1 files changed, 139 insertions, 0 deletions
diff --git a/src/librbd/crypto/luks/Magic.cc b/src/librbd/crypto/luks/Magic.cc
new file mode 100644
index 000000000..bc5e19704
--- /dev/null
+++ b/src/librbd/crypto/luks/Magic.cc
@@ -0,0 +1,139 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+
+#include "Magic.h"
+
+#include "common/dout.h"
+#include "common/errno.h"
+
+#define dout_subsys ceph_subsys_rbd
+#undef dout_prefix
+#define dout_prefix *_dout << "librbd::crypto::luks::Magic: " << __func__ \
+                           << ": "
+
+namespace librbd {
+namespace crypto {
+namespace luks {
+
+namespace {
+
+constexpr uint64_t MAGIC_LENGTH = 6;
+const std::string LUKS_MAGIC = "LUKS\xba\xbe";
+const std::string RBD_CLONE_MAGIC = "RBDL\xba\xbe";
+
+} // anonymous namespace
+
+int Magic::read(ceph::bufferlist &bl, uint32_t bl_off,
+                uint32_t read_size, char* result) {
+  if (bl_off + read_size > bl.length()) {
+    return -EINVAL;
+  }
+
+  memcpy(result, bl.c_str() + bl_off, read_size);
+  return 0;
+}
+
+int Magic::cmp(ceph::bufferlist &bl, uint32_t bl_off,
+               const std::string &cmp_str) {
+  auto cmp_length = cmp_str.length();
+
+  if (bl_off + cmp_length > bl.length()) {
+    return -EINVAL;
+  }
+
+  if (memcmp(bl.c_str() + bl_off, cmp_str.c_str(), cmp_length)) {
+    return 0;
+  }
+
+  return 1;
+}
+
+int Magic::is_luks(ceph::bufferlist& bl) {
+  return cmp(bl, 0, LUKS_MAGIC);
+}
+
+int Magic::is_rbd_clone(ceph::bufferlist& bl) {
+  return cmp(bl, 0, RBD_CLONE_MAGIC);
+}
+
+void Magic::transform_secondary_header_magic(char* magic) {
+  std::swap(magic[0], magic[3]);
+  std::swap(magic[1], magic[2]);
+}
+
+int Magic::replace_magic(CephContext* cct, ceph::bufferlist& bl) {
+  const std::string *old_magic, *new_magic;
+  if (is_luks(bl) > 0) {
+    old_magic = &LUKS_MAGIC;
+    new_magic = &RBD_CLONE_MAGIC;
+  } else if (is_rbd_clone(bl) > 0) {
+    old_magic = &RBD_CLONE_MAGIC;
+    new_magic = &LUKS_MAGIC;
+  } else {
+    lderr(cct) << "invalid magic: " << dendl;
+    return -EILSEQ;
+  }
+
+  // read luks version
+  uint16_t version;
+  auto r = read(bl, MAGIC_LENGTH, sizeof(version), (char*)&version);
+  if (r < 0) {
+    lderr(cct) << "cannot read header version: " << cpp_strerror(r) << dendl;
+    return r;
+  }
+  boost::endian::big_to_native_inplace(version);
+
+  switch (version) {
+    case 1: {
+      // LUKS1, no secondary header
+      break;
+    }
+    case 2: {
+      // LUKS2, secondary header follows primary header
+      // read header size
+      uint64_t hdr_size;
+      r = read(bl, MAGIC_LENGTH + sizeof(version), sizeof(hdr_size),
+                    (char*)&hdr_size);
+      if (r < 0) {
+        lderr(cct) << "cannot read header size: " << cpp_strerror(r) << dendl;
+        return r;
+      }
+      boost::endian::big_to_native_inplace(hdr_size);
+
+      if ((uint32_t)hdr_size + MAGIC_LENGTH > bl.length()) {
+        ldout(cct, 20) << "cannot replace secondary header magic" << dendl;
+        return -EINVAL;
+      }
+
+      // check secondary header magic
+      auto secondary_header_magic = bl.c_str() + hdr_size;
+      transform_secondary_header_magic(secondary_header_magic);
+      auto is_secondary_header_magic_valid =
+              !memcmp(secondary_header_magic, old_magic->c_str(), MAGIC_LENGTH);
+      if (!is_secondary_header_magic_valid) {
+        transform_secondary_header_magic(secondary_header_magic);
+        lderr(cct) << "invalid secondary header magic" << dendl;
+        return -EILSEQ;
+      }
+
+      // replace secondary header magic
+      memcpy(secondary_header_magic, new_magic->c_str(), MAGIC_LENGTH);
+      transform_secondary_header_magic(secondary_header_magic);
+
+      break;
+    }
+    default: {
+      lderr(cct) << "bad header version: " << version << dendl;
+      return -EINVAL;
+    }
+  }
+
+  // switch primary header magic
+  memcpy(bl.c_str(), new_magic->c_str(), MAGIC_LENGTH);
+
+  return 0;
+}
+
+} // namespace luks
+} // namespace crypto
+} // namespace librbd