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Diffstat (limited to 'include/llfio/v2.0/detail/impl/posix/path_discovery.ipp')
| -rw-r--r-- | include/llfio/v2.0/detail/impl/posix/path_discovery.ipp | 145 |
1 files changed, 145 insertions, 0 deletions
diff --git a/include/llfio/v2.0/detail/impl/posix/path_discovery.ipp b/include/llfio/v2.0/detail/impl/posix/path_discovery.ipp new file mode 100644 index 00000000..0d072a29 --- /dev/null +++ b/include/llfio/v2.0/detail/impl/posix/path_discovery.ipp @@ -0,0 +1,145 @@ +/* Discovery of various useful filesystem paths +(C) 2017 Niall Douglas <http://www.nedproductions.biz/> (20 commits) +File Created: Sept 2017 + + +Licensed under the Apache License, Version 2.0 (the "License"); +you may not use this file except in compliance with the License. +You may obtain a copy of the License in the accompanying file +Licence.txt or at + + http://www.apache.org/licenses/LICENSE-2.0 + +Unless required by applicable law or agreed to in writing, software +distributed under the License is distributed on an "AS IS" BASIS, +WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +See the License for the specific language governing permissions and +limitations under the License. + + +Distributed under the Boost Software License, Version 1.0. + (See accompanying file Licence.txt or copy at + http://www.boost.org/LICENSE_1_0.txt) +*/ + +#ifndef AFIO_PATH_DISCOVERY_INCLUDING +#error Must be included by ../path_discovery.ipp only +#endif + +#include "../../../algorithm/mapped_span.hpp" + +#include <pwd.h> + +AFIO_V2_NAMESPACE_EXPORT_BEGIN + +namespace path_discovery +{ + std::vector<std::pair<discovered_path::source_type, _store::_discovered_path>> _all_temporary_directories() + { + std::vector<std::pair<discovered_path::source_type, _store::_discovered_path>> ret; + filesystem::path::string_type buffer; + buffer.resize(PATH_MAX); + // Only observe environment variables if not a SUID or SGID situation + // FIXME? Is this actually enough? What about the non-standard saved uid/gid? + // Should I be checking if my executable is SUGID and its owning user is not mine? + if(getuid() == geteuid() && getgid() == getegid()) + { + // Note that XDG_RUNTIME_DIR is the systemd runtime directory for the current user, usually mounted with tmpfs + // XDG_CACHE_HOME is the systemd cache directory for the current user, usually at $HOME/.cache + static const char *variables[] = {"TMPDIR", "TMP", "TEMP", "TEMPDIR", "XDG_RUNTIME_DIR", "XDG_CACHE_HOME"}; + for(auto &variable : variables) + { + const char *env = getenv(variable); + if(env != nullptr) + { + ret.emplace_back(discovered_path::source_type::environment, env); + } + } + // Also try $HOME/.cache + const char *env = getenv("HOME"); + if(env != nullptr) + { + buffer = env; + buffer.append("/.cache"); + ret.emplace_back(discovered_path::source_type::environment, buffer); + } + } + + // Parse /etc/passwd for the effective user's home directory + // We do it by hand seeing as, amazingly, getpwent_r() isn't actually threadsafe :( + { + auto _passwdh = mapped_file_handle::mapped_file({}, "/etc/passwd"); + if(!_passwdh) + { + std::string msg("path_discovery::all_temporary_directories() failed to open /etc/passwd due to "); + msg.append(_passwdh.error().message().c_str()); + AFIO_LOG_WARN(nullptr, msg.c_str()); + } + else + { + algorithm::mapped_span<const char> passwd(_passwdh.value()); + /* This will consist of lines of the form: + + jsmith:x:1001:1000:Joe Smith,Room 1007,(234)555-8910,(234)555-0044,email:/home/jsmith:/bin/sh + ned:x:1000:1000:"",,,:/home/ned:/bin/bash + # Comments and blank lines also possible + + */ + string_view passwdfile(passwd.data(), passwd.size()); + size_t linestart = 0; + do + { + string_view line(passwdfile.substr(linestart)); + if(auto lineend = line.find(10)) + { + line = line.substr(0, lineend); + } + linestart += line.size() + 1; + // uid is two colons in + size_t colon = line.find(':'); + if(colon != string_view::npos) + { + colon = line.find(':', colon + 1); + if(colon != string_view::npos) + { + long uid = strtol(line.data() + 1, nullptr, 10); + if(uid == geteuid()) + { + // home directory is two colons from end + size_t homeend = line.rfind(':'); + if(homeend != string_view::npos) + { + colon = line.rfind(':', homeend - 1); + if(colon != string_view::npos) + { + auto homedir = line.substr(colon + 1, homeend - colon - 1); + buffer.assign(homedir.data(), homedir.size()); + buffer.append("/.cache"); + ret.emplace_back(discovered_path::source_type::system, buffer); + if(-1 == ::access(buffer.c_str(), F_OK)) + { + ::mkdir(buffer.c_str(), 0700); // only user has access + } + break; + } + } + } + } + } + } while(linestart < passwd.size()); + } + } + + // If everything earlier failed e.g. if our environment block is zeroed, + // fall back to /tmp and then /var/tmp, the last of which should succeed even if tmpfs is not mounted + ret.emplace_back(discovered_path::source_type::hardcoded, "/tmp"); + ret.emplace_back(discovered_path::source_type::hardcoded, "/var/tmp"); + // Effective user, not real user, to not create files owned by a different user + buffer = "/run/user/" + std::to_string(geteuid()); + ret.emplace_back(discovered_path::source_type::hardcoded, buffer); + ret.emplace_back(discovered_path::source_type::hardcoded, "/run/shm"); + return ret; + } +} // namespace path_discovery + +AFIO_V2_NAMESPACE_END |