Added SHA256 test certificates

With SHA-1 deprecation, we need a few certificates using algorithms in
the default support list. Most tests still use SHA-1 though.

The generation process for the new certificates is recorded in the makefile.
diff --git a/tests/data_files/Makefile b/tests/data_files/Makefile
new file mode 100644
index 0000000..e419ce9
--- /dev/null
+++ b/tests/data_files/Makefile
@@ -0,0 +1,49 @@
+OPENSSL = openssl
+
+cli_crt_key_file_rsa = cli-rsa.key
+cli_crt_extensions_file = cli.opensslconf
+test_ca_key_file_rsa = test-ca.key
+test_ca_pwd_rsa = PolarSSLTest
+test_ca_config_file = test-ca.opensslconf
+
+default: all_final
+
+all_intermediate := # temporary files
+all_final := # files used by tests
+
+test-ca.csr: $(test_ca_key_file_rsa) $(test_ca_config_file)
+	$(OPENSSL) req -new -config $(test_ca_config_file) -key $(test_ca_key_file_rsa) -passin "pass:$(test_ca_pwd_rsa)" -subj "/C=NL/O=PolarSSL/CN=PolarSSL Test CA" -out $@
+all_intermediate += test-ca.csr
+test-ca-sha1.crt: $(test_ca_key_file_rsa) $(test_ca_config_file) test-ca.csr
+	$(OPENSSL) req -x509 -config $(test_ca_config_file) -key $(test_ca_key_file_rsa) -passin "pass:$(test_ca_pwd_rsa)" -set_serial 0 -days 3653 -sha1 -in test-ca.csr -out $@
+all_final += test-ca-sha1.crt
+test-ca-sha256.crt: $(test_ca_key_file_rsa) $(test_ca_config_file) test-ca.csr
+	$(OPENSSL) req -x509 -config $(test_ca_config_file) -key $(test_ca_key_file_rsa) -passin "pass:$(test_ca_pwd_rsa)" -set_serial 0 -days 3653 -sha256 -in test-ca.csr -out $@
+all_final += test-ca-sha256.crt
+
+cli-rsa.csr: $(cli_crt_key_file_rsa)
+	$(OPENSSL) req -new -key $(cli_crt_key_file_rsa) -passin "pass:$(test_ca_pwd_rsa)" -subj "/C=NL/O=PolarSSL/CN=PolarSSL Client 2" -out $@
+all_intermediate += cli-rsa.csr
+cli-rsa-sha1.crt: $(cli_crt_key_file_rsa) test-ca-sha1.crt cli-rsa.csr
+	$(OPENSSL) x509 -req -extfile $(cli_crt_extensions_file) -extensions cli-rsa -CA test-ca-sha1.crt -CAkey $(test_ca_key_file_rsa) -passin "pass:$(test_ca_pwd_rsa)" -set_serial 4 -days 3653 -sha1 -in cli-rsa.csr -out $@
+all_final += cli-rsa-sha1.crt
+cli-rsa-sha256.crt: $(cli_crt_key_file_rsa) test-ca-sha256.crt cli-rsa.csr
+	$(OPENSSL) x509 -req -extfile $(cli_crt_extensions_file) -extensions cli-rsa -CA test-ca-sha256.crt -CAkey $(test_ca_key_file_rsa) -passin "pass:$(test_ca_pwd_rsa)" -set_serial 4 -days 3653 -sha256 -in cli-rsa.csr -out $@
+all_final += cli-rsa-sha256.crt
+
+all_final: $(all_final)
+all: $(all_intermediate) $(all_final)
+
+# These files should not be committed to the repository.
+list_intermediate:
+	@printf '%s\n' $(all_intermediate) | sort
+# These files should be committed to the repository so that the test data is
+# available upon checkout without running a randomized process depending on
+# third-party tools.
+list_final:
+	@printf '%s\n' $(all_final) | sort
+
+clean:
+	rm -f $(all_intermediate)
+neat: clean
+	rm -f $(all_final)