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ssl_socket_ =client_socket_factory_->CreateSSLClientSocket( //可能创建SSLClientSocketNSS(ssl_client_socket_nss.h)或SSLClientSocketOpenSSL(ssl_client_socket_openssl.h),factory应该不一样。实际上经调试，用的factory是DefaultClientSocketFactory。(client_socket_factory.cc)

transport_socket_handle_.Pass(),

params_->host_and_port(),

params_->ssl_config(),ssl的配置

context_);

returnssl_socket_->Connect(callback_);

}

callstack:

#0 net::SSLConnectJob::DoSSLConnect(this=this@entry=0x658f5698) at../../net/socket/ssl_client_socket_pool.cc:299 //准备ssl链接。

#1 0x61ebc886 in net::SSLConnectJob::DoLoop(this=this@entry=0x658f5698, result=<optimized out>) at../../net/socket/ssl_client_socket_pool.cc:205

#2 0x61ebc8ae in net::SSLConnectJob::OnIOComplete(this=0x658f5698, result=<optimized out>) at../../net/socket/ssl_client_socket_pool.cc:169

#3 0x61ebb172 in Run (a1=@0x63bff94c: 0, object=<optimizedout>, this=0x63bff930) at ../../base/bind_internal.h:190

#4 MakeItSo (a2=@0x63bff94c: 0, a1=<optimized out>,runnable=...) at ../../base/bind_internal.h:898

#5 base::internal::Invoker<1,base::internal::BindState<base::internal::RunnableAdapter<void(net::SSLConnectJob::*)(int)>, void (net::SSLConnectJob*, int),void (base::internal::UnretainedWrapper<net::SSLConnect

Job>)>, void (net::SSLConnectJob*,int)>::Run(base::internal::BindStateBase*, int const&)(base=<optimized out>, x2=@0x63bff94c: 0) at../../base/bind_internal.h:1224

#6 0x61eb8520 in Run (a1=@0x63bff94c: 0, this=0x63bff950) at../../base/callback.h:441

#7 net::ClientSocketHandle::OnIOComplete(this=<optimized out>, result=0) at../../net/socket/client_socket_handle.cc:143 //应该是clinetsocket链接完成

#8 0x61eb7d46 in Run (a1=@0x63bff984: 0, object=<optimizedout>, this=0x63bff968) at ../../base/bind_internal.h:190

#9 MakeItSo (a2=@0x63bff984: 0, a1=<optimized out>,runnable=...) at ../../base/bind_internal.h:898

#10 base::internal::Invoker<1,base::internal::BindState<base::internal::RunnableAdapter<void(net::ClientSocketHandle::*)(int)>, void(net::ClientSocketHandle*, int), void(base::internal::UnretainedWrapper<net::

ClientSocketHandle>)>, void (net::ClientSocketHandle*,int)>::Run(base::internal::BindStateBase*, int const&)(base=<optimized out>, x2=@0x63bff984: 0) at../../base/bind_internal.h:1224

#11 0x61f3ce34 in Run (a1=@0x63bff984: 0, this=0x63bff98c) at../../base/callback.h:441

#12 net::internal::ClientSocketPoolBaseHelper::InvokeUserCallback(this=0x64245410, handle=<optimized out>) at../../net/socket/client_socket_pool_base.cc:1133

#13 0x61f3e0c8 in Run (a1=@0x65b52fb0: 0x5fbcc920,object=<optimized out>, this=0x63bffa50) at../../base/bind_internal.h:190

#14 MakeItSo (a2=@0x65b52fb0: 0x5fbcc920, weak_ptr=...,runnable=...) at ../../base/bind_internal.h:909

#15 base::internal::Invoker<2,base::internal::BindState<base::internal::RunnableAdapter<void(net::internal::ClientSocketPoolBaseHelper::*)(net::ClientSocketHandle*)>,void (net::internal::ClientSocketPoolBaseHel

per*, net::ClientSocketHandle*), void(base::WeakPtr<net::internal::ClientSocketPoolBaseHelper>,net::ClientSocketHandle*)>, void(net::internal::ClientSocketPoolBaseHelper*,net::ClientSocketHandle*)>::Run(base::

internal::BindStateBase*) (base=0x65b52f98) at../../base/bind_internal.h:1253

#16 0x61cbbb5c in Run (this=0x63bffb60) at../../base/callback.h:401

#17 base::MessageLoop::RunTask (this=this@entry=0x62b81250,pending_task=...) at ../../base/message_loop/message_loop.cc:450

#18 0x61cbbc08 in base::MessageLoop::DeferOrRunPendingTask(this=this@entry=0x62b81250, pending_task=...) at../../base/message_loop/message_loop.cc:462

#19 0x61cbc312 in base::MessageLoop::DoWork (this=0x62b81250) at../../base/message_loop/message_loop.cc:576

#20 0x61c9fd8c in base::MessagePumpLibevent::Run (this=0x5c4e41f0,delegate=0x62b81250) at../../base/message_loop/message_pump_libevent.cc:232

#21 0x61cbbf3e in base::MessageLoop::RunHandler (this=0x62b81250)at ../../base/message_loop/message_loop.cc:400

#22 0x61cc3540 in base::RunLoop::Run (this=this@entry=0x63bffbf8)at ../../base/run_loop.cc:49

#23 0x61cbb570 in base::MessageLoop::Run(this=this@entry=0x62b81250) at../../base/message_loop/message_loop.cc:293

#24 0x61ccbe02 in base::Thread::Run (this=this@entry=0x62b64488,message_loop=message_loop@entry=0x62b81250) at../../base/threading/thread.cc:172

#25 0x61855afe in content::BrowserThreadImpl::IOThreadRun //io线程(this=this@entry=0x62b64488,message_loop=message_loop@entry=0x62b81250) at../../content/browser/browser_thread_impl.cc:217

#26 0x61855bca in content::BrowserThreadImpl::Run(this=0x62b64488, message_loop=0x62b81250) at../../content/browser/browser_thread_impl.cc:252

#27 0x61ccc1a6 in base::Thread::ThreadMain (this=0x62b64488) at../../base/threading/thread.cc:225

#28 0x61cc9fde in base::(anonymous namespace)::ThreadFunc(params=<optimized out>) at../../base/threading/platform_thread_posix.cc:80

#29 0x4017ba5c in __thread_entry () from/tmp/tshao-adb-gdb-libs/system/lib/libc.so

#30 0x4017bbd8 in pthread_create () from/tmp/tshao-adb-gdb-libs/system/lib/libc.so

virtual scoped_ptr<SSLClientSocket> CreateSSLClientSocket(

scoped_ptr<ClientSocketHandle> transport_socket,

const HostPortPair& host_and_port,

const SSLConfig& ssl_config,

const SSLClientSocketContext& context) OVERRIDE {

#if defined(USE_OPENSSL)/默认的使用openssl

return scoped_ptr<SSLClientSocket>(

new SSLClientSocketOpenSSL(transport_socket.Pass(),host_and_port,

ssl_config, context));

#elif defined(USE_NSS) ||defined(OS_MACOSX) || defined(OS_WIN)

return scoped_ptr<SSLClientSocket>(

new SSLClientSocketNSS(nss_task_runner.get(),

transport_socket.Pass(),

host_and_port,

ssl_config,

context));

#else

NOTIMPLEMENTED();

return scoped_ptr<SSLClientSocket>();

#endif

}

SSLClientSocketOpenSSL::Connect (ssl_clent_socket_openssl.cc)

-> init() ,这里面会根据sslconfig信息把使用的ssl版本信息设置到SslSetClearMask也就是options.里面。会根据版本等设置生成option,调用SSL_set_options(ssl_,options.set_mask); 以及 SSL_clear_options(ssl_,options.clear_mask); 设置到openssl模块里面，也就是SSL结构的options成员里。

GotoState(STATE_HANDSHAKE); 设置状态

rv = DoHandshakeLoop(OK);//下面是握手的逻辑

----> int SSLClientSocketOpenSSL::DoHandshakeLoop(intlast_io_result) { //这个循环会完成证书握手，证书验证。

int rv = last_io_result;

do {

State state = next_handshake_state_;

GotoState(STATE_NONE);

switch (state) {

case STATE_HANDSHAKE:

rv = DoHandshake();

break;

case STATE_VERIFY_CERT:

DCHECK(rv == OK);

rv = DoVerifyCert(rv);

break;

case STATE_VERIFY_CERT_COMPLETE:

rv = DoVerifyCertComplete(rv);

break;

case STATE_NONE:

default:

rv = ERR_UNEXPECTED;

NOTREACHED() << "unexpected state" <<state;

break;

}

bool network_moved = DoTransportIO();

if (network_moved && next_handshake_state_ ==STATE_HANDSHAKE) {

rv = OK; // This causes us to stay in the loop.

}

} while (rv != ERR_IO_PENDING && next_handshake_state_!= STATE_NONE);

return rv;

看一下SSLClientSocketOpenSSL：：DoHandShake

->SSL_do_handshake(SSL* ssl) // openssl的ssl_lib.c因为之前SSLClientSocketOpenSSL::init时，已经把配置设置到了SSL结构的option里，所以这里调用openssl的接口就开始握手了。握手结束后，就获取servier的证书并验证。当然，如果client证书也需要的话还得提供client证书。

Callstack:

#0 SSL_do_handshake(s=0x66102b28) at../../third_party/openssl/openssl/ssl/ssl_lib.c:2620

#1 0x620fc56a in net::SSLClientSocketOpenSSL::DoHandshake(this=this@entry=0x659c0de0) at../../net/socket/ssl_client_socket_openssl.cc:804

#2 0x620fc86a in net::SSLClientSocketOpenSSL::DoHandshakeLoop(this=this@entry=0x659c0de0, last_io_result=last_io_result@entry=0)at ../../net/socket/ssl_client_socket_openssl.cc:1002

#3 0x620fc8ea innet::SSLClientSocketOpenSSL::Connect(base::Callback<void(int)> const&) (this=0x659c0de0, callback=...) at../../net/socket/ssl_client_socket_openssl.cc:428

#4 0x620fd368 in net::SSLConnectJob::DoSSLConnect(this=this@entry=0x658f9b08) at../../net/socket/ssl_client_socket_pool.cc:324

#5 0x620fe886 in net::SSLConnectJob::DoLoop(this=this@entry=0x658f9b08, result=<optimized out>) at../../net/socket/ssl_client_socket_pool.cc:205

#6 0x620fe8ae in net::SSLConnectJob::OnIOComplete(this=0x658f9b08, result=<optimized out>) at../../net/socket/ssl_client_socket_pool.cc:169

#7 0x620fd172 in Run (a1=@0x63b4194c: 0, object=<optimizedout>, this=0x63b41930) at ../../base/bind_internal.h:190

#8 MakeItSo (a2=@0x63b4194c: 0, a1=<optimized out>,runnable=...) at ../../base/bind_internal.h:898

#9 base::internal::Invoker<1,base::internal::BindState<base::internal::RunnableAdapter<void(net::SSLConnectJob::*)(int)>, void (net::SSLConnectJob*, int),void (base::internal::UnretainedWrapper<net::SSLConnect

Job>)>, void (net::SSLConnectJob*,int)>::Run(base::internal::BindStateBase*, int const&)(base=<optimized out>, x2=@0x63b4194c: 0) at../../base/bind_internal.h:1224

#10 0x620fa520 in Run (a1=@0x63b4194c: 0, this=0x63b41950) at../../base/callback.h:441

#11 net::ClientSocketHandle::OnIOComplete (this=<optimizedout>, result=0) at ../../net/socket/client_socket_handle.cc:143

#12 0x620f9d46 in Run (a1=@0x63b41984: 0, object=<optimizedout>, this=0x63b41968) at ../../base/bind_internal.h:190

#13 MakeItSo (a2=@0x63b41984: 0, a1=<optimized out>,runnable=...) at ../../base/bind_internal.h:898

#14 base::internal::Invoker<1,base::internal::BindState<base::internal::RunnableAdapter<void(net::ClientSocketHandle::*)(int)>, void(net::ClientSocketHandle*, int), void(base::internal::UnretainedWrapper<net::

ClientSocketHandle>)>, void (net::ClientSocketHandle*,int)>::Run(base::internal::BindStateBase*, int const&)(base=<optimized out>, x2=@0x63b41984: 0) at../../base/bind_internal.h:1224

#15 0x6217ee34 in Run (a1=@0x63b41984: 0, this=0x63b4198c) at../../base/callback.h:441

#16 net::internal::ClientSocketPoolBaseHelper::InvokeUserCallback(this=0x64146c18, handle=<optimized out>) at../../net/socket/client_socket_pool_base.cc:1133

#17 0x621800c8 in Run (a1=@0x65943ae8: 0x658f9d00,object=<optimized out>, this=0x63b41a50) at../../base/bind_internal.h:190

#18 MakeItSo (a2=@0x65943ae8: 0x658f9d00, weak_ptr=...,runnable=...) at ../../base/bind_internal.h:909

#19 base::internal::Invoker<2,base::internal::BindState<base::internal::RunnableAdapter<void(net::internal::ClientSocketPoolBaseHelper::*)(net::ClientSocketHandle*)>,void (net::internal::ClientSocketPoolBaseHel

internal::BindStateBase*) (base=0x65943ad0) at../../base/bind_internal.h:1253

#20 0x61efdb5c in Run (this=0x63b41b60) at../../base/callback.h:401

#21 base::MessageLoop::RunTask (this=this@entry=0x60a163a8,pending_task=...) at ../../base/message_loop/message_loop.cc:450

#22 0x61efdc08 in base::MessageLoop::DeferOrRunPendingTask(this=this@entry=0x60a163a8, pending_task=...) at../../base/message_loop/message_loop.cc:462

#23 0x61efe312 in base::MessageLoop::DoWork (this=0x60a163a8) at../../base/message_loop/message_loop.cc:576

#24 0x61ee1d8c in base::MessagePumpLibevent::Run (this=0x60a164a0,delegate=0x60a163a8) at../../base/message_loop/message_pump_libevent.cc:232

#25 0x61efdf3e in base::MessageLoop::RunHandler (this=0x60a163a8)at ../../base/message_loop/message_loop.cc:400

#26 0x61f05540 in base::RunLoop::Run (this=this@entry=0x63b41bf8)at ../../base/run_loop.cc:49

#27 0x61efd570 in base::MessageLoop::Run(this=this@entry=0x60a163a8) at../../base/message_loop/message_loop.cc:293

#28 0x61f0de02 in base::Thread::Run (this=this@entry=0x60a14800,message_loop=message_loop@entry=0x60a163a8) at../../base/threading/thread.cc:172

#29 0x61a97afe in content::BrowserThreadImpl::IOThreadRun//io线程(this=this@entry=0x60a14800,message_loop=message_loop@entry=0x60a163a8) at../../content/browser/browser_thread_impl.cc:217

#30 0x61a97bca in content::BrowserThreadImpl::Run(this=0x60a14800, message_loop=0x60a163a8) at../../content/browser/browser_thread_impl.cc:252

#31 0x61f0e1a6 in base::Thread::ThreadMain (this=0x60a14800) at../../base/threading/thread.cc:225

可以从下面代码知道要控制ssl版本的使用，应该从那里入手：

int SSLClientSocketOpenSSL::Init() {

DCHECK(!ssl_);

DCHECK(!transport_bio_);

SSLContext* context = SSLContext::GetInstance();

crypto::OpenSSLErrStackTracer err_tracer(FROM_HERE);

ssl_ = SSL_new(context->ssl_ctx());

if (!ssl_ || !context->SetClientSocketForSSL(ssl_, this))

return ERR_UNEXPECTED;

if (!SSL_set_tlsext_host_name(ssl_,host_and_port_.host().c_str()))

return ERR_UNEXPECTED;

trying_cached_session_ =context->session_cache()->SetSSLSessionWithKey(

ssl_, GetSocketSessionCacheKey(*this));

BIO* ssl_bio = NULL;

// 0 => use default buffer sizes.

if (!BIO_new_bio_pair(&ssl_bio, 0, &transport_bio_, 0))

return ERR_UNEXPECTED;

DCHECK(ssl_bio);

DCHECK(transport_bio_);

SSL_set_bio(ssl_, ssl_bio, ssl_bio);

// OpenSSL defaults some options to on, others to off. To avoidambiguity,

// set everything we care about to an absolute value.

SslSetClearMask options;

options.ConfigureFlag(SSL_OP_NO_SSLv2, true);

bool ssl3_enabled =(ssl_config_.version_min == SSL_PROTOCOL_VERSION_SSL3); //要想禁用ssl3就得把ssl_config.version_min改了。

options.ConfigureFlag(SSL_OP_NO_SSLv3, !ssl3_enabled);

bool tls1_enabled = (ssl_config_.version_min <=SSL_PROTOCOL_VERSION_TLS1 &&

ssl_config_.version_max >=SSL_PROTOCOL_VERSION_TLS1);

options.ConfigureFlag(SSL_OP_NO_TLSv1, !tls1_enabled);

bool tls1_1_enabled =

(ssl_config_.version_min <= SSL_PROTOCOL_VERSION_TLS1_1&&

ssl_config_.version_max >= SSL_PROTOCOL_VERSION_TLS1_1);

options.ConfigureFlag(SSL_OP_NO_TLSv1_1, !tls1_1_enabled);

bool tls1_2_enabled =

(ssl_config_.version_min <= SSL_PROTOCOL_VERSION_TLS1_2&&

ssl_config_.version_max >= SSL_PROTOCOL_VERSION_TLS1_2);

options.ConfigureFlag(SSL_OP_NO_TLSv1_2, !tls1_2_enabled);

options.ConfigureFlag(SSL_OP_NO_COMPRESSION, true);

// TODO(joth): Set this conditionally, seehttp://crbug.com/55410

options.ConfigureFlag(SSL_OP_LEGACY_SERVER_CONNECT, true);

SSL_set_options(ssl_,options.set_mask);

SSL_clear_options(ssl_, options.clear_mask);

如果改了ssl_config.version_min改了，可以在这里加一个打印，看有没有效果。

查找ssl_config.version_min使用点。赋值的地方。

SSLConfig结构（ssl_client_socket_openssl.h中）：

// The minimum and maximumprotocol versions that are enabled.

// SSL 3.0 is 0x0300, TLS 1.0is 0x0301, TLS 1.1 is 0x0302, and so on.

// (Use theSSL_PROTOCOL_VERSION_xxx enumerators defined above.)

// SSL 2.0 is not supported.If version_max < version_min, it means no

// protocol versions areenabled.

uint16 version_min;

uint16 version_max;

SSLConfig构造函数有version_min默认值,要修改一下。

SSLConfigService, SSLConfigServiceManager,SSLConfigServiceManagerPref的关联是啥？干什么的？

SSLConfigService是基类，可以检查比较新旧两个配置,如果发生变化，那么就可以通知注册进来的一些observer配置变化了。

// This SSLConfigService always returns the default SSLConfigsettings. It is

// mainly useful for unittests, or for platforms that do not havea native

// implementation of SSLConfigService yet.

//基本没什么特殊功能，维护了一份配置

class NET_EXPORT SSLConfigServiceDefaults: public SSLConfigService {

// An SSLConfigService which stores a cached version of thecurrent SSLConfig

// prefs, which are updated by SSLConfigServiceManagerPref whenthe prefs

// change.

//提供了对可以persistent的ssl的prefs的支持，当ui线程发现sslprefs发生变化时，会通过SSLConfigServiceManagerPref来从pref读取配置，生成新的ssl配置结构，并设置给SSLConfigServicePref,它比较新的和旧的，如果有改变，就notifyobservers.注意notify的操作在io线程完成。

class SSLConfigServicePref: public net::SSLConfigService {

用的哪个SSLConfigService?

SSLConfigServiceManager是一个抽象类，作为接口。用来创建SSLConfigService实例。

class SSLConfigServiceManagerPref : publicSSLConfigServiceManager {

它有一些成员，比如ssl_version_min_，成员类型都是PrefMember，这些成员描述了configService关心的参数。在够造函数里，这些成员都被注册了一个callback:SSLConfigServiceManagerPref::OnPreferenceChanged.当这些成员变了，就调用该callback.该callback会从新读取这些成员的值，并付给一个SSLConfig结构。然后调用SSLConfigServicePref::SetNewSSLConfig,

void SSLConfigServicePref::SetNewSSLConfig(

const net::SSLConfig& new_config) {

net::SSLConfig orig_config = cached_config_;

cached_config_ = new_config;//替换当前的config.

ProcessConfigUpdate(orig_config, new_config);

}

->void SSLConfigService::ProcessConfigUpdate(const SSLConfig&orig_config,

const SSLConfig&new_config) {

->NotifySSLConfigChange, 通知监听者。

那么这些pref究竟谁改得？用户改的么？监听者都有谁？SSLClientSocketPool是一个监听者，其构造函数中把自己注册了进来。当SSLClientSocketPool收到改动通知后，会做一些操作。当然改动后的内容还是得从configsrevice来获取。

谁会修改配置以后再看。

先试一下在SSLConfig构造函数中修改最低版本看能否起作用。

ssl_config.cc中有constuint16 kDefaultSSLVersionMin = SSL_PROTOCOL_VERSION_SSL3;

把他的值改成SSL_PROTOCOL_VERSION_TLS1。

下面再分析一下ssl握手的流程：

SSLClientSocketOpenSSL::DoHandshakeLoop

int rv = last_io_result;

do {

// Default to STATE_NONEfor next state.

// (This is a quirkcarried over from the windows

// implementation. Itmakes reading the logs a bit harder.)

// State handlers canand often do call GotoState just

// to stay in thecurrent state.

State state =next_handshake_state_;

GotoState(STATE_NONE);

switch (state) {

case STATE_HANDSHAKE:

rv = DoHandshake();

break;

caseSTATE_VERIFY_CERT:

DCHECK(rv == OK);

rv =DoVerifyCert(rv);

break;

caseSTATE_VERIFY_CERT_COMPLETE:

rv =DoVerifyCertComplete(rv);

break;

case STATE_NONE:

default:

rv = ERR_UNEXPECTED;

NOTREACHED() <<"unexpected state" << state;

break;

}

bool network_moved =DoTransportIO();

if (network_moved &&next_handshake_state_ == STATE_HANDSHAKE) {

// In general we exitthe loop if rv is ERR_IO_PENDING. In this

// special case wekeep looping even if rv is ERR_IO_PENDING because

// the transport IOmay allow DoHandshake to make progress.

rv = OK; // Thiscauses us to stay in the loop.

}

} while (rv !=ERR_IO_PENDING && next_handshake_state_ != STATE_NONE);

return rv;

首先进入 rv = DoHandshake();调用openssl的api执行handshake,如果异步没完成，那么，状态依然保持STATE_HANDSHAKE.结果是IOPending。在Dohandleshakeloop里就执行一次TransportIO，也就是本socket数据读写，如果有数据io发生，那么就不退出dohandleshakeloop,返回值改为ok,因为此时状态还是<