apparmor: Deny AF_ALG sockets in default container profile#22
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apparmor: Deny AF_ALG sockets in default container profile#22
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The AF_ALG address family exposes the Linux kernel crypto API to userspace via sockets. This has been a source of container escape vulnerabilities (see https://copy.fail/). Unlike seccomp, which can only filter arguments of the direct socket(2) syscall, AppArmor hooks into the kernel's security_socket_create() LSM callback, which fires regardless of the syscall entry point. This means AppArmor also blocks AF_ALG sockets created via the legacy socketcall(2) multiplexer (used by 32-bit binaries), which seccomp cannot inspect because the address family is behind a userspace pointer that BPF cannot dereference. The "deny network alg," rule is placed right after the blanket "network," allow rule so the deny takes precedence for this specific address family. Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>
cpuguy83
approved these changes
May 5, 2026
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apparmor: Deny AF_ALG sockets in default container profile
The AF_ALG address family exposes the Linux kernel crypto API to userspace via sockets. This has been a source of container escape vulnerabilities (see https://copy.fail/).
Unlike seccomp, which can only filter arguments of the direct socket(2) syscall, AppArmor hooks into the kernel's security_socket_create() LSM callback, which fires regardless of the syscall entry point. This means AppArmor also blocks AF_ALG sockets created via the legacy socketcall(2) multiplexer (used by 32-bit binaries), which seccomp cannot inspect because the address family is behind a userspace pointer that BPF cannot dereference.
The "deny network alg," rule is placed right after the blanket
"network," allow rule so the deny takes precedence for this specific address family.