Remove optional block PB when adding new optional blocks

Let tr31_opt_block_alloc() remove all instances of optional block PB
when adding a new optional block. ANSI X9.143:2021, 6.3.6, states that
the padding block will always be the last optional block in the header.
Therefore, if optional block PB was previously added for whatever
reason, for example via an export header by tr31-tool, it should be
removed before adding further optional blocks. However, if no further
optional blocks are added, an existing optional block PB is
intentionally preserved specifically to allow the caller, or tr31-tool
using an export header, to specify exact content for optional block PB.

src/CMakeLists.txt

@@ -671,11 +671,21 @@ if(TARGET tr31-tool AND BUILD_TESTING)
 			PASS_REGULAR_EXPRESSION "D1840S0ES00N0400CT000405D6020002F0MIICLjCCAdSgAwIBAgIIGDrdWBxuNpAwCgYIKoZIzj0EAwIwMTEXMBUGA1UECgwOQWxwaGEgTWVyY2hhbnQxFjAUBgNVBAMMDVNhbXBsZSBFQ0MgQ0EwHhcNMjAwODE1MDIxMDEwWhcNMjEwODE1MDIxMDEwWjBPMRcwFQYDVQQKDA5BbHBoYSBNZXJjaGFudDEfMB0GA1UECwwWVExTIENsaWVudCBDZXJ0aWZpY2F0ZTETMBEGA1UEAwwKMTIzNDU2Nzg5MDBZMBMGByqGSM49AgEGCCqGSM49AwEHA0IABEI/SLrH6fITA9y6Y3BneuoT/5\\+EHSepZxCYeSstGll2sVvmSDZWWSbN6lh5Fb/zagrDjjQ/gZtWIOTf2wL1vSGjgbcwgbQwCQYDVR0TBAIwADAOBgNVHQ8BAf8EBAMCB4AwEwYDVR0lBAwwCgYIKwYBBQUHAwIwHQYDVR0OBBYEFHuvP526vFMywEoVoXZ5aXNfhnfeMB8GA1UdIwQYMBaAFI\\+ZFhOWF\\+oMtcfYwg15vH5WmWccMEIGA1UdHwQ7MDkwN6A1oDOGMWh0dHA6Ly9jcmwuYWxwaGEtbWVyY2hhbnQuZXhhbXBsZS9TYW1wbGVFQ0NDQS5jcmwwCgYIKoZIzj0EAwIDSAAwRQIhAPuWWvCTmOdvQzUjCUmTX7H4sX4Ebpw\\+CI\\+aOQLu1DqwAiA0eR4FdMtvXV4P6\\+WMz5B10oea5xtLTfSgoBDoTkvKYQ==0002C4MIICDjCCAbOgAwIBAgIIfnOsCbsxHjwwCgYIKoZIzj0EAwIwNjEXMBUGA1UECgwOQWxwaGEgTWVyY2hhbnQxGzAZBgNVBAMMElNhbXBsZSBSb290IEVDQyBDQTAeFw0yMDA4MTUwMjEwMDlaFw0zMDA4MTMwMjEwMDlaMDExFzAVBgNVBAoMDkFscGhhIE1lcmNoYW50MRYwFAYDVQQDDA1TYW1wbGUgRUNDIENBMFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEHCanM9n\\+Rji\\+3EROj\\+HlogmXMU1Fk1td7N3I/8rfFnre1GwWCUqXSePHxwQ9DRHCV3oht3OUU2kDfitfUIujA6OBrzCBrDASBgNVHRMBAf8ECDAGAQH/AgEAMA4GA1UdDwEB/wQEAwIBhjAdBgNVHQ4EFgQUj5kWE5YX6gy1x9jCDXm8flaZZxwwHwYDVR0jBBgwFoAUvElIifFlt6oeUaopV9Y0lJtyPVQwRgYDVR0fBD8wPTA7oDmgN4Y1aHR0cDovL2NybC5hbHBoYS1tZXJjaGFudC5leGFtcGxlL1NhbXBsZVJvb3RFQ0NDQS5jcmwwCgYIKoZIzj0EAwIDSQAwRgIhALT8\\+DG\\+\\+\\+KuqqUGyBQ4YG4s34fqbujclxZTHxYWVVSNAiEAn3v5Xmct7fkLpkjGexiHsy6D90r0K2LlUqpN/069y5s=010004asdfKP10012331550BC9TS1320200818004100ZPB07"
 	)
 
+	# test export header containing optional blocks and padding, but not adding additional optional blocks
 	add_test(NAME tr31_tool_test40
 		COMMAND tr31-tool --kbpk 88E1AB2A2E3DD38C1FA039A536500CC8A87AB9D62DC92C01058FA79F44657DE6 --export 3F419E1CB7079442AA37474C2EFBF8B8 --export-header D1234M7HG00N0200HM0621PB0A5V5E8F
 	)
 	set_tests_properties(tr31_tool_test40
 		PROPERTIES
-			PASS_REGULAR_EXPRESSION "^D0128M7HG00N0200HM0621PB0A5V5E8F"
+			PASS_REGULAR_EXPRESSION "^D0128M7HG00N0200HM0621PB0A5V5E8F" # note that optional block padding content is intentionally preserved
+	)
+
+	# test export header containing optional blocks and padding and also adding additional optional blocks
+	add_test(NAME tr31_tool_test41
+		COMMAND tr31-tool --kbpk 88E1AB2A2E3DD38C1FA039A536500CC8A87AB9D62DC92C01058FA79F44657DE6 --export 3F419E1CB7079442AA37474C2EFBF8B8 --export-header D1234M7HG00N0200HM0621PB0A5V5E8F --export-opt-block-LB "MyKey"
+	)
+	set_tests_properties(tr31_tool_test41
+		PROPERTIES
+			PASS_REGULAR_EXPRESSION "^D0144M7HG00N0300HM0621LB09MyKeyPB11"
 	)
 endif()

src/tr31.c

@@ -679,18 +679,44 @@ static struct tr31_opt_ctx_t* tr31_opt_block_alloc(
 )
 {
 	struct tr31_opt_ctx_t* opt_ctx;
+	bool opt_blk_pb_found = false;
 
 	if (!ctx) {
 		return NULL;
 	}
 
 	// repeated optional block IDs are not allowed
+	// and optional block PB must always be last
 	// see ANSI X9.143:2021, 6.3.6
 	for (size_t i = 0; i < ctx->opt_blocks_count; ++i) {
 		if (ctx->opt_blocks[i].id == id) {
 			// existing optional block found
 			return NULL;
 		}
+
+		if (ctx->opt_blocks[i].id == TR31_OPT_BLOCK_PB) {
+			// optional block PB found
+			opt_blk_pb_found = true;
+		}
+	}
+
+	// if optional block PB already exists, remove all instances
+	// NOTE: it will be recreated by tr31_export()
+	// NOTE: if no new optional blocks are added, PB is intentionally preserved
+	if (opt_blk_pb_found) {
+		for (size_t i = 0; i < ctx->opt_blocks_count; ++i) {
+			if (ctx->opt_blocks[i].id == TR31_OPT_BLOCK_PB) {
+				free(ctx->opt_blocks[i].data);
+				ctx->opt_blocks[i].data = NULL;
+
+				ctx->opt_blocks_count -= 1;
+				if (i < ctx->opt_blocks_count) {
+					size_t remaining_count = ctx->opt_blocks_count - i;
+					size_t remaining_bytes = sizeof(*ctx->opt_blocks) * remaining_count;
+					memmove(&ctx->opt_blocks[i], &ctx->opt_blocks[i + 1], remaining_bytes);
+				}
+			}
+		}
 	}
 
 	// grow optional block array