binder: create node flag to request sender's security context

To allow servers to verify client identity, allow a node
flag to be set that causes the sender's security context
to be delivered with the transaction. The BR_TRANSACTION
command is extended in BR_TRANSACTION_SEC_CTX to
contain a pointer to the security context string.

Signed-off-by: Todd Kjos <tkjos@google.com>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 83 insertions, 23 deletions

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index cdfc87629efb..5f6ef5e63b91 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -329,6 +329,8 @@ struct binder_error {
  *                        (invariant after initialized)
  * @min_priority:         minimum scheduling priority
  *                        (invariant after initialized)
+ * @txn_security_ctx:     require sender's security context
+ *                        (invariant after initialized)
  * @async_todo:           list of async work items
  *                        (protected by @proc->inner_lock)
  *
@@ -365,6 +367,7 @@ struct binder_node {
                  * invariant after initialization
                  */
                 u8 accept_fds:1;
+                u8 txn_security_ctx:1;
                 u8 min_priority;
         };
         bool has_async_transaction;
@@ -615,6 +618,7 @@ struct binder_transaction {
         long    saved_priority;
         kuid_t  sender_euid;
         struct list_head fd_fixups;
+        binder_uintptr_t security_ctx;
         /**
          * @lock:  protects @from, @to_proc, and @to_thread
          *
@@ -1152,6 +1156,7 @@ static struct binder_node *binder_init_node_ilocked(
         node->work.type = BINDER_WORK_NODE;
         node->min_priority = flags & FLAT_BINDER_FLAG_PRIORITY_MASK;
         node->accept_fds = !!(flags & FLAT_BINDER_FLAG_ACCEPTS_FDS);
+        node->txn_security_ctx = !!(flags & FLAT_BINDER_FLAG_TXN_SECURITY_CTX);
         spin_lock_init(&node->lock);
         INIT_LIST_HEAD(&node->work.entry);
         INIT_LIST_HEAD(&node->async_todo);
@@ -2778,6 +2783,8 @@ static void binder_transaction(struct binder_proc *proc,
         binder_size_t last_fixup_min_off = 0;
         struct binder_context *context = proc->context;
         int t_debug_id = atomic_inc_return(&binder_last_id);
+        char *secctx = NULL;
+        u32 secctx_sz = 0;
 
         e = binder_transaction_log_add(&binder_transaction_log);
         e->debug_id = t_debug_id;
@@ -3020,6 +3027,20 @@ static void binder_transaction(struct binder_proc *proc,
         t->flags = tr->flags;
         t->priority = task_nice(current);
 
+        if (target_node && target_node->txn_security_ctx) {
+                u32 secid;
+
+                security_task_getsecid(proc->tsk, &secid);
+                ret = security_secid_to_secctx(secid, &secctx, &secctx_sz);
+                if (ret) {
+                        return_error = BR_FAILED_REPLY;
+                        return_error_param = ret;
+                        return_error_line = __LINE__;
+                        goto err_get_secctx_failed;
+                }
+                extra_buffers_size += ALIGN(secctx_sz, sizeof(u64));
+        }
+
         trace_binder_transaction(reply, t, target_node);
 
         t->buffer = binder_alloc_new_buf(&target_proc->alloc, tr->data_size,
@@ -3036,6 +3057,19 @@ static void binder_transaction(struct binder_proc *proc,
                 t->buffer = NULL;
                 goto err_binder_alloc_buf_failed;
         }
+        if (secctx) {
+                size_t buf_offset = ALIGN(tr->data_size, sizeof(void *)) +
+                                    ALIGN(tr->offsets_size, sizeof(void *)) +
+                                    ALIGN(extra_buffers_size, sizeof(void *)) -
+                                    ALIGN(secctx_sz, sizeof(u64));
+                char *kptr = t->buffer->data + buf_offset;
+
+                t->security_ctx = (uintptr_t)kptr +
+                    binder_alloc_get_user_buffer_offset(&target_proc->alloc);
+                memcpy(kptr, secctx, secctx_sz);
+                security_release_secctx(secctx, secctx_sz);
+                secctx = NULL;
+        }
         t->buffer->debug_id = t->debug_id;
         t->buffer->transaction = t;
         t->buffer->target_node = target_node;
@@ -3305,6 +3339,9 @@ err_copy_data_failed:
         t->buffer->transaction = NULL;
         binder_alloc_free_buf(&target_proc->alloc, t->buffer);
 err_binder_alloc_buf_failed:
+        if (secctx)
+                security_release_secctx(secctx, secctx_sz);
+err_get_secctx_failed:
         kfree(tcomplete);
         binder_stats_deleted(BINDER_STAT_TRANSACTION_COMPLETE);
 err_alloc_tcomplete_failed:
@@ -4036,11 +4073,13 @@ retry:
 
         while (1) {
                 uint32_t cmd;
-                struct binder_transaction_data tr;
+                struct binder_transaction_data_secctx tr;
+                struct binder_transaction_data *trd = &tr.transaction_data;
                 struct binder_work *w = NULL;
                 struct list_head *list = NULL;
                 struct binder_transaction *t = NULL;
                 struct binder_thread *t_from;
+                size_t trsize = sizeof(*trd);
 
                 binder_inner_proc_lock(proc);
                 if (!binder_worklist_empty_ilocked(&thread->todo))
@@ -4240,8 +4279,8 @@ retry:
                 if (t->buffer->target_node) {
                         struct binder_node *target_node = t->buffer->target_node;
 
-                        tr.target.ptr = target_node->ptr;
-                        tr.cookie =  target_node->cookie;
+                        trd->target.ptr = target_node->ptr;
+                        trd->cookie =  target_node->cookie;
                         t->saved_priority = task_nice(current);
                         if (t->priority < target_node->min_priority &&
                             !(t->flags & TF_ONE_WAY))
@@ -4251,22 +4290,23 @@ retry:
                                 binder_set_nice(target_node->min_priority);
                         cmd = BR_TRANSACTION;
                 } else {
-                        tr.target.ptr = 0;
-                        tr.cookie = 0;
+                        trd->target.ptr = 0;
+                        trd->cookie = 0;
                         cmd = BR_REPLY;
                 }
-                tr.code = t->code;
-                tr.flags = t->flags;
-                tr.sender_euid = from_kuid(current_user_ns(), t->sender_euid);
+                trd->code = t->code;
+                trd->flags = t->flags;
+                trd->sender_euid = from_kuid(current_user_ns(), t->sender_euid);
 
                 t_from = binder_get_txn_from(t);
                 if (t_from) {
                         struct task_struct *sender = t_from->proc->tsk;
 
-                        tr.sender_pid = task_tgid_nr_ns(sender,
-                                                        task_active_pid_ns(current));
+                        trd->sender_pid =
+                                task_tgid_nr_ns(sender,
+                                                task_active_pid_ns(current));
                 } else {
-                        tr.sender_pid = 0;
+                        trd->sender_pid = 0;
                 }
 
                 ret = binder_apply_fd_fixups(t);
@@ -4297,15 +4337,20 @@ retry:
                         }
                         continue;
                 }
-                tr.data_size = t->buffer->data_size;
-                tr.offsets_size = t->buffer->offsets_size;
-                tr.data.ptr.buffer = (binder_uintptr_t)
+                trd->data_size = t->buffer->data_size;
+                trd->offsets_size = t->buffer->offsets_size;
+                trd->data.ptr.buffer = (binder_uintptr_t)
                         ((uintptr_t)t->buffer->data +
                         binder_alloc_get_user_buffer_offset(&proc->alloc));
-                tr.data.ptr.offsets = tr.data.ptr.buffer +
+                trd->data.ptr.offsets = trd->data.ptr.buffer +
                                         ALIGN(t->buffer->data_size,
                                             sizeof(void *));
 
+                tr.secctx = t->security_ctx;
+                if (t->security_ctx) {
+                        cmd = BR_TRANSACTION_SEC_CTX;
+                        trsize = sizeof(tr);
+                }
                 if (put_user(cmd, (uint32_t __user *)ptr)) {
                         if (t_from)
                                 binder_thread_dec_tmpref(t_from);
@@ -4316,7 +4361,7 @@ retry:
                         return -EFAULT;
                 }
                 ptr += sizeof(uint32_t);
-                if (copy_to_user(ptr, &tr, sizeof(tr))) {
+                if (copy_to_user(ptr, &tr, trsize)) {
                         if (t_from)
                                 binder_thread_dec_tmpref(t_from);
 
@@ -4325,7 +4370,7 @@ retry:
 
                         return -EFAULT;
                 }
-                ptr += sizeof(tr);
+                ptr += trsize;
 
                 trace_binder_transaction_received(t);
                 binder_stat_br(proc, thread, cmd);
@@ -4333,16 +4378,18 @@ retry:
                              "%d:%d %s %d %d:%d, cmd %d size %zd-%zd ptr %016llx-%016llx\n",
                              proc->pid, thread->pid,
                              (cmd == BR_TRANSACTION) ? "BR_TRANSACTION" :
-                             "BR_REPLY",
+                                (cmd == BR_TRANSACTION_SEC_CTX) ?
+                                     "BR_TRANSACTION_SEC_CTX" : "BR_REPLY",
                              t->debug_id, t_from ? t_from->proc->pid : 0,
                              t_from ? t_from->pid : 0, cmd,
                              t->buffer->data_size, t->buffer->offsets_size,
-                             (u64)tr.data.ptr.buffer, (u64)tr.data.ptr.offsets);
+                             (u64)trd->data.ptr.buffer,
+                             (u64)trd->data.ptr.offsets);
 
                 if (t_from)
                         binder_thread_dec_tmpref(t_from);
                 t->buffer->allow_user_free = 1;
-                if (cmd == BR_TRANSACTION && !(t->flags & TF_ONE_WAY)) {
+                if (cmd != BR_REPLY && !(t->flags & TF_ONE_WAY)) {
                         binder_inner_proc_lock(thread->proc);
                         t->to_parent = thread->transaction_stack;
                         t->to_thread = thread;
@@ -4690,7 +4737,8 @@ out:
         return ret;
 }
 
-static int binder_ioctl_set_ctx_mgr(struct file *filp)
+static int binder_ioctl_set_ctx_mgr(struct file *filp,
+                                    struct flat_binder_object *fbo)
 {
         int ret = 0;
         struct binder_proc *proc = filp->private_data;
@@ -4719,7 +4767,7 @@ static int binder_ioctl_set_ctx_mgr(struct file *filp)
         } else {
                 context->binder_context_mgr_uid = curr_euid;
         }
-        new_node = binder_new_node(proc, NULL);
+        new_node = binder_new_node(proc, fbo);
         if (!new_node) {
                 ret = -ENOMEM;
                 goto out;
@@ -4842,8 +4890,20 @@ static long binder_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
                 binder_inner_proc_unlock(proc);
                 break;
         }
+        case BINDER_SET_CONTEXT_MGR_EXT: {
+                struct flat_binder_object fbo;
+
+                if (copy_from_user(&fbo, ubuf, sizeof(fbo))) {
+                        ret = -EINVAL;
+                        goto err;
+                }
+                ret = binder_ioctl_set_ctx_mgr(filp, &fbo);
+                if (ret)
+                        goto err;
+                break;
+        }
         case BINDER_SET_CONTEXT_MGR:
-                ret = binder_ioctl_set_ctx_mgr(filp);
+                ret = binder_ioctl_set_ctx_mgr(filp, NULL);
                 if (ret)
                         goto err;
                 break;