diff options
Diffstat (limited to 'comm/third_party/botan/src/lib/entropy/proc_walk/proc_walk.cpp')
-rw-r--r-- | comm/third_party/botan/src/lib/entropy/proc_walk/proc_walk.cpp | 154 |
1 files changed, 154 insertions, 0 deletions
diff --git a/comm/third_party/botan/src/lib/entropy/proc_walk/proc_walk.cpp b/comm/third_party/botan/src/lib/entropy/proc_walk/proc_walk.cpp new file mode 100644 index 0000000000..d780cbf739 --- /dev/null +++ b/comm/third_party/botan/src/lib/entropy/proc_walk/proc_walk.cpp @@ -0,0 +1,154 @@ +/* +* Entropy source based on reading files in /proc on the assumption +* that a remote attacker will have difficulty guessing some of them. +* +* (C) 1999-2008,2012 Jack Lloyd +* +* Botan is released under the Simplified BSD License (see license.txt) +*/ + +#include <botan/internal/proc_walk.h> +#include <deque> + +#ifndef _POSIX_C_SOURCE + #define _POSIX_C_SOURCE 199309 +#endif + +#include <sys/types.h> +#include <sys/stat.h> +#include <unistd.h> +#include <dirent.h> +#include <fcntl.h> + +namespace Botan { + +namespace { + +class Directory_Walker final : public File_Descriptor_Source + { + public: + explicit Directory_Walker(const std::string& root) : + m_cur_dir(std::make_pair<DIR*, std::string>(nullptr, "")) + { + if(DIR* root_dir = ::opendir(root.c_str())) + m_cur_dir = std::make_pair(root_dir, root); + } + + ~Directory_Walker() + { + if(m_cur_dir.first) + ::closedir(m_cur_dir.first); + } + + int next_fd() override; + private: + std::pair<struct dirent*, std::string> get_next_dirent(); + + std::pair<DIR*, std::string> m_cur_dir; + std::deque<std::string> m_dirlist; + }; + +std::pair<struct dirent*, std::string> Directory_Walker::get_next_dirent() + { + while(m_cur_dir.first) + { + if(struct dirent* dir = ::readdir(m_cur_dir.first)) + return std::make_pair(dir, m_cur_dir.second); + + ::closedir(m_cur_dir.first); + m_cur_dir = std::make_pair<DIR*, std::string>(nullptr, ""); + + while(!m_dirlist.empty() && !m_cur_dir.first) + { + const std::string next_dir_name = m_dirlist[0]; + m_dirlist.pop_front(); + + if(DIR* next_dir = ::opendir(next_dir_name.c_str())) + m_cur_dir = std::make_pair(next_dir, next_dir_name); + } + } + + return std::make_pair<struct dirent*, std::string>(nullptr, ""); // nothing left + } + +int Directory_Walker::next_fd() + { + while(true) + { + std::pair<struct dirent*, std::string> entry = get_next_dirent(); + + if(!entry.first) + break; // no more dirs + + const std::string filename = entry.first->d_name; + + if(filename == "." || filename == "..") + continue; + + const std::string full_path = entry.second + "/" + filename; + + struct stat stat_buf; + if(::lstat(full_path.c_str(), &stat_buf) == -1) + continue; + + if(S_ISDIR(stat_buf.st_mode)) + { + m_dirlist.push_back(full_path); + } + else if(S_ISREG(stat_buf.st_mode) && (stat_buf.st_mode & S_IROTH)) + { + int fd = ::open(full_path.c_str(), O_RDONLY | O_NOCTTY); + + if(fd >= 0) + return fd; + } + } + + return -1; + } + +} + +size_t ProcWalking_EntropySource::poll(RandomNumberGenerator& rng) + { + const size_t MAX_FILES_READ_PER_POLL = 2048; + + lock_guard_type<mutex_type> lock(m_mutex); + + if(!m_dir) + m_dir.reset(new Directory_Walker(m_path)); + + m_buf.resize(4096); + + size_t bits = 0; + + for(size_t i = 0; i != MAX_FILES_READ_PER_POLL; ++i) + { + int fd = m_dir->next_fd(); + + // If we've exhaused this walk of the directory, halt the poll + if(fd == -1) + { + m_dir.reset(); + break; + } + + ssize_t got = ::read(fd, m_buf.data(), m_buf.size()); + ::close(fd); + + if(got > 0) + { + rng.add_entropy(m_buf.data(), static_cast<size_t>(got)); + + // Conservative estimate of 4 bits per file + bits += 4; + } + + if(bits > 128) + break; + } + + return bits; + } + +} |