Merge pull request #4131

ea37614 wallet: wipe seed from memory where appropriate (moneromooo-monero)
e9ffa91 store secret keys encrypted where possible (moneromooo-monero)
70271fa common: add a class to safely wrap mlock/munlock (moneromooo-monero)
ab74dc2 crypto: make secret_key automatically mlock (moneromooo-monero)

10 files changed, 480 insertions, 7 deletions

diff --git a/contrib/epee/include/fnv1.h b/contrib/epee/include/fnv1.h
new file mode 100644
index 000000000..c04389bca
--- /dev/null
+++ b/contrib/epee/include/fnv1.h
@@ -0,0 +1,45 @@
+// Copyright (c) 2018, The Monero Project
+// 
+// All rights reserved.
+// 
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+// 
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+// 
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+// 
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#pragma once
+
+namespace epee
+{
+
+namespace fnv
+{
+  inline uint64_t FNV1a(const char *ptr, size_t sz)
+  {
+    uint64_t h = 0xcbf29ce484222325;
+    for (size_t i = 0; i < sz; ++i)
+      h = (h ^ *(const uint8_t*)ptr++) * 0x100000001b3;
+    return h;
+  }
+}
+
+}
diff --git a/contrib/epee/include/hex.h b/contrib/epee/include/hex.h
index e960da1d2..02600c320 100644
--- a/contrib/epee/include/hex.h
+++ b/contrib/epee/include/hex.h
@@ -33,6 +33,7 @@
 #include <iosfwd>
 #include <string>
 
+#include "wipeable_string.h"
 #include "span.h"
 
 namespace epee
@@ -41,6 +42,8 @@ namespace epee
   {
     //! \return A std::string containing hex of `src`.
     static std::string string(const span<const std::uint8_t> src);
+    //! \return A epee::wipeable_string containing hex of `src`.
+    static epee::wipeable_string wipeable_string(const span<const std::uint8_t> src);
 
     //! \return An array containing hex of `src`.
     template<std::size_t N>
@@ -59,6 +62,8 @@ namespace epee
     static void formatted(std::ostream& out, const span<const std::uint8_t> src);
 
   private:
+    template<typename T> T static convert(const span<const std::uint8_t> src);
+
     //! Write `src` bytes as hex to `out`. `out` must be twice the length
     static void buffer_unchecked(char* out, const span<const std::uint8_t> src) noexcept;
   };
diff --git a/contrib/epee/include/mlocker.h b/contrib/epee/include/mlocker.h
new file mode 100644
index 000000000..d2fc2ed58
--- /dev/null
+++ b/contrib/epee/include/mlocker.h
@@ -0,0 +1,87 @@
+// Copyright (c) 2018, The Monero Project
+// 
+// All rights reserved.
+// 
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+// 
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+// 
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+// 
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#pragma once 
+
+#include <map>
+#include <boost/thread/mutex.hpp>
+
+namespace epee
+{
+  class mlocker
+  {
+  public:
+    mlocker(void *ptr, size_t len);
+    ~mlocker();
+
+    static size_t get_page_size();
+    static size_t get_num_locked_pages();
+    static size_t get_num_locked_objects();
+
+    static void lock(void *ptr, size_t len);
+    static void unlock(void *ptr, size_t len);
+
+  private:
+    static size_t page_size;
+    static size_t num_locked_objects;
+
+    static boost::mutex &mutex();
+    static std::map<size_t, unsigned int> &map();
+    static void lock_page(size_t page);
+    static void unlock_page(size_t page);
+
+    void *ptr;
+    size_t len;
+  };
+
+  /// Locks memory while in scope
+  ///
+  /// Primarily useful for making sure that private keys don't get swapped out
+  //  to disk
+  template <class T>
+  struct mlocked : public T {
+    using type = T;
+
+    mlocked(): T() { mlocker::lock(this, sizeof(T)); }
+    mlocked(const T &t): T(t) { mlocker::lock(this, sizeof(T)); }
+    mlocked(const mlocked<T> &mt): T(mt) { mlocker::lock(this, sizeof(T)); }
+    mlocked(const T &&t): T(t) { mlocker::lock(this, sizeof(T)); }
+    mlocked(const mlocked<T> &&mt): T(mt) { mlocker::lock(this, sizeof(T)); }
+    mlocked<T> &operator=(const mlocked<T> &mt) { T::operator=(mt); return *this; }
+    ~mlocked() { mlocker::unlock(this, sizeof(T)); }
+  };
+
+  template<typename T>
+  T& unwrap(mlocked<T>& src) { return src; }
+
+  template<typename T>
+  const T& unwrap(mlocked<T> const& src) { return src; }
+
+  template <class T, size_t N>
+  using mlocked_arr = mlocked<std::array<T, N>>;
+}
diff --git a/contrib/epee/include/serialization/keyvalue_serialization.h b/contrib/epee/include/serialization/keyvalue_serialization.h
index 5791e1998..fc5a21851 100644
--- a/contrib/epee/include/serialization/keyvalue_serialization.h
+++ b/contrib/epee/include/serialization/keyvalue_serialization.h
@@ -85,6 +85,14 @@ public: \
   static_assert(std::is_pod<decltype(this_ref.varialble)>::value, "t_type must be a POD type."); \
   KV_SERIALIZE_VAL_POD_AS_BLOB_FORCE_N(varialble, val_name)
 
+#define KV_SERIALIZE_VAL_POD_AS_BLOB_OPT_N(varialble, val_name, default_value) \
+  do { \
+    static_assert(std::is_pod<decltype(this_ref.varialble)>::value, "t_type must be a POD type."); \
+    bool ret = KV_SERIALIZE_VAL_POD_AS_BLOB_FORCE_N(varialble, val_name); \
+    if (!ret) \
+      epee::serialize_default(this_ref.varialble, default_value); \
+  } while(0);
+
 #define KV_SERIALIZE_CONTAINER_POD_AS_BLOB_N(varialble, val_name) \
   epee::serialization::selector<is_store>::serialize_stl_container_pod_val_as_blob(this_ref.varialble, stg, hparent_section, val_name);
 
@@ -92,6 +100,7 @@ public: \
 
 #define KV_SERIALIZE(varialble)                           KV_SERIALIZE_N(varialble, #varialble)
 #define KV_SERIALIZE_VAL_POD_AS_BLOB(varialble)           KV_SERIALIZE_VAL_POD_AS_BLOB_N(varialble, #varialble)
+#define KV_SERIALIZE_VAL_POD_AS_BLOB_OPT(varialble, def)  KV_SERIALIZE_VAL_POD_AS_BLOB_OPT_N(varialble, #varialble, def)
 #define KV_SERIALIZE_VAL_POD_AS_BLOB_FORCE(varialble)     KV_SERIALIZE_VAL_POD_AS_BLOB_FORCE_N(varialble, #varialble) //skip is_pod compile time check
 #define KV_SERIALIZE_CONTAINER_POD_AS_BLOB(varialble)     KV_SERIALIZE_CONTAINER_POD_AS_BLOB_N(varialble, #varialble)
 #define KV_SERIALIZE_OPT(variable,default_value)          KV_SERIALIZE_OPT_N(variable, #variable, default_value)
diff --git a/contrib/epee/include/string_tools.h b/contrib/epee/include/string_tools.h
index 8d8603076..aba065cc7 100644
--- a/contrib/epee/include/string_tools.h
+++ b/contrib/epee/include/string_tools.h
@@ -46,6 +46,7 @@
 #include <boost/algorithm/string/predicate.hpp>
 #include "hex.h"
 #include "memwipe.h"
+#include "mlocker.h"
 #include "span.h"
 #include "warnings.h"
 
@@ -358,6 +359,12 @@ POP_WARNINGS
     return hex_to_pod(hex_str, unwrap(s));
   }
   //----------------------------------------------------------------------------
+  template<class t_pod_type>
+  bool hex_to_pod(const std::string& hex_str, epee::mlocked<t_pod_type>& s)
+  {
+    return hex_to_pod(hex_str, unwrap(s));
+  }
+  //----------------------------------------------------------------------------
   bool validate_hex(uint64_t length, const std::string& str);
   //----------------------------------------------------------------------------
 	inline std::string get_extension(const std::string& str)
diff --git a/contrib/epee/include/wipeable_string.h b/contrib/epee/include/wipeable_string.h
index 70d1a9586..4cebe5fdf 100644
--- a/contrib/epee/include/wipeable_string.h
+++ b/contrib/epee/include/wipeable_string.h
@@ -28,28 +28,43 @@
 
 #pragma once
 
+#include <boost/optional/optional_fwd.hpp>
 #include <stddef.h>
 #include <vector>
 #include <string>
+#include "fnv1.h"
 
 namespace epee
 {
   class wipeable_string
   {
   public:
+    typedef char value_type;
+
     wipeable_string() {}
     wipeable_string(const wipeable_string &other);
     wipeable_string(wipeable_string &&other);
     wipeable_string(const std::string &other);
     wipeable_string(std::string &&other);
     wipeable_string(const char *s);
+    wipeable_string(const char *s, size_t len);
     ~wipeable_string();
     void wipe();
     void push_back(char c);
-    void pop_back();
+    void operator+=(char c);
+    void operator+=(const std::string &s);
+    void operator+=(const epee::wipeable_string &s);
+    void operator+=(const char *s);
+    void append(const char *ptr, size_t len);
+    char pop_back();
     const char *data() const noexcept { return buffer.data(); }
+    char *data() noexcept { return buffer.data(); }
     size_t size() const noexcept { return buffer.size(); }
+    size_t length() const noexcept { return buffer.size(); }
     bool empty() const noexcept { return buffer.empty(); }
+    void trim();
+    void split(std::vector<wipeable_string> &fields) const;
+    boost::optional<wipeable_string> parse_hexstr() const;
     void resize(size_t sz);
     void reserve(size_t sz);
     void clear();
@@ -65,3 +80,14 @@ namespace epee
     std::vector<char> buffer;
   };
 }
+
+namespace std
+{
+  template<> struct hash<epee::wipeable_string>
+  {
+    size_t operator()(const epee::wipeable_string &s) const
+    {
+      return epee::fnv::FNV1a(s.data(), s.size());
+    }
+  };
+}
diff --git a/contrib/epee/src/CMakeLists.txt b/contrib/epee/src/CMakeLists.txt
index c4750cea0..0b5e7ae6c 100644
--- a/contrib/epee/src/CMakeLists.txt
+++ b/contrib/epee/src/CMakeLists.txt
@@ -27,7 +27,7 @@
 # THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 add_library(epee STATIC hex.cpp http_auth.cpp mlog.cpp net_utils_base.cpp string_tools.cpp wipeable_string.cpp memwipe.c
-    connection_basic.cpp network_throttle.cpp network_throttle-detail.cpp)
+    connection_basic.cpp network_throttle.cpp network_throttle-detail.cpp mlocker.cpp)
 if (USE_READLINE AND GNU_READLINE_FOUND)
   add_library(epee_readline STATIC readline_buffer.cpp)
 endif()
diff --git a/contrib/epee/src/hex.cpp b/contrib/epee/src/hex.cpp
index c143b2dc2..5c8acc8be 100644
--- a/contrib/epee/src/hex.cpp
+++ b/contrib/epee/src/hex.cpp
@@ -52,17 +52,21 @@ namespace epee
     }
   }
 
-  std::string to_hex::string(const span<const std::uint8_t> src)
+  template<typename T>
+  T to_hex::convert(const span<const std::uint8_t> src)
   {
     if (std::numeric_limits<std::size_t>::max() / 2 < src.size())
       throw std::range_error("hex_view::to_string exceeded maximum size");
 
-    std::string out{};
+    T out{};
     out.resize(src.size() * 2);
-    buffer_unchecked(std::addressof(out[0]), src);
+    to_hex::buffer_unchecked((char*)out.data(), src); // can't see the non const version in wipeable_string??
     return out;
   }
 
+  std::string to_hex::string(const span<const std::uint8_t> src) { return convert<std::string>(src); }
+  epee::wipeable_string to_hex::wipeable_string(const span<const std::uint8_t> src) { return convert<epee::wipeable_string>(src); }
+
   void to_hex::buffer(std::ostream& out, const span<const std::uint8_t> src)
   {
     write_hex(std::ostreambuf_iterator<char>{out}, src);
diff --git a/contrib/epee/src/mlocker.cpp b/contrib/epee/src/mlocker.cpp
new file mode 100644
index 000000000..5573d591a
--- /dev/null
+++ b/contrib/epee/src/mlocker.cpp
@@ -0,0 +1,182 @@
+// Copyright (c) 2018, The Monero Project
+// 
+// All rights reserved.
+// 
+// Redistribution and use in source and binary forms, with or without modification, are
+// permitted provided that the following conditions are met:
+// 
+// 1. Redistributions of source code must retain the above copyright notice, this list of
+//    conditions and the following disclaimer.
+// 
+// 2. Redistributions in binary form must reproduce the above copyright notice, this list
+//    of conditions and the following disclaimer in the documentation and/or other
+//    materials provided with the distribution.
+// 
+// 3. Neither the name of the copyright holder nor the names of its contributors may be
+//    used to endorse or promote products derived from this software without specific
+//    prior written permission.
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
+// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#if defined __GNUC__ && !defined _WIN32
+#define HAVE_MLOCK 1
+#endif
+
+#include <unistd.h>
+#if defined HAVE_MLOCK
+#include <sys/mman.h>
+#endif
+#include "misc_log_ex.h"
+#include "syncobj.h"
+#include "mlocker.h"
+
+static size_t query_page_size()
+{
+#if defined HAVE_MLOCK
+  long ret = sysconf(_SC_PAGESIZE);
+  if (ret <= 0)
+  {
+    MERROR("Failed to determine page size");
+    return 0;
+  }
+  MINFO("Page size: " << ret);
+  return ret;
+#else
+#warning Missing query_page_size implementation
+#endif
+  return 0;
+}
+
+static void do_lock(void *ptr, size_t len)
+{
+#if defined HAVE_MLOCK
+  int ret = mlock(ptr, len);
+  if (ret < 0)
+    MERROR("Error locking page at " << ptr << ": " << strerror(errno));
+#else
+#warning Missing do_lock implementation
+#endif
+}
+
+static void do_unlock(void *ptr, size_t len)
+{
+#if defined HAVE_MLOCK
+  int ret = munlock(ptr, len);
+  if (ret < 0)
+    MERROR("Error unlocking page at " << ptr << ": " << strerror(errno));
+#else
+#warning Missing implementation of page size detection
+#endif
+}
+
+namespace epee
+{
+  size_t mlocker::page_size = 0;
+  size_t mlocker::num_locked_objects = 0;
+
+  boost::mutex &mlocker::mutex()
+  {
+    static boost::mutex vmutex;
+    return vmutex;
+  }
+  std::map<size_t, unsigned int> &mlocker::map()
+  {
+    static std::map<size_t, unsigned int> vmap;
+    return vmap;
+  }
+
+  size_t mlocker::get_page_size()
+  {
+    CRITICAL_REGION_LOCAL(mutex());
+    if (page_size == 0)
+      page_size = query_page_size();
+    return page_size;
+  }
+
+  mlocker::mlocker(void *ptr, size_t len): ptr(ptr), len(len)
+  {
+    lock(ptr, len);
+  }
+
+  mlocker::~mlocker()
+  {
+    unlock(ptr, len);
+  }
+
+  void mlocker::lock(void *ptr, size_t len)
+  {
+    size_t page_size = get_page_size();
+    if (page_size == 0)
+      return;
+
+    CRITICAL_REGION_LOCAL(mutex());
+    const size_t first = ((uintptr_t)ptr) / page_size;
+    const size_t last = (((uintptr_t)ptr) + len - 1) / page_size;
+    for (size_t page = first; page <= last; ++page)
+      lock_page(page);
+    ++num_locked_objects;
+  }
+
+  void mlocker::unlock(void *ptr, size_t len)
+  {
+    size_t page_size = get_page_size();
+    if (page_size == 0)
+      return;
+    CRITICAL_REGION_LOCAL(mutex());
+    const size_t first = ((uintptr_t)ptr) / page_size;
+    const size_t last = (((uintptr_t)ptr) + len - 1) / page_size;
+    for (size_t page = first; page <= last; ++page)
+      unlock_page(page);
+    --num_locked_objects;
+  }
+
+  size_t mlocker::get_num_locked_pages()
+  {
+    CRITICAL_REGION_LOCAL(mutex());
+    return map().size();
+  }
+
+  size_t mlocker::get_num_locked_objects()
+  {
+    CRITICAL_REGION_LOCAL(mutex());
+    return num_locked_objects;
+  }
+
+  void mlocker::lock_page(size_t page)
+  {
+    std::pair<std::map<size_t, unsigned int>::iterator, bool> p = map().insert(std::make_pair(page, 1));
+    if (p.second)
+    {
+      do_lock((void*)(page * page_size), page_size);
+    }
+    else
+    {
+      ++p.first->second;
+    }
+  }
+
+  void mlocker::unlock_page(size_t page)
+  {
+    std::map<size_t, unsigned int>::iterator i = map().find(page);
+    if (i == map().end())
+    {
+      MERROR("Attempt to unlock unlocked page at " << (void*)(page * page_size));
+    }
+    else
+    {
+      if (!--i->second)
+      {
+        map().erase(i);
+        do_unlock((void*)(page * page_size), page_size);
+      }
+    }
+  }
+}
diff --git a/contrib/epee/src/wipeable_string.cpp b/contrib/epee/src/wipeable_string.cpp
index 6ed4ee8a2..7c9722765 100644
--- a/contrib/epee/src/wipeable_string.cpp
+++ b/contrib/epee/src/wipeable_string.cpp
@@ -26,11 +26,22 @@
 // STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
 // THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+#include <boost/optional/optional.hpp>
 #include <string.h>
 #include "memwipe.h"
 #include "misc_log_ex.h"
 #include "wipeable_string.h"
 
+namespace
+{
+  int atolower(int c)
+  {
+    if (c >= 'A' && c <= 'Z')
+      c |= 32;
+    return c;
+  }
+}
+
 namespace epee
 {
 
@@ -69,6 +80,12 @@ wipeable_string::wipeable_string(const char *s)
   memcpy(buffer.data(), s, size());
 }
 
+wipeable_string::wipeable_string(const char *s, size_t len)
+{
+  grow(len);
+  memcpy(buffer.data(), s, len);
+}
+
 wipeable_string::~wipeable_string()
 {
   wipe();
@@ -109,9 +126,100 @@ void wipeable_string::push_back(char c)
   buffer.back() = c;
 }
 
-void wipeable_string::pop_back()
+void wipeable_string::operator+=(char c)
+{
+  push_back(c);
+}
+
+void wipeable_string::append(const char *ptr, size_t len)
+{
+  const size_t orgsz = size();
+  CHECK_AND_ASSERT_THROW_MES(orgsz < std::numeric_limits<size_t>::max() - len, "Appended data too large");
+  grow(orgsz + len);
+  if (len > 0)
+    memcpy(data() + orgsz, ptr, len);
+}
+
+void wipeable_string::operator+=(const char *s)
+{
+  append(s, strlen(s));
+}
+
+void wipeable_string::operator+=(const epee::wipeable_string &s)
+{
+  append(s.data(), s.size());
+}
+
+void wipeable_string::operator+=(const std::string &s)
+{
+  append(s.c_str(), s.size());
+}
+
+void wipeable_string::trim()
+{
+  size_t prefix = 0;
+  while (prefix < size() && data()[prefix] == ' ')
+    ++prefix;
+  if (prefix > 0)
+    memmove(buffer.data(), buffer.data() + prefix, size() - prefix);
+
+  size_t suffix = 0;
+  while (suffix < size()-prefix && data()[size() - 1 - prefix - suffix] == ' ')
+    ++suffix;
+
+  resize(size() - prefix - suffix);
+}
+
+void wipeable_string::split(std::vector<wipeable_string> &fields) const
+{
+  fields.clear();
+  size_t len = size();
+  const char *ptr = data();
+  bool space = true;
+  while (len--)
+  {
+    const char c = *ptr++;
+    if (c != ' ')
+    {
+      if (space)
+        fields.push_back({});
+      fields.back().push_back(c);
+    }
+    space = c == ' ';
+  }
+}
+
+boost::optional<epee::wipeable_string> wipeable_string::parse_hexstr() const
+{
+  if (size() % 2 != 0)
+    return boost::none;
+  boost::optional<epee::wipeable_string> res = epee::wipeable_string("");
+  const size_t len = size();
+  const char *d = data();
+  res->grow(0, len / 2);
+  static constexpr const char hex[] = u8"0123456789abcdef";
+  for (size_t i = 0; i < len; i += 2)
+  {
+    char c = atolower(d[i]);
+    const char *ptr0 = strchr(hex, c);
+    if (!ptr0)
+      return boost::none;
+    c = atolower(d[i+1]);
+    const char *ptr1 = strchr(hex, c);
+    if (!ptr1)
+      return boost::none;
+    res->push_back(((ptr0-hex)<<4) | (ptr1-hex));
+  }
+  return res;
+}
+
+char wipeable_string::pop_back()
 {
-  resize(size() - 1);
+  const size_t sz = size();
+  CHECK_AND_ASSERT_THROW_MES(sz > 0, "Popping from an empty string");
+  const char c = buffer.back();
+  resize(sz - 1);
+  return c;
 }
 
 void wipeable_string::resize(size_t sz)