From 8a90db837bfb06e02017256d77a15d4357595638 Mon Sep 17 00:00:00 2001
From: apio <blobs.trading@gmail.com>
Date: Wed, 22 Nov 2023 20:35:43 +0100
Subject: [PATCH] kernel+libc: Add support for supplementary groups (2/2)

Adds system calls for setting and getting groups, along with libc wrappers.
---
 kernel/src/api/Syscall.h      |  2 +-
 kernel/src/sys/id.cpp         | 51 +++++++++++++++++++++++++++++++++++
 libc/include/grp.h            |  3 +++
 libc/include/unistd.h         |  3 +++
 libc/src/grp.cpp              |  8 ++++++
 libc/src/unistd.cpp           |  6 +++++
 libluna/include/luna/Vector.h |  7 +++++
 7 files changed, 79 insertions(+), 1 deletion(-)

diff --git a/kernel/src/api/Syscall.h b/kernel/src/api/Syscall.h
index f05dd6fe..f6fd7960 100644
--- a/kernel/src/api/Syscall.h
+++ b/kernel/src/api/Syscall.h
@@ -9,7 +9,7 @@
                         _e(pivot_root) _e(sigreturn) _e(sigaction) _e(kill) _e(sigprocmask) _e(setpgid) _e(isatty)     \
                             _e(getpgid) _e(socket) _e(bind) _e(connect) _e(listen) _e(accept) _e(poll) _e(msync)       \
                                 _e(truncate) _e(ftruncate) _e(utimensat) _e(setitimer) _e(pledge) _e(memstat)          \
-                                    _e(setsid) _e(getsid)
+                                    _e(setsid) _e(getsid) _e(getgroups) _e(setgroups)
 
 enum Syscalls
 {
diff --git a/kernel/src/sys/id.cpp b/kernel/src/sys/id.cpp
index 7b7bb7c1..12dadd98 100644
--- a/kernel/src/sys/id.cpp
+++ b/kernel/src/sys/id.cpp
@@ -237,3 +237,54 @@ Result<u64> sys_fchownat(Registers*, SyscallArgs args)
 
     return 0;
 }
+
+Result<u64> sys_getgroups(Registers*, SyscallArgs args)
+{
+    int ngroups = (int)args[0];
+    gid_t* grouplist = (gid_t*)args[1];
+
+    auto* current = Scheduler::current();
+
+    TRY(check_pledge(current, Promise::p_stdio));
+
+    if (!ngroups) return current->extra_groups.size();
+    if (ngroups < 0) return err(EINVAL);
+
+    if (static_cast<usize>(ngroups) < current->extra_groups.size()) return err(EINVAL);
+
+    if (!MemoryManager::copy_to_user(grouplist, current->extra_groups.data(),
+                                     current->extra_groups.size() * sizeof(gid_t)))
+        return err(EFAULT);
+
+    return current->extra_groups.size();
+}
+
+Result<u64> sys_setgroups(Registers*, SyscallArgs args)
+{
+    int ngroups = (int)args[0];
+    const gid_t* grouplist = (const gid_t*)args[1];
+
+    auto* current = Scheduler::current();
+
+    TRY(check_pledge(current, Promise::p_id));
+
+    Credentials& auth = current->auth;
+    if (auth.euid != 0) return err(EPERM);
+
+    if (!ngroups)
+    {
+        current->extra_groups.clear();
+        return 0;
+    }
+
+    if (ngroups < 0 || ngroups > 32) return err(EINVAL);
+
+    TRY(current->extra_groups.try_reserve(ngroups));
+
+    current->extra_groups.mutate([&](gid_t* list, usize) -> usize {
+        if (MemoryManager::copy_from_user(grouplist, list, ngroups * sizeof(gid_t))) return ngroups;
+        return current->extra_groups.size();
+    });
+
+    return 0;
+}
diff --git a/libc/include/grp.h b/libc/include/grp.h
index e00eca0e..e7bf6294 100644
--- a/libc/include/grp.h
+++ b/libc/include/grp.h
@@ -33,6 +33,9 @@ extern "C"
     /* End group file parsing. */
     void endgrent(void);
 
+    /* Set this process's list of supplementary groups. */
+    int setgroups(int size, const gid_t* list);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/libc/include/unistd.h b/libc/include/unistd.h
index ef7cdca4..74c5ff64 100644
--- a/libc/include/unistd.h
+++ b/libc/include/unistd.h
@@ -205,6 +205,9 @@ extern "C"
     /* Restrict system operations. */
     int pledge(const char* promises, const char* execpromises);
 
+    /* Get this process's list of supplementary groups. */
+    int getgroups(int size, gid_t* list);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/libc/src/grp.cpp b/libc/src/grp.cpp
index d6a46905..3b4aaf6b 100644
--- a/libc/src/grp.cpp
+++ b/libc/src/grp.cpp
@@ -5,6 +5,8 @@
 #include <luna/Vector.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <sys/syscall.h>
+#include <unistd.h>
 
 static struct group grp;
 static FILE* f { nullptr };
@@ -112,4 +114,10 @@ extern "C"
             f = nullptr;
         }
     }
+
+    int setgroups(int size, const gid_t* list)
+    {
+        long rc = syscall(SYS_setgroups, size, list);
+        __errno_return(rc, int);
+    }
 }
diff --git a/libc/src/unistd.cpp b/libc/src/unistd.cpp
index bb54e0ee..69ae625c 100644
--- a/libc/src/unistd.cpp
+++ b/libc/src/unistd.cpp
@@ -545,4 +545,10 @@ extern "C"
         long rc = syscall(SYS_setsid);
         __errno_return(rc, pid_t);
     }
+
+    int getgroups(int size, gid_t* list)
+    {
+        long rc = syscall(SYS_getgroups, size, list);
+        __errno_return(rc, int);
+    }
 }
diff --git a/libluna/include/luna/Vector.h b/libluna/include/luna/Vector.h
index 28a578c5..6c7eb068 100644
--- a/libluna/include/luna/Vector.h
+++ b/libluna/include/luna/Vector.h
@@ -1,6 +1,7 @@
 #pragma once
 #include <luna/Alloc.h>
 #include <luna/CString.h>
+#include <luna/Common.h>
 #include <luna/Result.h>
 #include <luna/Slice.h>
 #include <luna/Types.h>
@@ -245,6 +246,12 @@ template <typename T> class Vector
         return other;
     }
 
+    template <typename Callback> void mutate(Callback callback)
+    {
+        usize size = callback(m_data, m_capacity);
+        m_size = min(m_capacity, size);
+    }
+
   private:
     T* m_data { nullptr };
     usize m_capacity { 0 };