/windows/native/libjava/canonicalize_md.c

/*
 * Copyright (c) 1998, 2025, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

/*
 * Pathname canonicalization for Win32 file systems
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <assert.h>
#include <sys/stat.h>

#include <windows.h>
#include <winbase.h>
#include <wchar.h>
#include <errno.h>

/* We should also include jdk_util.h here, for the prototype of JDK_Canonicalize.
   This isn't possible though because canonicalize_md.c is as well used in
   different contexts within Oracle.
*/
#include "io_util_md.h"

/* Copy bytes to dst, not going past dend; return dst + number of bytes copied,
   or NULL if dend would have been exceeded.  If first != '\0', copy that byte
   before copying bytes from src to send - 1. */
static WCHAR*
wcp(WCHAR *dst, WCHAR *dend, WCHAR first, WCHAR *src, WCHAR *send)
{
    WCHAR *p = src, *q = dst;
    if (first != L'\0') {
        if (q < dend) {
            *q++ = first;
        } else {
            errno = ENAMETOOLONG;
            return NULL;
        }
    }
    if (send - p > dend - q) {
        errno = ENAMETOOLONG;
        return NULL;
    }
    while (p < send)
        *q++ = *p++;
    return q;
}

/* Find first instance of '\\' at or following start.  Return the address of
   that byte or the address of the null terminator if '\\' is not found. */
static WCHAR *
wnextsep(WCHAR *start)
{
    WCHAR *p = start;
    int c;
    while ((c = *p) && (c != L'\\'))
        p++;
    return p;
}

/* Tell whether the given string contains any wildcard characters */
static int
wwild(const WCHAR *start)
{
    WCHAR *p = (WCHAR*)start;
    int c;
    while (c = *p) {
        if ((c == L'*') || (c == L'?'))
            return 1;
        p++;
    }
    return 0;
}

/* Tell whether the given string contains prohibited combinations of dots.
   In the canonicalized form no path element may have dots at its end.
   Allowed canonical paths: c:\xa...dksd\..ksa\.lk    c:\...a\.b\cd..x.x
   Prohibited canonical paths: c:\..\x  c:\x.\d c:\...
*/
static int
wdots(WCHAR *start)
{
    WCHAR *p = start;
    // Skip "\\.\" prefix
    if (wcslen(p) > 4 && !wcsncmp(p, L"\\\\.\\", 4))
        p = p + 4;

    while (*p) {
        if ((p = wcschr(p, L'.')) == NULL) // find next occurrence of '.'
            return 0; // no more dots
        p++; // next char
        while ((*p) == L'.') // go to the end of dots
            p++;
        if (*p && (*p != L'\\')) // path element does not end with a dot
            p++; // go to the next char
        else
            return 1; // path element does end with a dot - prohibited
    }
    return 0; // no prohibited combinations of dots found
}

/* If the lookup of a particular prefix fails because the file does not exist,
   because it is of the wrong type, because access is denied, or because the
   network is unreachable then canonicalization does not fail, it terminates
   successfully after copying the rest of the original path to the result path.
   Other I/O errors cause an error return.
*/
int
lastErrorReportable()
{
    DWORD errval = GetLastError();
    if ((errval == ERROR_FILE_NOT_FOUND)
        || (errval == ERROR_DIRECTORY)
        || (errval == ERROR_PATH_NOT_FOUND)
        || (errval == ERROR_BAD_NETPATH)
        || (errval == ERROR_BAD_NET_NAME)
        || (errval == ERROR_ACCESS_DENIED)
        || (errval == ERROR_NETWORK_UNREACHABLE)
        || (errval == ERROR_NETWORK_ACCESS_DENIED)
        || (errval == ERROR_NO_MORE_FILES)
        || (errval == ERROR_NETNAME_DELETED)) {
        return 0;
    }
    return 1;
}

//
// Return the final path of 'path'. If 'finalPath' is long enough, the final
// path is placed in it. If not, a new character array is allocated for the
// return value. If the return value does not equal the original 'finalPath'
// value, then the calling code might need to free the memory of the
// parameter. Non-NULL is returned on success, NULL on error.
//
WCHAR* getFinalPath(WCHAR* path, WCHAR* finalPath, DWORD size)
{
    HANDLE h = CreateFileW(path,
                           FILE_READ_ATTRIBUTES,
                           FILE_SHARE_DELETE |
                           FILE_SHARE_READ | FILE_SHARE_WRITE,
                           NULL,
                           OPEN_EXISTING,
                           FILE_FLAG_BACKUP_SEMANTICS,
                           NULL);

    if (h != INVALID_HANDLE_VALUE) {
        DWORD len = GetFinalPathNameByHandleW(h, finalPath, size, 0);
        if (len >= size) {
            if ((finalPath = (WCHAR*)malloc(len * sizeof(WCHAR))) == NULL)
                return NULL;
            len = GetFinalPathNameByHandleW(h, finalPath, len, 0);
        }
        CloseHandle(h);
        if (len != 0) {
            if (finalPath[0] == L'\\' && finalPath[1] == L'\\' &&
                finalPath[2] == L'?' && finalPath[3] == L'\\')
            {
                // Strip prefix (should be \\?\ or \\?\UNC)
                int isUnc = (finalPath[4] == L'U' &&
                             finalPath[5] == L'N' &&
                             finalPath[6] == L'C');
                int prefixLen = (isUnc) ? 7 : 4;
                // the amount to copy includes terminator
                int amountToCopy = len - prefixLen + 1;
                wmemmove(finalPath, finalPath + prefixLen, amountToCopy);
            }

            return finalPath;
        }
    }

    return NULL;
}

/* Convert a pathname to canonical form.  If a reparse point is encountered
   while traversing the path, then the final path is derived from the full path
   and returned as the canonical pathname.
 */
WCHAR*
wcanonicalize(const WCHAR *orig_path, WCHAR *result, int size)
{
    WIN32_FIND_DATAW fd;
    HANDLE h;
    WCHAR *path;    /* Working copy of path */
    WCHAR *src, *dst, *dend, c;

    /* Reject paths that contain wildcards */
    if (wwild(orig_path)) {
        errno = EINVAL;
        return NULL;
    }

    if ((path = (WCHAR*)malloc(size * sizeof(WCHAR))) == NULL)
        return NULL;

    /* Collapse instances of "foo\.." and ensure absoluteness.  Note that
       contrary to the documentation, the _fullpath procedure does not require
       the drive to be available.  */
    if(!_wfullpath(path, orig_path, size)) {
        goto err;
    }

    if (wdots(path)) /* Check for prohibited combinations of dots */
        goto err;

    src = path;            /* Start scanning here */
    dst = result;        /* Place results here */
    dend = dst + size;        /* Don't go to or past here */

    /* Copy prefix, assuming path is absolute */
    c = src[0];
    if (((c <= L'z' && c >= L'a') || (c <= L'Z' && c >= L'A'))
        && (src[1] == L':') && (src[2] == L'\\')) {
        /* Drive specifier */
        *src = towupper(*src);    /* Canonicalize drive letter */
        if (!(dst = wcp(dst, dend, L'\0', src, src + 2))) {
            goto err;
        }

        src += 2;
    } else if ((src[0] == L'\\') && (src[1] == L'\\')) {
        /* UNC pathname */
        WCHAR *p;
        p = wnextsep(src + 2);    /* Skip past host name */
        if (!*p) {
            /* A UNC pathname must begin with "\\\\host\\share",
               so reject this path as invalid if there is no share name */
            errno = EINVAL;
            goto err;
        }
        p = wnextsep(p + 1);    /* Skip past share name */
        if (!(dst = wcp(dst, dend, L'\0', src, p)))
            goto err;
        src = p;
    } else {
        /* Invalid path */
        errno = EINVAL;
        goto err;
    }
    /* At this point we have copied either a drive specifier ("z:") or a UNC
       prefix ("\\\\host\\share") to the result buffer, and src points to the
       first byte of the remainder of the path.  We now scan through the rest
       of the path, looking up each prefix in order to find the true name of
       the last element of each prefix, thereby computing the full true name of
       the original path. */
    while (*src) {
        WCHAR *p = wnextsep(src + 1);    /* Find next separator */
        WCHAR c = *p;
        WCHAR *pathbuf;
        int pathlen;

        assert(*src == L'\\');        /* Invariant */
        *p = L'\0';            /* Temporarily clear separator */

        if ((pathlen = (int)wcslen(path)) > MAX_PATH - 1) {
            pathbuf = getPrefixed(path, pathlen);
            h = FindFirstFileW(pathbuf, &fd);    /* Look up prefix */
            free(pathbuf);
        } else
            h = FindFirstFileW(path, &fd);    /* Look up prefix */

        *p = c;                /* Restore separator */
        if (h != INVALID_HANDLE_VALUE) {
            /* Lookup succeeded; append true name to result and continue */
            FindClose(h);

            // If a reparse point is encountered, get the final path.
            if ((fd.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) != 0) {
                // Do not fail if the final path cannot be obtained as the
                // canonicalization may still be otherwise correct
                WCHAR* fp = NULL;
                if ((fp = getFinalPath(path, result, size)) != NULL) {
                    free(path);
                    return fp;
                }
            }

            if (!(dst = wcp(dst, dend, L'\\', fd.cFileName,
                            fd.cFileName + wcslen(fd.cFileName)))){
                goto err;
            }
            src = p;
            continue;
        } else {
            if (!lastErrorReportable()) {
                if (!(dst = wcp(dst, dend, L'\0', src, src + wcslen(src)))){
                    goto err;
                }
                break;
            } else {
                goto err;
            }
        }
    }

    if (dst >= dend) {
        errno = ENAMETOOLONG;
        goto err;
    }
    *dst = L'\0';
    free(path);
    return result;

 err:
    free(path);
    return NULL;
}

/* Non-Wide character version of canonicalize.
   Converts to wchar and delegates to wcanonicalize. */
JNIEXPORT int
JDK_Canonicalize(const char *orig, char *out, int len) {
    wchar_t* wpath = NULL;
    wchar_t* wresult = NULL;
    wchar_t* wcanon = NULL;
    int wpath_len;
    int ret = -1;

    /* Get required buffer size to convert to Unicode */
    wpath_len = MultiByteToWideChar(CP_ACP, MB_ERR_INVALID_CHARS,
                                    orig, -1, NULL, 0);
    if (wpath_len == 0) {
        goto finish;
    }

    if ((wpath = (wchar_t*) malloc(sizeof(wchar_t) * wpath_len)) == NULL) {
        goto finish;
    }

    if (MultiByteToWideChar(CP_ACP, MB_ERR_INVALID_CHARS,
                            orig, -1, wpath, wpath_len) == 0) {
        goto finish;
    }

    if ((wresult = (wchar_t*) malloc(sizeof(wchar_t) * len)) == NULL) {
        goto finish;
    }

    if ((wcanon = wcanonicalize(wpath, wresult, len)) == NULL) {
        goto finish;
    }

    if (WideCharToMultiByte(CP_ACP, 0,
                            wcanon, -1, out, len, NULL, NULL) == 0) {
        goto finish;
    }

    // Change return value to success.
    ret = 0;

 finish:
    if (wcanon != NULL && wcanon != wresult)
        free(wcanon);
    if (wresult != NULL)
        free(wresult);
    if (wpath != NULL)
        free(wpath);

    return ret;
}

/* The appropriate location of getPrefixed() is io_util_md.c */

/* copy \\?\ or \\?\UNC\ to the front of path */
JNIEXPORT WCHAR*
getPrefixed(const WCHAR* path, int pathlen) {
    WCHAR* pathbuf = (WCHAR*)malloc((pathlen + 10) * sizeof (WCHAR));
    if (pathbuf != 0) {
        if (path[0] == L'\\' && path[1] == L'\\') {
            if (path[2] == L'?' && path[3] == L'\\'){
                /* if it already has a \\?\ don't do the prefix */
                wcscpy(pathbuf, path );
            } else {
                /* only UNC pathname includes double slashes here */
                wcscpy(pathbuf, L"\\\\?\\UNC\0");
                wcscat(pathbuf, path + 1);
            }
        } else {
            wcscpy(pathbuf, L"\\\\?\\\0");
            wcscat(pathbuf, path );
        }
    }
    return pathbuf;
}