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Dmitrii Kuvaiskii
735f54d22c
Previously, Graphene-SGX did not protect send/recv of checkpoint from
parent to child. This leaked all memory contents of the parent process.
This commit adds TLS-PSK (TLS with Pre-Shared Key) wrapper for process
communication. Graphene-SGX already has the logic for SGX-based local
attestation and generation of the shared key for each parent <-> child
communication channel via Diffie–Hellman key exchange. This commit
uses this pre-shared key to create an mbedTLS-based session based on
UNIX domain socketpair (parent.process.stream <-> child.process.stream).
_DkStreamSecure{Init,Free,Read,Write} internal Linux-SGX PAL functions
are added and used during child process creation and sending of the
parent-generated checkpoint. These functions are backed by crypto-layer
lib_SSL{Init,Free,Read,Write} functions which in turn use mbedTLS.
Configuration of mbedTLS is expanded to support TLS-PSK; note that for
entropy source we use only rdrand instruction inside SGX enclave (i.e.,
no untrusted host-platform sources of entropy). The only ciphersuite
currently supported for IPC is MBEDTLS_TLS_PSK_WITH_AES_128_GCM_SHA256.
This commit adds protection only for checkpoint IPC. After the checkpoint
is sent/received, the parent/child processes downgrade their sockets to
plain non-secure ones (by disabling TLS). This is done because child
may spawn a grandchild that also wants to communicate with grandparent,
but it is impossible for multiple processes to share same TLS context.
Additionally, this commit sanitizes "process" PAL handles during send-
handle checkpoint send (via DkSendHandle): shared key and TLS context
are zeroed out.