Add TPM2 RNG

configure.py

@@ -580,7 +580,7 @@ def add_enable_disable_pair(group, what, default, msg=optparse.SUPPRESS_HELP):
                             'disable building of deprecated features and modules')
 
     # Should be derived from info.txt but this runs too early
-    third_party = ['boost', 'bzip2', 'lzma', 'commoncrypto', 'sqlite3', 'zlib', 'tpm']
+    third_party = ['boost', 'bzip2', 'lzma', 'commoncrypto', 'sqlite3', 'zlib', 'tpm', 'tpm2']
 
     for mod in third_party:
         mods_group.add_option('--with-%s' % (mod),

doc/api_ref/ffi.rst

@@ -177,6 +177,10 @@ The following enum values are defined in the FFI header:
    calling :cpp:func:`botan_hash_destroy` on a ``botan_rng_t`` object will cause
    this error.
 
+.. cpp:enumerator:: BOTAN_FFI_TPM_ERROR = -78
+
+   An error occured when performing TPM2 interactions.
+
 .. cpp:enumerator:: BOTAN_FFI_ERROR_UNKNOWN_ERROR = -100
 
    Something bad happened, but we are not sure why or how.

src/lib/ffi/ffi.cpp

@@ -67,13 +67,15 @@ int ffi_map_error_type(Botan::ErrorType err) {
       case Botan::ErrorType::IoError:
       case Botan::ErrorType::Pkcs11Error:
       case Botan::ErrorType::CommonCryptoError:
-      case Botan::ErrorType::TPMError:
       case Botan::ErrorType::ZlibError:
       case Botan::ErrorType::Bzip2Error:
       case Botan::ErrorType::LzmaError:
       case Botan::ErrorType::DatabaseError:
          return BOTAN_FFI_ERROR_SYSTEM_ERROR;
 
+      case Botan::ErrorType::TPMError:
+         return BOTAN_FFI_ERROR_TPM_ERROR;
+
       case Botan::ErrorType::NotImplemented:
          return BOTAN_FFI_ERROR_NOT_IMPLEMENTED;
       case Botan::ErrorType::OutOfMemory:

src/lib/ffi/ffi.h

@@ -127,6 +127,7 @@ enum BOTAN_FFI_ERROR {
    BOTAN_FFI_ERROR_TLS_ERROR = -75,
    BOTAN_FFI_ERROR_HTTP_ERROR = -76,
    BOTAN_FFI_ERROR_ROUGHTIME_ERROR = -77,
+   BOTAN_FFI_ERROR_TPM_ERROR = -78,
 
    BOTAN_FFI_ERROR_UNKNOWN_ERROR = -100,
 };
@@ -259,6 +260,33 @@ BOTAN_FFI_EXPORT(2, 3) int botan_base64_decode(const char* base64_str, size_t in
 */
 typedef struct botan_rng_struct* botan_rng_t;
 
+/**
+* TPM2 context
+*/
+typedef struct botan_tpm2_ctx_struct* botan_tpm2_ctx_t;
+
+/**
+* Initialize a TPM2 context
+* @param ctx_out output TPM2 context
+* @param tcti_nameconf TCTI config (may be nullpointer)
+* @return 0 on success
+*/
+BOTAN_FFI_EXPORT(3, 6) int botan_tpm2_ctx_init(botan_tpm2_ctx_t* ctx_out, const char* tcti_nameconf);
+
+/**
+* Frees all resouces of a TPM2 context
+* @param ctx TPM2 context
+* @return 0 on success
+*/
+BOTAN_FFI_EXPORT(3, 6) int botan_tpm2_ctx_destroy(botan_tpm2_ctx_t ctx);
+
+/**
+* Initialize a random number generator object via TPM2
+* @param rng_out rng object to create
+* @param ctx TPM2 context
+*/
+BOTAN_FFI_EXPORT(3, 6) int botan_tpm2_rng_init(botan_rng_t* rng_out, botan_tpm2_ctx_t ctx);
+
 /**
 * Initialize a random number generator object
 * @param rng rng object

src/lib/ffi/ffi_tpm2.cpp

@@ -0,0 +1,89 @@
+/*
+* (C) 2024 Jack Lloyd
+* (C) 2024 René Meusel, Amos Treiber - Rohde & Schwarz Cybersecurity GmbH
+*
+* Botan is released under the Simplified BSD License (see license.txt)
+*/
+
+#include <botan/ffi.h>
+
+#include <botan/internal/ffi_rng.h>
+#include <botan/internal/ffi_util.h>
+
+#if defined(BOTAN_HAS_TPM2)
+   #include <botan/tpm2.h>
+   #include <botan/tpm2_rng.h>
+#endif
+
+extern "C" {
+
+using namespace Botan_FFI;
+
+#if defined(BOTAN_HAS_TPM2)
+/**
+ * This wrapper is required since BOTAN_FFI_DECLARE_STRUCT internally produces a unique pointer,
+ * but the TPM2_Context is meant to be used as a shared pointer.
+ */
+struct botan_tpm2_ctx_wrapper {
+      std::shared_ptr<Botan::TPM2_Context> ctx;
+};
+
+BOTAN_FFI_DECLARE_STRUCT(botan_tpm2_ctx_struct, botan_tpm2_ctx_wrapper, 0xD2B95E15);
+#endif
+
+int botan_tpm2_ctx_init(botan_tpm2_ctx_t* ctx_out, const char* tcti_nameconf) {
+#if defined(BOTAN_HAS_TPM2)
+   return ffi_guard_thunk(__func__, [=]() -> int {
+      if(ctx_out == nullptr) {
+         return BOTAN_FFI_ERROR_NULL_POINTER;
+      }
+      auto ctx = std::make_unique<botan_tpm2_ctx_wrapper>();
+
+      auto tcti = [=]() -> std::optional<std::string> {
+         if(tcti_nameconf == nullptr) {
+            return {};
+         } else {
+            return std::string(tcti_nameconf);
+         }
+      }();
+
+      ctx->ctx = Botan::TPM2_Context::create(std::move(tcti));
+      *ctx_out = new botan_tpm2_ctx_struct(std::move(ctx));
+      return BOTAN_FFI_SUCCESS;
+   });
+#else
+   BOTAN_UNUSED(ctx_out, tcti_nameconf);
+   return BOTAN_FFI_ERROR_NOT_IMPLEMENTED;
+#endif
+}
+
+/**
+ * Frees all resouces of a TPM2 context
+ * @param ctx TPM2 context
+ * @return 0 on success
+ */
+int botan_tpm2_ctx_destroy(botan_tpm2_ctx_t ctx) {
+#if defined(BOTAN_HAS_TPM2)
+   return BOTAN_FFI_CHECKED_DELETE(ctx);
+#else
+   BOTAN_UNUSED(ctx);
+   return BOTAN_FFI_ERROR_NOT_IMPLEMENTED;
+#endif
+}
+
+int botan_tpm2_rng_init(botan_rng_t* rng_out, botan_tpm2_ctx_t ctx) {
+#if defined(BOTAN_HAS_TPM2)
+   return BOTAN_FFI_VISIT(ctx, [=](botan_tpm2_ctx_wrapper& ctx_wrapper) -> int {
+      if(rng_out == nullptr) {
+         return BOTAN_FFI_ERROR_NULL_POINTER;
+      }
+
+      *rng_out = new botan_rng_struct(std::make_unique<Botan::TPM2_RNG>(ctx_wrapper.ctx));
+      return BOTAN_FFI_SUCCESS;
+   });
+#else
+   BOTAN_UNUSED(rng_out, ctx);
+   return BOTAN_FFI_ERROR_NOT_IMPLEMENTED;
+#endif
+}
+}

src/lib/prov/tpm2/info.txt

@@ -0,0 +1,27 @@
+<defines>
+TPM2 -> 20240610
+</defines>
+
+<module_info>
+name -> "TPM2"
+brief -> "Wrappers and Utilites to interact with TPM2"
+</module_info>
+
+load_on vendor
+
+<libs>
+all -> tss2-esys,tss2-rc,tss2-tctildr
+</libs>
+
+<requires>
+rng
+</requires>
+
+<header:internal>
+tpm2_util.h
+</header:internal>
+
+<header:public>
+tpm2.h
+tpm2_rng.h
+</header:public>

src/lib/prov/tpm2/tpm2.cpp

@@ -0,0 +1,58 @@
+/*
+* TPM 2 interface
+* (C) 2024 Jack Lloyd
+* (C) 2024 René Meusel, Amos Treiber - Rohde & Schwarz Cybersecurity GmbH
+*
+* Botan is released under the Simplified BSD License (see license.txt)
+*/
+
+#include <botan/tpm2.h>
+
+#include <botan/internal/fmt.h>
+#include <botan/internal/tpm2_util.h>
+
+#include <tss2/tss2_esys.h>
+#include <tss2/tss2_tcti.h>
+#include <tss2/tss2_tctildr.h>
+
+namespace Botan {
+
+TPM2_Error::TPM2_Error(std::string_view location, uint32_t rc) :
+      Exception(fmt("TPM2 Exception in {}: Code {} ({})", location, rc, Tss2_RC_Decode(rc))), m_rc(rc) {}
+
+std::string TPM2_Error::error_message() const {
+   return Tss2_RC_Decode(m_rc);
+}
+
+struct TPM2_Context::Impl {
+      TSS2_TCTI_CONTEXT* m_tcti_ctx;
+      ESYS_CONTEXT* m_ctx;
+};
+
+std::shared_ptr<TPM2_Context> TPM2_Context::create(std::optional<std::string> tcti_nameconf) {
+   const auto tcti_nameconf_ptr = [&]() -> const char* {
+      if(tcti_nameconf.has_value()) {
+         return tcti_nameconf->c_str();
+      } else {
+         return nullptr;
+      }
+   }();
+   // We cannot std::make_shared as the constructor is private
+   return std::shared_ptr<TPM2_Context>(new TPM2_Context(tcti_nameconf_ptr));
+}
+
+TPM2_Context::TPM2_Context(const char* tcti_nameconf) : m_impl(std::make_unique<Impl>()) {
+   check_tss2_rc("TCTI Initialization", Tss2_TctiLdr_Initialize(tcti_nameconf, &m_impl->m_tcti_ctx));
+   check_tss2_rc("TPM2 Initialization", Esys_Initialize(&m_impl->m_ctx, m_impl->m_tcti_ctx, nullptr /* ABI version */));
+}
+
+void* TPM2_Context::get() {
+   return m_impl->m_ctx;
+}
+
+TPM2_Context::~TPM2_Context() {
+   Esys_Finalize(&m_impl->m_ctx);
+   Tss2_TctiLdr_Finalize(&m_impl->m_tcti_ctx);
+}
+
+}  // namespace Botan

src/lib/prov/tpm2/tpm2.h

@@ -0,0 +1,65 @@
+/*
+* TPM 2 interface
+* (C) 2024 Jack Lloyd
+* (C) 2024 René Meusel, Amos Treiber - Rohde & Schwarz Cybersecurity GmbH
+*
+* Botan is released under the Simplified BSD License (see license.txt)
+*/
+
+#ifndef BOTAN_TPM2_H_
+#define BOTAN_TPM2_H_
+
+#include <botan/exceptn.h>
+
+#include <memory>
+#include <optional>
+
+namespace Botan {
+class BOTAN_PUBLIC_API(3, 6) TPM2_Error final : public Exception {
+   public:
+      TPM2_Error(std::string_view location, uint32_t rc);
+
+      ErrorType error_type() const noexcept override { return ErrorType::TPMError; }
+
+      uint32_t code() const { return m_rc; }
+
+      int error_code() const noexcept override {
+         // RC is uint32 but the maximum value is within int32 range as per tss2_common.h
+         return static_cast<int>(m_rc);
+      }
+
+      std::string error_message() const;
+
+   private:
+      uint32_t m_rc;
+};
+
+class BOTAN_PUBLIC_API(3, 6) TPM2_Context final {
+   public:
+      /**
+       * @param tcti_nameconf  if set this is passed to Tss2_TctiLdr_Initialize verbatim
+       *                       otherwise a nullptr is passed.
+       */
+      static std::shared_ptr<TPM2_Context> create(std::optional<std::string> tcti_nameconf = {});
+
+      TPM2_Context(const TPM2_Context&) = delete;
+      TPM2_Context(TPM2_Context&& ctx) noexcept = default;
+      ~TPM2_Context();
+
+      TPM2_Context& operator=(const TPM2_Context&) = delete;
+      TPM2_Context& operator=(TPM2_Context&& ctx) noexcept = default;
+
+      /// @return an ESYS_CONTEXT* for use in other TPM2 functions.
+      void* get();
+
+   private:
+      TPM2_Context(const char* tcti_nameconf);
+
+   private:
+      struct Impl;  // PImpl to avoid TPM2-TSS includes in this header
+      std::unique_ptr<Impl> m_impl;
+};
+
+}  // namespace Botan
+
+#endif

src/lib/prov/tpm2/tpm2_rng.cpp

@@ -0,0 +1,54 @@
+/*
+* TPM 2 RNG interface
+* (C) 2024 Jack Lloyd
+* (C) 2024 René Meusel, Amos Treiber - Rohde & Schwarz Cybersecurity GmbH
+*
+* Botan is released under the Simplified BSD License (see license.txt)
+*/
+
+#include <botan/tpm2_rng.h>
+
+#include <botan/internal/stl_util.h>
+#include <botan/internal/tpm2_util.h>
+
+#include <source_location>
+#include <tss2/tss2_esys.h>
+
+namespace Botan {
+
+void TPM2_RNG::fill_bytes_with_input(std::span<uint8_t> output, std::span<const uint8_t> input) {
+   constexpr size_t MAX_STIR_RANDOM_SIZE = 128;  // From specification of tpm2-tool's tpm2_stirrandom
+
+   BufferSlicer in(input);
+
+   while(!in.empty()) {
+      TPM2B_SENSITIVE_DATA data;
+      data.size = std::min(in.remaining(), MAX_STIR_RANDOM_SIZE);
+      in.copy_into({data.buffer, data.size});
+
+      check_tss2_rc(
+         "StirRandom",
+         Esys_StirRandom(static_cast<ESYS_CONTEXT*>(m_ctx->get()), ESYS_TR_NONE, ESYS_TR_NONE, ESYS_TR_NONE, &data));
+   }
+
+   BufferStuffer out(output);
+   while(!out.full()) {
+      TPM2B_DIGEST* digest = nullptr;
+      const auto requested_bytes = std::min(sizeof(digest->buffer), out.remaining_capacity());
+      check_tss2_rc("GetRandom",
+                    Esys_GetRandom(static_cast<ESYS_CONTEXT*>(m_ctx->get()),
+                                   ESYS_TR_NONE,
+                                   ESYS_TR_NONE,
+                                   ESYS_TR_NONE,
+                                   requested_bytes,
+                                   &digest));
+
+      // Ensure Esys_Free(digest) is called even if assertions fail and we leave this block
+      auto clean_buffer = scoped_cleanup([&digest] { Esys_Free(digest); });
+
+      BOTAN_ASSERT_NOMSG(digest->size == requested_bytes);
+      out.append({digest->buffer, digest->size});
+   }
+}
+
+}  // namespace Botan