令人作呕的OpenSSL

{
    if ()
       return ret;
     else if ()
       return ret2;
}

for (...) {
    if () {
        flag = 1;
    }
   ...
    if (flag2 == 2) {
       flag = 2;
    }
    ...
}
if (flag == 3 || flag2 == 1) {
...
}

some_function(...)
{
...
        return(n);
        }


    /* If we get here, then type != rr->type; if we have a handshake
     * message, then it was unexpected (Hello Request or Client Hello). */

    /* In case of record types for which we have 'fragment' storage,
     * fill that so that we can process the data at a fixed place.
     */
        {
        unsigned int dest_maxlen = 0;
        unsigned char *dest = NULL;
        unsigned int *dest_len = NULL;

        if (rr->type == SSL3_RT_HANDSHAKE)
            {
            dest_maxlen = sizeof s->s3->handshake_fragment;
            dest = s->s3->handshake_fragment;
            dest_len = &s->s3->handshake_fragment_len;
            }
...
}

#define ARGV Argv

int
main(int Argc, char *ARGV[])

#if 0 /* worked only because C operator preferences are not as expected (and
       * because this is not really needed for clients except for detecting
       * protocol violations): */
            s->state=SSL_ST_BEFORE|(s->server)
                ?SSL_ST_ACCEPT
                :SSL_ST_CONNECT;
#else
            s->state = s->server ? SSL_ST_ACCEPT : SSL_ST_CONNECT;
#endif

int func()
    {
    ...
    a=b;
    c = d;
}

some_function(...)
{
    ...
    if (s->session->sess_cert != NULL)
        {
#ifndef OPENSSL_NO_RSA
        if (s->session->sess_cert->peer_rsa_tmp != NULL)
            {
            ...
            }
#endif
        ...
        }
    else
        {
        ...;
        }
    ...
#ifndef OPENSSL_NO_RSA
    if (alg & SSL_kRSA)
        {
        ...
        }
#else /* OPENSSL_NO_RSA */
    if (0)
        ;
#endif
#ifndef OPENSSL_NO_DH
    else if (alg & SSL_kEDH)
        {
        ...
#ifndef OPENSSL_NO_RSA
        if (alg & SSL_aRSA)
            ...
#else
        if (0)
            ;
#endif
#ifndef OPENSSL_NO_DSA
        else if (alg & SSL_aDSS)
            ...;
#endif
        /* else anonymous DH, so no certificate or pkey. */
        ...
        }
    else if ((alg & SSL_kDHr) || (alg & SSL_kDHd))
        {
        ...
        goto f_err;
        }
#endif /* !OPENSSL_NO_DH */

#ifndef OPENSSL_NO_ECDH
    else if (alg & SSL_kECDHE)
        {
        ...
        if (0) ;
#ifndef OPENSSL_NO_RSA
        else if (alg & SSL_aRSA)
            ...;
#endif
#ifndef OPENSSL_NO_ECDSA
        else if (alg & SSL_aECDSA)
            ...;
#endif
        /* else anonymous ECDH, so no certificate or pkey. */
        ...
        }
    else if (alg & SSL_kECDH)
        {
        ...
        goto f_err;
        }
#endif /* !OPENSSL_NO_ECDH */
    if (alg & SSL_aFZA)
        {
        ...
        goto f_err;
        }


    /* p points to the next byte, there are 'n' bytes left */

    /* if it was signed, check the signature */
    if (pkey != NULL)
        {
        ...
        if ((i != n) || (n > j) || (n <= 0))
            {
            /* wrong packet length */
            ...
            goto f_err;
            }

#ifndef OPENSSL_NO_RSA
        if (pkey->type == EVP_PKEY_RSA)
            {
            ...
            for (num=2; num > 0; num--)
                {
                ...
                }
            ...
            if (i < 0)
                {
                ...
                goto f_err;
                }
            if (i == 0)
                {
                /* bad signature */
                ...
                goto f_err;
                }
            }
        else
#endif
#ifndef OPENSSL_NO_DSA
            if (pkey->type == EVP_PKEY_DSA)
            {
            /* lets do DSS */
            ...
            if (EVP_VerifyFinal(&md_ctx,p,(int)n,pkey) <= 0)
                {
                /* bad signature */
                ...
                goto f_err;
                }
            }
        else
#endif
#ifndef OPENSSL_NO_ECDSA
            if (pkey->type == EVP_PKEY_EC)
            {
            /* let's do ECDSA */
            ...
            if (EVP_VerifyFinal(&md_ctx,p,(int)n,pkey) <= 0)
                {
                /* bad signature */
                ...
                goto f_err;
                }
            }
        else
#endif
            {
            ...
            goto err;
            }
        }
    else
        {
        /* still data left over */
        if (!(alg & SSL_aNULL))
            {
            ...
            goto err;
            }
        if (n != 0)
            {
            ...
            goto f_err;
            }
        }
    ...
    return(1);
f_err:
    ...;
err:
    ...;
#ifndef OPENSSL_NO_RSA
    if (rsa != NULL)
        RSA_free(rsa);
#endif
#ifndef OPENSSL_NO_DH
    if (dh != NULL)
        DH_free(dh);
#endif
#ifndef OPENSSL_NO_ECDH
    ...;
    if (ecdh != NULL)
        EC_KEY_free(ecdh);
#endif
    ...;
    return(-1);
}

        if(!ok) goto end;
        if (0)
                {
end:
                X509_get_pubkey_parameters(NULL,ctx->chain);
                }

do {
...
if (...)
    break;
...
}while(0);

int ssl3_write_bytes(SSL *s, int type, const void *buf_, int len)
    {
    ...

    n=(len-tot);
    for (;;)
        {
        if (n > SSL3_RT_MAX_PLAIN_LENGTH)
            nw=SSL3_RT_MAX_PLAIN_LENGTH;
        else
            nw=n;
       // 我觉得这是个核心函数
        i=do_ssl3_write(s, type, &(buf[tot]), nw, 0);
        if (i <= 0)
            {
            s->s3->wnum=tot;
            return i;
            }

        if ((i == (int)n) ||
            (type == SSL3_RT_APPLICATION_DATA &&
             (s->mode & SSL_MODE_ENABLE_PARTIAL_WRITE)))
            {
            /* next chunk of data should get another prepended empty fragment
             * in ciphersuites with known-IV weakness: */
            s->s3->empty_fragment_done = 0;
           
            return tot+i;
            }

        n-=i;
        tot+=i;
        }
    }

static int do_ssl3_write(SSL *s, int type, const unsigned char *buf,
             unsigned int len, int create_empty_fragment)
    {
    unsigned char *p,*plen;
    int i,mac_size,clear=0;
    int prefix_len = 0;
    SSL3_RECORD *wr;
    SSL3_BUFFER *wb;
    SSL_SESSION *sess;

    /* first check if there is a SSL3_BUFFER still being written
     * out.  This will happen with non blocking IO */
    if (s->s3->wbuf.left != 0)  // 在一开始的位置，处理逻辑就被劫持了，因此我就必须注意left在什么情况下不为0
       // 这个执行流跳转得很诡异！太诡异！
        return(ssl3_write_pending(s,type,buf,len));

    /* If we have an alert to send, lets send it */
    if (s->s3->alert_dispatch)
        {
        i=s->method->ssl_dispatch_alert(s);
        if (i <= 0)
            return(i);
        /* if it went, fall through and send more stuff */
        }
   // create_empty_fragment？难道还有不这样做的？Fxxxing，在上层调用的时候，这个参数为0，这就意味着
   // 肯定有什么地方以1为参数调用了本函数。这个empty fragment我后面会解释。
    if (len == 0 && !create_empty_fragment)
        return 0;

    wr= &(s->s3->wrec);
    wb= &(s->s3->wbuf);
    sess=s->session;
   ...
    if (clear)
        mac_size=0;
    else
        mac_size=EVP_MD_size(s->write_hash);

    /* 'create_empty_fragment' is true only when this function calls itself */
    if (!clear && !create_empty_fragment && !s->s3->empty_fragment_done)
        {
        /* countermeasure against known-IV weakness in CBC ciphersuites
         * (see http://www.openssl.org/~bodo/tls-cbc.txt) */

        if (s->s3->need_empty_fragments && type == SSL3_RT_APPLICATION_DATA)
            {
            /* recursive function call with 'create_empty_fragment' set;
             * this prepares and buffers the data for an empty fragment
             * (these 'prefix_len' bytes are sent out later
             * together with the actual payload) */
            // 递归调用？我kao，这个函数竟然有两段逻辑：
            // 1.默默创建一个新的record；
            // 2.创建封装buf的record并和递归调用中默默创建的那个record一起发送
            prefix_len = do_ssl3_write(s, type, buf, 0, 1);
            if (prefix_len <= 0)
                goto err;

            if (s->s3->wbuf.len < (size_t)prefix_len + SSL3_RT_MAX_PACKET_SIZE)
                {
                /* insufficient space */
                SSLerr(SSL_F_DO_SSL3_WRITE, ERR_R_INTERNAL_ERROR);
                goto err;
                }
            }
       
        s->s3->empty_fragment_done = 1;
        }
   // wb->buf是和SSL绑定的一个发送buf，事先已经malloc好了内存，真TM慷慨！
   // 一个prefix_len表示在真正的record发送前紧接着的那个默默创建的record，调用者并不知道
   // 会创建并发送这样一个record
    p = wb->buf + prefix_len;

    /* write the header */
    // 这段代码还算清晰
    // 但是，记住，在需要empty fragment的情况下会跑到这里两次
    *(p++)=type&0xff;
    wr->type=type;
    *(p++)=(s->version>>8);
    *(p++)=s->version&0xff;

    /* field where we are to write out packet length */
    plen=p;
    p+=2;

    /* lets setup the record stuff. */
    wr->data=p;
    wr->length=(int)len;
    wr->input=(unsigned char *)buf;

    /* we now 'read' from wr->input, wr->length bytes into
     * wr->data */

    /* first we compress */
    if (s->compress != NULL)
        {
        if (!ssl3_do_compress(s))
            {
            SSLerr(SSL_F_DO_SSL3_WRITE,SSL_R_COMPRESSION_FAILURE);
            goto err;
            }
        }
    else
        {
        memcpy(wr->data,wr->input,wr->length);
        wr->input=wr->data;
        }

    /* we should still have the output to wr->data and the input
     * from wr->input.  Length should be wr->length.
     * wr->data still points in the wb->buf */

    if (mac_size != 0)
        {
        s->method->ssl3_enc->mac(s,&(p[wr->length]),1);
        wr->length+=mac_size;
        wr->input=p;
        wr->data=p;
        }

    /* ssl3_enc can only have an error on read */
    s->method->ssl3_enc->enc(s,1);

    /* record length after mac and block padding */
    s2n(wr->length,plen);

    /* we should now have
     * wr->data pointing to the encrypted data, which is
     * wr->length long */
    wr->type=type; /* not needed but helps for debugging */
    wr->length+=SSL3_RT_HEADER_LENGTH;
 
    if (create_empty_fragment)
        {
        /* we are in a recursive call;
         * just return the length, don't write out anything here
         */
       // 如果是默默创建的那个record，则并不直接发送，目的是想将真实的record在内存上
       // 紧随这个默默构造好的record作为一个buffer直接发送给下层BIO。为何不分别发送两个
       // record呢？我想是为了紧凑使用SSL的s3->wbuf缓冲区吧，该缓冲区事先建立，而且还
       // 真不小：16K+！唉，真不觉得实现者想不出更好的办法了啊
        return wr->length;
        }

    /* now let's set up wb */
    wb->left = prefix_len + wr->length;
    wb->offset = 0;

    /* memorize arguments so that ssl3_write_pending can detect bad write retries later */
    s->s3->wpend_tot=len;
    s->s3->wpend_buf=buf;
    s->s3->wpend_type=type;
    s->s3->wpend_ret=len;

    /* we now just need to write the buffer */
    return ssl3_write_pending(s,type,buf,len);
err:
    return -1;
    }

build_record {
    操作SSL的s3->wbuf。我觉得好，就继续用
}
write_raw {
    往下层BIO写入SSL的s3->wbuf.buf的某一段
}
do_ssl3_build {
    if (need_empty) {
        build_record;
    }
build_record;
...
}

ssl3_write_bytes
{
    if (left) {
        write_pending
    }
    do_ssl3_build
    for (;;) {
        write_raw;
    }
}

ssl_write()
{
    if( ssl->state != SSL_HANDSHAKE_OVER ) {
        handshack;
    }
    if (left) {
        flush_pending and return <=0
    }
    build and write record, return num
}

static int write_ssl_data( ssl_context *ssl, unsigned char *buf, size_t len )
{
    int ret;
    printf("\n%s", buf);
    while( len && ( ret = ssl_write( ssl, buf, len ) ) <= 0 )
    {
        if( ret != POLARSSL_ERR_NET_WANT_READ && ret != POLARSSL_ERR_NET_WANT_WRITE )
        {
            printf( " failed\n  ! ssl_write returned %d\n\n", ret );
            return -1;
        }
    }
    return( 0 );
}