Kernel+Userland: Implement setuid() and setgid() and add /bin/su

Also show setuid and setgid bits in "ls -l" output. :^)

Base/etc/passwd

@@ -1,2 +1,3 @@
 root:x:0:0:root:/:/bin/sh
 anon:x:100:100:Anonymous,,,:/home/anon:/bin/sh
+nona:x:200:200:Nona,,,:/home/nona:/bin/sh

Kernel/Process.cpp

@@ -411,6 +411,11 @@ int Process::do_exec(String path, Vector<String> arguments, Vector<String> envir
     m_initial_arguments = move(arguments);
     m_initial_environment = move(environment);
 
+    if (descriptor->metadata().is_setuid())
+        m_euid = descriptor->metadata().uid;
+    if (descriptor->metadata().is_setgid())
+        m_egid = descriptor->metadata().gid;
+
 #ifdef TASK_DEBUG
     kprintf("Process %u (%s) exec'd %s @ %p\n", pid(), name().characters(), path.characters(), m_tss.eip);
 #endif
@@ -1352,14 +1357,22 @@ int Process::sys$killpg(int pgrp, int signum)
     ASSERT_NOT_REACHED();
 }
 
-int Process::sys$setuid(uid_t)
+int Process::sys$setuid(uid_t uid)
 {
-    ASSERT_NOT_REACHED();
+    if (uid != m_uid && !is_superuser())
+        return -EPERM;
+    m_uid = uid;
+    m_euid = uid;
+    return 0;
 }
 
-int Process::sys$setgid(gid_t)
+int Process::sys$setgid(gid_t gid)
 {
-    ASSERT_NOT_REACHED();
+    if (gid != m_gid && !is_superuser())
+        return -EPERM;
+    m_gid = gid;
+    m_egid = gid;
+    return 0;
 }
 
 unsigned Process::sys$alarm(unsigned seconds)
@@ -1900,7 +1913,7 @@ int Process::sys$getgroups(int count, gid_t* gids)
 
 int Process::sys$setgroups(size_t count, const gid_t* gids)
 {
-    if (!is_root())
+    if (!is_superuser())
         return -EPERM;
     if (count >= MAX_PROCESS_GIDS)
         return -EINVAL;

Kernel/Process.h

@@ -283,7 +283,7 @@ public:
     Process* fork(RegisterDump&);
     int exec(String path, Vector<String> arguments, Vector<String> environment);
 
-    bool is_root() const { return m_euid == 0; }
+    bool is_superuser() const { return m_euid == 0; }
 
     bool wakeup_requested() { return m_wakeup_requested; }
     void request_wakeup() { m_wakeup_requested = true; }

Kernel/sync.sh

@@ -32,7 +32,10 @@ ln -s /proc/self/fd/0 mnt/dev/stdin
 ln -s /proc/self/fd/1 mnt/dev/stdout
 ln -s /proc/self/fd/2 mnt/dev/stderr
 cp -vR ../Base/* mnt/
+mkdir mnt/home/anon
+mkdir mnt/home/nona
 chown -vR 100:100 mnt/home/anon
+chown -vR 200:200 mnt/home/nona
 cp -v ../Userland/sh mnt/bin/sh
 cp -v ../Userland/id mnt/bin/id
 cp -v ../Userland/ps mnt/bin/ps
@@ -65,6 +68,8 @@ cp -v ../Userland/chmod mnt/bin/chmod
 cp -v ../Userland/top mnt/bin/top
 cp -v ../Userland/ln mnt/bin/ln
 cp -v ../Userland/df mnt/bin/df
+cp -v ../Userland/su mnt/bin/su
+chmod 4755 mnt/bin/su
 cp -v ../Applications/Terminal/Terminal mnt/bin/Terminal
 cp -v ../Applications/FontEditor/FontEditor mnt/bin/FontEditor
 cp -v ../Applications/Launcher/Launcher mnt/bin/Launcher

LibC/unistd.h

@@ -31,6 +31,8 @@ gid_t getgid();
 pid_t getpid();
 int getgroups(int size, gid_t list[]);
 int setgroups(size_t, const gid_t*);
+int setuid(uid_t);
+int setgid(gid_t);
 pid_t tcgetpgrp(int fd);
 int tcsetpgrp(int fd, pid_t pgid);
 int open(const char* path, int options, ...);

Userland/.gitignore

@@ -33,3 +33,4 @@ chmod
 pape
 ln
 df
+su

Userland/Makefile

@@ -29,6 +29,7 @@ OBJS = \
        top.o \
        df.o \
        ln.o \
+       su.o \
        rm.o
 
 APPS = \
@@ -63,6 +64,7 @@ APPS = \
        top \
        ln \
        df \
+       su \
        rm
 
 ARCH_FLAGS =
@@ -179,6 +181,9 @@ ln: ln.o
 df: df.o
 	$(LD) -o $@ $(LDFLAGS) $< ../LibC/LibC.a
 
+su: su.o
+	$(LD) -o $@ $(LDFLAGS) $< ../LibC/LibC.a
+
 .cpp.o:
 	@echo "CXX $<"; $(CXX) $(CXXFLAGS) -o $@ -c $<
 

Userland/ls.cpp

@@ -148,10 +148,10 @@ int do_dir(const char* path)
         printf("%c%c%c%c%c%c%c%c",
             st.st_mode & S_IRUSR ? 'r' : '-',
             st.st_mode & S_IWUSR ? 'w' : '-',
-            st.st_mode & S_IXUSR ? 'x' : '-',
+            st.st_mode & S_ISUID ? 's' : (st.st_mode & S_IXUSR ? 'x' : '-'),
             st.st_mode & S_IRGRP ? 'r' : '-',
             st.st_mode & S_IWGRP ? 'w' : '-',
-            st.st_mode & S_IXGRP ? 'x' : '-',
+            st.st_mode & S_ISGID ? 's' : (st.st_mode & S_IXGRP ? 'x' : '-'),
             st.st_mode & S_IROTH ? 'r' : '-',
             st.st_mode & S_IWOTH ? 'w' : '-'
         );

Userland/su.cpp

@@ -0,0 +1,44 @@
+#include <unistd.h>
+#include <stdio.h>
+#include <pwd.h>
+#include <grp.h>
+#include <alloca.h>
+
+extern "C" int main(int, char**);
+
+int main(int argc, char** argv)
+{
+    uid_t uid;
+    gid_t gid;
+    if (argc == 1) {
+        uid = 0;
+        gid = 0;
+    } else {
+        auto* pwd = getpwnam(argv[1]);
+        if (!pwd) {
+            fprintf(stderr, "No such user: %s\n", argv[1]);
+            return 1;
+        }
+        uid = pwd->pw_uid;
+        gid = pwd->pw_gid;
+    }
+
+    int rc = setgid(uid);
+    if (rc < 0) {
+        perror("setgid");
+        return 1;
+    }
+
+    rc = setuid(gid);
+    if (rc < 0) {
+        perror("setuid");
+        return 1;
+    }
+
+    rc = execl("/bin/sh", "sh", nullptr);
+    if (rc < 0) {
+        perror("execl");
+        return 1;
+    }
+    return 0;
+}