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SSL连接建立过程分析(1) – mengfanrong

Https协议:SSL建立过程分析

web訪问的两种方式 :

http协议 ,我们普通情况下是通过它訪问web,由于它不要求太多的安全机制,使用起来也简单,非常多web网站也仅仅支持这样的方式下的訪问.

https协议 (Hypertext Transfer Protocol over Secure Socket Layer),对于安全性要求比較高的情况,能够通过它訪问web,比方工商银行 https://www.icbc.com.cn/icbc/ (当然也能够通过http协议訪问,仅仅是没那么安全了).其安全基础是SSL协议.

SSL协议 ,当前版本号为3.1(SSL3.1就是TLS1.0)。它已被广泛地用于Web浏览器与server之间的身份认证和加密传输数据.它位于TCP/IP协议与各种应用层协议之间,为数据通讯提供安全支持。SSL协议可分为两层: SSL记录协议(SSL Record Protocol):它建立在可靠的传输协议(如TCP)之上,为高层协议提供数据封装、压缩、加密等基本功能的支持。 SSL握手协议(SSL Handshake Protocol):它建立在SSL记录协议之上,用于在实际的传输数据開始前,通讯两方进行身份认证、协商加密算法、交换加密密钥等。

为了了解具体过程,能够通过网络抓包工具(Commview,Iris)分析https协议,SSL连接建立过程中,数据包交换情况.

数据包分析过程用到的几个图.

图,SSL Protocol Stack

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图.SSL Record Format

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图.SSL Record Protocol Payload

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图.Handshake Protocol Action

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它们来之. Cryptography and Network Security Principles and Practices, Fourth Edition-Chapter 17. Web Security-17.2. Secure Socket Layer and Transport Layer Security(password学与网络安全 原理与实践第四版,17章web安全,17.2节,SSL与TLS)详细细节參考本书.

以下跟踪握手过程(图 Handshake Protocol Action )中,数据包的交换.

以为https方式訪问 www.sun.com 为样例,一般大型公司,银行的web都支持https訪问,如工商银行,sun,微软,IBM.

在IE中输入:https://wwww.sun.com,由于这是https协议,所以在实际訪问web前,会建立SSL连接.

通过Commview抓包工具,过滤443port(普通情况下,HTTPS使用 port 443,HTTP使用port80)能够得到数据包.

数据包大致情况和(图 Handshake Protocol Action) 相应 .

SSL连接建立过程分析(1)

1. 应用程序接口

1.1 SSL初始化

SSL_CTX* InitSSL(int server, char *cert, char *key, char *pw)

{

SSL_CTX* ctx;

SSL_METHOD *meth;

int status;

// 算法初始化

// 载入SSL错误信息

SSL_load_error_strings();

// 加入SSL的加密/HASH算法

SSLeay_add_ssl_algorithms();

// 服务器还是客户端

If(server)

meth = SSLv23_server_method();

else

meth = SSLv23_client_method();

// 建立新的SSL上下文

ctx = SSL_CTX_new (meth);

if(!ctx) return NULL;

// 设置证书文件的口令

SSL_CTX_set_default_passwd_cb_userdata(ctx, pw);

//载入本地证书文件

status=SSL_CTX_use_certificate_file(ctx, cert, SSL_FILETYPE_ASN1);

if (status <= 0) {

frintf(stderr, “Use cert fail, status=%d/n”, status);

goto bad;

}

// 载入私钥文件

if (SSL_CTX_use_PrivateKey_file(ctx, key, SSL_FILETYPE_PEM) <= 0) {

fprintf(stderr, “Use private key fail/n”);

goto bad;

}

// 检查证书和私钥是否匹配

if (!SSL_CTX_check_private_key(ctx)) {

fprintf(“Private key does not match the certificate public key/n”);

goto bad;

}

fprintf(“Cert and key OK/n”);

return ctx;

bad:

SSL_CTX_free (ctx);

return NULL;

}

1.2 建立SSL新连接

server:

// 建立SSL

ssl = SSL_new (ctx);

// 将SSL与TCP socket连接

SSL_set_fd (ssl, sd);

//接受新SSL连接

err = SSL_accept (ssl);

client:

// 建立SSL

ssl = SSL_new (ctx);

// 将SSL与TCP socket连接

SSL_set_fd (ssl, sd);

// SSL连接

err = SSL_connect (ssl);

server的SSL_accept()和client的SSL_connect()函数共同完毕SSL的握手协商过程。

1.3 SSL通信

和普通的read()/write()调用一样,用以下的函数完毕数据的SSL发送和接收,函数输入数据是明文,SSL自己主动将数据封装进SSL中:

读/接收:SSL_read() 写/发送:SSL_write()

1.4 SSL释放

SSL释放非常easy:

SSL_free (ssl);

2. SSL实现分析

下面SSL源码取自openssl-0.9.7b。

2.1 SSL_load_error_strings

该函数载入错误字符串信息:

void SSL_load_error_strings(void)

{

#ifndef OPENSSL_NO_ERR

ERR_load_crypto_strings();

ERR_load_SSL_strings();

#endif

}

最后将会进入函数:

static void err_load_strings(int lib, ERR_STRING_DATA *str)

{

while (str->error)

{

str->error|=ERR_PACK(lib,0,0);

ERRFN(err_set_item)(str);

str++;

}

}

当中:

#define ERR_PACK(l,f,r)  (((((unsigned long)l)&0xffL)*0x1000000)| /

((((unsigned long)f)&0xfffL)*0x1000)| /

((((unsigned long)r)&0xfffL)))

#define ERRFN(a) err_fns->cb_##a

ERRFN(err_set_item)(str)的实际函数实现为:

static ERR_STRING_DATA *int_err_set_item(ERR_STRING_DATA *d)

{

ERR_STRING_DATA *p;

LHASH *hash;

err_fns_check();

hash = ERRFN(err_get)(1);

if (!hash)

return NULL;

CRYPTO_w_lock(CRYPTO_LOCK_ERR);

p = (ERR_STRING_DATA *)lh_insert(hash, d);

CRYPTO_w_unlock(CRYPTO_LOCK_ERR);

return p; }

Lh_insert()将错误信息插入到一个链表中

如关于加密算法的错误信息:

/* crypto/err/err.c */

static ERR_STRING_DATA ERR_str_functs[]=

……

static ERR_STRING_DATA ERR_str_libraries[]=

……

static ERR_STRING_DATA ERR_str_reasons[]=

……

2.2 SSLeay_add_ssl_algorithms()

这实际是个宏:

#define OpenSSL_add_ssl_algorithms()    SSL_library_init()

#define SSLeay_add_ssl_algorithms() SSL_library_init()

实际函数为SSL_library_init(),函数比較简单,就是载入各种加密和HASH算法:

/* ssl/ssl_algs.c */

int SSL_library_init(void)

{

#ifndef OPENSSL_NO_DES

EVP_add_cipher(EVP_des_cbc());

EVP_add_cipher(EVP_des_ede3_cbc());

#endif

#ifndef OPENSSL_NO_IDEA

EVP_add_cipher(EVP_idea_cbc());

#endif

#ifndef OPENSSL_NO_RC4

EVP_add_cipher(EVP_rc4());

#endif

#ifndef OPENSSL_NO_RC2

EVP_add_cipher(EVP_rc2_cbc());

#endif

#ifndef OPENSSL_NO_AES

EVP_add_cipher(EVP_aes_128_cbc());

EVP_add_cipher(EVP_aes_192_cbc());

EVP_add_cipher(EVP_aes_256_cbc());

#endif

#ifndef OPENSSL_NO_MD2

EVP_add_digest(EVP_md2());

#endif

#ifndef OPENSSL_NO_MD5

EVP_add_digest(EVP_md5());

EVP_add_digest_alias(SN_md5,”ssl2-md5″);

EVP_add_digest_alias(SN_md5,”ssl3-md5″);

#endif

#ifndef OPENSSL_NO_SHA

EVP_add_digest(EVP_sha1()); /* RSA with sha1 */

EVP_add_digest_alias(SN_sha1,”ssl3-sha1″);

EVP_add_digest_alias(SN_sha1WithRSAEncryption,SN_sha1WithRSA);

#endif

#if !defined(OPENSSL_NO_SHA) && !defined(OPENSSL_NO_DSA)

EVP_add_digest(EVP_dss1()); /* DSA with sha1 */

EVP_add_digest_alias(SN_dsaWithSHA1,SN_dsaWithSHA1_2);

EVP_add_digest_alias(SN_dsaWithSHA1,”DSS1″);

EVP_add_digest_alias(SN_dsaWithSHA1,”dss1″);

#endif

/* If you want support for phased out ciphers, add the following */

#if 0

EVP_add_digest(EVP_sha());

EVP_add_digest(EVP_dss());

#endif

return(1);

}

2.3 SSL23_server_method()

建立服务器端的方法库,这是个通用函数,可动态选择SSL协议。假设想固定协议,能够仅仅用SSLv2_server_method(), SSLv3_server_method() 等函数来初始化,该函数返回一个SSL_METHOD结构:

/* ssl/ssl.h */

/* Used to hold functions for SSLv2 or SSLv3/TLSv1 functions */

typedef struct ssl_method_st

{

int version; // 版本号号

int (*ssl_new)(SSL *s); // 建立新SSL

void (*ssl_clear)(SSL *s); // 清除SSL

void (*ssl_free)(SSL *s);  // 释放SSL

int (*ssl_accept)(SSL *s); // server接受SSL连接

int (*ssl_connect)(SSL *s); // client的SSL连接

int (*ssl_read)(SSL *s,void *buf,int len); // SSL读

int (*ssl_peek)(SSL *s,void *buf,int len); // SSL查看数据

int (*ssl_write)(SSL *s,const void *buf,int len); // SSL写

int (*ssl_shutdown)(SSL *s); // SSL半关闭

int (*ssl_renegotiate)(SSL *s); // SSL重协商

int (*ssl_renegotiate_check)(SSL *s); // SSL重协商检查

long (*ssl_ctrl)(SSL *s,int cmd,long larg,void *parg); // SSL控制

long (*ssl_ctx_ctrl)(SSL_CTX *ctx,int cmd,long larg,void *parg); //SSL上下文控制

SSL_CIPHER *(*get_cipher_by_char)(const unsigned char *ptr); // 通过名称获取SSL的算法

int (*put_cipher_by_char)(const SSL_CIPHER *cipher,unsigned char *ptr);

int (*ssl_pending)(SSL *s);

int (*num_ciphers)(void); // 算法数

SSL_CIPHER *(*get_cipher)(unsigned ncipher); // 获取算法

struct ssl_method_st *(*get_ssl_method)(int version);

long (*get_timeout)(void); // 超时

struct ssl3_enc_method *ssl3_enc; /* Extra SSLv3/TLS stuff */ // SSL3加密

int (*ssl_version)(); // SSL版本号

long (*ssl_callback_ctrl)(SSL *s, int cb_id, void (*fp)()); // SSL控制回调函数

long (*ssl_ctx_callback_ctrl)(SSL_CTX *s, int cb_id, void (*fp)()); //SSL上下文控制回调函数

} SSL_METHOD;

/* ssl/s23_srvr.c */

SSL_METHOD *SSLv23_server_method(void)

{

static int init=1;

// 静态量,每一个进程仅仅初始化一次

static SSL_METHOD SSLv23_server_data;

if (init)

{

CRYPTO_w_lock(CRYPTO_LOCK_SSL_METHOD);

if (init)

{

// ssl23的基本方法结构

memcpy((char *)&SSLv23_server_data,

(char *)sslv23_base_method(),sizeof(SSL_METHOD));

// 服务器,所以要定义accept方法

SSLv23_server_data.ssl_accept=ssl23_accept;

// 依据SSL的版本号设置SSL的详细方法函数

SSLv23_server_data.get_ssl_method=ssl23_get_server_method;

init=0;

}

CRYPTO_w_unlock(CRYPTO_LOCK_SSL_METHOD);

}

return(&SSLv23_server_data);

}

static SSL_METHOD *ssl23_get_server_method(int ver)

{

#ifndef OPENSSL_NO_SSL2

if (ver == SSL2_VERSION)

return(SSLv2_server_method());

#endif

if (ver == SSL3_VERSION)

return(SSLv3_server_method());

else if (ver == TLS1_VERSION)

return(TLSv1_server_method());

// 随着TLS1.1(RFC4346)的推出,预计不久将出现TLSv1_1_server_method()

else

return(NULL);

}

// SSL23的方法基本数据定义

/* ssl/s23_lib.c */

SSL_METHOD *sslv23_base_method(void)

{

return(&SSLv23_data);

}

static SSL_METHOD SSLv23_data= {

TLS1_VERSION,

tls1_new,

tls1_clear,

tls1_free,

ssl_undefined_function,

ssl_undefined_function,

ssl23_read,

ssl23_peek,

ssl23_write,

ssl_undefined_function,

ssl_undefined_function,

ssl_ok,

ssl3_ctrl,

ssl3_ctx_ctrl,

ssl23_get_cipher_by_char,

ssl23_put_cipher_by_char,

ssl_undefined_function,

ssl23_num_ciphers,

ssl23_get_cipher,

ssl_bad_method,

ssl23_default_timeout,

&ssl3_undef_enc_method,

ssl_undefined_function,

ssl3_callback_ctrl,

ssl3_ctx_callback_ctrl,

};

以SSL3的server方法函数为例,其它方法相似:

/* ssl/s3_srvr.c */

SSL_METHOD *SSLv3_server_method(void)

{

static int init=1;

static SSL_METHOD SSLv3_server_data;

// 仅仅初始化一次

if (init)

{

CRYPTO_w_lock(CRYPTO_LOCK_SSL_METHOD);

if (init)

{

// ssl3的基本方法结构

memcpy((char *)&SSLv3_server_data,(char *)sslv3_base_method(),

sizeof(SSL_METHOD));

// ssl3的接受方法

SSLv3_server_data.ssl_accept=ssl3_accept;

// ssl3获取服务器的方法函数

SSLv3_server_data.get_ssl_method=ssl3_get_server_method;

init=0;

}

CRYPTO_w_unlock(CRYPTO_LOCK_SSL_METHOD);

}

return(&SSLv3_server_data);

}

// SSL3的方法基本数据定义

/* ssl/s3_lib.c */

static SSL_METHOD SSLv3_data= {

SSL3_VERSION,

ssl3_new,

ssl3_clear,

ssl3_free,

ssl_undefined_function,

ssl_undefined_function,

ssl3_read,

ssl3_peek,

ssl3_write,

ssl3_shutdown,

ssl3_renegotiate,

ssl3_renegotiate_check,

ssl3_ctrl,

ssl3_ctx_ctrl,

ssl3_get_cipher_by_char,

ssl3_put_cipher_by_char,

ssl3_pending,

ssl3_num_ciphers,

ssl3_get_cipher,

ssl_bad_method,

ssl3_default_timeout,

&SSLv3_enc_data,

ssl_undefined_function,

ssl3_callback_ctrl,

ssl3_ctx_callback_ctrl,

};

2.4 SSL23_client_method()

和server端的事实上是同样的,仅仅是不定义结构中的ssl_accept而是定义ssl_connnect:

SSL_METHOD *SSLv23_client_method(void)

{

static int init=1;

static SSL_METHOD SSLv23_client_data;

if (init)

{

CRYPTO_w_lock(CRYPTO_LOCK_SSL_METHOD);

if (init)

{

memcpy((char *)&SSLv23_client_data,

(char *)sslv23_base_method(),sizeof(SSL_METHOD));

SSLv23_client_data.ssl_connect=ssl23_connect;

SSLv23_client_data.get_ssl_method=ssl23_get_client_method;

init=0;

}

CRYPTO_w_unlock(CRYPTO_LOCK_SSL_METHOD);

}

return(&SSLv23_client_data);

}

2.5 SSL_CTX_new ()

该函数依据SSL方法获取一个SSL上下文结构,该结构定义为:

/* ssl/ssl.h */

struct ssl_ctx_st

{

SSL_METHOD *method;

STACK_OF(SSL_CIPHER) *cipher_list;

/* same as above but sorted for lookup */

STACK_OF(SSL_CIPHER) *cipher_list_by_id;

struct x509_store_st /* X509_STORE */ *cert_store;

struct lhash_st /* LHASH */ *sessions; /* a set of SSL_SESSIONs */

/* Most session-ids that will be cached, default is

* SSL_SESSION_CACHE_MAX_SIZE_DEFAULT. 0 is unlimited. */

unsigned long session_cache_size;

struct ssl_session_st *session_cache_head;

struct ssl_session_st *session_cache_tail;

/* This can have one of 2 values, ored together,

* SSL_SESS_CACHE_CLIENT,

* SSL_SESS_CACHE_SERVER,

* Default is SSL_SESSION_CACHE_SERVER, which means only

* SSL_accept which cache SSL_SESSIONS. */

int session_cache_mode;

/* If timeout is not 0, it is the default timeout value set

* when SSL_new() is called.  This has been put in to make

* life easier to set things up */

long session_timeout;

/* If this callback is not null, it will be called each

* time a session id is added to the cache.  If this function

* returns 1, it means that the callback will do a

* SSL_SESSION_free() when it has finished using it.  Otherwise,

* on 0, it means the callback has finished with it.

* If remove_session_cb is not null, it will be called when

* a session-id is removed from the cache.  After the call,

* OpenSSL will SSL_SESSION_free() it. */

int (*new_session_cb)(struct ssl_st *ssl,SSL_SESSION *sess);

void (*remove_session_cb)(struct ssl_ctx_st *ctx,SSL_SESSION *sess);

SSL_SESSION *(*get_session_cb)(struct ssl_st *ssl,

unsigned char *data,int len,int *copy);

struct

{

int sess_connect; /* SSL new conn – started */

int sess_connect_renegotiate;/* SSL reneg – requested */

int sess_connect_good; /* SSL new conne/reneg – finished */

int sess_accept; /* SSL new accept – started */

int sess_accept_renegotiate;/* SSL reneg – requested */

int sess_accept_good; /* SSL accept/reneg – finished */

int sess_miss;  /* session lookup misses  */

int sess_timeout; /* reuse attempt on timeouted session */

int sess_cache_full; /* session removed due to full cache */

int sess_hit;  /* session reuse actually done */

int sess_cb_hit; /* session-id that was not

* in the cache was

* passed back via the callback.  This

* indicates that the application is

* supplying session-id’s from other

* processes – spooky 🙂 */

} stats;

int references;

/* if defined, these override the X509_verify_cert() calls */

int (*app_verify_callback)(X509_STORE_CTX *, void *);

void *app_verify_arg;

/* before OpenSSL 0.9.7, ‘app_verify_arg’ was ignored

* (‘app_verify_callback’ was called with just one argument) */

/* Default password callback. */ pem_password_cb *default_passwd_callback;

/* Default password callback user data. */ void *default_passwd_callback_userdata;

/* get client cert callback */ int (*client_cert_cb)(SSL *ssl, X509 **x509, EVP_PKEY **pkey);

CRYPTO_EX_DATA ex_data;

const EVP_MD *rsa_md5;/* For SSLv2 – name is ‘ssl2-md5’ */

const EVP_MD *md5; /* For SSLv3/TLSv1 ‘ssl3-md5’ */

const EVP_MD *sha1;   /* For SSLv3/TLSv1 ‘ssl3->sha1’ */

STACK_OF(X509) *extra_certs; STACK_OF(SSL_COMP) *comp_methods; /* stack of SSL_COMP, SSLv3/TLSv1 */

/* Default values used when no per-SSL value is defined follow */

void (*info_callback)(const SSL *ssl,int type,int val); /* used if SSL’s info_callback is NULL */

/* what we put in client cert requests */ STACK_OF(X509_NAME) *client_CA;

/* Default values to use in SSL structures follow (these are copied by SSL_new) */

unsigned long options;

unsigned long mode;

long max_cert_list;

struct cert_st /* CERT */ *cert; int read_ahead;

/* callback that allows applications to peek at protocol messages */

void (*msg_callback)(int write_p, int version, int content_type, const void *buf, size_t len, SSL *ssl, void *arg);

void *msg_callback_arg;

int verify_mode;

int verify_depth;

unsigned int sid_ctx_length;

unsigned char sid_ctx[SSL_MAX_SID_CTX_LENGTH];

int (*default_verify_callback)(int ok,X509_STORE_CTX *ctx); /* called ‘verify_callback’ in the SSL */

/* Default generate session ID callback. */ GEN_SESSION_CB generate_session_id;

int purpose;  /* Purpose setting */ int trust;  /* Trust setting */

int quiet_shutdown; };

typedef struct ssl_ctx_st SSL_CTX;

/* ssl/ssl_lib.h */

SSL_CTX *SSL_CTX_new(SSL_METHOD *meth)

{

SSL_CTX *ret=NULL;

if (meth == NULL)

{

SSLerr(SSL_F_SSL_CTX_NEW,SSL_R_NULL_SSL_METHOD_PASSED);

return(NULL);

}

if (SSL_get_ex_data_X509_STORE_CTX_idx() < 0)

{

SSLerr(SSL_F_SSL_CTX_NEW,SSL_R_X509_VERIFICATION_SETUP_PROBLEMS);

goto err;

}

// 分配上下文的内存空间

ret=(SSL_CTX *)OPENSSL_malloc(sizeof(SSL_CTX));

if (ret == NULL)

goto err;

memset(ret,0,sizeof(SSL_CTX));

// 初始化上下文的结构參数 ret->method=meth;

ret->cert_store=NULL;

ret->session_cache_mode=SSL_SESS_CACHE_SERVER;

ret->session_cache_size=SSL_SESSION_CACHE_MAX_SIZE_DEFAULT;

ret->session_cache_head=NULL;

ret->session_cache_tail=NULL;

/* We take the system default */ ret->session_timeout=meth->get_timeout();

ret->new_session_cb=0;

ret->remove_session_cb=0;

ret->get_session_cb=0;

ret->generate_session_id=0;

memset((char *)&ret->stats,0,sizeof(ret->stats));

ret->references=1; ret->quiet_shutdown=0;

/* ret->cipher=NULL;*/

/* ret->s2->challenge=NULL;

ret->master_key=NULL;

ret->key_arg=NULL;

ret->s2->conn_id=NULL; */

ret->info_callback=NULL;

ret->app_verify_callback=0; ret->app_verify_arg=NULL;

ret->max_cert_list=SSL_MAX_CERT_LIST_DEFAULT;

ret->read_ahead=0;

ret->msg_callback=0;

ret->msg_callback_arg=NULL;

ret->verify_mode=SSL_VERIFY_NONE;

ret->verify_depth=-1; /* Don’t impose a limit (but x509_lu.c does) */

ret->sid_ctx_length=0;

ret->default_verify_callback=NULL;

if ((ret->cert=ssl_cert_new()) == NULL)

goto err;

ret->default_passwd_callback=0;

ret->default_passwd_callback_userdata=NULL;

ret->client_cert_cb=0;

ret->sessions=lh_new(LHASH_HASH_FN(SSL_SESSION_hash),

LHASH_COMP_FN(SSL_SESSION_cmp));

if (ret->sessions == NULL) goto err;

ret->cert_store=X509_STORE_new();

if (ret->cert_store == NULL) goto err;

// 建立加密算法链表

ssl_create_cipher_list(ret->method,

&ret->cipher_list,&ret->cipher_list_by_id,

SSL_DEFAULT_CIPHER_LIST);

if (ret->cipher_list == NULL

|| sk_SSL_CIPHER_num(ret->cipher_list) <= 0)

{

SSLerr(SSL_F_SSL_CTX_NEW,SSL_R_LIBRARY_HAS_NO_CIPHERS);

goto err2;

}

// 定义上下文结构中HASH算法

if ((ret->rsa_md5=EVP_get_digestbyname(“ssl2-md5”)) == NULL)

{

SSLerr(SSL_F_SSL_CTX_NEW,SSL_R_UNABLE_TO_LOAD_SSL2_MD5_ROUTINES);

goto err2;

}

if ((ret->md5=EVP_get_digestbyname(“ssl3-md5”)) == NULL)

{

SSLerr(SSL_F_SSL_CTX_NEW,SSL_R_UNABLE_TO_LOAD_SSL3_MD5_ROUTINES);

goto err2;

}

if ((ret->sha1=EVP_get_digestbyname(“ssl3-sha1”)) == NULL)

{

SSLerr(SSL_F_SSL_CTX_NEW,SSL_R_UNABLE_TO_LOAD_SSL3_SHA1_ROUTINES);

goto err2;

}

if ((ret->client_CA=sk_X509_NAME_new_null()) == NULL) goto err;

CRYPTO_new_ex_data(CRYPTO_EX_INDEX_SSL_CTX, ret, &ret->ex_data);

ret->extra_certs=NULL;

// 压缩算法

ret->comp_methods=SSL_COMP_get_compression_methods();

return(ret);

err:

SSLerr(SSL_F_SSL_CTX_NEW,ERR_R_MALLOC_FAILURE);

err2:

if (ret != NULL) SSL_CTX_free(ret);

return(NULL);

}

…待续…

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