util: add a SHA256 function

src/common/CMakeLists.txt

@@ -76,6 +76,7 @@ target_link_libraries(common
   PUBLIC
     epee
     crypto
+    -lcrypto
     ${UNBOUND_LIBRARY}
     ${LIBUNWIND_LIBRARIES}
     ${Boost_DATE_TIME_LIBRARY}

src/common/util.cpp

@@ -31,6 +31,7 @@
 #include <cstdio>
 
 #include "include_base_utils.h"
+#include "file_io_utils.h"
 using namespace epee;
 
 #include "util.h"
@@ -46,7 +47,7 @@ using namespace epee;
 #endif
 #include <boost/filesystem.hpp>
 #include <boost/asio.hpp>
-
+#include <openssl/sha.h>
 
 namespace tools
 {
@@ -585,4 +586,36 @@ std::string get_nix_version_display_string()
     }
     return 0;
   }
+
+  bool sha256sum(const std::string &filename, crypto::hash &hash)
+  {
+    if (!epee::file_io_utils::is_file_exist(filename))
+      return false;
+    std::ifstream f;
+    f.exceptions(std::ifstream::failbit | std::ifstream::badbit);
+    f.open(filename, std::ios_base::binary | std::ios_base::in | std::ios::ate);
+    if (!f)
+      return false;
+    std::ifstream::pos_type file_size = f.tellg();
+    SHA256_CTX ctx;
+    if (!SHA256_Init(&ctx))
+      return false;
+    size_t size_left = file_size;
+    f.seekg(0, std::ios::beg);
+    while (size_left)
+    {
+      char buf[4096];
+      std::ifstream::pos_type read_size = size_left > sizeof(buf) ? sizeof(buf) : size_left;
+      f.read(buf, read_size);
+      if (!f || !f.good())
+        return false;
+      if (!SHA256_Update(&ctx, buf, read_size))
+        return false;
+      size_left -= read_size;
+    }
+    f.close();
+    if (!SHA256_Final((unsigned char*)hash.data, &ctx))
+      return false;
+    return true;
+  }
 }

src/common/util.h

@@ -184,4 +184,6 @@ namespace tools
 
   bool is_local_address(const std::string &address);
   int vercmp(const char *v0, const char *v1); // returns < 0, 0, > 0, similar to strcmp, but more human friendly than lexical - does not attempt to validate
+
+  bool sha256sum(const std::string &filename, crypto::hash &hash);
 }