Add GetLStat

faccessat() does not support AT_SYMLINK_NOFOLLOW on OS X, so instead,
we use the success of lstat() to determine if the file (not following
symbolic links) exists. Also allowed for some refactoring.

src/libpsl-native/src/CMakeLists.txt

@@ -1,5 +1,6 @@
 add_library(psl-native SHARED
   getstat.cpp
+  getlstat.cpp
   getpwuid.cpp
   getuserfrompid.cpp
   getfileowner.cpp

src/libpsl-native/src/getlstat.cpp

@@ -0,0 +1,95 @@
+//! @file getlstat.cpp
+//! @author Andrew Schwartzmeyer <andschwa@microsoft.com>
+//! @brief returns the lstat of a file
+
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <pwd.h>
+#include <string.h>
+#include <unistd.h>
+#include "getlstat.h"
+
+//! @brief GetLStat returns the lstat of a file. This simply delegates to the
+//! lstat() system call and maps errno to the expected values for GetLastError.
+//!
+//! GetLstat
+//!
+//! @param[in] path
+//! @parblock
+//! A pointer to the buffer that contains the file name
+//!
+//! char* is marshaled as an LPStr, which on Linux is UTF-8.
+//! @endparblock
+//!
+//! @param[in] lstat
+//! @parblock
+//! A pointer to the buffer in which to place the lstat information
+//! @endparblock
+//!
+//! @exception errno Passes these errors via errno to GetLastError:
+//! - ERROR_INVALID_PARAMETER: parameter is not valid
+//! - ERROR_FILE_NOT_FOUND: file does not exist
+//! - ERROR_ACCESS_DENIED: access is denied
+//! - ERROR_INVALID_ADDRESS: attempt to access invalid address
+//! - ERROR_STOPPED_ON_SYMLINK: too many symbolic links
+//! - ERROR_GEN_FAILURE: I/O error occurred
+//! - ERROR_INVALID_NAME: file provided is not a symbolic link
+//! - ERROR_INVALID_FUNCTION: incorrect function
+//! - ERROR_BAD_PATH_NAME: pathname is too long
+//! - ERROR_OUTOFMEMORY insufficient kernel memory
+//!
+//! @retval 0 if successful
+//! @retval -1 if failed
+//!
+
+int32_t GetLStat(const char* path, struct stat* buf)
+{
+    errno = 0;
+
+    if (!path)
+    {
+        errno = ERROR_INVALID_PARAMETER;
+        return -1;
+    }
+
+    int32_t ret = lstat(path, buf);
+
+    if (ret != 0)
+    {
+        switch(errno)
+        {
+        case EACCES:
+            errno = ERROR_ACCESS_DENIED;
+            break;
+        case EBADF:
+            errno = ERROR_FILE_NOT_FOUND;
+            break;
+        case EFAULT:
+            errno = ERROR_INVALID_ADDRESS;
+            break;
+        case ELOOP:
+            errno = ERROR_STOPPED_ON_SYMLINK;
+            break;
+        case ENAMETOOLONG:
+            errno = ERROR_GEN_FAILURE;
+            break;
+        case ENOENT:
+            errno = ERROR_FILE_NOT_FOUND;
+            break;
+        case ENOMEM:
+            errno = ERROR_NO_SUCH_USER;
+            break;
+        case ENOTDIR:
+            errno = ERROR_INVALID_NAME;
+            break;
+        case EOVERFLOW:
+            errno = ERROR_BUFFER_OVERFLOW;
+            break;
+        default:
+            errno = ERROR_INVALID_FUNCTION;
+        }
+    }
+
+    return ret;
+}

src/libpsl-native/src/getlstat.h

@@ -0,0 +1,10 @@
+#pragma once
+
+#include <sys/stat.h>
+#include "pal.h"
+
+PAL_BEGIN_EXTERNC
+
+int32_t GetLStat(const char* path, struct stat* buf);
+
+PAL_END_EXTERNC

src/libpsl-native/src/getstat.cpp

@@ -89,8 +89,7 @@ int32_t GetStat(const char* path, struct stat* buf)
         default:
             errno = ERROR_INVALID_FUNCTION;
         }
-        return -1;
     }
 
-    return 0;
+    return ret;
 }

src/libpsl-native/src/isdirectory.cpp

@@ -31,7 +31,6 @@
 //!
 bool IsDirectory(const char* path)
 {
-    int32_t ret = 0;
     errno = 0;
 
     if (!path)
@@ -41,7 +40,7 @@ bool IsDirectory(const char* path)
     }
 
     struct stat buf;
-    ret = GetStat(path, &buf);
+    int32_t ret = GetStat(path, &buf);
     if (ret != 0)
     {
         return false;

src/libpsl-native/src/isfile.cpp

@@ -9,6 +9,7 @@
 #include <string.h>
 #include <fcntl.h>
 #include <unistd.h>
+#include "getlstat.h"
 #include "isfile.h"
 
 //! @brief returns if the path is a file or directory
@@ -37,6 +38,6 @@ bool IsFile(const char* path)
         return false;
     }
 
-    // Resolve relative paths to cwd of process, and do not follow symlinks
-    return faccessat(AT_FDCWD, path, F_OK, AT_SYMLINK_NOFOLLOW) != -1;
+    struct stat buf;
+    return GetLStat(path, &buf) == 0;
 }

src/libpsl-native/src/issymlink.cpp

@@ -7,6 +7,7 @@
 #include <sys/stat.h>
 #include <unistd.h>
 #include <string>
+#include "getlstat.h"
 #include "issymlink.h"
 
 //! @brief IsSymlink determines if path is a symbolic link
@@ -48,46 +49,12 @@ bool IsSymLink(const char* path)
         return false;
     }
 
-    struct stat statBuf;
-
-    int ret = lstat(path, &statBuf);
-
+    struct stat buf;
+    int32_t ret = GetLStat(path, &buf);
     if (ret != 0)
     {
-        switch(errno)
-        {
-        case EACCES:
-            errno = ERROR_ACCESS_DENIED;
-            break;
-        case EBADF:
-            errno = ERROR_FILE_NOT_FOUND;
-            break;
-        case EFAULT:
-            errno = ERROR_INVALID_ADDRESS;
-            break;
-        case ELOOP:
-            errno = ERROR_STOPPED_ON_SYMLINK;
-            break;
-        case ENAMETOOLONG:
-            errno = ERROR_GEN_FAILURE;
-            break;
-        case ENOENT:
-            errno = ERROR_FILE_NOT_FOUND;
-            break;
-        case ENOMEM:
-            errno = ERROR_NO_SUCH_USER;
-            break;
-        case ENOTDIR:
-            errno = ERROR_INVALID_NAME;
-            break;
-        case EOVERFLOW:
-            errno = ERROR_BUFFER_OVERFLOW;
-            break;
-        default:
-            errno = ERROR_INVALID_FUNCTION;
-        }
         return false;
     }
 
-    return S_ISLNK(statBuf.st_mode);
+    return S_ISLNK(buf.st_mode);
 }