From 39fdbd097a147b5c719dac9ad2759e6c44eb3a4e Mon Sep 17 00:00:00 2001
From: Kevin Rocard <krocard@google.com>
Date: Mon, 13 Nov 2017 11:15:27 -0800
Subject: [PATCH] IAudioPolicyService: Add attribute tags sanitization

When audio_attributes_t was read from the binder parcel,
the string tags field was copied without checking that
it contained a '\0'.

This could lead to read past the end when tags were used.

This patch always adds a '\0' at the end of the buffer when
deserializing.

Bug: 68953950
Test: manual playback/record
Test: send binder payload without \0 in tags attribute, check that only
      AUDIO_ATTRIBUTES_TAGS_MAX_SIZE - 1 char are printed.
Change-Id: I285258cbf7cfaf26b191d1f31b3b1e2d724c4934
Merged-In: I285258cbf7cfaf26b191d1f31b3b1e2d724c4934
Signed-off-by: Kevin Rocard <krocard@google.com>
---
 media/libaudioclient/IAudioPolicyService.cpp         | 12 ++++++++++++
 .../include/media/IAudioPolicyService.h              |  2 ++
 2 files changed, 14 insertions(+)

diff --git a/media/libaudioclient/IAudioPolicyService.cpp b/media/libaudioclient/IAudioPolicyService.cpp
index ceba211466..d838975fba 100644
--- a/media/libaudioclient/IAudioPolicyService.cpp
+++ b/media/libaudioclient/IAudioPolicyService.cpp
@@ -960,6 +960,7 @@ status_t BnAudioPolicyService::onTransact(
             bool hasAttributes = data.readInt32() != 0;
             if (hasAttributes) {
                 data.read(&attr, sizeof(audio_attributes_t));
+                sanetizeAudioAttributes(&attr);
             }
             audio_session_t session = (audio_session_t)data.readInt32();
             audio_stream_type_t stream = AUDIO_STREAM_DEFAULT;
@@ -1025,6 +1026,7 @@ status_t BnAudioPolicyService::onTransact(
             CHECK_INTERFACE(IAudioPolicyService, data, reply);
             audio_attributes_t attr;
             data.read(&attr, sizeof(audio_attributes_t));
+            sanetizeAudioAttributes(&attr);
             audio_io_handle_t input = (audio_io_handle_t)data.readInt32();
             audio_session_t session = (audio_session_t)data.readInt32();
             pid_t pid = (pid_t)data.readInt32();
@@ -1400,6 +1402,7 @@ status_t BnAudioPolicyService::onTransact(
             data.read(&source, sizeof(struct audio_port_config));
             audio_attributes_t attributes;
             data.read(&attributes, sizeof(audio_attributes_t));
+            sanetizeAudioAttributes(&attributes);
             audio_patch_handle_t handle = AUDIO_PATCH_HANDLE_NONE;
             status_t status = startAudioSource(&source, &attributes, &handle);
             reply->writeInt32(status);
@@ -1450,6 +1453,15 @@ status_t BnAudioPolicyService::onTransact(
     }
 }
 
+void BnAudioPolicyService::sanetizeAudioAttributes(audio_attributes_t* attr)
+{
+    const size_t tagsMaxSize = AUDIO_ATTRIBUTES_TAGS_MAX_SIZE;
+    if (strnlen(attr->tags, tagsMaxSize) >= tagsMaxSize) {
+        android_errorWriteLog(0x534e4554, "68953950"); // SafetyNet logging
+    }
+    attr->tags[tagsMaxSize - 1] = '\0';
+}
+
 // ----------------------------------------------------------------------------
 
 } // namespace android
diff --git a/media/libaudioclient/include/media/IAudioPolicyService.h b/media/libaudioclient/include/media/IAudioPolicyService.h
index 9b3e35ea57..60ba4ba28b 100644
--- a/media/libaudioclient/include/media/IAudioPolicyService.h
+++ b/media/libaudioclient/include/media/IAudioPolicyService.h
@@ -183,6 +183,8 @@ public:
                                     const Parcel& data,
                                     Parcel* reply,
                                     uint32_t flags = 0);
+private:
+    void sanetizeAudioAttributes(audio_attributes_t* attr);
 };
 
 // ----------------------------------------------------------------------------