Sometimes we need to prevent the compiler from reading or writing to
a memory location twice to prevent certain TOCTOU bugs. This can now
be achieved by using the introduced macros and this commit does so in
enclave_ocalls.c for Linux-SGX.
This commit completely reworks VMA subsystem along with its usages.
New version should be: cleaner (easier to maintain), faster and allow
for bookkeeping requests from Pal.
It also fixes some bugs and inconsistencies found in the process and
changes brk and mmap/munmap implementations (at least partially).
mbedTLS configuration used in Graphene is not thread-safe (because
this would require the use of a threading library like pthread which
is not possible in the LibOS/Pal layers). However, some mbedTLS
functions use shared state, in particular TLS context initialization
functions. This led to data races during encrypted-pipe creation,
since it requires two threads performing a TLS handshake. This commit
refactors TLS init into SSLInit (not thread-safe) and SSLHandshake
(thread-safe) and adds spinlocks around SSLInit to protect the racy
mbedTLS logic.
Previously, Linux-SGX PAL did not encrypt pipe/socketpair
communication (only process checkpoint send/receive was encrypted).
This commit encrypts all pipe/socketpair IPC between threads of
the same enclave and between enclave processes. In particular, all
offsprings of the "first" enclave inherit the same master key and
derive IPC session keys from this master key based on pipe name.
When two pipe/socketpair endpoints are first created, they establish
a TLS-PSK session via intra-enclave handshake (requires a spawn of
an intermediate enclave thread). During clone/fork/exec, endpoints'
TLS contexts are serialized and sent to the child that deserializes
them (using mbedtls_ssl_context_{save,load} functions).
Note that multicast pipes (with more than two communicating entities)
are not supported since TLS protocol doesn't support it.
This commit modifies the PAL `SendHandle` test to correctly test
pipe communication, as well as adds the LibOS `pipe` test.
Previously, Graphene used the notation "pipe:<uint32_t>" to emulate
pipes, socketpairs, and UNIX domain sockets. In particular, pipes
and socketpairs received random integer IDs, and sockets received
deterministic integer IDs. However, 32-bit randomly generated IDs
may collide quite often. Since pipe IDs/names should *not* repeat
(otherwise e.g. derived crypto keys will be reused), this commit
changes pipe IDs (pipeid) from uint32_t to char[96], and pipe IDs
(names) become 256-bit random sequences.
Previously, Graphene with SGX performed self-remote attestation
by retrieving the SGX quote from the Quoting Enclave, sending it
to the Intel Attestation Service via Curl (in an HTTPS request),
and parsing the received from IAS remote-attestation certificate.
This self-attestation functionality is meaningless and is removed.
Moreover, since EPID-based remote attestation requires client key
(Ocp-Apim-Subscription-Key), and this key must be kept secret,
specifying it in the Graphene manifest (as was done previously) is
insecure. Therefore, the whole remote attestation functionality is
moved out of Graphene and to another trusted party (or to the app
on top of Graphene). Only the SGX quote retrieval from the Quoting
Enclave is kept in Graphene.
Previously, Linux-SGX logic of allocating/freeing enclave pages was
complicated and hard to read. This commit refactors this code for
readability, without changes in functionality.
Stefan Berger