Impact
This vulnerability is a memory safety Issue when using patch
or merge
on state
and assign the result back to state
.
In this case affected versions of Tremor and the tremor-script crate maintains references to memory that might have been freed already. And these memory regions can be accessed by retrieving the state
, e.g. send it over TCP or HTTP. This requires the Tremor server (or any other program using tremor-script) to execute a tremor-script script that uses the mentioned language construct.
Details
If affects the following two tremor-script language constructs:
- A Merge where we assign the result back to the target expression
and the expression to be merged needs to reference the event
:
let state = merge state of event end;
- A Patch where we assign the result back to the target expression
and the patch operations used need to reference the event
:
let state = patch state of insert event.key => event.value end;
For constructs like this (it does not matter what it references in the expression to be merged or the patch operations) an optimization
was applied to manipulate the target value in-place, instead of cloning it.
Our Value
struct, which underpins all event data in tremor-script
, is representing strings as borrowed beef::Cow<'lifetime, str>
,
that reference the raw data Vec<u8>
the event is based upon. We keep this raw byte-array next to the Value
structure inside our Event
as a self-referential struct,
so we make sure that the structured Value
and its references are valid across its whole lifetime.
The optimization was considered safe as long as it was only possible to merge or patch event
data or static data.
When state
was introduced to tremor-script
(in version 0.7.3) a new possibility to keep Value
data around for longer than the lifetime of an event emerged.
If event
data is merged or patched into state
without cloning it first, it can still reference keys or values from
the previous event, which will now be invalid. This allows access to those already freed regions of memory and to get their content out over the wire.
Patches
The issue has been patched in https://crates.io/crates/tremor-script/0.11.6 and https://github.com/tremor-rs/tremor-runtime/releases/tag/v0.11.6 via commit 1a2efcd by removing the optimization
and always clone the target expression of a Merge or [Patch](https://www.tremor.rs/docs/tremor-script/index#patch.
Workarounds
If an upgrade is not possible, a possible workaround is to avoid the optimization
by introducing a temporary variable and not immediately reassigning to state
:
let tmp = merge state of event end;
let state = tmp
References
The actual fix is applied in this PR: tremor-rs/tremor-runtime#1217
For more information
If you have any questions or comments about this advisory:
References
Impact
This vulnerability is a memory safety Issue when using
patch
ormerge
onstate
and assign the result back tostate
.In this case affected versions of Tremor and the tremor-script crate maintains references to memory that might have been freed already. And these memory regions can be accessed by retrieving the
state
, e.g. send it over TCP or HTTP. This requires the Tremor server (or any other program using tremor-script) to execute a tremor-script script that uses the mentioned language construct.Details
If affects the following two tremor-script language constructs:
and the expression to be merged needs to reference the
event
:and the patch operations used need to reference the
event
:For constructs like this (it does not matter what it references in the expression to be merged or the patch operations) an optimization
was applied to manipulate the target value in-place, instead of cloning it.
Our
Value
struct, which underpins all event data intremor-script
, is representing strings as borrowedbeef::Cow<'lifetime, str>
,that reference the raw data
Vec<u8>
the event is based upon. We keep this raw byte-array next to theValue
structure inside ourEvent
as a self-referential struct,so we make sure that the structured
Value
and its references are valid across its whole lifetime.The optimization was considered safe as long as it was only possible to merge or patch
event
data or static data.When
state
was introduced totremor-script
(in version 0.7.3) a new possibility to keepValue
data around for longer than the lifetime of an event emerged.If
event
data is merged or patched intostate
without cloning it first, it can still reference keys or values fromthe previous event, which will now be invalid. This allows access to those already freed regions of memory and to get their content out over the wire.
Patches
The issue has been patched in https://crates.io/crates/tremor-script/0.11.6 and https://github.com/tremor-rs/tremor-runtime/releases/tag/v0.11.6 via commit 1a2efcd by removing the optimization
and always clone the target expression of a Merge or [Patch](https://www.tremor.rs/docs/tremor-script/index#patch.
Workarounds
If an upgrade is not possible, a possible workaround is to avoid the optimization
by introducing a temporary variable and not immediately reassigning to
state
:References
The actual fix is applied in this PR: tremor-rs/tremor-runtime#1217
For more information
If you have any questions or comments about this advisory:
References