evmctl: Implement support for EVMCTL_KEY_PASSWORD environment variable

If the user did not use the --pass option to provide a key password,
get the key password from the EVMCTL_KEY_PASSWORD environment variable.

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

src/evmctl.c

@@ -2534,6 +2534,9 @@ static void usage(void)
 		"      --ignore-violations ignore ToMToU measurement violations\n"
 		"  -v                 increase verbosity level\n"
 		"  -h, --help         display this help and exit\n"
+		"\n"
+		"Environment variables:\n\n"
+		"EVMCTL_KEY_PASSWORD  : Private key password to use; do not use --pass option\n"
 		"\n");
 }
 
@@ -2822,6 +2825,9 @@ int main(int argc, char *argv[])
 		}
 	}
 
+	if (!imaevm_params.keypass)
+		imaevm_params.keypass = getenv("EVMCTL_KEY_PASSWORD");
+
 	if (argv[optind] == NULL)
 		usage();
 	else