Fix broken sigining of EXT2 rootfs

tests/sign/Makefile

@@ -0,0 +1,56 @@
+TOP=$(abspath ../..)
+include $(TOP)/defs.mak
+
+APPDIR = appdir
+CFLAGS = -fPIC
+LDFLAGS = -Wl,-rpath=$(MUSL_LIB)
+
+all:
+	$(MAKE) myst
+	$(MAKE) rootfs
+
+rootfs: hello.c
+	mkdir -p $(APPDIR)/bin
+	$(CC) $(CFLAGS) -o $(APPDIR)/bin/hello hello.c $(LDFLAGS)
+	$(MYST) mkext2 $(APPDIR) rootfs
+
+OPTS =
+
+ifdef STRACE
+OPTS += --strace
+endif
+
+ifdef PERF
+OPTS += --perf
+endif
+
+OPTS += --thread-stack-size=1048576
+
+tests: all
+	$(RUNTEST) $(MYST_EXEC) rootfs /bin/hello $(OPTS)
+	$(MAKE) sign
+	$(MAKE) verify
+	$(MAKE) fail
+	@ echo "=== passed all tests"
+
+sign:
+	$(MYST) fssig --roothash rootfs > roothash
+	rm -rf hello.signed
+	$(MYST) sign-sgx rootfs private.pem config.json --roothash=roothash
+
+verify:
+	( cd hello.signed; ./bin/myst exec-sgx rootfs /bin/hello $(OPTS) )
+
+myst:
+	$(MAKE) -C $(TOP)/tools/myst
+
+clean:
+	rm -rf $(APPDIR) rootfs export ramfs hello.signed roothash
+
+##
+## Negative test to verify that hacking rootfs fails loading.
+##
+fail:
+	$(MAKE) sign
+	$(MYST) mkext2 --force $(APPDIR) hello.signed/rootfs
+	$(MAKE) verify 2> /dev/null; test $$? -eq 2

tests/sign/README.md

@@ -0,0 +1,5 @@
+sign
+====
+
+This test verifies that a simple Mystikos application can be signed and
+executed.

tests/sign/config.json

@@ -0,0 +1,13 @@
+{
+    "version": "0.1",
+    "Debug": 0,
+    "ProductID": 1,
+    "SecurityVersion": 1,
+    "MemorySize": "40m",
+    "ThreadStackSize": "16m",
+    "ApplicationPath": "/bin/hello",
+    "ApplicationParameters": [],
+    "HostApplicationParameters": false,
+    "EnvironmentVariables": [],
+    "HostEnvironmentVariables": []
+}

tests/sign/hello.c

@@ -0,0 +1,17 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+#include <assert.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+int main(int argc, const char* argv[])
+{
+    printf("Hello!\n");
+    printf("=== passed test (%s)\n", argv[0]);
+
+    return 0;
+}

tools/myst/host/sign.c

@@ -17,6 +17,7 @@
 #include <myst/file.h>
 #include <myst/strings.h>
 #include <myst/types.h>
+#include <myst/cpio.h>
 #include <openenclave/host.h>
 #include "../config.h"
 #include "myst_u.h"
@@ -293,6 +294,7 @@ int _sign(int argc, const char* argv[])
     const char* signing_engine_name = NULL;
     const char* signing_engine_path = NULL;
     myst_buf_t roothash_buf = MYST_BUF_INITIALIZER;
+    char rootfs_path[] = "/tmp/mystXXXXXX";
 
     // We are in the right operation, right?
     assert(
@@ -341,6 +343,7 @@ int _sign(int argc, const char* argv[])
 
     const char* program_file = get_program_file();
     const char* rootfs_file = argv[2];
+    const char* rootfs = argv[2];
     const char* pem_file = argv[3];
     const char* config_file = argv[4];
     const char* target = NULL;  // Extracted from config file
@@ -440,10 +443,28 @@ int _sign(int argc, const char* argv[])
     assert(myst_validate_file_path(program_file));
     assert(myst_validate_file_path(temp_oeconfig_file));
 
+    /* if not a CPIO archive, create a zero-filled file with one page */
+    if (myst_cpio_test(rootfs) == -ENOTSUP)
+    {
+        int fd;
+        uint8_t page[PAGE_SIZE];
+
+        if ((fd = mkstemp(rootfs_path)) < 0)
+            _err("failed to create temporary file");
+
+        memset(page, 0, sizeof(page));
+
+        if (write(fd, page, sizeof(page)) != sizeof(page))
+            _err("failed to create file");
+
+        close(fd);
+        rootfs = rootfs_path;
+    }
+
     // Setup all the regions
     if ((details = create_region_details_from_files(
              target,
-             rootfs_file,
+             rootfs,
              pubkeys_opt,
              roothashes_opt,
              config_file,