FIX: potential use-after-free in ./botan tls_proxy
#4177
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If the TLS session to the client was established (when tls_session_activated() was called), and the connection to the server was also established successfully (ec in onConnect() callback was not set); but -- in the mean time -- the this- pointer was deallocated via std::enable_shared_from_this, we end up in a use- after free situation. This sporadically appeared in CI but wasn't reproducible locally, see randombit#4112.
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Subtle! Nice work tracking this down. |
randombit
approved these changes
Jul 4, 2024
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I was "so" close to just rewrite the |
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This fixes an issue that, in rare cases, causes a use-after-free in the
tls_proxyCLI tool.sequenceDiagram Client->>+Proxy: Connect Client->>Proxy: TLS Handshake Proxy-->>Client: Proxy->>+Server: Connect Client->>Proxy: Disconnect Proxy-->>-Client: Note left of Proxy: this-ptr invalidated Server-->>-Proxy: ACK Note over Proxy: Crash!If the TLS session to the client was established (when
tls_session_activated()was called), and the connection to the server was also established successfully (error code inonConnect()callback was not set); but (in the mean time) thethis-pointer was deallocated viastd::enable_shared_from_this, we end up in a use-after-free situation.This sporadically appeared in CI after updating to Ubuntu 24.04 but wasn't reproducible locally, see #4112. I am confident that we did see this race on Windows in January but didn't investigate any further.
NOTE: This alone won't fix the glitches in CI. They just won't make
./botan tls_proxycrash any longer. I'll address the CI glitches independently.