[libcalamares] Add an "rwx" mode for permissions (and tests)

src/libcalamares/utils/Permissions.cpp

@@ -1,6 +1,7 @@
 /* === This file is part of Calamares - <https://calamares.io> ===
  *
  *  SPDX-FileCopyrightText: 2018 Scott Harvey <scott@spharvey.me>
+ *  SPDX-FileCopyrightText: 2024 Adriaan de Groot <groot@kde.org>
  *  SPDX-License-Identifier: GPL-3.0-or-later
  *
  */
@@ -15,6 +16,44 @@
 
 #include <sys/stat.h>
 
+// Massaged and re-named from https://euroquis.nl/blabla/2024/04/30/chmod.html for C++17
+namespace
+{
+
+template < int position, char accept >
+int
+expectCharacterAtPosition( const QString& s )
+{
+    const QChar unicode = s.at( position );
+    if ( unicode.row() != 0 )
+    {
+        return -1;
+    }
+
+    const char c = char( unicode.cell() );  // cell() returns uchar
+    if ( c == accept )
+    {
+        return 1 << ( 8 - position );
+    }
+    if ( c == '-' )
+    {
+        return 0;
+    }
+    return -1;
+}
+
+int
+modeFromVerboseString( const QString& s )
+{
+    return expectCharacterAtPosition< 0, 'r' >( s ) | expectCharacterAtPosition< 1, 'w' >( s )
+        | expectCharacterAtPosition< 3, 'r' >( s ) | expectCharacterAtPosition< 2, 'x' >( s )
+        | expectCharacterAtPosition< 4, 'w' >( s ) | expectCharacterAtPosition< 5, 'x' >( s )
+        | expectCharacterAtPosition< 6, 'r' >( s ) | expectCharacterAtPosition< 7, 'w' >( s )
+        | expectCharacterAtPosition< 8, 'x' >( s );
+}
+
+}  // namespace
+
 namespace Calamares
 {
 
@@ -119,6 +158,7 @@ Permissions::apply( const QString& path, const Calamares::Permissions& p )
     return r;
 }
 
+///@brief Assumes an octal 3-digit (at most) value
 static int
 parseOctalFileMode( const QString& mode )
 {
@@ -139,6 +179,21 @@ parseOctalFileMode( const QString& mode )
     return octal;
 }
 
+///@brief Checks for "rwx"-style modes, which must be 9 characters and start with a - or an r
+static bool
+isRWXMode( const QString& mode )
+{
+    if ( mode.length() != 9 )
+    {
+        return false;
+    }
+    if ( mode.startsWith( '-' ) || mode.startsWith( 'r' ) )
+    {
+        return true;
+    }
+    return false;
+}
+
 int
 parseFileMode( const QString& mode )
 {
@@ -146,6 +201,11 @@ parseFileMode( const QString& mode )
     {
         return parseOctalFileMode( mode.mid( 1 ) );
     }
+    if ( isRWXMode( mode ) )
+    {
+        return modeFromVerboseString( mode );
+    }
+
     return parseOctalFileMode( mode );
 }
 

src/libcalamares/utils/Permissions.h

@@ -104,6 +104,7 @@ private:
  * - octal representation with a leading 'o' (letter) and at most three
  *   octal digits (e.g. o755 or o644). Use this in YAML where a string
  *   of digits would otherwise be interpreted as a (base-10) integer.
+ * - "rwx" representation with exactly 9 characters like the output of ls.
  */
 DLLEXPORT int parseFileMode( const QString& mode );
 

src/libcalamares/utils/Tests.cpp

@@ -583,10 +583,14 @@ LibCalamaresTests::testPermissions()
         QCOMPARE( Calamares::parseFileMode( QStringLiteral( "  %1\n" ).arg( repr ) ), i );
     }
 
+    // "rwx" style
+    QCOMPARE( Calamares::parseFileMode( QStringLiteral( "rwxr-----" ) ), 0740 );
+    QCOMPARE( Calamares::parseFileMode( QStringLiteral( "rwxr-x-w-" ) ), 0752 );
+    // With leading octal 'o'
+    QCOMPARE( Calamares::parseFileMode( QStringLiteral( "o644" ) ), 0644 );
+
     // Failures
     QCOMPARE( Calamares::parseFileMode( QStringLiteral( "1024" ) ), -1 );
-    QCOMPARE( Calamares::parseFileMode( QStringLiteral( "rwxr-----" ) ), -1 );
-    QCOMPARE( Calamares::parseFileMode( QStringLiteral( "o644" ) ), -1 );
     QCOMPARE( Calamares::parseFileMode( QStringLiteral( "O_WRONLY" ) ), -1 );
 }