Handle win32 reparse points properly

7 files changed, 966 insertions, 132 deletions

diff --git a/src/win32/posix.h b/src/win32/posix.h
index e5a32b510..7f9d57cc3 100644
--- a/src/win32/posix.h
+++ b/src/win32/posix.h
@@ -30,7 +30,7 @@ GIT_INLINE(int) p_link(const char *old, const char *new)
 extern int p_mkdir(const char *path, mode_t mode);
 extern int p_unlink(const char *path);
 extern int p_lstat(const char *file_name, struct stat *buf);
-extern int p_readlink(const char *link, char *target, size_t target_len);
+extern int p_readlink(const char *path, char *buf, size_t bufsiz);
 extern int p_symlink(const char *old, const char *new);
 extern char *p_realpath(const char *orig_path, char *buffer);
 extern int p_vsnprintf(char *buffer, size_t count, const char *format, va_list argptr);
diff --git a/src/win32/posix_w32.c b/src/win32/posix_w32.c
index 868be6017..bef65a354 100644
--- a/src/win32/posix_w32.c
+++ b/src/win32/posix_w32.c
@@ -9,12 +9,13 @@
 #include "path.h"
 #include "utf-conv.h"
 #include "repository.h"
+#include "reparse.h"
 #include <errno.h>
 #include <io.h>
 #include <fcntl.h>
 #include <ws2tcpip.h>
 
-#if defined(__MINGW32__)
+#ifndef FILE_NAME_NORMALIZED
 # define FILE_NAME_NORMALIZED 0
 #endif
 
@@ -100,29 +101,79 @@ GIT_INLINE(time_t) filetime_to_time_t(const FILETIME *ft)
 	return (time_t)winTime;
 }
 
-#define WIN32_IS_WSEP(CH) ((CH) == L'/' || (CH) == L'\\')
-
-static int do_lstat(
-	const char *file_name, struct stat *buf, int posix_enotdir)
+/* On success, returns the length, in characters, of the path stored in dest.
+ * On failure, returns a negative value. */
+static int readlink_w(
+	git_win32_path dest,
+	const git_win32_path path)
 {
-	WIN32_FILE_ATTRIBUTE_DATA fdata;
-	git_win32_path fbuf;
-	wchar_t lastch;
-	int flen;
+	BYTE buf[MAXIMUM_REPARSE_DATA_BUFFER_SIZE];
+	GIT_REPARSE_DATA_BUFFER *reparse_buf = (GIT_REPARSE_DATA_BUFFER *)buf;
+	HANDLE handle = NULL;
+	DWORD ioctl_ret;
+	wchar_t *target;
+	size_t target_len;
+
+	int error = -1;
 
-	if ((flen = utf8_to_16_with_errno(fbuf, file_name)) < 0)
+	handle = CreateFileW(path, GENERIC_READ,
+		FILE_SHARE_READ | FILE_SHARE_DELETE, NULL, OPEN_EXISTING,
+		FILE_FLAG_OPEN_REPARSE_POINT | FILE_FLAG_BACKUP_SEMANTICS, NULL);
+
+	if (INVALID_HANDLE_VALUE == handle) {
+		errno = ENOENT;
 		return -1;
+	}
 
-	/* truncate trailing slashes */
-	for (; flen > 0; --flen) {
-		lastch = fbuf[flen - 1];
-		if (WIN32_IS_WSEP(lastch))
-			fbuf[flen - 1] = L'\0';
-		else if (lastch != L'\0')
-			break;
+	if (!DeviceIoControl(handle, FSCTL_GET_REPARSE_POINT, NULL, 0,
+		reparse_buf, sizeof(buf), &ioctl_ret, NULL)) {
+		errno = EINVAL;
+		goto on_error;
 	}
 
-	if (GetFileAttributesExW(fbuf, GetFileExInfoStandard, &fdata)) {
+	switch (reparse_buf->ReparseTag) {
+	case IO_REPARSE_TAG_SYMLINK:
+		target = reparse_buf->SymbolicLinkReparseBuffer.PathBuffer +
+			(reparse_buf->SymbolicLinkReparseBuffer.SubstituteNameOffset / sizeof(WCHAR));
+		target_len = reparse_buf->SymbolicLinkReparseBuffer.SubstituteNameLength / sizeof(WCHAR);
+		break;
+	case IO_REPARSE_TAG_MOUNT_POINT:
+		target = reparse_buf->MountPointReparseBuffer.PathBuffer +
+			(reparse_buf->MountPointReparseBuffer.SubstituteNameOffset / sizeof(WCHAR));
+		target_len = reparse_buf->MountPointReparseBuffer.SubstituteNameLength / sizeof(WCHAR);
+		break;
+	default:
+		errno = EINVAL;
+		goto on_error;
+	}
+
+	if (target_len) {
+		/* The path may need to have a prefix removed. */
+		target_len = git_win32__to_dos(target, target_len);
+
+		/* Need one additional character in the target buffer
+		 * for the terminating NULL. */
+		if (GIT_WIN_PATH_UTF16 > target_len) {
+			wcscpy(dest, target);
+			error = (int)target_len;
+		}
+	}
+
+on_error:
+	CloseHandle(handle);
+	return error;
+}
+
+#define WIN32_IS_WSEP(CH) ((CH) == L'/' || (CH) == L'\\')
+
+static int lstat_w(
+	wchar_t *path,
+	struct stat *buf,
+	bool posix_enotdir)
+{
+	WIN32_FILE_ATTRIBUTE_DATA fdata;
+
+	if (GetFileAttributesExW(path, GetFileExInfoStandard, &fdata)) {
 		int fMode = S_IREAD;
 
 		if (!buf)
@@ -136,12 +187,6 @@ static int do_lstat(
 		if (!(fdata.dwFileAttributes & FILE_ATTRIBUTE_READONLY))
 			fMode |= S_IWRITE;
 
-		if (fdata.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT)
-			fMode |= S_IFLNK;
-
-		if ((fMode & (S_IFDIR | S_IFLNK)) == (S_IFDIR | S_IFLNK)) // junction
-			fMode ^= S_IFLNK;
-
 		buf->st_ino = 0;
 		buf->st_gid = 0;
 		buf->st_uid = 0;
@@ -153,16 +198,17 @@ static int do_lstat(
 		buf->st_mtime = filetime_to_time_t(&(fdata.ftLastWriteTime));
 		buf->st_ctime = filetime_to_time_t(&(fdata.ftCreationTime));
 
-		/* Windows symlinks have zero file size, call readlink to determine
-		 * the length of the path pointed to, which we expect everywhere else
-		 */
-		if (S_ISLNK(fMode)) {
-			git_win32_utf8_path target;
+		if (fdata.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) {
+			git_win32_path target;
 
-			if (p_readlink(file_name, target, GIT_WIN_PATH_UTF8) == -1)
-				return -1;
+			if (readlink_w(target, path) >= 0) {
+				buf->st_mode = (buf->st_mode & ~S_IFMT) | S_IFLNK;
 
-			buf->st_size = strlen(target);
+				/* st_size gets the UTF-8 length of the target name, in bytes,
+				 * not counting the NULL terminator */
+				if ((buf->st_size = git__utf16_to_8(NULL, 0, target)) < 0)
+					return -1;
+			}
 		}
 
 		return 0;
@@ -174,18 +220,23 @@ static int do_lstat(
 	 * file path is a regular file, otherwise set ENOENT.
 	 */
 	if (posix_enotdir) {
+		size_t path_len = wcslen(path);
+
 		/* scan up path until we find an existing item */
 		while (1) {
+			DWORD attrs;
+
 			/* remove last directory component */
-			for (--flen; flen > 0 && !WIN32_IS_WSEP(fbuf[flen]); --flen);
+			for (path_len--; path_len > 0 && !WIN32_IS_WSEP(path[path_len]); path_len--);
 
-			if (flen <= 0)
+			if (path_len <= 0)
 				break;
 
-			fbuf[flen] = L'\0';
+			path[path_len] = L'\0';
+			attrs = GetFileAttributesW(path);
 
-			if (GetFileAttributesExW(fbuf, GetFileExInfoStandard, &fdata)) {
-				if (!(fdata.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY))
+			if (INVALID_FILE_ATTRIBUTES != attrs) {
+				if (!(attrs & FILE_ATTRIBUTE_DIRECTORY))
 					errno = ENOTDIR;
 				break;
 			}
@@ -195,105 +246,51 @@ static int do_lstat(
 	return -1;
 }
 
-int p_lstat(const char *filename, struct stat *buf)
+static int do_lstat(const char *path, struct stat *buf, bool posixly_correct)
 {
-	return do_lstat(filename, buf, 0);
+	git_win32_path path_w;
+	int len;
+
+	if ((len = utf8_to_16_with_errno(path_w, path)) < 0)
+		return -1;
+
+	git_win32__path_trim_end(path_w, len);
+
+	return lstat_w(path_w, buf, posixly_correct);
 }
 
-int p_lstat_posixly(const char *filename, struct stat *buf)
+int p_lstat(const char *filename, struct stat *buf)
 {
-	return do_lstat(filename, buf, 1);
+	return do_lstat(filename, buf, false);
 }
 
-/*
- * Returns the address of the GetFinalPathNameByHandleW function.
- * This function is available on Windows Vista and higher.
- */
-static PFGetFinalPathNameByHandleW get_fpnbyhandle(void)
+int p_lstat_posixly(const char *filename, struct stat *buf)
 {
-	static PFGetFinalPathNameByHandleW pFunc = NULL;
-	PFGetFinalPathNameByHandleW toReturn = pFunc;
-
-	if (!toReturn) {
-		HMODULE hModule = GetModuleHandleW(L"kernel32");
-
-		if (hModule)
-			toReturn = (PFGetFinalPathNameByHandleW)GetProcAddress(hModule, "GetFinalPathNameByHandleW");
-
-		pFunc = toReturn;
-	}
-
-	assert(toReturn);
-
-	return toReturn;
+	return do_lstat(filename, buf, true);
 }
 
-/*
- * Parts of the The p_readlink function are heavily inspired by the php 
- * readlink function in link_win32.c
- *
- * Copyright (c) 1999 - 2012 The PHP Group. All rights reserved.
- *
- * For details of the PHP license see http://www.php.net/license/3_01.txt
- */
-int p_readlink(const char *link, char *target, size_t target_len)
+int p_readlink(const char *path, char *buf, size_t bufsiz)
 {
-	static const wchar_t prefix[] = L"\\\\?\\";
-	PFGetFinalPathNameByHandleW pgfp = get_fpnbyhandle();
-	HANDLE hFile = NULL;
-	wchar_t *target_w = NULL;
-	bool trim_prefix;
-	git_win32_path link_w;
-	DWORD dwChars, dwLastError;
-	int error = -1;
-
-	/* Check that we found the function, and convert to UTF-16 */
-	if (!pgfp || utf8_to_16_with_errno(link_w, link) < 0)
-		goto on_error;
-
-	/* Use FILE_FLAG_BACKUP_SEMANTICS so we can open a directory. Do not
-	 * specify FILE_FLAG_OPEN_REPARSE_POINT; we want to open a handle to the
-	 * target of the link. */
-	hFile = CreateFileW(link_w, GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_DELETE,
-		NULL, OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, NULL);
-
-	if (hFile == INVALID_HANDLE_VALUE)
-		goto on_error;
-
-	/* Find out how large the buffer should be to hold the result */
-	if (!(dwChars = pgfp(hFile, NULL, 0, FILE_NAME_NORMALIZED)))
-		goto on_error;
-
-	if (!(target_w = git__malloc(dwChars * sizeof(wchar_t))))
-		goto on_error;
-
-	/* Call a second time */
-	dwChars = pgfp(hFile, target_w, dwChars, FILE_NAME_NORMALIZED);
-
-	if (!dwChars)
-		goto on_error;
-
-	/* Do we need to trim off a \\?\ from the start of the path? */
-	trim_prefix = (dwChars >= ARRAY_SIZE(prefix)) &&
-		!wcsncmp(prefix, target_w, ARRAY_SIZE(prefix));
-
-	/* Convert the result to UTF-8 */
-	if (git__utf16_to_8(target, target_len, trim_prefix ? target_w + 4 : target_w) < 0)
-		goto on_error;
+	git_win32_path path_w, target_w;
+	git_win32_utf8_path target;
+	int len;
 
-	error = 0;
+	/* readlink(2) does not NULL-terminate the string written
+	 * to the target buffer. Furthermore, the target buffer need
+	 * not be large enough to hold the entire result. A truncated
+	 * result should be written in this case. Since this truncation
+	 * could occur in the middle of the encoding of a code point,
+	 * we need to buffer the result on the stack. */
 
-on_error:
-	dwLastError = GetLastError();
-
-	if (hFile && INVALID_HANDLE_VALUE != hFile)
-		CloseHandle(hFile);
+	if (utf8_to_16_with_errno(path_w, path) < 0 ||
+		readlink_w(target_w, path_w) < 0 ||
+		(len = git_win32_path_to_utf8(target, target_w)) < 0)
+		return -1;
 
-	if (target_w)
-		git__free(target_w);
+	bufsiz = min((size_t)len, bufsiz);
+	memcpy(buf, target, bufsiz);
 
-	SetLastError(dwLastError);
-	return error;
+	return (int)bufsiz;
 }
 
 int p_symlink(const char *old, const char *new)
@@ -356,20 +353,94 @@ int p_getcwd(char *buffer_out, size_t size)
 	return 0;
 }
 
+/*
+ * Returns the address of the GetFinalPathNameByHandleW function.
+ * This function is available on Windows Vista and higher.
+ */
+static PFGetFinalPathNameByHandleW get_fpnbyhandle(void)
+{
+	static PFGetFinalPathNameByHandleW pFunc = NULL;
+	PFGetFinalPathNameByHandleW toReturn = pFunc;
+
+	if (!toReturn) {
+		HMODULE hModule = GetModuleHandleW(L"kernel32");
+
+		if (hModule)
+			toReturn = (PFGetFinalPathNameByHandleW)GetProcAddress(hModule, "GetFinalPathNameByHandleW");
+
+		pFunc = toReturn;
+	}
+
+	assert(toReturn);
+
+	return toReturn;
+}
+
+static int getfinalpath_w(
+	git_win32_path dest,
+	const wchar_t *path)
+{
+	PFGetFinalPathNameByHandleW pgfp = get_fpnbyhandle();
+	HANDLE hFile;
+	DWORD dwChars;
+
+	if (!pgfp)
+		return -1;
+
+	/* Use FILE_FLAG_BACKUP_SEMANTICS so we can open a directory. Do not
+	* specify FILE_FLAG_OPEN_REPARSE_POINT; we want to open a handle to the
+	* target of the link. */
+	hFile = CreateFileW(path, GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_DELETE,
+		NULL, OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, NULL);
+
+	if (hFile == INVALID_HANDLE_VALUE)
+		return -1;
+
+	/* Call GetFinalPathNameByHandle */
+	dwChars = pgfp(hFile, dest, GIT_WIN_PATH_UTF16, FILE_NAME_NORMALIZED);
+
+	if (!dwChars || dwChars >= GIT_WIN_PATH_UTF16) {
+		DWORD error = GetLastError();
+		CloseHandle(hFile);
+		SetLastError(error);
+		return -1;
+	}
+
+	CloseHandle(hFile);
+
+	/* The path may be delivered to us with a prefix; canonicalize */
+	return (int)git_win32__to_dos(dest, dwChars);
+}
+
+static int follow_and_lstat_link(git_win32_path path, struct stat* buf)
+{
+	git_win32_path target_w;
+
+	if (getfinalpath_w(target_w, path) < 0)
+		return -1;
+
+	return lstat_w(target_w, buf, false);
+}
+
 int p_stat(const char* path, struct stat* buf)
 {
-	git_win32_utf8_path target;
-	int error = 0;
+	git_win32_path path_w;
+	int len;
 
-	error = do_lstat(path, buf, 0);
+	if ((len = utf8_to_16_with_errno(path_w, path)) < 0)
+		return -1;
 
-	/* We need not do this in a loop to unwind chains of symlinks since
-	 * p_readlink calls GetFinalPathNameByHandle which does it for us. */
-	if (error >= 0 && S_ISLNK(buf->st_mode) &&
-		(error = p_readlink(path, target, GIT_WIN_PATH_UTF8)) >= 0)
-		error = do_lstat(target, buf, 0);
+	git_win32__path_trim_end(path_w, len);
 
-	return error;
+	if (lstat_w(path_w, buf, false) < 0)
+		return -1;
+
+	/* The item is a symbolic link or mount point. No need to iterate
+	 * to follow multiple links; use GetFinalPathNameFromHandle. */
+	if (S_ISLNK(buf->st_mode))
+		return follow_and_lstat_link(path_w, buf);
+
+	return 0;
 }
 
 int p_chdir(const char* path)
diff --git a/src/win32/reparse.h b/src/win32/reparse.h
new file mode 100644
index 000000000..4f56ed055
--- /dev/null
+++ b/src/win32/reparse.h
@@ -0,0 +1,57 @@
+/*
+* Copyright (C) the libgit2 contributors. All rights reserved.
+*
+* This file is part of libgit2, distributed under the GNU GPL v2 with
+* a Linking Exception. For full terms see the included COPYING file.
+*/
+
+#ifndef INCLUDE_git_win32_reparse_h__
+#define INCLUDE_git_win32_reparse_h__
+
+/* This structure is defined on MSDN at
+* http://msdn.microsoft.com/en-us/library/windows/hardware/ff552012(v=vs.85).aspx
+*
+* It was formerly included in the Windows 2000 SDK and remains defined in
+* MinGW, so we must define it with a silly name to avoid conflicting.
+*/
+typedef struct _GIT_REPARSE_DATA_BUFFER {
+	ULONG  ReparseTag;
+	USHORT ReparseDataLength;
+	USHORT Reserved;
+	union {
+		struct {
+			USHORT SubstituteNameOffset;
+			USHORT SubstituteNameLength;
+			USHORT PrintNameOffset;
+			USHORT PrintNameLength;
+			ULONG  Flags;
+			WCHAR  PathBuffer[1];
+		} SymbolicLinkReparseBuffer;
+		struct {
+			USHORT SubstituteNameOffset;
+			USHORT SubstituteNameLength;
+			USHORT PrintNameOffset;
+			USHORT PrintNameLength;
+			WCHAR  PathBuffer[1];
+		} MountPointReparseBuffer;
+		struct {
+			UCHAR DataBuffer[1];
+		} GenericReparseBuffer;
+	};
+} GIT_REPARSE_DATA_BUFFER;
+
+#define REPARSE_DATA_HEADER_SIZE			8
+#define REPARSE_DATA_MOUNTPOINT_HEADER_SIZE	8
+#define REPARSE_DATA_UNION_SIZE				12
+
+/* Missing in MinGW */
+#ifndef FSCTL_GET_REPARSE_POINT
+# define FSCTL_GET_REPARSE_POINT			0x000900a8
+#endif
+
+/* Missing in MinGW */
+#ifndef FSCTL_SET_REPARSE_POINT
+# define FSCTL_SET_REPARSE_POINT			0x000900a4
+#endif
+
+#endif
\ No newline at end of file
diff --git a/src/win32/w32_util.c b/src/win32/w32_util.c
index 246b30a6b..50b85a334 100644
--- a/src/win32/w32_util.c
+++ b/src/win32/w32_util.c
@@ -7,6 +7,8 @@
 
 #include "w32_util.h"
 
+#define CONST_STRLEN(x) ((sizeof(x)/sizeof(x[0])) - 1)
+
 /**
  * Creates a FindFirstFile(Ex) filter string from a UTF-8 path.
  * The filter string enumerates all items in the directory.
@@ -67,3 +69,71 @@ int git_win32__sethidden(const char *path)
 
 	return 0;
 }
+
+/**
+ * Removes any trailing backslashes from a path, except in the case of a drive
+ * letter path (C:\, D:\, etc.). This function cannot fail.
+ *
+ * @param path The path which should be trimmed.
+ * @return The length of the modified string (<= the input length)
+ */
+size_t git_win32__path_trim_end(wchar_t *str, size_t len)
+{
+	while (1) {
+		if (!len || str[len - 1] != L'\\')
+			break;
+
+		/* Don't trim backslashes from drive letter paths, which
+		 * are 3 characters long and of the form C:\, D:\, etc. */
+		if (3 == len && git_win32__isalpha(str[0]) && str[1] == ':')
+			break;
+
+		len--;
+	}
+
+	str[len] = L'\0';
+
+	return len;
+}
+
+/**
+ * Removes any of the following namespace prefixes from a path,
+ * if found: "\??\", "\\?\", "\\?\UNC\". This function cannot fail.
+ *
+ * @param path The path which should be converted.
+ * @return The length of the modified string (<= the input length)
+ */
+size_t git_win32__to_dos(wchar_t *str, size_t len)
+{
+	static const wchar_t dosdevices_prefix[] = L"\\\?\?\\";
+	static const wchar_t nt_prefix[] = L"\\\\?\\";
+	static const wchar_t unc_prefix[] = L"UNC\\";
+	size_t to_advance = 0;
+
+	/* "\??\" -- DOS Devices prefix */
+	if (len >= CONST_STRLEN(dosdevices_prefix) &&
+		!wcsncmp(str, dosdevices_prefix, CONST_STRLEN(dosdevices_prefix))) {
+		to_advance += CONST_STRLEN(dosdevices_prefix);
+		len -= CONST_STRLEN(dosdevices_prefix);
+	}
+	/* "\\?\" -- NT namespace prefix */
+	else if (len >= CONST_STRLEN(nt_prefix) &&
+		!wcsncmp(str, nt_prefix, CONST_STRLEN(nt_prefix))) {
+		to_advance += CONST_STRLEN(nt_prefix);
+		len -= CONST_STRLEN(nt_prefix);
+	}
+
+	/* "\??\UNC\", "\\?\UNC\" -- UNC prefix */
+	if (to_advance && len >= CONST_STRLEN(unc_prefix) &&
+		!wcsncmp(str + to_advance, unc_prefix, CONST_STRLEN(unc_prefix))) {
+		to_advance += CONST_STRLEN(unc_prefix);
+		len -= CONST_STRLEN(unc_prefix);
+	}
+
+	if (to_advance) {
+		memmove(str, str + to_advance, len * sizeof(wchar_t));
+		str[len] = L'\0';
+	}
+
+	return git_win32__path_trim_end(str, len);
+}
\ No newline at end of file
diff --git a/src/win32/w32_util.h b/src/win32/w32_util.h
index cd02bd7b2..acdee3d69 100644
--- a/src/win32/w32_util.h
+++ b/src/win32/w32_util.h
@@ -10,6 +10,11 @@
 
 #include "utf-conv.h"
 
+GIT_INLINE(bool) git_win32__isalpha(wchar_t c)
+{
+	return ((c >= L'A' && c <= L'Z') || (c >= L'a' && c <= L'z'));
+}
+
 /**
  * Creates a FindFirstFile(Ex) filter string from a UTF-8 path.
  * The filter string enumerates all items in the directory.
@@ -28,4 +33,22 @@ bool git_win32__findfirstfile_filter(git_win32_path dest, const char *src);
  */
 int git_win32__sethidden(const char *path);
 
+/**
+ * Removes any trailing backslashes from a path, except in the case of a drive
+ * letter path (C:\, D:\, etc.). This function cannot fail.
+ *
+ * @param path The path which should be trimmed.
+ * @return The length of the modified string (<= the input length)
+ */
+size_t git_win32__path_trim_end(wchar_t *str, size_t len);
+
+/**
+ * Removes any of the following namespace prefixes from a path,
+ * if found: "\??\", "\\?\", "\\?\UNC\". This function cannot fail.
+ *
+ * @param path The path which should be converted.
+ * @return The length of the modified string (<= the input length)
+ */
+size_t git_win32__to_dos(wchar_t *str, size_t len);
+
 #endif
diff --git a/tests/clar_libgit2.h b/tests/clar_libgit2.h
index d395bd66f..082fa9f4a 100644
--- a/tests/clar_libgit2.h
+++ b/tests/clar_libgit2.h
@@ -29,6 +29,17 @@
 
 #define cl_git_fail_with(expr, error) cl_assert_equal_i(error,expr)
 
+/**
+ * Like cl_git_pass, only for Win32 error code conventions
+ */
+#define cl_win32_pass(expr) do { \
+	int _win32_res; \
+	if ((_win32_res = (expr)) == 0) { \
+		giterr_set(GITERR_OS, "Returned: %d, system error code: %d", _win32_res, GetLastError()); \
+		cl_git_report_failure(_win32_res, __FILE__, __LINE__, "System call failed: " #expr); \
+	} \
+	} while(0)
+
 void cl_git_report_failure(int, const char *, int, const char *);
 
 #define cl_assert_at_line(expr,file,line) \
diff --git a/tests/core/link.c b/tests/core/link.c
new file mode 100644
index 000000000..20d2706f7
--- /dev/null
+++ b/tests/core/link.c
@@ -0,0 +1,602 @@
+#include "clar_libgit2.h"
+#include "posix.h"
+#include "buffer.h"
+#include "path.h"
+
+#ifdef GIT_WIN32
+# include "win32/reparse.h"
+#endif
+
+void test_core_link__cleanup(void)
+{
+#ifdef GIT_WIN32
+	RemoveDirectory("lstat_junction");
+	RemoveDirectory("lstat_dangling");
+	RemoveDirectory("lstat_dangling_dir");
+	RemoveDirectory("lstat_dangling_junction");
+
+	RemoveDirectory("stat_junction");
+	RemoveDirectory("stat_dangling");
+	RemoveDirectory("stat_dangling_dir");
+	RemoveDirectory("stat_dangling_junction");
+#endif
+}
+
+#ifdef GIT_WIN32
+static bool is_administrator(void)
+{
+	static SID_IDENTIFIER_AUTHORITY authority = { SECURITY_NT_AUTHORITY };
+	PSID admin_sid;
+	BOOL is_admin;
+
+	cl_win32_pass(AllocateAndInitializeSid(&authority, 2, SECURITY_BUILTIN_DOMAIN_RID, DOMAIN_ALIAS_RID_ADMINS, 0, 0, 0, 0, 0, 0, &admin_sid));
+	cl_win32_pass(CheckTokenMembership(NULL, admin_sid, &is_admin));
+	FreeSid(admin_sid);
+
+	return is_admin ? true : false;
+}
+#endif
+
+static void do_symlink(const char *old, const char *new, int is_dir)
+{
+#ifndef GIT_WIN32
+	GIT_UNUSED(is_dir);
+
+	cl_must_pass(symlink(old, new));
+#else
+	typedef DWORD (WINAPI *create_symlink_func)(LPCTSTR, LPCTSTR, DWORD);
+	HMODULE module;
+	create_symlink_func pCreateSymbolicLink;
+
+	if (!is_administrator())
+		clar__skip();
+
+	cl_assert(module = GetModuleHandle("kernel32"));
+	cl_assert(pCreateSymbolicLink = (create_symlink_func)GetProcAddress(module, "CreateSymbolicLinkA"));
+
+	cl_win32_pass(pCreateSymbolicLink(new, old, is_dir));
+#endif
+}
+
+static void do_hardlink(const char *old, const char *new)
+{
+#ifndef GIT_WIN32
+	cl_must_pass(link(old, new));
+#else
+	typedef DWORD (WINAPI *create_hardlink_func)(LPCTSTR, LPCTSTR, LPSECURITY_ATTRIBUTES);
+	HMODULE module;
+	create_hardlink_func pCreateHardLink;
+
+	if (!is_administrator())
+		clar__skip();
+
+	cl_assert(module = GetModuleHandle("kernel32"));
+	cl_assert(pCreateHardLink = (create_hardlink_func)GetProcAddress(module, "CreateHardLinkA"));
+
+	cl_win32_pass(pCreateHardLink(new, old, 0));
+#endif
+}
+
+#ifdef GIT_WIN32
+
+static void do_junction(const char *old, const char *new)
+{
+	GIT_REPARSE_DATA_BUFFER *reparse_buf;
+	HANDLE handle;
+	git_buf unparsed_buf = GIT_BUF_INIT;
+	wchar_t *subst_utf16, *print_utf16;
+	DWORD ioctl_ret;
+	int subst_utf16_len, subst_byte_len, print_utf16_len, print_byte_len, ret;
+	USHORT reparse_buflen;
+	size_t i;
+
+	/* Junction targets must be the unparsed name, starting with \??\, using
+	 * backslashes instead of forward, and end in a trailing backslash.
+	 * eg: \??\C:\Foo\
+	 */
+	git_buf_puts(&unparsed_buf, "\\??\\");
+
+	for (i = 0; i < strlen(old); i++)
+		git_buf_putc(&unparsed_buf, old[i] == '/' ? '\\' : old[i]);
+
+	git_buf_putc(&unparsed_buf, '\\');
+
+	subst_utf16_len = git__utf8_to_16(NULL, 0, git_buf_cstr(&unparsed_buf));
+	subst_byte_len = subst_utf16_len * sizeof(WCHAR);
+
+	print_utf16_len = subst_utf16_len - 4;
+	print_byte_len = subst_byte_len - (4 * sizeof(WCHAR));
+
+	/* The junction must be an empty directory before the junction attribute
+	 * can be added.
+	 */
+	cl_win32_pass(CreateDirectoryA(new, NULL));
+
+	handle = CreateFileA(new, GENERIC_WRITE, 0, NULL, OPEN_EXISTING,
+		FILE_FLAG_OPEN_REPARSE_POINT | FILE_FLAG_BACKUP_SEMANTICS, NULL);
+	cl_win32_pass(handle != INVALID_HANDLE_VALUE);
+
+	reparse_buflen = (USHORT)(REPARSE_DATA_HEADER_SIZE +
+		REPARSE_DATA_MOUNTPOINT_HEADER_SIZE +
+		subst_byte_len + sizeof(WCHAR) +
+		print_byte_len + sizeof(WCHAR));
+
+	reparse_buf = LocalAlloc(LMEM_FIXED|LMEM_ZEROINIT, reparse_buflen);
+	cl_assert(reparse_buf);
+
+	subst_utf16 = reparse_buf->MountPointReparseBuffer.PathBuffer;
+	print_utf16 = subst_utf16 + subst_utf16_len + 1;
+
+	ret = git__utf8_to_16(subst_utf16, subst_utf16_len + 1,
+		git_buf_cstr(&unparsed_buf));
+	cl_assert_equal_i(subst_utf16_len, ret);
+
+	ret = git__utf8_to_16(print_utf16,
+		print_utf16_len + 1, git_buf_cstr(&unparsed_buf) + 4);
+	cl_assert_equal_i(print_utf16_len, ret);
+
+	reparse_buf->ReparseTag = IO_REPARSE_TAG_MOUNT_POINT;
+	reparse_buf->MountPointReparseBuffer.SubstituteNameOffset = 0;
+	reparse_buf->MountPointReparseBuffer.SubstituteNameLength =	subst_byte_len;
+	reparse_buf->MountPointReparseBuffer.PrintNameOffset = (USHORT)(subst_byte_len + sizeof(WCHAR));
+	reparse_buf->MountPointReparseBuffer.PrintNameLength = print_byte_len;
+	reparse_buf->ReparseDataLength = reparse_buflen - REPARSE_DATA_HEADER_SIZE;
+
+	cl_win32_pass(DeviceIoControl(handle, FSCTL_SET_REPARSE_POINT,
+		reparse_buf, reparse_buflen, NULL, 0, &ioctl_ret, NULL));
+
+	CloseHandle(handle);
+	LocalFree(reparse_buf);
+}
+
+static void do_custom_reparse(const char *path)
+{
+	REPARSE_GUID_DATA_BUFFER *reparse_buf;
+	HANDLE handle;
+	DWORD ioctl_ret;
+
+	const char *reparse_data = "Reparse points are silly.";
+	size_t reparse_buflen = REPARSE_GUID_DATA_BUFFER_HEADER_SIZE +
+		strlen(reparse_data) + 1;
+
+	reparse_buf = LocalAlloc(LMEM_FIXED|LMEM_ZEROINIT, reparse_buflen);
+	cl_assert(reparse_buf);
+
+	reparse_buf->ReparseTag = 42;
+	reparse_buf->ReparseDataLength = (WORD)(strlen(reparse_data) + 1);
+
+	reparse_buf->ReparseGuid.Data1 = 0xdeadbeef;
+	reparse_buf->ReparseGuid.Data2 = 0xdead;
+	reparse_buf->ReparseGuid.Data3 = 0xbeef;
+	reparse_buf->ReparseGuid.Data4[0] = 42;
+	reparse_buf->ReparseGuid.Data4[1] = 42;
+	reparse_buf->ReparseGuid.Data4[2] = 42;
+	reparse_buf->ReparseGuid.Data4[3] = 42;
+	reparse_buf->ReparseGuid.Data4[4] = 42;
+	reparse_buf->ReparseGuid.Data4[5] = 42;
+	reparse_buf->ReparseGuid.Data4[6] = 42;
+	reparse_buf->ReparseGuid.Data4[7] = 42;
+	reparse_buf->ReparseGuid.Data4[8] = 42;
+
+	memcpy(reparse_buf->GenericReparseBuffer.DataBuffer,
+		reparse_data, strlen(reparse_data) + 1);
+
+	handle = CreateFileA(path, GENERIC_WRITE, 0, NULL, OPEN_EXISTING,
+		FILE_FLAG_OPEN_REPARSE_POINT | FILE_FLAG_BACKUP_SEMANTICS, NULL);
+	cl_win32_pass(handle != INVALID_HANDLE_VALUE);
+
+	cl_win32_pass(DeviceIoControl(handle, FSCTL_SET_REPARSE_POINT,
+		reparse_buf,
+		reparse_buf->ReparseDataLength + REPARSE_GUID_DATA_BUFFER_HEADER_SIZE,
+		NULL, 0, &ioctl_ret, NULL));
+
+	CloseHandle(handle);
+	LocalFree(reparse_buf);
+}
+
+#endif
+
+git_buf *unslashify(git_buf *buf)
+{
+#ifdef GIT_WIN32
+	size_t i;
+
+	for (i = 0; i < buf->size; i++)
+		if (buf->ptr[i] == '/')
+			buf->ptr[i] = '\\';
+#endif
+
+	return buf;
+}
+
+void test_core_link__stat_regular_file(void)
+{
+	struct stat st;
+
+	cl_git_rewritefile("stat_regfile", "This is a regular file!\n");
+
+	cl_must_pass(p_stat("stat_regfile", &st));
+	cl_assert(S_ISREG(st.st_mode));
+	cl_assert_equal_i(24, st.st_size);
+}
+
+void test_core_link__lstat_regular_file(void)
+{
+	struct stat st;
+
+	cl_git_rewritefile("lstat_regfile", "This is a regular file!\n");
+
+	cl_must_pass(p_stat("lstat_regfile", &st));
+	cl_assert(S_ISREG(st.st_mode));
+	cl_assert_equal_i(24, st.st_size);
+}
+
+void test_core_link__stat_symlink(void)
+{
+	struct stat st;
+
+	cl_git_rewritefile("stat_target", "This is the target of a symbolic link.\n");
+	do_symlink("stat_target", "stat_symlink", 0);
+
+	cl_must_pass(p_stat("stat_target", &st));
+	cl_assert(S_ISREG(st.st_mode));
+	cl_assert_equal_i(39, st.st_size);
+
+	cl_must_pass(p_stat("stat_symlink", &st));
+	cl_assert(S_ISREG(st.st_mode));
+	cl_assert_equal_i(39, st.st_size);
+}
+
+void test_core_link__stat_symlink_directory(void)
+{
+	struct stat st;
+
+	p_mkdir("stat_dirtarget", 0777);
+	do_symlink("stat_dirtarget", "stat_dirlink", 1);
+
+	cl_must_pass(p_stat("stat_dirtarget", &st));
+	cl_assert(S_ISDIR(st.st_mode));
+
+	cl_must_pass(p_stat("stat_dirlink", &st));
+	cl_assert(S_ISDIR(st.st_mode));
+}
+
+void test_core_link__stat_symlink_chain(void)
+{
+	struct stat st;
+
+	cl_git_rewritefile("stat_final_target", "Final target of some symbolic links...\n");
+	do_symlink("stat_final_target", "stat_chain_3", 0);
+	do_symlink("stat_chain_3", "stat_chain_2", 0);
+	do_symlink("stat_chain_2", "stat_chain_1", 0);
+
+	cl_must_pass(p_stat("stat_chain_1", &st));
+	cl_assert(S_ISREG(st.st_mode));
+	cl_assert_equal_i(39, st.st_size);
+}
+
+void test_core_link__stat_dangling_symlink(void)
+{
+	struct stat st;
+
+	do_symlink("stat_nonexistent", "stat_dangling", 0);
+
+	cl_must_fail(p_stat("stat_nonexistent", &st));
+	cl_must_fail(p_stat("stat_dangling", &st));
+}
+
+void test_core_link__stat_dangling_symlink_directory(void)
+{
+	struct stat st;
+
+	do_symlink("stat_nonexistent", "stat_dangling_dir", 1);
+
+	cl_must_fail(p_stat("stat_nonexistent_dir", &st));
+	cl_must_fail(p_stat("stat_dangling", &st));
+}
+
+void test_core_link__lstat_symlink(void)
+{
+	git_buf target_path = GIT_BUF_INIT;
+	struct stat st;
+
+	/* Windows always writes the canonical path as the link target, so
+	 * write the full path on all platforms.
+	 */
+	git_buf_join(&target_path, '/', clar_sandbox_path(), "lstat_target");
+
+	cl_git_rewritefile("lstat_target", "This is the target of a symbolic link.\n");
+	do_symlink(git_buf_cstr(&target_path), "lstat_symlink", 0);
+
+	cl_must_pass(p_lstat("lstat_target", &st));
+	cl_assert(S_ISREG(st.st_mode));
+	cl_assert_equal_i(39, st.st_size);
+
+	cl_must_pass(p_lstat("lstat_symlink", &st));
+	cl_assert(S_ISLNK(st.st_mode));
+	cl_assert_equal_i(git_buf_len(&target_path), st.st_size);
+
+	git_buf_free(&target_path);
+}
+
+void test_core_link__lstat_symlink_directory(void)
+{
+	git_buf target_path = GIT_BUF_INIT;
+	struct stat st;
+
+	git_buf_join(&target_path, '/', clar_sandbox_path(), "lstat_dirtarget");
+
+	p_mkdir("lstat_dirtarget", 0777);
+	do_symlink(git_buf_cstr(&target_path), "lstat_dirlink", 1);
+
+	cl_must_pass(p_lstat("lstat_dirtarget", &st));
+	cl_assert(S_ISDIR(st.st_mode));
+
+	cl_must_pass(p_lstat("lstat_dirlink", &st));
+	cl_assert(S_ISLNK(st.st_mode));
+	cl_assert_equal_i(git_buf_len(&target_path), st.st_size);
+
+	git_buf_free(&target_path);
+}
+
+void test_core_link__lstat_dangling_symlink(void)
+{
+	struct stat st;
+
+	do_symlink("lstat_nonexistent", "lstat_dangling", 0);
+
+	cl_must_fail(p_lstat("lstat_nonexistent", &st));
+
+	cl_must_pass(p_lstat("lstat_dangling", &st));
+	cl_assert(S_ISLNK(st.st_mode));
+	cl_assert_equal_i(strlen("lstat_nonexistent"), st.st_size);
+}
+
+void test_core_link__lstat_dangling_symlink_directory(void)
+{
+	struct stat st;
+
+	do_symlink("lstat_nonexistent", "lstat_dangling_dir", 1);
+
+	cl_must_fail(p_lstat("lstat_nonexistent", &st));
+
+	cl_must_pass(p_lstat("lstat_dangling_dir", &st));
+	cl_assert(S_ISLNK(st.st_mode));
+	cl_assert_equal_i(strlen("lstat_nonexistent"), st.st_size);
+}
+
+void test_core_link__stat_junction(void)
+{
+#ifdef GIT_WIN32
+	git_buf target_path = GIT_BUF_INIT;
+	struct stat st;
+
+	git_buf_join(&target_path, '/', clar_sandbox_path(), "stat_junctarget");
+
+	p_mkdir("stat_junctarget", 0777);
+	do_junction(git_buf_cstr(&target_path), "stat_junction");
+
+	cl_must_pass(p_stat("stat_junctarget", &st));
+	cl_assert(S_ISDIR(st.st_mode));
+
+	cl_must_pass(p_stat("stat_junction", &st));
+	cl_assert(S_ISDIR(st.st_mode));
+
+	git_buf_free(&target_path);
+#endif
+}
+
+void test_core_link__stat_dangling_junction(void)
+{
+#ifdef GIT_WIN32
+	git_buf target_path = GIT_BUF_INIT;
+	struct stat st;
+
+	git_buf_join(&target_path, '/', clar_sandbox_path(), "stat_nonexistent_junctarget");
+
+	p_mkdir("stat_nonexistent_junctarget", 0777);
+	do_junction(git_buf_cstr(&target_path), "stat_dangling_junction");
+
+	RemoveDirectory("stat_nonexistent_junctarget");
+
+	cl_must_fail(p_stat("stat_nonexistent_junctarget", &st));
+	cl_must_fail(p_stat("stat_dangling_junction", &st));
+
+	git_buf_free(&target_path);
+#endif
+}
+
+void test_core_link__lstat_junction(void)
+{
+#ifdef GIT_WIN32
+	git_buf target_path = GIT_BUF_INIT;
+	struct stat st;
+
+	git_buf_join(&target_path, '/', clar_sandbox_path(), "lstat_junctarget");
+
+	p_mkdir("lstat_junctarget", 0777);
+	do_junction(git_buf_cstr(&target_path), "lstat_junction");
+
+	cl_must_pass(p_lstat("lstat_junctarget", &st));
+	cl_assert(S_ISDIR(st.st_mode));
+
+	cl_must_pass(p_lstat("lstat_junction", &st));
+	cl_assert(S_ISLNK(st.st_mode));
+
+	git_buf_free(&target_path);
+#endif
+}
+
+void test_core_link__lstat_dangling_junction(void)
+{
+#ifdef GIT_WIN32
+	git_buf target_path = GIT_BUF_INIT;
+	struct stat st;
+
+	git_buf_join(&target_path, '/', clar_sandbox_path(), "lstat_nonexistent_junctarget");
+
+	p_mkdir("lstat_nonexistent_junctarget", 0777);
+	do_junction(git_buf_cstr(&target_path), "lstat_dangling_junction");
+
+	RemoveDirectory("lstat_nonexistent_junctarget");
+
+	cl_must_fail(p_lstat("lstat_nonexistent_junctarget", &st));
+
+	cl_must_pass(p_lstat("lstat_dangling_junction", &st));
+	cl_assert(S_ISLNK(st.st_mode));
+	cl_assert_equal_i(git_buf_len(&target_path), st.st_size);
+
+	git_buf_free(&target_path);
+#endif
+}
+
+void test_core_link__stat_hardlink(void)
+{
+	struct stat st;
+
+	cl_git_rewritefile("stat_hardlink1", "This file has many names!\n");
+	do_hardlink("stat_hardlink1", "stat_hardlink2");
+
+	cl_must_pass(p_stat("stat_hardlink1", &st));
+	cl_assert(S_ISREG(st.st_mode));
+	cl_assert_equal_i(26, st.st_size);
+
+	cl_must_pass(p_stat("stat_hardlink2", &st));
+	cl_assert(S_ISREG(st.st_mode));
+	cl_assert_equal_i(26, st.st_size);
+}
+
+void test_core_link__lstat_hardlink(void)
+{
+	struct stat st;
+
+	cl_git_rewritefile("lstat_hardlink1", "This file has many names!\n");
+	do_hardlink("lstat_hardlink1", "lstat_hardlink2");
+
+	cl_must_pass(p_lstat("lstat_hardlink1", &st));
+	cl_assert(S_ISREG(st.st_mode));
+	cl_assert_equal_i(26, st.st_size);
+
+	cl_must_pass(p_lstat("lstat_hardlink2", &st));
+	cl_assert(S_ISREG(st.st_mode));
+	cl_assert_equal_i(26, st.st_size);
+}
+
+void test_core_link__stat_reparse_point(void)
+{
+#ifdef GIT_WIN32
+	struct stat st;
+
+	/* Generic reparse points should be treated as regular files, only
+	 * symlinks and junctions should be treated as links.
+	 */
+
+	cl_git_rewritefile("stat_reparse", "This is a reparse point!\n");
+	do_custom_reparse("stat_reparse");
+
+	cl_must_pass(p_lstat("stat_reparse", &st));
+	cl_assert(S_ISREG(st.st_mode));
+	cl_assert_equal_i(25, st.st_size);
+#endif
+}
+
+void test_core_link__lstat_reparse_point(void)
+{
+#ifdef GIT_WIN32
+	struct stat st;
+
+	cl_git_rewritefile("lstat_reparse", "This is a reparse point!\n");
+	do_custom_reparse("lstat_reparse");
+
+	cl_must_pass(p_lstat("lstat_reparse", &st));
+	cl_assert(S_ISREG(st.st_mode));
+	cl_assert_equal_i(25, st.st_size);
+#endif
+}
+
+void test_core_link__readlink_nonexistent_file(void)
+{
+	char buf[2048];
+
+	cl_must_fail(p_readlink("readlink_nonexistent", buf, 2048));
+	cl_assert_equal_i(ENOENT, errno);
+}
+
+void test_core_link__readlink_normal_file(void)
+{
+	char buf[2048];
+
+	cl_git_rewritefile("readlink_regfile", "This is a regular file!\n");
+	cl_must_fail(p_readlink("readlink_regfile", buf, 2048));
+	cl_assert_equal_i(EINVAL, errno);
+}
+
+void test_core_link__readlink_symlink(void)
+{
+	git_buf target_path = GIT_BUF_INIT;
+	int len;
+	char buf[2048];
+
+	git_buf_join(&target_path, '/', clar_sandbox_path(), "readlink_target");
+
+	cl_git_rewritefile("readlink_target", "This is the target of a symlink\n");
+	do_symlink(git_buf_cstr(&target_path), "readlink_link", 0);
+
+	len = p_readlink("readlink_link", buf, 2048);
+	cl_must_pass(len);
+
+	buf[len] = 0;
+
+	cl_assert_equal_s(git_buf_cstr(unslashify(&target_path)), buf);
+
+	git_buf_free(&target_path);
+}
+
+void test_core_link__readlink_dangling(void)
+{
+	git_buf target_path = GIT_BUF_INIT;
+	int len;
+	char buf[2048];
+
+	git_buf_join(&target_path, '/', clar_sandbox_path(), "readlink_nonexistent");
+
+	do_symlink(git_buf_cstr(&target_path), "readlink_dangling", 0);
+
+	len = p_readlink("readlink_dangling", buf, 2048);
+	cl_must_pass(len);
+
+	buf[len] = 0;
+
+	cl_assert_equal_s(git_buf_cstr(unslashify(&target_path)), buf);
+
+	git_buf_free(&target_path);
+}
+
+void test_core_link__readlink_multiple(void)
+{
+	git_buf target_path = GIT_BUF_INIT,
+		path3 = GIT_BUF_INIT, path2 = GIT_BUF_INIT, path1 = GIT_BUF_INIT;
+	int len;
+	char buf[2048];
+
+	git_buf_join(&target_path, '/', clar_sandbox_path(), "readlink_final");
+	git_buf_join(&path3, '/', clar_sandbox_path(), "readlink_3");
+	git_buf_join(&path2, '/', clar_sandbox_path(), "readlink_2");
+	git_buf_join(&path1, '/', clar_sandbox_path(), "readlink_1");
+
+	do_symlink(git_buf_cstr(&target_path), git_buf_cstr(&path3), 0);
+	do_symlink(git_buf_cstr(&path3), git_buf_cstr(&path2), 0);
+	do_symlink(git_buf_cstr(&path2), git_buf_cstr(&path1), 0);
+
+	len = p_readlink("readlink_1", buf, 2048);
+	cl_must_pass(len);
+
+	buf[len] = 0;
+
+	cl_assert_equal_s(git_buf_cstr(unslashify(&path2)), buf);
+
+	git_buf_free(&path1);
+	git_buf_free(&path2);
+	git_buf_free(&path3);
+	git_buf_free(&target_path);
+}