implement unwrap command to retrieve binary files from containers

src/unwrap.c

@@ -0,0 +1,168 @@
+#include "commands.h"
+#include "misc.h"
+#include "read.h"
+
+#include <blue/cmd.h>
+#include <blue/term.h>
+#include <errno.h>
+#include <stdlib.h>
+
+enum {
+	ARG_CONTAINER,
+	OPT_TAG,
+	OPT_TAG_IDENT,
+};
+
+static int unwrap(
+	const b_command *self,
+	const b_arglist *opt,
+	const b_array *args)
+{
+	const char *in_path = NULL;
+	b_arglist_get_string(
+		opt,
+		B_COMMAND_INVALID_ID,
+		ARG_CONTAINER,
+		0,
+		&in_path);
+
+	FILE *inp = fopen(in_path, "rb");
+	if (!inp) {
+		b_err("cannot open '%s'", in_path);
+		b_i("reason: %s", strerror(errno));
+		return -1;
+	}
+
+	struct ec3_reader *reader = NULL;
+	enum ec3_status status = ec3_reader_create(inp, &reader);
+
+	if (status != EC3_SUCCESS) {
+		fclose(inp);
+
+		b_err("cannot open '%s'", in_path);
+		b_i("reason: corrupted/unknown file format");
+		return -1;
+	}
+
+	const struct ec3_container_info *c_info
+		= ec3_reader_get_container_info(reader);
+	if (c_info->c_nr_tags == 0) {
+		ec3_reader_finish(reader);
+		fclose(inp);
+
+		b_i("container '%s' has no tags", in_path);
+		return -1;
+	}
+
+	uint64_t target_tag_ident = 0;
+	const char *target_tag_ident_str = NULL;
+	b_arglist_get_string(
+		opt,
+		OPT_TAG,
+		OPT_TAG_IDENT,
+		0,
+		&target_tag_ident_str);
+
+	if (target_tag_ident_str) {
+		ec3_identifier_from_string(
+			target_tag_ident_str,
+			&target_tag_ident);
+	} else {
+		const struct ec3_tag_info *tags = ec3_reader_get_tags(reader);
+		target_tag_ident = tags[0].tag_ident;
+	}
+
+	char ident_str[32];
+	ec3_identifier_to_string(target_tag_ident, ident_str, sizeof ident_str);
+
+	struct ec3_tag_reader *tag_reader = NULL;
+	status = ec3_reader_open_tag(reader, target_tag_ident, &tag_reader);
+	if (status != EC3_SUCCESS) {
+		b_i("container '%s' has no %s tag", in_path, ident_str);
+
+		ec3_reader_finish(reader);
+		fclose(inp);
+		return -1;
+	}
+
+	const struct ec3_tag_info *target_tag_info
+		= ec3_reader_get_tag_info(reader, target_tag_ident);
+	size_t tag_length = target_tag_info->tag_total_length;
+
+	printf("reading %zu bytes from tag %s...\n", tag_length, ident_str);
+
+	char *buf = malloc(c_info->c_cluster_size);
+
+	int ret = 0;
+	FILE *outp = fopen("data.bin", "wb");
+	for (size_t i = 0;; i++) {
+		size_t nr_read = 0;
+		enum ec3_status status
+			= ec3_tag_reader_read(tag_reader, i, 1, buf, &nr_read);
+
+		if (status != EC3_SUCCESS) {
+			b_err("I/O failure while reading from container",
+			      in_path);
+			ret = -1;
+			break;
+		}
+
+		printf("read %zu bytes from cluster %zu\n", nr_read, i);
+		fwrite(buf, 1, nr_read, outp);
+
+		if (nr_read < c_info->c_cluster_size) {
+			break;
+		}
+	}
+
+	free(buf);
+
+	fclose(inp);
+	fclose(outp);
+	return ret;
+}
+
+B_COMMAND(CMD_UNWRAP, CMD_ROOT)
+{
+	B_COMMAND_NAME("unwrap");
+	B_COMMAND_SHORT_NAME('U');
+	B_COMMAND_DESC(
+		"retrieve a binary or executable blob from an ec3 "
+		"container.");
+	B_COMMAND_FLAGS(B_COMMAND_SHOW_HELP_BY_DEFAULT);
+	B_COMMAND_FUNCTION(unwrap);
+
+	B_COMMAND_HELP_OPTION();
+
+	B_COMMAND_ARG(ARG_CONTAINER)
+	{
+		B_ARG_NAME("container");
+		B_ARG_DESC("the container to retrieve the blob from");
+		B_ARG_NR_VALUES(1);
+	}
+
+	B_COMMAND_OPTION(OPT_TAG)
+	{
+		B_OPTION_SHORT_NAME('T');
+		B_OPTION_LONG_NAME("tag");
+		B_OPTION_DESC("the identifier of the blob tag to retrieve");
+
+		B_OPTION_ARG(OPT_TAG_IDENT)
+		{
+			B_ARG_NAME("identifier");
+			B_ARG_DESC("the identifier");
+			B_ARG_NR_VALUES(1);
+		}
+	}
+
+	B_COMMAND_USAGE()
+	{
+		B_COMMAND_USAGE_ARG(ARG_CONTAINER);
+	}
+
+	B_COMMAND_USAGE()
+	{
+		B_COMMAND_USAGE_OPT(OPT_TAG);
+		B_COMMAND_USAGE_ARG(ARG_CONTAINER);
+	}
+}