new(utils): add new helper to calculate file sha256sum

Signed-off-by: Melissa Kilby <[email protected]>

userspace/engine/falco_utils.cpp

@@ -22,6 +22,7 @@ limitations under the License.
 #include <libsinsp/utils.h>
 
 #include <re2/re2.h>
+#include <openssl/sha.h>
 
 #include <cstring>
 #include <fstream>
@@ -117,6 +118,36 @@ uint64_t parse_prometheus_interval(std::string interval_str)
 	return interval;
 }
 
+std::string calculate_file_sha256sum(const std::string& filename)
+{
+	std::ifstream file(filename, std::ios::binary);
+	if (!file.is_open())
+	{
+		return "";
+	}
+
+	SHA256_CTX sha256_context;
+	SHA256_Init(&sha256_context);
+
+	constexpr size_t buffer_size = 4096;
+	char buffer[buffer_size];
+	while (file.read(buffer, buffer_size))
+	{
+		SHA256_Update(&sha256_context, buffer, buffer_size);
+	}
+	SHA256_Update(&sha256_context, buffer, file.gcount());
+
+	unsigned char digest[SHA256_DIGEST_LENGTH];
+	SHA256_Final(digest, &sha256_context);
+
+	std::stringstream ss;
+	for (int i = 0; i < SHA256_DIGEST_LENGTH; ++i)
+	{
+		ss << std::hex << std::setw(2) << std::setfill('0') << static_cast<unsigned>(digest[i]);
+	}
+	return ss.str();
+}
+
 std::string wrap_text(const std::string& in, uint32_t indent, uint32_t line_len)
 {
 	std::istringstream is(in);

userspace/engine/falco_utils.h

@@ -27,6 +27,8 @@ namespace falco::utils
 {
 uint64_t parse_prometheus_interval(std::string interval_str);
 
+std::string calculate_file_sha256sum(const std::string& filename);
+
 std::string wrap_text(const std::string& in, uint32_t indent, uint32_t linelen);
 
 void readfile(const std::string& filename, std::string& data);