区块链教程Fabric1.0源代码分析policy（背书策略），2018年下半年，区块链行业正逐渐褪去发展之初的浮躁、回归理性，表面上看相关人才需求与身价似乎正在回落。但事实上，正是初期泡沫的渐退，让人们更多的关注点放在了区块链真正的技术之上。

Fabric 1.0源代码笔记 之 policy（背书策略）

1、policy概述

policy代码分布在core/policy、core/policyprovider、common/policies目录下。目录结构如下：

• core/policy/policy.go，PolicyChecker接口定义及实现、PolicyCheckerFactory接口定义。
• core/policyprovider/provider.go，PolicyChecker工厂默认实现。
• common/policies目录
      * policy.go，ChannelPolicyManagerGetter接口及实现。

    * implicitmeta_util.go，通道策略工具函数。

2、PolicyChecker工厂

2.1、PolicyCheckerFactory接口定义

type PolicyCheckerFactory interface {
    NewPolicyChecker() PolicyChecker //构造PolicyChecker实例
}

var pcFactory PolicyCheckerFactory //全局变量定义及赋值函数
func RegisterPolicyCheckerFactory(f PolicyCheckerFactory) {
    pcFactory = f
}
//代码在core/policy/policy.go

2.2、PolicyCheckerFactory接口默认实现

type defaultFactory struct{}

//构造policy.PolicyChecker
func (f *defaultFactory) NewPolicyChecker() policy.PolicyChecker {
    return policy.NewPolicyChecker(
        peer.NewChannelPolicyManagerGetter(), //&channelPolicyManagerGetter{}
        mgmt.GetLocalMSP(),
        mgmt.NewLocalMSPPrincipalGetter(),
    )
}

//获取policy.PolicyChecker，即调用policy.GetPolicyChecker()
func GetPolicyChecker() policy.PolicyChecker

func init() { //初始化全局变量pcFactory
    policy.RegisterPolicyCheckerFactory(&defaultFactory{})
}

3、PolicyChecker接口定义及实现

3.1、PolicyChecker接口定义

type PolicyChecker interface {
    CheckPolicy(channelID, policyName string, signedProp *pb.SignedProposal) error
    CheckPolicyBySignedData(channelID, policyName string, sd []*common.SignedData) error
    CheckPolicyNoChannel(policyName string, signedProp *pb.SignedProposal) error
}
//代码在core/policy/policy.go

3.2、PolicyChecker接口实现

PolicyChecker接口实现，即policyChecker结构体及方法。

type policyChecker struct {
    channelPolicyManagerGetter policies.ChannelPolicyManagerGetter //通道策略管理器
    localMSP                   msp.IdentityDeserializer //身份
    principalGetter            mgmt.MSPPrincipalGetter //委托人
}

//构造policyChecker
func NewPolicyChecker(channelPolicyManagerGetter policies.ChannelPolicyManagerGetter, localMSP msp.IdentityDeserializer, principalGetter mgmt.MSPPrincipalGetter) PolicyChecker
//检查签名提案是否符合通道策略
func (p *policyChecker) CheckPolicy(channelID, policyName string, signedProp *pb.SignedProposal) error
func (p *policyChecker) CheckPolicyNoChannel(policyName string, signedProp *pb.SignedProposal) error
//检查签名数据是否符合通道策略，获取策略并调取policy.Evaluate(sd)
func (p *policyChecker) CheckPolicyBySignedData(channelID, policyName string, sd []*common.SignedData) error
func GetPolicyChecker() PolicyChecker //pcFactory.NewPolicyChecker()
//代码在core/policy/policy.go

func (p policyChecker) CheckPolicy(channelID, policyName string, signedProp pb.SignedProposal) error代码如下：

func (p *policyChecker) CheckPolicy(channelID, policyName string, signedProp *pb.SignedProposal) error {
    if channelID == "" { //channelID为空，调取CheckPolicyNoChannel()
        return p.CheckPolicyNoChannel(policyName, signedProp)
    }
    
    policyManager, _ := p.channelPolicyManagerGetter.Manager(channelID)
    proposal, err := utils.GetProposal(signedProp.ProposalBytes) //获取proposal
    header, err := utils.GetHeader(proposal.Header)
    shdr, err := utils.GetSignatureHeader(header.SignatureHeader) //SignatureHeader
    sd := []*common.SignedData{&common.SignedData{
        Data:      signedProp.ProposalBytes,
        Identity:  shdr.Creator,
        Signature: signedProp.Signature,
    }}
    return p.CheckPolicyBySignedData(channelID, policyName, sd)
}
//代码在core/policy/policy.go

4、ChannelPolicyManagerGetter接口及实现

4.1、ChannelPolicyManagerGetter接口定义

type ChannelPolicyManagerGetter interface {
    Manager(channelID string) (Manager, bool)
}
//代码在common/policies/policy.go

4.2、ChannelPolicyManagerGetter接口实现

ChannelPolicyManagerGetter接口实现，即ManagerImpl结构体及方法。

type ManagerImpl struct {
    parent        *ManagerImpl
    basePath      string
    fqPrefix      string
    providers     map[int32]Provider //type Provider interface
    config        *policyConfig //type policyConfig struct
    pendingConfig map[interface{}]*policyConfig //type policyConfig struct
    pendingLock   sync.RWMutex
    SuppressSanityLogMessages bool
}

type Provider interface {
    NewPolicy(data []byte) (Policy, proto.Message, error)
}

type policyConfig struct {
    policies map[string]Policy //type Policy interface
    managers map[string]*ManagerImpl
    imps     []*implicitMetaPolicy
}

type Policy interface {
    //对给定的签名数据，按规则检验确认是否符合约定的条件
    Evaluate(signatureSet []*cb.SignedData) error
}

//构造ManagerImpl
func NewManagerImpl(basePath string, providers map[int32]Provider) *ManagerImpl
//获取pm.basePath
func (pm *ManagerImpl) BasePath() string
//获取pm.config.policies，即map[string]Policy中Key列表
func (pm *ManagerImpl) PolicyNames() []string
//获取指定路径的子管理器
func (pm *ManagerImpl) Manager(path []string) (Manager, bool)
//获取pm.config.policies[relpath]
//获取Policy
func (pm *ManagerImpl) GetPolicy(id string) (Policy, bool)
func (pm *ManagerImpl) BeginPolicyProposals(tx interface{}, groups []string) ([]Proposer, error)
func (pm *ManagerImpl) RollbackProposals(tx interface{})
func (pm *ManagerImpl) PreCommit(tx interface{}) error
func (pm *ManagerImpl) CommitProposals(tx interface{})
func (pm *ManagerImpl) ProposePolicy(tx interface{}, key string, configPolicy *cb.ConfigPolicy) (proto.Message, error)
//代码在common/policies/policy.go

type implicitMetaPolicy struct {
    conf        *cb.ImplicitMetaPolicy
    threshold   int
    subPolicies []Policy
}
//代码在common/policies/implicitmeta.go

5、通道策略工具函数

type ImplicitMetaPolicy_Rule int32
const (
    ImplicitMetaPolicy_ANY      ImplicitMetaPolicy_Rule = 0 //任意
    ImplicitMetaPolicy_ALL      ImplicitMetaPolicy_Rule = 1 //所有
    ImplicitMetaPolicy_MAJORITY ImplicitMetaPolicy_Rule = 2 //大多数
)
//代码在protos/common/policies.pb.go

//构造cb.Policy
func ImplicitMetaPolicyWithSubPolicy(subPolicyName string, rule cb.ImplicitMetaPolicy_Rule) *cb.ConfigPolicy
func TemplateImplicitMetaPolicyWithSubPolicy(path []string, policyName string, subPolicyName string, rule cb.ImplicitMetaPolicy_Rule) *cb.ConfigGroup

//调取TemplateImplicitMetaPolicyWithSubPolicy(path, policyName, policyName, rule)
func TemplateImplicitMetaPolicy(path []string, policyName string, rule cb.ImplicitMetaPolicy_Rule) *cb.ConfigGroup

//任意，TemplateImplicitMetaPolicy(path, policyName, cb.ImplicitMetaPolicy_ANY)
func TemplateImplicitMetaAnyPolicy(path []string, policyName string) *cb.ConfigGroup

//所有，TemplateImplicitMetaPolicy(path, policyName, cb.ImplicitMetaPolicy_ALL)
func TemplateImplicitMetaAllPolicy(path []string, policyName string) *cb.ConfigGroup

//大多数，TemplateImplicitMetaPolicy(path, policyName, cb.ImplicitMetaPolicy_MAJORITY)
func TemplateImplicitMetaMajorityPolicy(path []string, policyName string) *cb.ConfigGroup
//代码在common/policies/implicitmeta_util.go