user.cpp - openbmc/phosphor-user-manager - Gitiles

 /**
  * Copyright © 2017 IBM Corporation
  *
  * 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 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.
  */
 #include <cstring>
 #include <unistd.h>
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <shadow.h>
 #include <array>
 #include <random>
 #include <errno.h>
 #include <xyz/openbmc_project/Common/error.hpp>
 #include <phosphor-logging/log.hpp>
 #include <phosphor-logging/elog.hpp>
 #include <phosphor-logging/elog-errors.hpp>
 #include "user.hpp"
 #include "file.hpp"
 #include "shadowlock.hpp"
 #include "config.h"
 namespace phosphor
 {
 namespace user
 {

 constexpr auto SHADOW_FILE = "/etc/shadow";

 // See crypt(3)
 constexpr int SALT_LENGTH = 16;

 using namespace phosphor::logging;
 using InsufficientPermission = sdbusplus::xyz::openbmc_project::Common::
                                     Error::InsufficientPermission;
 using InternalFailure = sdbusplus::xyz::openbmc_project::Common::
                                     Error::InternalFailure;
 // Sets or updates the password
 void User::setPassword(std::string newPassword)
 {
     // Gate any access to /etc/shadow
     phosphor::user::shadow::Lock lock();

     // rewind to the start of shadow entry
     setspent();

     // Generate a random string from set [A-Za-z0-9./]
     std::string salt{};
     salt.resize(SALT_LENGTH);
     salt = randomString(SALT_LENGTH);

     // Apply the change. Updates could be directly made to shadow
     // but then any update must be contained within the boundary
     // of that user, else it would run into next entry and thus
     // corrupting it. Classic example is when a password is set on
     // a user ID that does not have a prior password
     applyPassword(SHADOW_FILE, newPassword, salt);
     return;
 }

 void User::applyPassword(const std::string& shadowFile,
                          const std::string& password,
                          const std::string& salt)
 {
     // Needed by getspnam_r
     struct spwd shdp;
     struct spwd* pshdp;

     // This should be fine even if SHA512 is used.
     std::array<char,1024> buffer{};

     // Open the shadow file for reading
     phosphor::user::File shadow(shadowFile, "r");
     if ((shadow)() == NULL)
     {
         return raiseException(errno, "Error opening shadow file");
     }

     // open temp shadow file, by suffixing random name in shadow file name.
     std::vector<char> tempFileName(shadowFile.begin(), shadowFile.end());
     std::vector<char> fileTemplate = {
                              '_', '_', 'X', 'X', 'X', 'X', 'X', 'X', '\0' };
     tempFileName.insert(
               tempFileName.end(), fileTemplate.begin(), fileTemplate.end());

     int fd = mkstemp(tempFileName.data());
     if (fd == -1)
     {
         return raiseException(errno, "Error creating temp shadow file");
     }

     std::string strTempFileName(tempFileName.data());
     // Open the temp shadow file for writing from provided fd
     // By "true", remove it at exit if still there.
     // This is needed to cleanup the temp file at exception
     phosphor::user::File temp(fd, strTempFileName, "w", true);
     if ((temp)() == NULL)
     {
         close(fd);
         return raiseException(errno, "Error opening temp shadow file");
     }
     fd = -1; // don't use fd anymore, as the File object owns it

     // Change the permission of this new temp file
     // to be same as shadow so that it's secure
     struct stat st{};
     auto r = fstat(fileno((shadow)()), &st);
     if (r < 0)
     {
         return raiseException(errno, "Error reading shadow file mode");
     }

     r = fchmod(fileno((temp)()), st.st_mode);
     if (r < 0)
     {
         return raiseException(errno, "Error setting temp file mode");
     }

     // Read shadow file and process
     while (true)
     {
         auto r = fgetspent_r((shadow)(), &shdp, buffer.data(),
                              buffer.max_size(), &pshdp);
         if (r)
         {
             if (errno == EACCES || errno == ERANGE)
             {
                 return raiseException(errno, "Error reading shadow file");
             }
             else
             {
                 // Seem to have run over all
                 break;
             }
         }

         // Hash of password if the user matches
         std::string hash{};

         // Matched user
         if (user == shdp.sp_namp)
         {
             // Update with new hashed password
             hash = hashPassword(shdp.sp_pwdp, password, salt);
             shdp.sp_pwdp = const_cast<char*>(hash.c_str());
         }

         // Apply
         r = putspent(&shdp, (temp)());
         if (r < 0)
         {
             return raiseException(errno, "Error updating temp shadow file");
         }
     } // All entries

     // Done
     endspent();
     // flush contents to file first, before renaming to avoid
     // corruption during power failure
     fflush((temp)());

     // Everything must be fine at this point
     fs::rename(strTempFileName, shadowFile);
     return;
 }

 void User::raiseException(int errNo, const std::string& errMsg)
 {
     using namespace std::string_literals;
     if (errNo == EACCES)
     {
         auto message = "Access denied "s + errMsg;
         log<level::ERR>(message.c_str());
         elog<InsufficientPermission>();
     }
     else
     {
         log<level::ERR>(errMsg.c_str(),
                 entry("USER=%s",user.c_str()),
                     entry("ERRNO=%d", errNo));
         elog<InternalFailure>();
     }
 }

 std::string User::hashPassword(char* spPwdp,
                                const std::string& password,
                                const std::string& salt)
 {
     // Parse and get crypt algo
     auto cryptAlgo = getCryptField(spPwdp);
     if (cryptAlgo.empty())
     {
         log<level::ERR>("Error finding crypt algo",
                 entry("USER=%s",user.c_str()));
         elog<InternalFailure>();
     }

     // Update shadow password pointer with hash
     auto saltString = getSaltString(cryptAlgo, salt);
     return generateHash(password, saltString);
 }

 // Returns a random string in set [A-Za-z0-9./]
 // of size numChars
 const std::string User::randomString(int length)
 {
     // Populated random string
     std::string random{};

     // Needed per crypt(3)
     std::string set = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijk"
                       "lmnopqrstuvwxyz0123456789./";

     // Will be used to obtain a seed for the random number engine
     std::random_device rd;

     // Standard mersenne_twister_engine seeded with rd()
     std::mt19937 gen(rd());

     std::uniform_int_distribution<> dis(0, set.size()-1);
     for (int count = 0; count < length; count++)
     {
         // Use dis to transform the random unsigned int generated by
         // gen into a int in [1, SALT_LENGTH]
         random.push_back(set.at(dis(gen)));
     }
     return random;
 }

 // Extract crypto algorithm field
 CryptAlgo User::getCryptField(char* spPwdp)
 {
     char* savePtr{};
     if (std::string{spPwdp}.front() != '$')
     {
         return DEFAULT_CRYPT_ALGO;
     }
     return strtok_r(spPwdp, "$", &savePtr);
 }

 // Returns specific format of salt string
 std::string User::getSaltString(const std::string& crypt,
                                 const std::string& salt)
 {
     return '$' + crypt + '$' + salt + '$';
 }

 // Given a password and salt, generates hash
 std::string User::generateHash(const std::string& password,
                                const std::string& salt)
 {
     return crypt(password.c_str(), salt.c_str());
 }

 } // namespace user
 } // namespace phosphor
	/**
	* Copyright © 2017 IBM Corporation
	*
	* 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 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.
	*/
	#include <cstring>
	#include <unistd.h>
	#include <sys/types.h>
	#include <sys/stat.h>
	#include <shadow.h>
	#include <array>
	#include <random>
	#include <errno.h>
	#include <xyz/openbmc_project/Common/error.hpp>
	#include <phosphor-logging/log.hpp>
	#include <phosphor-logging/elog.hpp>
	#include <phosphor-logging/elog-errors.hpp>
	#include "user.hpp"
	#include "file.hpp"
	#include "shadowlock.hpp"
	#include "config.h"
	namespace phosphor
	{
	namespace user
	{

	constexpr auto SHADOW_FILE = "/etc/shadow";

	// See crypt(3)
	constexpr int SALT_LENGTH = 16;

	using namespace phosphor::logging;
	using InsufficientPermission = sdbusplus::xyz::openbmc_project::Common::
	Error::InsufficientPermission;
	using InternalFailure = sdbusplus::xyz::openbmc_project::Common::
	Error::InternalFailure;
	// Sets or updates the password
	void User::setPassword(std::string newPassword)
	{
	// Gate any access to /etc/shadow
	phosphor::user::shadow::Lock lock();

	// rewind to the start of shadow entry
	setspent();

	// Generate a random string from set [A-Za-z0-9./]
	std::string salt{};
	salt.resize(SALT_LENGTH);
	salt = randomString(SALT_LENGTH);

	// Apply the change. Updates could be directly made to shadow
	// but then any update must be contained within the boundary
	// of that user, else it would run into next entry and thus
	// corrupting it. Classic example is when a password is set on
	// a user ID that does not have a prior password
	applyPassword(SHADOW_FILE, newPassword, salt);
	return;
	}

	void User::applyPassword(const std::string& shadowFile,
	const std::string& password,
	const std::string& salt)
	{
	// Needed by getspnam_r
	struct spwd shdp;
	struct spwd* pshdp;

	// This should be fine even if SHA512 is used.
	std::array<char,1024> buffer{};

	// Open the shadow file for reading
	phosphor::user::File shadow(shadowFile, "r");
	if ((shadow)() == NULL)
	{
	return raiseException(errno, "Error opening shadow file");
	}

	// open temp shadow file, by suffixing random name in shadow file name.
	std::vector<char> tempFileName(shadowFile.begin(), shadowFile.end());
	std::vector<char> fileTemplate = {
	'_', '_', 'X', 'X', 'X', 'X', 'X', 'X', '\0' };
	tempFileName.insert(
	tempFileName.end(), fileTemplate.begin(), fileTemplate.end());

	int fd = mkstemp(tempFileName.data());
	if (fd == -1)
	{
	return raiseException(errno, "Error creating temp shadow file");
	}

	std::string strTempFileName(tempFileName.data());
	// Open the temp shadow file for writing from provided fd
	// By "true", remove it at exit if still there.
	// This is needed to cleanup the temp file at exception
	phosphor::user::File temp(fd, strTempFileName, "w", true);
	if ((temp)() == NULL)
	{
	close(fd);
	return raiseException(errno, "Error opening temp shadow file");
	}
	fd = -1; // don't use fd anymore, as the File object owns it

	// Change the permission of this new temp file
	// to be same as shadow so that it's secure
	struct stat st{};
	auto r = fstat(fileno((shadow)()), &st);
	if (r < 0)
	{
	return raiseException(errno, "Error reading shadow file mode");
	}

	r = fchmod(fileno((temp)()), st.st_mode);
	if (r < 0)
	{
	return raiseException(errno, "Error setting temp file mode");
	}

	// Read shadow file and process
	while (true)
	{
	auto r = fgetspent_r((shadow)(), &shdp, buffer.data(),
	buffer.max_size(), &pshdp);
	if (r)
	{
	if (errno == EACCES \|\| errno == ERANGE)
	{
	return raiseException(errno, "Error reading shadow file");
	}
	else
	{
	// Seem to have run over all
	break;
	}
	}

	// Hash of password if the user matches
	std::string hash{};

	// Matched user
	if (user == shdp.sp_namp)
	{
	// Update with new hashed password
	hash = hashPassword(shdp.sp_pwdp, password, salt);
	shdp.sp_pwdp = const_cast<char*>(hash.c_str());
	}

	// Apply
	r = putspent(&shdp, (temp)());
	if (r < 0)
	{
	return raiseException(errno, "Error updating temp shadow file");
	}
	} // All entries

	// Done
	endspent();
	// flush contents to file first, before renaming to avoid
	// corruption during power failure
	fflush((temp)());

	// Everything must be fine at this point
	fs::rename(strTempFileName, shadowFile);
	return;
	}

	void User::raiseException(int errNo, const std::string& errMsg)
	{
	using namespace std::string_literals;
	if (errNo == EACCES)
	{
	auto message = "Access denied "s + errMsg;
	log<level::ERR>(message.c_str());
	elog<InsufficientPermission>();
	}
	else
	{
	log<level::ERR>(errMsg.c_str(),
	entry("USER=%s",user.c_str()),
	entry("ERRNO=%d", errNo));
	elog<InternalFailure>();
	}
	}

	std::string User::hashPassword(char* spPwdp,
	const std::string& password,
	const std::string& salt)
	{
	// Parse and get crypt algo
	auto cryptAlgo = getCryptField(spPwdp);
	if (cryptAlgo.empty())
	{
	log<level::ERR>("Error finding crypt algo",
	entry("USER=%s",user.c_str()));
	elog<InternalFailure>();
	}

	// Update shadow password pointer with hash
	auto saltString = getSaltString(cryptAlgo, salt);
	return generateHash(password, saltString);
	}

	// Returns a random string in set [A-Za-z0-9./]
	// of size numChars
	const std::string User::randomString(int length)
	{
	// Populated random string
	std::string random{};

	// Needed per crypt(3)
	std::string set = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijk"
	"lmnopqrstuvwxyz0123456789./";

	// Will be used to obtain a seed for the random number engine
	std::random_device rd;

	// Standard mersenne_twister_engine seeded with rd()
	std::mt19937 gen(rd());

	std::uniform_int_distribution<> dis(0, set.size()-1);
	for (int count = 0; count < length; count++)
	{
	// Use dis to transform the random unsigned int generated by
	// gen into a int in [1, SALT_LENGTH]
	random.push_back(set.at(dis(gen)));
	}
	return random;
	}

	// Extract crypto algorithm field
	CryptAlgo User::getCryptField(char* spPwdp)
	{
	char* savePtr{};
	if (std::string{spPwdp}.front() != '$')
	{
	return DEFAULT_CRYPT_ALGO;
	}
	return strtok_r(spPwdp, "$", &savePtr);
	}

	// Returns specific format of salt string
	std::string User::getSaltString(const std::string& crypt,
	const std::string& salt)
	{
	return '$' + crypt + '$' + salt + '$';
	}

	// Given a password and salt, generates hash
	std::string User::generateHash(const std::string& password,
	const std::string& salt)
	{
	return crypt(password.c_str(), salt.c_str());
	}

	} // namespace user
	} // namespace phosphor