/*

* Copyright (C) 2010 The Android Open Source Project

*

* Licensed under the Apache License, Version 2.0 (the "License");

* you may not use this file except in compliance with the License.

* You may obtain a copy of the License at

*

* http://www.apache.org/licenses/LICENSE-2.0

*

* Unless required by applicable law or agreed to in writing, software

* distributed under the License is distributed on an "AS IS" BASIS,

* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

* See the License for the specific language governing permissions and

* limitations under the License.

*/

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include

#include "fuse.h"

/* README

*

* What is this?

*

* sdcard is a program that uses FUSE to emulate FAT-on-sdcard style

* directory permissions (all files are given fixed owner, group, and

* permissions at creation, owner, group, and permissions are not

* changeable, symlinks and hardlinks are not createable, etc.

*

* usage: sdcard

*

* It must be run as root, but will change to uid/gid as soon as it

* mounts a filesystem on /mnt/sdcard. It will refuse to run if uid or

* gid are zero.

*

*

* Things I believe to be true:

*

* - ops that return a fuse_entry (LOOKUP, MKNOD, MKDIR, LINK, SYMLINK,

* CREAT) must bump that node's refcount

* - don't forget that FORGET can forget multiple references (req->nlookup)

* - if an op that returns a fuse_entry fails writing the reply to the

* kernel, you must rollback the refcount to reflect the reference the

* kernel did not actually acquire

*

*

* Bugs:

*

* - need to move/rename node on RENAME

*/

#define FUSE_TRACE 0

#if FUSE_TRACE

#define TRACE(x...) fprintf(stderr,x)

#else

#define TRACE(x...) do {} while (0)

#endif

#define ERROR(x...) fprintf(stderr,x)

#define FUSE_UNKNOWN_INO 0xffffffff

#define MOUNT_POINT "/mnt/sdcard"

struct handle {

struct node *node;

int fd;

};

struct dirhandle {

struct node *node;

DIR *d;

};

struct node {

__u64 nid;

__u64 gen;

struct node *next;

struct node *child;

struct node *all;

struct node *parent;

__u32 refcount;

__u32 namelen;

char name[1];

};

struct fuse {

__u64 next_generation;

__u64 next_node_id;

int fd;

struct node *all;

struct node root;

char rootpath[1024];

};

#define PATH_BUFFER_SIZE 1024

char *node_get_path(struct node *node, char *buf, const char *name)

{

char *out = buf + PATH_BUFFER_SIZE - 1;

int len;

out[0] = 0;

if (name) {

len = strlen(name);

goto start;

}

while (node) {

name = node->name;

len = node->namelen;

node = node->parent;

start:

if ((len + 1) > (out - buf))

return 0;

out -= len;

memcpy(out, name, len);

out --;

out[0] = '/';

}

return out;

}

void attr_from_stat(struct fuse_attr *attr, struct stat *s)

{

attr->ino = s->st_ino;

attr->size = s->st_size;

attr->blocks = s->st_blocks;

attr->atime = s->st_atime;

attr->mtime = s->st_mtime;

attr->ctime = s->st_ctime;

attr->atimensec = s->st_atime_nsec;

attr->mtimensec = s->st_mtime_nsec;

attr->ctimensec = s->st_ctime_nsec;

attr->mode = s->st_mode;

attr->nlink = s->st_nlink;

/* force permissions to something reasonable:

* world readable

* writable by the sdcard group

*/

if (attr->mode & 0100) {

attr->mode = (attr->mode & (~0777)) | 0775;

} else {

attr->mode = (attr->mode & (~0777)) | 0664;

}

/* all files owned by root.sdcard */

attr->uid = 0;

attr->gid = AID_SDCARD_RW;

}

int node_get_attr(struct node *node, struct fuse_attr *attr)

{

int res;

struct stat s;

char *path, buffer[PATH_BUFFER_SIZE];

path = node_get_path(node, buffer, 0);

res = lstat(path, &s);

if (res < 0) {

ERROR("lstat('%s') errno %d\n", path, errno);

return -1;

}

attr_from_stat(attr, &s);

attr->ino = node->nid;

return 0;

}

struct node *node_create(struct node *parent, const char *name, __u64 nid, __u64 gen)

{

struct node *node;

int namelen = strlen(name);

node = calloc(1, sizeof(struct node) + namelen);

if (node == 0) {

return 0;

}

node->nid = nid;

node->gen = gen;

node->parent = parent;

node->next = parent->child;

parent->child = node;

memcpy(node->name, name, namelen + 1);

node->namelen = namelen;

parent->refcount++;

return node;

}

void fuse_init(struct fuse *fuse, int fd, const char *path)

{

fuse->fd = fd;

fuse->next_node_id = 2;

fuse->next_generation = 0;

fuse->all = &fuse->root;

fuse->root.nid = FUSE_ROOT_ID; /* 1 */

fuse->root.next = 0;

fuse->root.child = 0;

fuse->root.parent = 0;

fuse->root.all = 0;

fuse->root.refcount = 2;

strcpy(fuse->root.name, path);

fuse->root.namelen = strlen(fuse->root.name);

}

static inline void *id_to_ptr(__u64 nid)

{

return (void *) nid;

}

static inline __u64 ptr_to_id(void *ptr)

{

return (__u64) ptr;

}

struct node *lookup_by_inode(struct fuse *fuse, __u64 nid)

{

if (nid == FUSE_ROOT_ID) {

return &fuse->root;

} else {

return id_to_ptr(nid);

}

}

struct node *lookup_child_by_name(struct node *node, const char *name)

{

for (node = node->child; node; node = node->next) {

if (!strcmp(name, node->name)) {

return node;

}

}

return 0;

}

struct node *lookup_child_by_inode(struct node *node, __u64 nid)

{

for (node = node->child; node; node = node->next) {

if (node->nid == nid) {

return node;

}

}

return 0;

}

struct node *node_lookup(struct fuse *fuse, struct node *parent, const char *name,

struct fuse_attr *attr)

{

int res;

struct stat s;

char *path, buffer[PATH_BUFFER_SIZE];

struct node *node;

path = node_get_path(parent, buffer, name);

/* XXX error? */

res = lstat(path, &s);

if (res < 0)

return 0;

node = lookup_child_by_name(parent, name);

if (!node) {

node = node_create(parent, name, fuse->next_node_id++, fuse->next_generation++);

if (!node)

return 0;

node->nid = ptr_to_id(node);

node->all = fuse->all;

fuse->all = node;

}

attr_from_stat(attr, &s);

attr->ino = node->nid;

return node;

}

void node_release(struct node *node)

{

TRACE("RELEASE %p (%s) rc=%d\n", node, node->name, node->refcount);

node->refcount--;

if (node->refcount == 0) {

if (node->parent->child == node) {

node->parent->child = node->parent->child->next;

} else {

struct node *node2;

node2 = node->parent->child;

while (node2->next != node)

node2 = node2->next;

node2->next = node->next;

}

TRACE("DESTROY %p (%s)\n", node, node->name);

node_release(node->parent);

node->parent = 0;

node->next = 0;

/* TODO: remove debugging - poison memory */

memset(node, 0xef, sizeof(*node) + strlen(node->name));

free(node);

}

}

void fuse_status(struct fuse *fuse, __u64 unique, int err)

{

struct fuse_out_header hdr;

hdr.len = sizeof(hdr);

hdr.error = err;

hdr.unique = unique;

if (err) {

// ERROR("*** %d ***\n", err);

}

write(fuse->fd, &hdr, sizeof(hdr));

}

void fuse_reply(struct fuse *fuse, __u64 unique, void *data, int len)

{

struct fuse_out_header hdr;

struct iovec vec[2];

int res;

hdr.len = len + sizeof(hdr);

hdr.error = 0;

hdr.unique = unique;

vec[0].iov_base = &hdr;

vec[0].iov_len = sizeof(hdr);

vec[1].iov_base = data;

vec[1].iov_len = len;

res = writev(fuse->fd, vec, 2);

if (res < 0) {

ERROR("*** REPLY FAILED *** %d\n", errno);

}

}

void lookup_entry(struct fuse *fuse, struct node *node,

const char *name, __u64 unique)

{

struct fuse_entry_out out;

memset(&out, 0, sizeof(out));

node = node_lookup(fuse, node, name, &out.attr);

if (!node) {

fuse_status(fuse, unique, -ENOENT);

return;

}

node->refcount++;

// fprintf(stderr,"ACQUIRE %p (%s) rc=%d\n", node, node->name, node->refcount);

out.nodeid = node->nid;

out.generation = node->gen;

out.entry_valid = 10;

out.attr_valid = 10;

fuse_reply(fuse, unique, &out, sizeof(out));

}

void handle_fuse_request(struct fuse *fuse, struct fuse_in_header *hdr, void *data, unsigned len)

{

struct node *node;

if ((len < sizeof(*hdr)) || (hdr->len != len)) {

ERROR("malformed header\n");

return;

}

len -= hdr->len;

if (hdr->nodeid) {

node = lookup_by_inode(fuse, hdr->nodeid);

if (!node) {

fuse_status(fuse, hdr->unique, -ENOENT);

return;

}

} else {

node = 0;

}

switch (hdr->opcode) {

case FUSE_LOOKUP: { /* bytez[] -> entry_out */

TRACE("LOOKUP %llx %s\n", hdr->nodeid, (char*) data);

lookup_entry(fuse, node, (char*) data, hdr->unique);

return;

}

case FUSE_FORGET: {

struct fuse_forget_in *req = data;

TRACE("FORGET %llx (%s) #%lld\n", hdr->nodeid, node->name, req->nlookup);

/* no reply */

while (req->nlookup--)

node_release(node);

return;

}

case FUSE_GETATTR: { /* getattr_in -> attr_out */

struct fuse_getattr_in *req = data;

struct fuse_attr_out out;

TRACE("GETATTR flags=%x fh=%llx\n",req->getattr_flags, req->fh);

memset(&out, 0, sizeof(out));

node_get_attr(node, &out.attr);

out.attr_valid = 10;

fuse_reply(fuse, hdr->unique, &out, sizeof(out));

return;

}

case FUSE_SETATTR: { /* setattr_in -> attr_out */

struct fuse_setattr_in *req = data;

struct fuse_attr_out out;

TRACE("SETATTR fh=%llx id=%llx valid=%x\n",

req->fh, hdr->nodeid, req->valid);

/* XXX */

memset(&out, 0, sizeof(out));

node_get_attr(node, &out.attr);

out.attr_valid = 10;

fuse_reply(fuse, hdr->unique, &out, sizeof(out));

return;

}

// case FUSE_READLINK:

// case FUSE_SYMLINK:

case FUSE_MKNOD: { /* mknod_in, bytez[] -> entry_out */

struct fuse_mknod_in *req = data;

char *path, buffer[PATH_BUFFER_SIZE];

char *name = ((char*) data) + sizeof(*req);

int res;

TRACE("MKNOD %s @ %llx\n", name, hdr->nodeid);

path = node_get_path(node, buffer, name);

req->mode = (req->mode & (~0777)) | 0664;

res = mknod(path, req->mode, req->rdev); /* XXX perm?*/

if (res < 0) {

fuse_status(fuse, hdr->unique, -errno);

} else {

lookup_entry(fuse, node, name, hdr->unique);

}

return;

}

case FUSE_MKDIR: { /* mkdir_in, bytez[] -> entry_out */

struct fuse_mkdir_in *req = data;

struct fuse_entry_out out;

char *path, buffer[PATH_BUFFER_SIZE];

char *name = ((char*) data) + sizeof(*req);

int res;

TRACE("MKDIR %s @ %llx 0%o\n", name, hdr->nodeid, req->mode);

path = node_get_path(node, buffer, name);

req->mode = (req->mode & (~0777)) | 0775;

res = mkdir(path, req->mode);

if (res < 0) {

fuse_status(fuse, hdr->unique, -errno);

} else {

lookup_entry(fuse, node, name, hdr->unique);

}

return;

}

case FUSE_UNLINK: { /* bytez[] -> */

char *path, buffer[PATH_BUFFER_SIZE];

int res;

TRACE("UNLINK %s @ %llx\n", (char*) data, hdr->nodeid);

path = node_get_path(node, buffer, (char*) data);

res = unlink(path);

fuse_status(fuse, hdr->unique, res ? -errno : 0);

return;

}

case FUSE_RMDIR: { /* bytez[] -> */

char *path, buffer[PATH_BUFFER_SIZE];

int res;

TRACE("RMDIR %s @ %llx\n", (char*) data, hdr->nodeid);

path = node_get_path(node, buffer, (char*) data);

res = rmdir(path);

fuse_status(fuse, hdr->unique, res ? -errno : 0);

return;

}

case FUSE_RENAME: { /* rename_in, oldname, newname -> */

struct fuse_rename_in *req = data;

char *oldname = ((char*) data) + sizeof(*req);

char *newname = oldname + strlen(oldname) + 1;

char *oldpath, oldbuffer[PATH_BUFFER_SIZE];

char *newpath, newbuffer[PATH_BUFFER_SIZE];

struct node *newnode;

int res;

newnode = lookup_by_inode(fuse, req->newdir);

if (!newnode) {

fuse_status(fuse, hdr->unique, -ENOENT);

return;

}

oldpath = node_get_path(node, oldbuffer, oldname);

newpath = node_get_path(newnode, newbuffer, newname);

res = rename(oldpath, newpath);

fuse_status(fuse, hdr->unique, res ? -errno : 0);

return;

}

// case FUSE_LINK:

case FUSE_OPEN: { /* open_in -> open_out */

struct fuse_open_in *req = data;

struct fuse_open_out out;

char *path, buffer[PATH_BUFFER_SIZE];

struct handle *h;

h = malloc(sizeof(*h));

if (!h) {

fuse_status(fuse, hdr->unique, -ENOMEM);

return;

}

path = node_get_path(node, buffer, 0);

TRACE("OPEN %llx '%s' 0%o fh=%p\n", hdr->nodeid, path, req->flags, h);

h->fd = open(path, req->flags);

if (h->fd < 0) {

ERROR("ERROR\n");

fuse_status(fuse, hdr->unique, errno);

free(h);

return;

}

out.fh = ptr_to_id(h);

out.open_flags = 0;

out.padding = 0;

fuse_reply(fuse, hdr->unique, &out, sizeof(out));

return;

}

case FUSE_READ: { /* read_in -> byte[] */

char buffer[128 * 1024];

struct fuse_read_in *req = data;

struct handle *h = id_to_ptr(req->fh);

int res;

TRACE("READ %p(%d) %u@%llu\n", h, h->fd, req->size, req->offset);

if (req->size > sizeof(buffer)) {

fuse_status(fuse, hdr->unique, -EINVAL);

return;

}

res = pread(h->fd, buffer, req->size, req->offset);

if (res < 0) {

fuse_status(fuse, hdr->unique, errno);

return;

}

fuse_reply(fuse, hdr->unique, buffer, res);

return;

}

case FUSE_WRITE: { /* write_in, byte[write_in.size] -> write_out */

struct fuse_write_in *req = data;

struct fuse_write_out out;

struct handle *h = id_to_ptr(req->fh);

int res;

TRACE("WRITE %p(%d) %u@%llu\n", h, h->fd, req->size, req->offset);

res = pwrite(h->fd, ((char*) data) + sizeof(*req), req->size, req->offset);

if (res < 0) {

fuse_status(fuse, hdr->unique, errno);

return;

}

out.size = res;

fuse_reply(fuse, hdr->unique, &out, sizeof(out));

goto oops;

}

case FUSE_STATFS: { /* getattr_in -> attr_out */

struct statfs stat;

struct fuse_statfs_out out;

int res;

TRACE("STATFS\n");

if (statfs(fuse->root.name, &stat)) {

fuse_status(fuse, hdr->unique, -errno);

return;

}

memset(&out, 0, sizeof(out));

out.st.blocks = stat.f_blocks;

out.st.bfree = stat.f_bfree;

out.st.bavail = stat.f_bavail;

out.st.files = stat.f_files;

out.st.ffree = stat.f_ffree;

out.st.bsize = stat.f_bsize;

out.st.namelen = stat.f_namelen;

out.st.frsize = stat.f_frsize;

fuse_reply(fuse, hdr->unique, &out, sizeof(out));

return;

}

case FUSE_RELEASE: { /* release_in -> */

struct fuse_release_in *req = data;

struct handle *h = id_to_ptr(req->fh);

TRACE("RELEASE %p(%d)\n", h, h->fd);

close(h->fd);

free(h);

fuse_status(fuse, hdr->unique, 0);

return;

}

// case FUSE_FSYNC:

// case FUSE_SETXATTR:

// case FUSE_GETXATTR:

// case FUSE_LISTXATTR:

// case FUSE_REMOVEXATTR:

case FUSE_FLUSH:

fuse_status(fuse, hdr->unique, 0);

return;

case FUSE_OPENDIR: { /* open_in -> open_out */

struct fuse_open_in *req = data;

struct fuse_open_out out;

char *path, buffer[PATH_BUFFER_SIZE];

struct dirhandle *h;

h = malloc(sizeof(*h));

if (!h) {

fuse_status(fuse, hdr->unique, -ENOMEM);

return;

}

path = node_get_path(node, buffer, 0);

TRACE("OPENDIR %llx '%s'\n", hdr->nodeid, path);

h->d = opendir(path);

if (h->d == 0) {

ERROR("ERROR\n");

fuse_status(fuse, hdr->unique, -errno);

free(h);

return;

}

out.fh = ptr_to_id(h);

fuse_reply(fuse, hdr->unique, &out, sizeof(out));

return;

}

case FUSE_READDIR: {

struct fuse_read_in *req = data;

char buffer[8192];

struct fuse_dirent *fde = (struct fuse_dirent*) buffer;

struct dirent *de;

struct dirhandle *h = id_to_ptr(req->fh);

TRACE("READDIR %p\n", h);

de = readdir(h->d);

if (!de) {

fuse_status(fuse, hdr->unique, 0);

return;

}

fde->ino = FUSE_UNKNOWN_INO;

fde->off = 0;

fde->type = de->d_type;

fde->namelen = strlen(de->d_name);

memcpy(fde->name, de->d_name, fde->namelen + 1);

fuse_reply(fuse, hdr->unique, fde,

FUSE_DIRENT_ALIGN(sizeof(struct fuse_dirent) + fde->namelen));

return;

}

case FUSE_RELEASEDIR: { /* release_in -> */

struct fuse_release_in *req = data;

struct dirhandle *h = id_to_ptr(req->fh);

TRACE("RELEASEDIR %p\n",h);

closedir(h->d);

free(h);

fuse_status(fuse, hdr->unique, 0);

return;

}

// case FUSE_FSYNCDIR:

case FUSE_INIT: { /* init_in -> init_out */

struct fuse_init_in *req = data;

struct fuse_init_out out;

TRACE("INIT ver=%d.%d maxread=%d flags=%x\n",

req->major, req->minor, req->max_readahead, req->flags);

out.major = FUSE_KERNEL_VERSION;

out.minor = FUSE_KERNEL_MINOR_VERSION;

out.max_readahead = req->max_readahead;

out.flags = 0;

out.max_background = 32;

out.congestion_threshold = 32;

out.max_write = 256 * 1024;

fuse_reply(fuse, hdr->unique, &out, sizeof(out));

return;

}

default: {

struct fuse_out_header h;

ERROR("NOTIMPL op=%d uniq=%llx nid=%llx\n",

hdr->opcode, hdr->unique, hdr->nodeid);

oops:

h.len = sizeof(h);

h.error = -ENOSYS;

h.unique = hdr->unique;

write(fuse->fd, &h, sizeof(h));

break;

}

}

}

void handle_fuse_requests(struct fuse *fuse)

{

unsigned char req[256 * 1024 + 128];

int len;

for (;;) {

len = read(fuse->fd, req, 8192);

if (len < 0) {

if (errno == EINTR)

continue;

ERROR("handle_fuse_requests: errno=%d\n", errno);

return;

}

handle_fuse_request(fuse, (void*) req, (void*) (req + sizeof(struct fuse_in_header)), len);

}

}

int main(int argc, char **argv)

{

struct fuse fuse;

char opts[256];

int fd;

int res;

unsigned uid;

unsigned gid;

const char *path;

if (argc != 4) {

ERROR("usage: sdcard \n");

return -1;

}

uid = strtoul(argv[2], 0, 10);

gid = strtoul(argv[3], 0, 10);

if (!uid || !gid) {

ERROR("uid and gid must be nonzero\n");

return -1;

}

path = argv[1];

/* cleanup from previous instance, if necessary */

umount2(MOUNT_POINT, 2);

fd = open("/dev/fuse", O_RDWR);

if (fd < 0){

ERROR("cannot open fuse device (%d)\n", errno);

return -1;

}

sprintf(opts, "fd=%i,rootmode=40000,default_permissions,allow_other,"

"user_id=%d,group_id=%d", fd, uid, gid);

res = mount("/dev/fuse", MOUNT_POINT, "fuse", MS_NOSUID | MS_NODEV, opts);

if (res < 0) {

ERROR("cannot mount fuse filesystem (%d)\n", errno);

return -1;

}

if (setgid(gid) < 0) {

ERROR("cannot setgid!\n");

return -1;

}

if (setuid(uid) < 0) {

ERROR("cannot setuid!\n");

return -1;

}

fuse_init(&fuse, fd, path);

umask(0);

handle_fuse_requests(&fuse);

return 0;

}