Proof-of-concept _untested_ stub for Gramine support.

Proper integration of SGX-Step with different runtimes is
still an outstanding issue (#28). Currently, only the Intel SDK is
"officially" supported. An (untested) stub to start on integration with
Gramine is, furthermore, provided "as is" in the `gramine` directory.

.gitmodules

@@ -4,3 +4,6 @@
 [submodule "sdk/intel-sdk/linux-sgx"]
 	path = sdk/intel-sdk/linux-sgx
 	url = https://github.com/01org/linux-sgx.git
+[submodule "sdk/gramine"]
+	path = sdk/gramine/gramine
+	url = https://github.com/gramineproject/gramine.git

sdk/README.md

@@ -1 +1,7 @@
 TODO list the expected SDK hooks here used by `libsgxstep` and how to port to a new libOS/SDK.
+
+> :warning: **Note.** Proper integration of SGX-Step with different runtimes is
+> still an outstanding issue (#28). Currently, only the Intel SDK is
+> "officially" supported. An (untested) stub to start on integration with
+> Gramine is, furthermore, provided "as is" in the `gramine` directory.
+

sdk/gramine/0001-SGX-Step-Gramine-patches-to-reconfigure-AEP-TCS.patch

@@ -0,0 +1,113 @@
+From f3d05a71a513445e9c3eec9e2ab6d4ab30f52d46 Mon Sep 17 00:00:00 2001
+From: Jo Van Bulck <jo.vanbulck@cs.kuleuven.be>
+Date: Wed, 12 Oct 2022 16:58:07 +0200
+Subject: [PATCH 1/2] SGX-Step Gramine patches to reconfigure AEP/TCS.
+
+---
+ pal/src/host/linux-sgx/host_entry.S | 50 +++++++++++++++++++++++++++--
+ pal/src/host/linux-sgx/meson.build  | 11 +++++++
+ 2 files changed, 58 insertions(+), 3 deletions(-)
+
+diff --git a/pal/src/host/linux-sgx/host_entry.S b/pal/src/host/linux-sgx/host_entry.S
+index bb38ced4..b84803d2 100644
+--- a/pal/src/host/linux-sgx/host_entry.S
++++ b/pal/src/host/linux-sgx/host_entry.S
+@@ -2,6 +2,21 @@
+
+ #include "asm-offsets.h"
+
++    .data
++g_aep_pointer:
++    .word 0x0
++    .word 0x0
++    .word 0x0
++    .word 0x0
++
++    .data
++g_tcs:
++    .word 0x0
++    .word 0x0
++    .word 0x0
++    .word 0x0
++
++    .text
+     .extern tcs_base
+     .extern g_in_aex_profiling
+
+@@ -36,11 +51,18 @@ sgx_ecall:
+
+     # RBX has to be the TCS of the thread
+     movq %gs:PAL_HOST_TCB_TCS, %rbx
++    leaq        g_tcs(%rip), %rax
++    movq        %rbx, (%rax)
+
+     # RCX has to be the AEP (Asynchronous Exit Pointer)
+-    leaq async_exit_pointer(%rip), %rcx
+-
+-    movq $EENTER, %rax
++    leaq        g_aep_pointer(%rip), %rax
++    movq        (%rax), %rcx                    /* aep addr */
++    cmp         $0x0, %rcx
++    jnz 1f
++    leaq        async_exit_pointer(%rip), %rcx
++    movq        %rcx, (%rax)
++
++1:  movq        $EENTER, %rax                /* EENTER leaf */
+     ENCLU
+
+     # currently only ECALL_THREAD_RESET returns
+@@ -178,3 +200,25 @@ sgx_raise:
+     # RSI - external event
+     jmp .Ldo_ecall
+     .cfi_endproc
++
++
++.macro DECLARE_GLOBAL_FUNC name
++    .globl \name
++    .type \name, @function
++\name:
++.endm
++
++DECLARE_GLOBAL_FUNC sgx_get_aep
++    leaq        g_aep_pointer(%rip), %rax
++    movq        (%rax), %rax
++    ret
++ 
++DECLARE_GLOBAL_FUNC sgx_set_aep
++    leaq        g_aep_pointer(%rip), %rax
++    movq        %rdi, (%rax)
++    ret
++
++DECLARE_GLOBAL_FUNC sgx_get_tcs
++    leaq        g_tcs(%rip), %rax
++    movq        (%rax), %rax
++    ret
+diff --git a/pal/src/host/linux-sgx/meson.build b/pal/src/host/linux-sgx/meson.build
+index 3e77bdcc..c40794fa 100644
+--- a/pal/src/host/linux-sgx/meson.build
++++ b/pal/src/host/linux-sgx/meson.build
+@@ -152,10 +152,21 @@ libpal_sgx_host = executable('loader',
+         # host part of PAL uses stack protector with standard parameters (not the ones defined for
+         # PAL/LibOS)
+         '-fstack-protector-strong',
++
++        # XXX add libsgxstep include path
++        '-I../../..',
++        # XXX FORTIFY_SOURCE conflicts with regular libc header includes in libsgxstep
++        '-D_FORTIFY_SOURCE=0',
++        # XXX libsgxstep needs Intel SDK headers (only for error reporting; can be hacked out if needed)
++        '-I/opt/intel/sgxsdk/include/'
+     ],
+     link_args: [
+         '-Wl,-zrelro',
+         '-Wl,-znow',
++
++        # XXX link in libsgxstep library
++        '-L../../../libsgxstep',
++        '-lsgx-step',
+     ],
+     pie: true,
+
+-- 
+2.34.1
+

sdk/gramine/0002-Example-usage-of-libsgxstep-functionality-on-Gramine.patch

@@ -0,0 +1,66 @@
+From 0a276da7b6ba82ced095a795f66ac7f3ad0870a1 Mon Sep 17 00:00:00 2001
+From: Jo Van Bulck <jo.vanbulck@cs.kuleuven.be>
+Date: Wed, 12 Oct 2022 16:58:44 +0200
+Subject: [PATCH 2/2] Example usage of libsgxstep functionality on Gramine's
+ enclave entry.
+
+---
+ pal/src/host/linux-sgx/host_ecalls.c | 35 ++++++++++++++++++++++++++++
+ 1 file changed, 35 insertions(+)
+
+diff --git a/pal/src/host/linux-sgx/host_ecalls.c b/pal/src/host/linux-sgx/host_ecalls.c
+index 9387266b..a740df24 100644
+--- a/pal/src/host/linux-sgx/host_ecalls.c
++++ b/pal/src/host/linux-sgx/host_ecalls.c
+@@ -6,6 +6,31 @@
+ #include "pal_ecall_types.h"
+ #include "pal_rpc_queue.h"
+
++/*****************************************************************************/
++/* XXX SGX-Step library includes and callbacks */
++
++#define  SGX_STEP_ENABLE        1
++
++#if SGX_STEP_ENABLE
++    #include "libsgxstep/debug.h"
++    #include "libsgxstep/enclave.h"
++    
++    int aep_fired = 0;
++    
++    void aep_cb_func(void)
++    {
++        gprsgx_region_t gprsgx = {0};
++        uint64_t erip = edbgrd_erip() - (uint64_t) get_enclave_base();
++        info("Hello world from AEP callback %d with erip=%#llx! Resuming enclave..", aep_fired, erip); 
++    
++        edbgrd(get_enclave_ssa_gprsgx_adrs(), &gprsgx, sizeof(gprsgx_region_t));
++        dump_gprsgx_region(&gprsgx);
++    
++        aep_fired++;
++    }
++#endif
++/*****************************************************************************/
++
+ int ecall_enclave_start(char* libpal_uri, char* args, size_t args_size, char* env,
+                         size_t env_size, int parent_stream_fd, sgx_target_info_t* qe_targetinfo,
+                         struct pal_topo_info* topo_info, struct pal_dns_host_conf* dns_conf) {
+@@ -32,6 +57,16 @@ int ecall_enclave_start(char* libpal_uri, char* args, size_t args_size, char* en
+     ms.ms_topo_info        = topo_info;
+     ms.ms_dns_host_conf    = dns_conf;
+     ms.rpc_queue           = g_rpc_queue;
++
++    /*****************************************************************************/
++    #if SGX_STEP_ENABLE
++        /* XXX example of custom SGX-Step code before entering the victim enclave */
++        info("entering victim enclave");
++        register_aep_cb(aep_cb_func);
++        print_enclave_info();
++    #endif
++    /*****************************************************************************/
++
+     return sgx_ecall(ECALL_ENCLAVE_START, &ms);
+ }
+
+-- 
+2.34.1
+

sdk/gramine/README.md

@@ -0,0 +1,40 @@
+## Proof-of-concept _untested_ Gramine support
+
+> :warning: **Note.** Integration with Gramine (v1.3.1) is currently _untested_
+> and only provided as an example/starter for people wishing to experiment with
+> SGX-Step on Gramine (e.g., see issue #47). Particularly, the patches below
+> were validated to successfully compile but were never actually ran(!)
+> Furthermore, single-stepping itself is not currently provided for Gramine,
+> but should be straightforwardly feasible based on the existing code for the
+> Intel SDK. As always, issues/PRs are welcome if you want to contribute
+> improvements for a work-in-progress Gramine port.
+
+1. First, apply the patches in the untrusted Gramine runtime `host_entry.S` to
+be able to link to `libsgxstep`:
+
+```bash
+$ ./patch_entry.sh
+```
+
+2. Build the patched Gramine runtime and validate that the patches were
+properly applied in the modified Gramine loader:
+
+```bash
+$ cd gramine
+$ meson configure build/ -Dsgx=enabled
+$ ninja -C build
+$ objdump -d build/pal/src/host/linux-sgx/loader | grep sgx_set_aep
+000000000000924c <sgx_set_aep>:
+```
+
+3. Now, you can implement the required attack code in Gramine's untrusted
+runtime using `libsgxstep` functionality as usual. For example, the following
+patch in `host_ecalls.c` demonstrates some basic usages:
+
+```bash
+$ ./patch_ecall.sh
+$ cd gramine
+$ ninja -C build
+$ objdump -d build/pal/src/host/linux-sgx/loader | grep sgx_step
+   18631:	48 8d 05 2c 1c 00 00 	lea    0x1c2c(%rip),%rax        # 1a264 <sgx_step_aep_trampoline>
+```

sdk/gramine/patch_ecall.sh

@@ -0,0 +1,6 @@
+#!/bin/bash
+
+cd gramine
+
+echo "=== patching ECALL ==="
+patch -p1 < ../0002-Example-usage-of-libsgxstep-functionality-on-Gramine.patch

sdk/gramine/patch_entry.sh

@@ -0,0 +1,6 @@
+#!/bin/bash
+
+cd gramine
+
+echo "=== patching AEP/TCS ==="
+patch -p1 < ../0001-SGX-Step-Gramine-patches-to-reconfigure-AEP-TCS.patch