[LibOS] Make all pipe and UDS names Gramine-instance-specific

[dimakuv]

Description of the changes

Commit "[LibOS,PAL] Move assigning name to a pipe/UDS from PAL to LibOS" had a small bug: the new LibOS logic lost the Gramine-instance-specific part of the name for some pipes and all UNIX Domain Sockets (UDSes).

This led to a benign but annoying bug of e.g. two gramine-direct Gramine instances being able to establish a common UDS. This could have been considered a feature, but two gramine-sgx Gramine instances would (correctly) fail to establish a common UDS, because each gramine-sgx instance has its own encryption key, and thus two UDSes would not be able to establish a secure TLS channel (even though they see each other because of this bug).

To make behavior of gramine-direct and gramine-sgx uniform, this commit forces all pipe names and UDS names to have the Gramine-instance-specific part in the name. I.e., previously UDSes had names on the host Linux like @/gramine/<hash-of-uds-name> and now they have names like @/gramine/<gramine-instance-id>/<hash-of-uds-name>.

References:

• https://github.com/gramineproject/gramine/blob/master/pal/src/host/linux-common/gramine_unix_socket_addr.c
• https://github.com/gramineproject/gramine/blob/master/libos/src/net/unix.c
• https://github.com/gramineproject/gramine/blob/master/libos/src/libos_init.c
• dd1d3dc

How to test this PR?

Run two Gramine instances, one creating and listening on the UDS, another connecting to the same UDS.

• Without this PR, two gramine-direct instances will establish a connection. (gramine-sgx instances won't because of failed TLS handshake.)
• With this PR, two gramine-direct instances will not be able to establish a connection.

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This change is 

[mkow]

Reviewed 2 of 2 files at r1, all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion, not enough approvals from maintainers (1 more required), not enough approvals from different teams (1 more required, approved so far: Intel) (waiting on @dimakuv)

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libos/src/libos_init.c line 585 at r1 (raw file):

    *hdl = pipe;
    len = snprintf(uri, size, URI_PREFIX_PIPE "%lu/%s", g_pal_public_state->instance_id, pipename);
    assert(len < size); /* must hold because above we did the same but with longer prefix */

I don't like this, it silently assumes that one prefix is longer than the other and will silently turn into a bug if we rename the prefixes.
Please either add a static assert for the lengths or just turn this into a normal if.

[dimakuv]

Reviewable status: 1 of 2 files reviewed, 1 unresolved discussion, not enough approvals from maintainers (1 more required), not enough approvals from different teams (1 more required, approved so far: Intel), "fixup! " found in commit messages' one-liners (waiting on @mkow)

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libos/src/libos_init.c line 585 at r1 (raw file):

Previously, mkow (Michał Kowalczyk) wrote…

I don't like this, it silently assumes that one prefix is longer than the other and will silently turn into a bug if we rename the prefixes.
Please either add a static assert for the lengths or just turn this into a normal if.

Done.

[mkow]

Reviewed 1 of 1 files at r2, all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion, not enough approvals from maintainers (1 more required), not enough approvals from different teams (1 more required, approved so far: Intel), "fixup! " found in commit messages' one-liners (waiting on @dimakuv)

---

libos/src/libos_init.c line 586 at r2 (raw file):

    len = snprintf(uri, size, URI_PREFIX_PIPE "%lu/%s", g_pal_public_state->instance_id, pipename);
    static_assert(static_strlen(URI_PREFIX_PIPE) < static_strlen(URI_PREFIX_PIPE_SRV),
                  "pipe prefixes are wrong");

Suggestion:

"without this condition the assert below should be changed into an `if`"

[dimakuv]

Reviewable status: 1 of 2 files reviewed, 1 unresolved discussion, not enough approvals from maintainers (1 more required), not enough approvals from different teams (1 more required, approved so far: Intel), "fixup! " found in commit messages' one-liners (waiting on @mkow)

---

libos/src/libos_init.c line 586 at r2 (raw file):

    len = snprintf(uri, size, URI_PREFIX_PIPE "%lu/%s", g_pal_public_state->instance_id, pipename);
    static_assert(static_strlen(URI_PREFIX_PIPE) < static_strlen(URI_PREFIX_PIPE_SRV),
                  "pipe prefixes are wrong");

Done.

[mkow]

Reviewed 1 of 1 files at r3, all commit messages.
Reviewable status: all files reviewed, all discussions resolved, "fixup! " found in commit messages' one-liners

[kailun-qin]

Reviewed 1 of 2 files at r1, 1 of 1 files at r3, all commit messages.
Reviewable status: all files reviewed, all discussions resolved, "fixup! " found in commit messages' one-liners

[mkow]

Reviewed all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved

[kailun-qin]

Reviewed all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved