Dmytro Shteflyuk created THRIFT-6100:
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Summary: Ruby MemoryBufferTransport should respect frozen
destination buffers
Key: THRIFT-6100
URL: https://issues.apache.org/jira/browse/THRIFT-6100
Project: Thrift
Issue Type: Bug
Reporter: Dmytro Shteflyuk
Assignee: Dmytro Shteflyuk
h3. Problem
The native implementation of {{Thrift::MemoryBufferTransport#read_into_buffer}}
writes directly into the destination string without first asking Ruby to make
the string mutable.
As a result, a frozen destination string can be modified when {{thrift_native}}
is loaded. The pure-Ruby implementation follows normal Ruby string semantics
and raises {{FrozenError}} instead.
h3. Client impact
This affects Ruby clients using {{MemoryBufferTransport}} with the native
extension. Code that freezes a destination string can reasonably expect that
object to remain unchanged, but a positive-length native read can currently
overwrite it and consume input from the transport.
The behavior also differs depending on whether the native extension is
available.
h3. Reproduction
{code:ruby}
require "thrift"
transport = Thrift::MemoryBufferTransport.new("ab")
destination = "xy".freeze
transport.read_into_buffer(destination, 2)
{code}
With the native extension loaded, the call can succeed and change
{{destination}} to {{"ab"}}. Without the extension, Ruby raises {{FrozenError}}.
h3. Expected behavior
A positive-length read into a frozen string should raise {{FrozenError}} before
either the destination or the transport is modified.
A zero-length read should remain a no-op: it should return zero without
modifying the destination, consuming input, or raising {{FrozenError}}.
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