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When OpenSSL is built with the devcrypto engine, crypto operations are serviced via ioctl() calls on /dev/crypto. The pre-auth child inherits the open fd from the monitor but the seccomp filter only whitelists FIONREAD and TIOCGWINSZ, causing any cryptodev ioctl to trigger SIGSYS. The child is killed immediately after authentication succeeds, during the keystate transfer phase where it first attempts to perform a cipher or MAC operation through the devcrypto engine: ``` monitor_child_preauth: preauth child terminated by signal 31 ``` As this was tested on the Airoha AN7581 with Cortex-A53 cores, signal 31 on aarch64 is SIGSYS, confirming seccomp violation rather than a code defect. Add a BPF rule that allows ioctl commands with type byte 'c' (0x63), which is the ioctl type used by all cryptodev operations (CIOCGSESSION, CIOCCRYPT, CIOCFSESSION, etc.). The rule matches on the type byte rather than the exact ioctl command values because cryptodev is an out-of-tree kernel module and its header is not available at OpenSSH build time. The rule is gated on ALLOW_CRYPTODEV_IOCTL, defined by the build system only when libopenssl-devcrypto is enabled. Signed-off-by: Kenneth Kasilag <kenneth@kasilag.me>
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📦 Package Details
Maintainer: @hnyman
Description:
When OpenSSL is built with the devcrypto engine, crypto operations are serviced via ioctl() calls on /dev/crypto.
The pre-auth child inherits the open fd from the monitor but the seccomp filter only whitelists FIONREAD and TIOCGWINSZ, causing any cryptodev ioctl to trigger SIGSYS.
The child is killed immediately after authentication succeeds, during the keystate transfer phase where it first attempts to perform a cipher or MAC operation through the devcrypto engine:
As this was tested on the Airoha AN7581 with Cortex-A53 cores, signal 31 on aarch64 is SIGSYS, confirming seccomp violation rather than a code defect.
Add a BPF rule that allows ioctl commands with type byte 'c' (0x63), which is the ioctl type used by all cryptodev operations (CIOCGSESSION, CIOCCRYPT, CIOCFSESSION, etc.).
The rule matches on the type byte rather than the exact ioctl command values because cryptodev is an out-of-tree kernel module and its header is not available at OpenSSH build time.
The rule is gated on ALLOW_CRYPTODEV_IOCTL, defined by the build system only when libopenssl-devcrypto is enabled.
🧪 Run Testing Details
✅ Formalities
If your PR contains a patch:
git am(e.g., subject line, commit description, etc.)
We must try to upstream patches to reduce maintenance burden.