v4.3.9

Security release. Released together with 5.2.4, 5.1.6, 5.0.12, 4.3.9 and 3.2.15: a connection shared by several threads or fibers could get out of step during a quiet block or after a get_multi that stopped early, so that reads returned another key's value (GHSA-5xvx-r8rg-5qm2). Upgrading is strongly recommended. It also includes backported bug fixes, listed below.

Security:

• Keep a connection shared by several threads or fibers in step during a quiet block (GHSA-5xvx-r8rg-5qm2)
  • A quiet (or multi) block is quiet only for the thread or fiber that runs it. memcached still replies to a quiet request that fails (for example an add of a key that exists), and another thread or fiber using the same client while the block was open read that reply as its own, so its later requests could return another key's value. A non-quiet request now reads any pending quiet replies first
• Don't let a get_multi that stopped early leave replies for a later request (GHSA-5xvx-r8rg-5qm2)
  • A pipelined get_multi stopped by a non-network exception (its block raising or breaking, Timeout.timeout, or a value that can't be deserialized) left its unread replies in the response buffer, and a later get_multi large enough to use the interleaved path returned them as its own. The buffer is now cleared when a connection closes or a pipelined get starts, and unfinished pipelines are aborted
  • Affects every supported line (the get_multi issue, 4.3 and later), with both protocols; with the binary protocol the connection stayed out of step after the block ended. Fixed in 5.2.4, 5.1.6, 5.0.12, 4.3.9 and 3.2.15

Bug fixes:

• A per-request raw: true write no longer compresses the value (backport of #1213)
  • Values at or above the compression threshold (4 KB by default) were compressed and flagged even with raw: true. Raw reads ignore flags, so reading them back with raw: true returned the compressed bytes
  • Raw values are now stored exactly as given. Callers that pass raw: true without compress: false store large values uncompressed; Rails' MemCacheStore passes compress: false and isn't affected
• Handle failed TLS handshakes like other connection failures, and warn when TLS verification is off (backport of #1215)
  • A failed or timed-out handshake left the TCP socket open until GC and raised OpenSSL::SSL::SSLError directly, so the server was never marked down. The socket is now closed, and the error goes through the usual retry and socket_max_failures handling, raising Dalli::NetworkError (or Dalli::RingError once no server is available)
  • Certificate and hostname checks come only from the ssl_context you pass, and a bare OpenSSL::SSL::SSLContext.new checks neither. Dalli now logs a warning once per process when verify_mode doesn't include VERIFY_PEER or verify_hostname is false; see the new TLS section in the README
• A reply line longer than 8 KiB without a CRLF, or one cut short by the connection closing, is now a network error that closes the connection. Before, the line had no length limit (backport of #1216)
• One value that can't be stored no longer discards other buffered writes (backport of #1218)
  • A value that raised Dalli::MarshalError or Dalli::ValueOverMaxSize closed the connection, which dropped writes still buffered from the same quiet block or set_multi, and set_multi did this without raising
  • set_multi now stores every other key, skips the bad one, and then raises