/**
 * @file llmail.cpp
 * @brief smtp helper functions.
 *
 * $LicenseInfo:firstyear=2001&license=viewerlgpl$
 * Second Life Viewer Source Code
 * Copyright (C) 2010, Linden Research, Inc.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation;
 * version 2.1 of the License only.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
 * $/LicenseInfo$
 */

#include "linden_common.h"

#include "llmail.h"

#include "llwin32headers.h"
#include <string>
#include <sstream>

#include "apr_pools.h"
#include "apr_network_io.h"

#include "llapr.h"
#include "llbase32.h"   // IM-to-email address
#include "llblowfishcipher.h"
#include "llerror.h"
#include "llhost.h"
#include "llsd.h"
#include "llstring.h"
#include "lluuid.h"
#include "net.h"

//
// constants
//
const size_t LL_MAX_KNOWN_GOOD_MAIL_SIZE = 4096;

static bool gMailEnabled = true;
static apr_pool_t* gMailPool;
static apr_sockaddr_t* gSockAddr;
static apr_socket_t* gMailSocket;

bool connect_smtp();
void disconnect_smtp();

//#if LL_WINDOWS
//SOCKADDR_IN gMailDstAddr, gMailSrcAddr, gMailLclAddr;
//#else
//struct sockaddr_in gMailDstAddr, gMailSrcAddr, gMailLclAddr;
//#endif

// Define this for a super-spammy mail mode.
//#define LL_LOG_ENTIRE_MAIL_MESSAGE_ON_SEND 1

bool connect_smtp()
{
    // Prepare an soket to talk smtp
    apr_status_t status;
    status = apr_socket_create(
        &gMailSocket,
        gSockAddr->sa.sin.sin_family,
        SOCK_STREAM,
        APR_PROTO_TCP,
        gMailPool);
    if(ll_apr_warn_status(status)) return false;
    status = apr_socket_connect(gMailSocket, gSockAddr);
    if(ll_apr_warn_status(status))
    {
        status = apr_socket_close(gMailSocket);
        ll_apr_warn_status(status);
        return false;
    }
    return true;
}

void disconnect_smtp()
{
    if(gMailSocket)
    {
        apr_status_t status = apr_socket_close(gMailSocket);
        ll_apr_warn_status(status);
        gMailSocket = NULL;
    }
}

// Returns true on success.
// message should NOT be SMTP escaped.
// static
bool LLMail::send(
    const char* from_name,
    const char* from_address,
    const char* to_name,
    const char* to_address,
    const char* subject,
    const char* message,
    const LLSD& headers)
{
    std::string header = buildSMTPTransaction(
        from_name,
        from_address,
        to_name,
        to_address,
        subject,
        headers);
    if(header.empty())
    {
        return false;
    }

    std::string message_str;
    if(message)
    {
        message_str = message;
    }
    bool rv = send(header, message_str, to_address, from_address);
    if(rv) return true;
    return false;
}

// static
void LLMail::init(const std::string& hostname, apr_pool_t* pool)
{
    gMailSocket = NULL;
    if(hostname.empty() || !pool)
    {
        gMailPool = NULL;
        gSockAddr = NULL;
    }
    else
    {
        gMailPool = pool;

        // collect all the information into a socaddr sturcture. the
        // documentation is a bit unclear, but I either have to
        // specify APR_UNSPEC or not specify any flags. I am not sure
        // which option is better.
        apr_status_t status = apr_sockaddr_info_get(
            &gSockAddr,
            hostname.c_str(),
            APR_UNSPEC,
            25,
            APR_IPV4_ADDR_OK,
            gMailPool);
        ll_apr_warn_status(status);
    }
}

// static
void LLMail::enable(bool mail_enabled)
{
    gMailEnabled = mail_enabled;
}

// Test a subject line for RFC2822 compliance.
static bool valid_subject_chars(const char *subject)
{
    for (; *subject != '\0'; subject++)
    {
        unsigned char c = *subject;

        if (c == '\xa' || c == '\xd' || c > '\x7f')
        {
            return false;
        }
    }

    return true;
}

// static
std::string LLMail::buildSMTPTransaction(
    const char* from_name,
    const char* from_address,
    const char* to_name,
    const char* to_address,
    const char* subject,
    const LLSD& headers)
{
    if(!from_address || !to_address)
    {
        LL_INFOS() << "send_mail build_smtp_transaction reject: missing to and/or"
            << " from address." << LL_ENDL;
        return std::string();
    }
    if(!valid_subject_chars(subject))
    {
        LL_INFOS() << "send_mail build_smtp_transaction reject: bad subject header: "
            << "to=<" << to_address
            << ">, from=<" << from_address << ">"
            << LL_ENDL;
        return std::string();
    }
    std::ostringstream from_fmt;
    if(from_name && from_name[0])
    {
        // "My Name" <myaddress@example.com>
        from_fmt << "\"" << from_name << "\" <" << from_address << ">";
    }
    else
    {
        // <myaddress@example.com>
        from_fmt << "<" << from_address << ">";
    }
    std::ostringstream to_fmt;
    if(to_name && to_name[0])
    {
        to_fmt << "\"" << to_name << "\" <" << to_address << ">";
    }
    else
    {
        to_fmt << "<" << to_address << ">";
    }
    std::ostringstream header;
    header
        << "HELO lindenlab.com\r\n"
        << "MAIL FROM:<" << from_address << ">\r\n"
        << "RCPT TO:<" << to_address << ">\r\n"
        << "DATA\r\n"
        << "From: " << from_fmt.str() << "\r\n"
        << "To: " << to_fmt.str() << "\r\n"
        << "Subject: " << subject << "\r\n";

    if(headers.isMap())
    {
        LLSD::map_const_iterator iter = headers.beginMap();
        LLSD::map_const_iterator end = headers.endMap();
        for(; iter != end; ++iter)
        {
            header << (*iter).first << ": " << ((*iter).second).asString()
                << "\r\n";
        }
    }

    header << "\r\n";
    return header.str();
}

// static
bool LLMail::send(
    const std::string& header,
    const std::string& raw_message,
    const char* from_address,
    const char* to_address)
{
    if(!from_address || !to_address)
    {
        LL_INFOS() << "send_mail reject: missing to and/or from address."
            << LL_ENDL;
        return false;
    }

    // remove any "." SMTP commands to prevent injection (DEV-35777)
    // we don't need to worry about "\r\n.\r\n" because of the
    // "\n" --> "\n\n" conversion going into rfc2822_msg below
    std::string message = raw_message;
    std::string bad_string = "\n.\n";
    std::string good_string = "\n..\n";
    while (1)
    {
        auto index = message.find(bad_string);
        if (index == std::string::npos) break;
        message.replace(index, bad_string.size(), good_string);
    }

    // convert all "\n" into "\r\n"
    std::ostringstream rfc2822_msg;
    for(U32 i = 0; i < message.size(); ++i)
    {
        switch(message[i])
        {
        case '\0':
            break;
        case '\n':
            // *NOTE: this is kinda busted if we're fed \r\n
            rfc2822_msg << "\r\n";
            break;
        default:
            rfc2822_msg << message[i];
            break;
        }
    }

    if(!gMailEnabled)
    {
        LL_INFOS() << "send_mail reject: mail system is disabled: to=<"
            << to_address << ">, from=<" << from_address
            << ">" << LL_ENDL;
        // Any future interface to SMTP should return this as an
        // error.  --mark
        return true;
    }
    if(!gSockAddr)
    {
        LL_WARNS() << "send_mail reject: mail system not initialized: to=<"
            << to_address << ">, from=<" << from_address
            << ">" << LL_ENDL;
        return false;
    }

    if(!connect_smtp())
    {
        LL_WARNS() << "send_mail reject: SMTP connect failure: to=<"
            << to_address << ">, from=<" << from_address
            << ">" << LL_ENDL;
        return false;
    }

    std::ostringstream smtp_fmt;
    smtp_fmt << header << rfc2822_msg.str() << "\r\n" << ".\r\n" << "QUIT\r\n";
    std::string smtp_transaction = smtp_fmt.str();
    size_t original_size = smtp_transaction.size();
    apr_size_t send_size = original_size;
    apr_status_t status = apr_socket_send(
        gMailSocket,
        smtp_transaction.c_str(),
        (apr_size_t*)&send_size);
    disconnect_smtp();
    if(ll_apr_warn_status(status))
    {
        LL_WARNS() << "send_mail socket failure: unable to write "
            << "to=<" << to_address
            << ">, from=<" << from_address << ">"
            << ", bytes=" << original_size
            << ", sent=" << send_size << LL_ENDL;
        return false;
    }
    if(send_size >= LL_MAX_KNOWN_GOOD_MAIL_SIZE)
    {
        LL_WARNS() << "send_mail message has been shown to fail in testing "
            << "when sending messages larger than " << LL_MAX_KNOWN_GOOD_MAIL_SIZE
            << " bytes. The next log about success is potentially a lie." << LL_ENDL;
    }
    LL_DEBUGS() << "send_mail success: "
        << "to=<" << to_address
        << ">, from=<" << from_address << ">"
        << ", bytes=" << original_size
        << ", sent=" << send_size << LL_ENDL;

#if LL_LOG_ENTIRE_MAIL_MESSAGE_ON_SEND
    LL_INFOS() << rfc2822_msg.str() << LL_ENDL;
#endif
    return true;
}


// static
std::string LLMail::encryptIMEmailAddress(const LLUUID& from_agent_id,
                                            const LLUUID& to_agent_id,
                                            U32 time,
                                            const U8* secret,
                                            size_t secret_size)
{
#if LL_WINDOWS
    return "blowfish-not-supported-on-windows";
#else
    size_t data_size = 4 + UUID_BYTES + UUID_BYTES;
    // Convert input data into a binary blob
    std::vector<U8> data;
    data.resize(data_size);
    // *NOTE: This may suffer from endian issues.  Could be htolememcpy.
    memcpy(&data[0], &time, 4);
    memcpy(&data[4], &from_agent_id.mData[0], UUID_BYTES);
    memcpy(&data[4 + UUID_BYTES], &to_agent_id.mData[0], UUID_BYTES);

    // Encrypt the blob
    LLBlowfishCipher cipher(secret, secret_size);
    size_t encrypted_size = cipher.requiredEncryptionSpace(data.size());
    U8* encrypted = new U8[encrypted_size];
    cipher.encrypt(&data[0], data_size, encrypted, encrypted_size);

    std::string address = LLBase32::encode(encrypted, encrypted_size);

    // Make it more pretty for humans.
    LLStringUtil::toLower(address);

    delete [] encrypted;

    return address;
#endif
}