From a181e61ca0119b8c3fd2daa4b8d23add2cda3ed0 Mon Sep 17 00:00:00 2001
From: Miklos Szeredi <miklos@szeredi.hu>
Date: Tue, 6 Nov 2001 12:03:23 +0000
Subject: bugfixes

---
 usermux.c | 252 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 252 insertions(+)
 create mode 100644 usermux.c

(limited to 'usermux.c')

diff --git a/usermux.c b/usermux.c
new file mode 100644
index 0000000..4caacb9
--- /dev/null
+++ b/usermux.c
@@ -0,0 +1,252 @@
+#include <fuse.h>
+
+#include <pthread.h>
+#include <glib.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <string.h>
+#include <signal.h>
+#include <wait.h>
+#include <errno.h>
+#include <pwd.h>
+#include <grp.h>
+
+#define MOUNTDIR "/mnt/avfs"
+
+static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
+
+static struct fuse *um_fuse;
+static const char *um_dir;
+
+#define MAX_USERS 100
+static uid_t users[MAX_USERS];
+static size_t numusers = 0;
+
+void avfs_main(struct fuse *fuse);
+
+static void reset_signal_handlers()
+{
+    struct sigaction sa;
+	
+    sa.sa_handler = SIG_DFL;
+    sigemptyset(&(sa.sa_mask));
+    sa.sa_flags = 0;
+	
+    sigaction(SIGCHLD, &sa, NULL);
+}
+
+
+static void start_avfs(uid_t uid)
+{
+    int res;
+    char *userdir;
+    struct fuse *user_fuse;
+    struct passwd pw_buf;
+    struct passwd *pw;
+    char buf[1024];
+
+    res = getpwuid_r(uid, &pw_buf, buf, sizeof(buf), &pw);
+    if(pw == NULL)
+        return;
+
+    user_fuse = fuse_new(0);
+    
+    userdir = g_strdup_printf("%s/%010u", MOUNTDIR, uid);
+    mkdir(userdir, 0755);
+    chown(userdir, pw->pw_uid, pw->pw_gid);
+    res = fuse_mount(user_fuse, userdir);
+    g_free(userdir);
+
+    if(res == -1)
+        return;
+
+    res = fork();
+    if(res == 0) {
+        reset_signal_handlers();
+
+        initgroups(pw->pw_name, pw->pw_gid);
+        setgid(pw->pw_gid);
+        setuid(pw->pw_uid);
+        
+        avfs_main(user_fuse);
+        exit(0);
+    }
+
+    fuse_destroy(user_fuse);
+}
+
+
+static int find_user(const char *userstr, uid_t *uid)
+{
+    size_t i;
+    char *end;
+    
+    *uid = strtol(userstr, &end, 10);
+    if(*end != '\0')
+        return 0;
+
+    pthread_mutex_lock(&lock);
+    for(i = 0; i < numusers; i++) {
+        if(users[i] == *uid) {
+            pthread_mutex_unlock(&lock);
+            return 1;
+        }
+    }
+    if(numusers == MAX_USERS) {
+        memmove(users, users + sizeof(users[0]),
+                (MAX_USERS - 1) * sizeof(users[0]));
+        numusers --;
+    }
+
+    users[numusers++] = *uid;
+    pthread_mutex_unlock(&lock);
+
+    start_avfs(*uid);
+
+    return 1;
+}
+
+static void root_attr(struct stat *stbuf)
+{
+    stbuf->st_mode = S_IFDIR | 0555;
+    stbuf->st_nlink = 2 + numusers;
+    stbuf->st_size = MAX_USERS;
+    stbuf->st_blksize = 1024;
+}
+
+static int um_getattr(struct fuse_cred *cred, const char *path,
+                      struct stat *stbuf)
+{
+    uid_t uid;
+    memset(stbuf, 0, sizeof(*stbuf));
+
+    if(strcmp(path, "/") == 0) {
+        root_attr(stbuf);
+        return 0;
+    }
+
+    if(!find_user(path+1, &uid))
+        return -ENOENT;
+
+    stbuf->st_mode = S_IFLNK | 0777;
+    stbuf->st_nlink = 1;
+    stbuf->st_size = strlen(MOUNTDIR) + 1 + 10;
+    stbuf->st_blksize = 1024;
+    stbuf->st_uid = uid;
+
+    return 0;
+}
+
+static int um_readlink(struct fuse_cred *cred, const char *path, char *buf,
+                       size_t size)
+{
+    uid_t uid;
+
+    if(!find_user(path+1, &uid))
+        return -ENOENT;
+
+    snprintf(buf, size, "%s/%010u", MOUNTDIR, uid);
+    return 0;
+}
+
+static int um_getdir(struct fuse_cred *cred, const char *path, fuse_dirh_t h,
+                     fuse_dirfil_t filler)
+{
+    size_t i;
+
+    if(strcmp(path, "/") != 0)
+        return 0;
+    
+    filler(h, ".", 0);
+    filler(h, "..", 0);
+
+    pthread_mutex_lock(&lock);
+    for(i = 0; i < numusers; i++) {
+        char buf[32];
+
+        sprintf(buf, "%u", users[i]);
+        filler(h, buf, 0);
+    }
+    pthread_mutex_unlock(&lock);
+
+    return 0;
+}
+
+
+static void exit_handler()
+{
+    exit(0);
+}
+
+static void child_handler()
+{
+    int status;
+    wait(&status);
+}
+
+static void set_signal_handlers()
+{
+    struct sigaction sa;
+
+    sa.sa_handler = exit_handler;
+    sigemptyset(&(sa.sa_mask));
+    sa.sa_flags = 0;
+
+    if (sigaction(SIGHUP, &sa, NULL) == -1 || 
+	sigaction(SIGINT, &sa, NULL) == -1 || 
+	sigaction(SIGTERM, &sa, NULL) == -1) {
+	
+	perror("Cannot set exit signal handlers");
+        exit(1);
+    }
+
+    sa.sa_handler = SIG_IGN;
+    
+    if(sigaction(SIGPIPE, &sa, NULL) == -1) {
+	perror("Cannot set ignored signals");
+        exit(1);
+    }
+
+    sa.sa_handler = child_handler;
+    if(sigaction(SIGCHLD, &sa, NULL) == -1) {
+	perror("Cannot set child signal handler");
+        exit(1);
+    }
+}
+
+static void cleanup()
+{
+    fuse_unmount(um_fuse);
+    fuse_destroy(um_fuse);
+}
+
+static struct fuse_operations um_oper = {
+    getattr:	um_getattr,
+    getdir:     um_getdir,
+    readlink:	um_readlink,
+};
+
+int main(int argc, char *argv[])
+{
+    int res;
+    if(argc != 2) {
+        fprintf(stderr, "usage: %s mount_dir\n", argv[0]);
+        exit(1);
+    }
+    
+    um_dir = argv[1];
+
+    set_signal_handlers();
+    atexit(cleanup);
+
+    um_fuse = fuse_new(0);
+    res = fuse_mount(um_fuse, um_dir);
+    if(res == -1)
+        exit(1);
+        
+    fuse_set_operations(um_fuse, &um_oper);
+    fuse_loop(um_fuse);
+
+    return 0;
+}
-- 
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