LibCore: Sync groups, getgrent to getgrent_r, fix gr_mem bug

Userland/Libraries/LibCore/Group.cpp

@@ -6,13 +6,71 @@
 
 #include <AK/CharacterTypes.h>
 #include <AK/ScopeGuard.h>
+#include <AK/StringBuilder.h>
 #include <LibCore/File.h>
 #include <LibCore/Group.h>
 #include <LibCore/System.h>
+#include <LibCore/UmaskScope.h>
 #include <errno.h>
+#include <unistd.h>
 
 namespace Core {
 
+ErrorOr<String> Group::generate_group_file() const
+{
+    StringBuilder builder;
+
+    ScopeGuard grent_guard([] { endgrent(); });
+    setgrent();
+    errno = 0;
+#ifndef AK_OS_MACOS
+    struct group group;
+    struct group* gr = nullptr;
+    char buffer[1024] = { 0 };
+    while (getgrent_r(&group, buffer, sizeof(buffer), &gr) == 0 && gr) {
+#else
+    for (auto const* gr = getgrent(); gr; gr = getgrent()) {
+#endif
+        if (gr->gr_name == m_name)
+            builder.appendff("{}:x:{}:{}\n", m_name, m_id, String::join(',', m_members));
+        else {
+            Vector<String> members;
+            for (size_t i = 0; gr->gr_mem[i]; ++i)
+                members.append(gr->gr_mem[i]);
+
+            builder.appendff("{}:x:{}:{}\n", gr->gr_name, gr->gr_gid, String::join(',', members));
+        }
+    }
+
+    if (errno)
+        return Error::from_errno(errno);
+
+    return builder.to_string();
+}
+
+ErrorOr<void> Group::sync()
+{
+    Core::UmaskScope umask_scope(0777);
+
+    auto new_group_file_content = TRY(generate_group_file());
+
+    char new_group_name[] = "/etc/group.XXXXXX";
+    size_t new_group_name_length = strlen(new_group_name);
+
+    {
+        auto new_group_fd = TRY(Core::System::mkstemp({ new_group_name, new_group_name_length }));
+        ScopeGuard new_group_fd_guard([new_group_fd] { close(new_group_fd); });
+        TRY(Core::System::fchmod(new_group_fd, 0664));
+
+        auto nwritten = TRY(Core::System::write(new_group_fd, new_group_file_content.bytes()));
+        VERIFY(static_cast<size_t>(nwritten) == new_group_file_content.length());
+    }
+
+    TRY(Core::System::rename({ new_group_name, new_group_name_length }, "/etc/group"sv));
+
+    return {};
+}
+
 #if !defined(AK_OS_BSD_GENERIC) && !defined(AK_OS_ANDROID)
 ErrorOr<void> Group::add_group(Group& group)
 {
@@ -69,10 +127,17 @@ ErrorOr<Vector<Group>> Group::all()
     ScopeGuard grent_guard([] { endgrent(); });
     setgrent();
     errno = 0;
+#ifndef AK_OS_MACOS
+    struct group group;
+    struct group* gr = nullptr;
+    char buffer[1024] = { 0 };
+    while (getgrent_r(&group, buffer, sizeof(buffer), &gr) == 0 && gr) {
+#else
     for (auto const* gr = getgrent(); gr; gr = getgrent()) {
+#endif
         Vector<String> members;
         for (size_t i = 0; gr->gr_mem[i]; ++i)
-            members.append(*gr->gr_mem);
+            members.append(gr->gr_mem[i]);
 
         groups.append({ gr->gr_name, gr->gr_gid, members });
     }

Userland/Libraries/LibCore/Group.h

@@ -34,11 +34,15 @@ public:
 
     Vector<String>& members() { return m_members; }
 
+    ErrorOr<void> sync();
+
 private:
     static ErrorOr<bool> name_exists(StringView name);
     static ErrorOr<bool> id_exists(gid_t id);
     ErrorOr<struct group> to_libc_group();
 
+    ErrorOr<String> generate_group_file() const;
+
     String m_name;
     gid_t m_id { 0 };
     Vector<String> m_members;