有关smtp/esmtp协议(用sniffer捕获了263的esmtp服务器的返回应答,已搞定)中的base64编码规则。

那天我用自己的sniffer捕获了一个发往263的一份邮件，内容是：

======================================================
Source: 202.96.44.20  --->  Dest: 192.168.0.9
Protocal type: TCP
Length: 24
Context:
220 smtp.263.net ESMTP

======================================================

======================================================
Source: 192.168.0.9  --->  Dest: 202.96.44.20
Protocal type: TCP
Length: 9
Context:
HELO vc

======================================================

======================================================
Source: 202.96.44.20  --->  Dest: 192.168.0.9
Protocal type: TCP
Length: 18
Context:
250 smtp.263.net

======================================================

======================================================
Source: 192.168.0.9  --->  Dest: 202.96.44.20
Protocal type: TCP
Length: 32
Context:
VRFY "zc1949" <zc1949@263.net>

======================================================

======================================================
Source: 202.96.44.20  --->  Dest: 192.168.0.9
Protocal type: TCP
Length: 27
Context:
252 Send mail to find out

======================================================

======================================================
Source: 192.168.0.9  --->  Dest: 202.96.44.20
Protocal type: TCP
Length: 12
Context:
auth LOGIN

======================================================

======================================================
Source: 202.96.44.20  --->  Dest: 192.168.0.9
Protocal type: TCP
Length: 18
Context:
334 VXNlcm5hbWU6

======================================================

======================================================
Source: 192.168.0.9  --->  Dest: 202.96.44.20
Protocal type: TCP
Length: 10
Context:
aDdAaOTQ5

======================================================

======================================================
Source: 202.96.44.20  --->  Dest: 192.168.0.9
Protocal type: TCP
Length: 18
Context:
334 UGFav34acmQ6

======================================================

======================================================
Source: 192.168.0.9  --->  Dest: 202.96.44.20
Protocal type: TCP
Length: 14
Context:
yMadfaNveQ==

======================================================

======================================================
Source: 202.96.44.20  --->  Dest: 192.168.0.9
Protocal type: TCP
Length: 31
Context:
235 Authentication successful

======================================================

======================================================
Source: 192.168.0.9  --->  Dest: 202.96.44.20
Protocal type: TCP
Length: 28
Context:
MAIL FROM:<zc1949@263.net>

======================================================

======================================================
Source: 202.96.44.20  --->  Dest: 192.168.0.9
Protocal type: TCP
Length: 8
Context:
250 Ok

======================================================

======================================================
Source: 192.168.0.9  --->  Dest: 202.96.44.20
Protocal type: TCP
Length: 27
Context:
RCPT TO:<iamhxh@sina.com>

======================================================

======================================================
Source: 202.96.44.20  --->  Dest: 192.168.0.9
Protocal type: TCP
Length: 8
Context:
250 Ok

======================================================

======================================================
Source: 192.168.0.9  --->  Dest: 202.96.44.20
Protocal type: TCP
Length: 6
Context:
DATA

======================================================

======================================================
Source: 202.96.44.20  --->  Dest: 192.168.0.9
Protocal type: TCP
Length: 37
Context:
354 End data with <CR><LF>.<CR><LF>

======================================================

======================================================
Source: 192.168.0.9  --->  Dest: 202.96.44.20
Protocal type: TCP
Length: 60
Context:
Message-Id: <263WingBox.2001.10.30.blsjttafhspkcren@a.b.c>

======================================================

======================================================
Source: 192.168.0.9  --->  Dest: 202.96.44.20
Protocal type: TCP
Length: 442
Context:
Date: Tue, 30 Oct 2001 10:47:52 +0800
X-Priority: 3
From: "zc1949" <zc1949@263.net>
X-Mailer: 263WingBoxBeta2
To: iamhxh@sina.com
MIME-Version: 1.0
Subject: =?gb2312?B?xOO/tLW9ztK4+MTjtcRFX21haWzBy8Lwo78=?=
Content-Type: text/plain; charset=gb2312
Content-Transfer-Encoding: base64

aHhoOg0KICAgICAgICAgv7S1vcHLwvCjv7K70qrTw3dwc6Os08N3b3Jkv8nS1MLwo78NCiAgICAg
ICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgICAgIGxlbW9uDQo=

.

======================================================

======================================================
Source: 202.96.44.20  --->  Dest: 192.168.0.9
Protocal type: TCP
Length: 33
Context:
250 Ok: queued as 747341CCCFE63

======================================================

======================================================
Source: 192.168.0.9  --->  Dest: 202.96.44.20
Protocal type: TCP
Length: 6
Context:
RSET

======================================================

======================================================
Source: 202.96.44.20  --->  Dest: 192.168.0.9
Protocal type: TCP
Length: 8
Context:
250 Ok

======================================================

但在邮件头出现了：
Subject: =?gb2312?B?xOO/tLW9ztK4+MTjtcRFX21haWzBy8Lwo78=?=
Content-Type: text/plain; charset=gb2312
Content-Transfer-Encoding: base64

题目是中文的，但编了码过后就成了别的了，它的编码规则是base64。我想问以下哪位同事知道。向大家透露一个事：263的smtp要先经过授权后你才可以发送邮件，这一点我也搞不清楚，害的我看了好久的rfc821，结果后来才晓得它用的是esmtp，然后自己又修改了sendmail源程序，提供了auth LOGIN命令（授权）,而且取消了一些久的命令，HELP命令就是被delete了。

6 个解决方案

#1

CString CBase64::m_sBase64Alphabet =
_T( "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/" );

int CBase64::m_nMask[] = { 0, 1, 3, 7, 15, 31, 63, 127, 255 };
int CBase64::Decode(LPTSTR szDecoding, LPTSTR szOutput)
{
    int c, lp =0;
int nDigit;
    int nDecode[ 256 ];
int nLen = strlen(szDecoding);

ASSERT( szDecoding != NULL );
ASSERT( szOutput != NULL );
if( szOutput == NULL )
return 0;
if( szDecoding == NULL )
return 0;
if(  nLen == 0 )
return 0;

m_nBitsRemaining = 0;
//
//建立解码表
for( int i = 0; i < 256; i++ )
nDecode[i] = -2; // 无效数字
for( i=0; i < 64; i++ )
{
nDecode[ m_sBase64Alphabet[ i ] ] = i;
nDecode[ m_sBase64Alphabet[ i ] | 0x80 ] = i; // 忽略每八个字节
nDecode[ '=' ] = -1;
nDecode[ '=' | 0x80 ] = -1; // 忽略MIME填充字符
    }

// 清除输出缓存
memset( szOutput, 0, nLen + 1 );

// 对输入缓存解码
//
for( lp = 0, i = 0; lp < nLen; lp++ )
{
c = szDecoding[ lp ];
nDigit = nDecode[ c & 0x7F ];
if( nDigit < -1 )
{
return 0;
}
else if( nDigit >= 0 )
// i (输出索引) 由write_bits()添加
write_bits( nDigit & 0x3F, 6, szOutput, i );
    }
return i;
}

UINT CBase64::read_bits(int nNumBits, int * pBitsRead, int& lp)
{
    ULONG lScratch;
    while( ( m_nBitsRemaining < nNumBits ) &&
   ( lp < m_nInputSize ) )
{
int c = m_szInput[ lp++ ];
        m_lBitStorage <<= 8;
        m_lBitStorage |= (c & 0xff);
m_nBitsRemaining += 8;
    }
    if( m_nBitsRemaining < nNumBits )
{
lScratch = m_lBitStorage << ( nNumBits - m_nBitsRemaining );
*pBitsRead = m_nBitsRemaining;
m_nBitsRemaining = 0;
    }
else
{
lScratch = m_lBitStorage >> ( m_nBitsRemaining - nNumBits );
*pBitsRead = nNumBits;
m_nBitsRemaining -= nNumBits;
    }
    return (UINT)lScratch & m_nMask[nNumBits];
}

void CBase64::write_bits(UINT nBits,
int nNumBits,
LPTSTR szOutput,
int& i)
{
UINT nScratch;

m_lBitStorage = (m_lBitStorage << nNumBits) | nBits;
m_nBitsRemaining += nNumBits;

while( m_nBitsRemaining > 7 )
{
nScratch = m_lBitStorage >> (m_nBitsRemaining - 8);
szOutput[ i++ ] = nScratch & 0xFF;
m_nBitsRemaining -= 8;
}
}

#2

to sunhang(悟空):
你是在什么地方看见的相关资料？

#3

曾经编写一个支持POP3下载并解析邮件的COM组件，其中一小段代码是从CodeGuru弄来的，正是你所问的BASE64编码这一段。

#4

我已经搞出来了，谢谢。
BOOL CEDCoder::EncodeBase64(const char *pszIn, int nInLen, char *pszOut, int nOutSize, int *nOutLen)
{
    ASSERT(pszIn);
    ASSERT(pszOut);
    ASSERT(nOutSize);
    ASSERT(nOutSize >= Base64BufferSize(nInLen));

    #ifndef _DEBUG
        nOutSize;
    #endif

    //初始化编码过程中的循环变量
        int nInPos = 0;
        int nOutPos = 0;
        int nLineLen = 0;
    //一次从源串中取得三个字符并编码
        for( int i=0 ; i<nInLen/3 ; i++)
        {
            //取得三个字符
            int c1 = pszIn[nInPos++]&0xFF;
            int c2 = pszIn[nInPos++]&0xFF;
            int c3 = pszIn[nInPos++]&0xFF;
            //将三个字符进行Base64编码
            pszOut[nOutPos++] = m_base64tab[(c1&0xFC)>>2];
            pszOut[nOutPos++] = m_base64tab[((c1&0x03)<<4)|((c2&0xF0)>>4)];
            pszOut[nOutPos++] = m_base64tab[((c2&0x0F)<<2)|((c3&0xC0)>>6)];
            pszOut[nOutPos++] = m_base64tab[c3&0x3F];
            nLineLen += 4;
            //处理行数越界的情况
            if(nLineLen >= BASE64_MAXLINE-3)
            {
                char* cp = EOL;
                pszOut[nOutPos++] = *cp++;
                if(*cp)
                    pszOut[nOutPos++] = *cp;
                nLineLen = 0;
            }
        }
        //处理剩余的1或2个字符
        char* cp;
        switch(nInLen%3)
        {
        case 0:
            {
                cp = EOL;
                pszOut[nOutPos++] = *cp++;
                if(*cp)
                    pszOut[nOutPos] = *cp;
                break;
            }
        case 1:
            {
                int c1 = pszIn[nInPos]&0xFF;
                pszOut[nOutPos++] = m_base64tab[(c1&0xFC)>>2];
                pszOut[nOutPos++] = m_base64tab[(c1&0x03)<<4];
                pszOut[nOutPos++] = '=';
                pszOut[nOutPos++] = '=';
                cp = EOL;
                pszOut[nOutPos++] = *cp++;
                if(*cp)
                    pszOut[nOutPos++] = *cp;
                break;
            }
        case 2:
            {
                int c1 = pszIn[nInPos++]&0xFF;
                int c2 = pszIn[nInPos]&0xFF;
                pszOut[nOutPos++] = m_base64tab[(c1&0xFC)>>2];
                pszOut[nOutPos++] = m_base64tab[((c1&0x03)<<4)|((c2&0xF0)>>4)];
                pszOut[nOutPos++] = m_base64tab[(c2&0x0F)<<2];
                pszOut[nOutPos++] = '=';
                cp = EOL;
                pszOut[nOutPos++] = *cp++;
                if(*cp)
                    pszOut[nOutPos++] = *cp;
                break;
            }
        default:
            {
                //出错了！！
                ASSERT(FALSE);
                break;
            }
        }

        pszOut[nOutPos] = 0;
        *nOutLen = nOutPos;

    return TRUE;
}

#5

你的编码风格不错

#6

呵呵，常来看看啊！

#1

#2

to sunhang(悟空):
你是在什么地方看见的相关资料？

#3

曾经编写一个支持POP3下载并解析邮件的COM组件，其中一小段代码是从CodeGuru弄来的，正是你所问的BASE64编码这一段。

秒客网

有关smtp/esmtp协议(用sniffer捕获了263的esmtp服务器的返回应答,已搞定)中的base64编码规则。

6 个解决方案

#1

#2

#3

#4

#5

#6

#1

#2

#3

#4

#5

#6

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