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Set a default ACL on the top-level OBB directory.

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Since installers can create directories in Android/obb, make sure those
directories end up with the correct ACL bits as well.

Bug: 146419093
Test: inspect filesystem manually
Change-Id: I211e921197560a40599938463f3171a0ff92d9aa
This commit is contained in:
Martijn Coenen 2020-02-18 13:44:59 +01:00
parent 10570c00db
commit 442bb83828
1 changed files with 16 additions and 7 deletions
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23
Utils.cpp
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@ -124,9 +124,8 @@ status_t DestroyDeviceNode(const std::string& path) {
}
}
// Sets a default ACL where the owner and group can read/write/execute.
// Other users aren't allowed anything.
int SetDefault770Acl(const std::string& path, uid_t uid, gid_t gid) {
// Sets a default ACL on the directory.
int SetDefaultAcl(const std::string& path, mode_t mode, uid_t uid, gid_t gid) {
if (IsFilesystemSupported("sdcardfs")) {
// sdcardfs magically takes care of this
return OK;
@ -143,15 +142,21 @@ int SetDefault770Acl(const std::string& path, uid_t uid, gid_t gid) {
reinterpret_cast<posix_acl_xattr_entry*>(buf.get() + sizeof(posix_acl_xattr_header));
entry[0].e_tag = ACL_USER_OBJ;
entry[0].e_perm = ACL_READ | ACL_WRITE | ACL_EXECUTE;
// The existing mode_t mask has the ACL in the lower 9 bits:
// the lowest 3 for "other", the next 3 the group, the next 3 for the owner
// Use the mode_t masks to get these bits out, and shift them to get the
// correct value per entity.
//
// Eg if mode_t = 0700, rwx for the owner, then & S_IRWXU >> 6 results in 7
entry[0].e_perm = (mode & S_IRWXU) >> 6;
entry[0].e_id = uid;
entry[1].e_tag = ACL_GROUP_OBJ;
entry[1].e_perm = ACL_READ | ACL_WRITE | ACL_EXECUTE;
entry[1].e_perm = (mode & S_IRWXG) >> 3;
entry[1].e_id = gid;
entry[2].e_tag = ACL_OTHER;
entry[2].e_perm = 0;
entry[2].e_perm = mode & S_IRWXO;
entry[2].e_id = 0;
int ret = setxattr(path.c_str(), XATTR_NAME_POSIX_ACL_DEFAULT, acl_header, size, 0);
@ -310,7 +315,7 @@ int PrepareAppDirFromRoot(const std::string& path, const std::string& root, int
// installers and MTP, that require access here.
//
// See man (5) acl for more details.
ret = SetDefault770Acl(pathToCreate, uid, gid);
ret = SetDefaultAcl(pathToCreate, mode, uid, gid);
if (ret != 0) {
return ret;
}
@ -1357,6 +1362,10 @@ status_t PrepareAndroidDirs(const std::string& volumeRoot) {
PLOG(ERROR) << "Failed to create " << androidObbDir;
return -errno;
}
// Some other apps, like installers, have write access to the OBB directory
// to pre-download them. To make sure newly created folders in this directory
// have the right permissions, set a default ACL.
SetDefaultAcl(androidObbDir, mode, AID_MEDIA_RW, obbGid);
if (fs_prepare_dir(androidMediaDir.c_str(), mode, AID_MEDIA_RW, AID_MEDIA_RW) != 0) {
PLOG(ERROR) << "Failed to create " << androidMediaDir;