Config file now optional for signed enclaves

This replicates the behavior of the `oesign` tool. If a config file
is provided, the values in this file will override the properties
already written to the signed enclave binary.

See `oesign sign --help` for more details on that

firmware/build/extract-mrenclave

@@ -1,12 +1,15 @@
 #! /usr/bin/env bash
 
 function print_usage() {
-    echo "Usage: $0 <enclave_binary> <config_file>"
+    echo "Usage: $0 <signed_enclave> [config_file]"
+    echo "  or   $0 <unsigned_enclave> <config_file>"
     echo ""
     echo "Options:"
-    echo "  enclave_binary:    path of an enclave binary file."
+    echo "  signed_enclave:    path of a signed enclave binary file."
+    echo "  unsigned_enclave:  path of an unsigned enclave binary file."
     echo "  config_file:       configuration file specifying the enclave properties."
     echo "                     refer to the oesign sign --help for the list of properties."
+    echo "                     this option is only required for unsigned enclaves."
     echo ""
     echo "Description:"
     echo "  This script extracts the MRENCLAVE and the DIGEST values from the enclave"
@@ -17,14 +20,16 @@ function print_usage() {
     echo "    The MRENCLAVE and DIGEST are calculated from the signed enclave binary and"
     echo "    the enclave properties specified in the configuration file. Both values are"
     echo "    printed in hexadecimal format to stdout."
+    echo "    If a configuration file is provided, the properties in the file will override"
+    echo "    the properties that were already defined in the signed enclave binary."
     echo ""
     echo "  Unsigned binaries:"
     echo "    The DIGEST is calculated from the unsigned enclave binary and the enclave"
     echo "    properties specified in the configuration file. The MRENCLAVE is set to zero."
     echo "    Both values are printed in hexadecimal format to stdout."
 }
 
-if [[ $# -lt 2 ]]; then
+if [[ $# -lt 1 ]]; then
     print_usage
     exit 1
 fi
@@ -42,15 +47,18 @@ ENCLAVE_BIN=$(realpath $1 --relative-to=$HSM_ROOT)
 if [[ ! -f $ENCLAVE_BIN ]]; then
     echo "Invalid signed enclave path: $ENCLAVE_BIN"
     exit 1
+else
+    ENCLAVE_ARG="-e $ENCLAVE_BIN"
 fi
-CONFIG_FILE=$(realpath $2 --relative-to=$HSM_ROOT)
-if [[ ! -f $CONFIG_FILE ]]; then
-    echo "Invalid config file path: $CONFIG_FILE"
-    exit 1
+
+if [[ $# -eq 1 ]]; then
+    CONFIG_ARG=""
+else
+    CONFIG_ARG="-c $(realpath $2 --relative-to=$HSM_ROOT)"
 fi
 
-DIGEST_CMD="oesign digest -e $ENCLAVE_BIN -c $CONFIG_FILE -d /tmp/enclave_digest > /dev/null && hexdump -v -e '/1 \"%02x\"' /tmp/enclave_digest"
-MRENCLAVE_CMD="oesign dump -e $ENCLAVE_BIN | grep mrenclave | cut -d '=' -f 2"
+DIGEST_CMD="oesign digest $ENCLAVE_ARG $CONFIG_ARG -d /tmp/enclave_digest > /dev/null && hexdump -v -e '/1 \"%02x\"' /tmp/enclave_digest"
+MRENCLAVE_CMD="oesign dump $ENCLAVE_ARG | grep mrenclave | cut -d '=' -f 2"
 EXTRACT_CMD="\$SGX_ENVSETUP && echo digest: \$($DIGEST_CMD) && echo mrenclave: \$($MRENCLAVE_CMD)"
 
 DOCKER_USER="$(id -u):$(id -g)"