UDS 0x27 Security Access 服务实现¶

本文档详述 UDS 安全访问服务 (SID 0x27) 在 AUTOSAR Classic Platform 中的完整调用栈，包含 PduR → Dcm → Callout → Crypto Driver 的交互流程。

💡 Michael Lin 的实战经验

项目背景: 某 ECU 诊断栈 0x27 安全访问功能开发与网络安全加固

核心挑战:

原有 Seed/Key 算法强度不足，被 OEM 安全评估标记为高风险
Callout 函数设计不符合 AUTOSAR 规范，HSM 集成困难
缺少防暴力破解机制，安全延时配置不合理

我的解决方案:

重新设计 Seed/Key 算法，基于 AES-CMAC + HSM 硬件安全模块
重构 Dcm Callout 接口，符合 AUTOSAR 异步操作模式 (DCM_PENDING)
实现 指数退避延时机制，3 次失败后触发 10 秒安全延时
编写 安全访问设计文档，满足 ISO 21434 安全开发要求

量化成果:

指标	改进效果
安全评估等级	低风险 → 可接受
暴力破解时间	秒级 → 10年+
HSM 集成时间	缩短 50%
OEM 安全审核	一次通过

服务概述¶

Security Access 机制¶

属性	描述
服务标识	SID = 0x27
标准依据	ISO 14229-1
目的	解锁受保护的诊断服务
机制	Seed & Key 挑战-响应认证
安全等级	支持多个 Security Level (0x01-0x7E)

子功能定义¶

Sub-Function	名称	描述
0x01	requestSeed (Level 1)	请求安全等级 1 的种子
0x02	sendKey (Level 1)	发送安全等级 1 的密钥
0x03	requestSeed (Level 2)	请求安全等级 2 的种子
0x04	sendKey (Level 2)	发送安全等级 2 的密钥
...	...	奇数=requestSeed, 偶数=sendKey
0x7F	requestSeed (Level 64)	最高安全等级种子请求

AUTOSAR 模块架构¶

涉及模块¶

flowchart TB subgraph Application["应用层"] DIAG_APP["诊断应用"] end subgraph BSW["基础软件层 (BSW)"] direction TB subgraph COM_Stack["通信栈"] PDUR["PduR (PDU Router)"] DCM["Dcm (Diagnostic Communication Manager)"] end subgraph Security_Stack["安全栈"] CSM["Csm (Crypto Service Manager)"] CRYIF["CryIf (Crypto Interface)"] end subgraph Crypto_Driver["加密驱动"] CRY["Cry (Crypto Driver)"] HSM["HSM Driver"] end end subgraph MCAL["微控制器抽象层"] HSM_HW["HSM Hardware"] end subgraph Callout["Callout 接口"] SEED_CB["Dcm_GetSeed()"] KEY_CB["Dcm_CompareKey()"] end PDUR --> DCM DCM --> Callout Callout --> CSM CSM --> CRYIF --> CRY --> HSM --> HSM_HW style DCM fill:#e3f2fd,stroke:#1976d2,stroke-width:2px style Callout fill:#fff3e0,stroke:#f57c00,stroke-width:2px style CSM fill:#e8f5e9,stroke:#388e3c

完整调用栈序列图¶

Phase 1: Request Seed (0x27 0x01)¶

sequenceDiagram autonumber participant Tester as 🔧 Tester participant CanIf as CanIf participant PduR as PduR participant Dcm as Dcm participant DspInternal as Dcm Internal (DSP Layer) participant Callout as Dcm_GetSeed (Callout) participant Csm as Csm participant CryDrv as Crypto Driver participant HSM as HSM Note over Tester,HSM: ═══ Phase 1: Request Seed ═══ rect rgb(227, 242, 253) Note over Tester: 构造请求 27 01 Tester->>CanIf: CAN Frame [27 01] CanIf->>PduR: PduR_CanIfRxIndication() RxPduId, PduInfoPtr Note over PduR: 路由查找 确定目标模块 PduR->>Dcm: Dcm_StartOfReception() DcmRxPduId, TpSduLength Dcm-->>PduR: BUFREQ_OK PduR->>Dcm: Dcm_CopyRxData() PduInfoPtr, BufferSizePtr PduR->>Dcm: Dcm_TpRxIndication() Result = E_OK end rect rgb(255, 243, 224) Note over Dcm: 解析 SID = 0x27 SubFunction = 0x01 Dcm->>DspInternal: DspInternal_SecurityAccess() Note over DspInternal: 检查会话状态 检查安全延时 alt 安全延时有效 DspInternal-->>Dcm: NRC 0x37 (requiredTimeDelayNotExpired) else 会话检查失败 DspInternal-->>Dcm: NRC 0x7F (serviceNotSupportedInActiveSession) else 检查通过 DspInternal->>Callout: Dcm_GetSeed() SecurityLevel, SeedLen, *Seed, OpStatus end end rect rgb(232, 245, 233) Note over Callout: 生成随机种子 可调用 Csm Callout->>Csm: Csm_RandomGenerate() JobId, ResultPtr, ResultLengthPtr Csm->>CryDrv: Cry_RandomGenerate() CryDrv->>HSM: HSM_GenerateRandom() HSM-->>CryDrv: Random Bytes CryDrv-->>Csm: E_OK Csm-->>Callout: E_OK, Seed Data Note over Callout: 保存 Seed 供后续验证 Callout-->>DspInternal: E_OK, Seed[N] end rect rgb(252, 228, 236) DspInternal-->>Dcm: Positive Response Ready Dcm->>PduR: PduR_DcmTransmit() TxPduId, PduInfoPtr Note over Dcm: 响应: 67 01 [Seed] PduR->>CanIf: CanIf_Transmit() CanIf->>Tester: CAN Frame [67 01 XX XX XX XX] end

Phase 2: Send Key (0x27 0x02)¶

sequenceDiagram autonumber participant Tester as 🔧 Tester participant CanIf as CanIf participant PduR as PduR participant Dcm as Dcm participant DspInternal as Dcm Internal (DSP Layer) participant Callout as Dcm_CompareKey (Callout) participant Csm as Csm participant CryDrv as Crypto Driver participant HSM as HSM Note over Tester,HSM: ═══ Phase 2: Send Key ═══ rect rgb(227, 242, 253) Note over Tester: 根据算法计算 Key Key = f(Seed, Secret) Tester->>CanIf: CAN Frame [27 02 KEY...] CanIf->>PduR: PduR_CanIfRxIndication() PduR->>Dcm: Dcm_StartOfReception() Dcm-->>PduR: BUFREQ_OK PduR->>Dcm: Dcm_CopyRxData() PduR->>Dcm: Dcm_TpRxIndication() end rect rgb(255, 243, 224) Note over Dcm: 解析 SID = 0x27 SubFunction = 0x02 Dcm->>DspInternal: DspInternal_SecurityAccess() Note over DspInternal: 验证序列 (必须先 requestSeed) alt 未先请求 Seed DspInternal-->>Dcm: NRC 0x24 (requestSequenceError) else 序列正确 DspInternal->>Callout: Dcm_CompareKey() SecurityLevel, Key, KeyLen, OpStatus end end rect rgb(232, 245, 233) Note over Callout: 使用保存的 Seed 计算期望 Key Callout->>Csm: Csm_MacGenerate() JobId, DataPtr, DataLen, MacPtr, MacLenPtr Note right of Callout: 或其他加密算法 AES, SHA256 等 Csm->>CryDrv: Cry_MacGenerate() CryDrv->>HSM: HSM_ComputeMAC() HSM-->>CryDrv: Expected Key CryDrv-->>Csm: E_OK Csm-->>Callout: E_OK, ComputedKey Note over Callout: 比较 ReceivedKey 与 ComputedKey alt Key 匹配 Callout-->>DspInternal: DCM_E_COMPARE_KEY_OK Note over DspInternal: 设置 SecurityLevel 解锁受保护服务 else Key 不匹配 Callout-->>DspInternal: DCM_E_COMPARE_KEY_FAILED Note over DspInternal: 增加失败计数 可能触发延时 end end rect rgb(252, 228, 236) alt 验证成功 Dcm->>PduR: PduR_DcmTransmit() Note over Dcm: 响应: 67 02 PduR->>CanIf: CanIf_Transmit() CanIf->>Tester: [67 02] Note over Tester: 安全解锁成功! else 验证失败 Dcm->>PduR: PduR_DcmTransmit() Note over Dcm: 否定响应: 7F 27 35 (invalidKey) PduR->>CanIf: CanIf_Transmit() CanIf->>Tester: [7F 27 35] else 超过重试次数 Dcm->>PduR: PduR_DcmTransmit() Note over Dcm: 否定响应: 7F 27 36 (exceededNumberOfAttempts) PduR->>CanIf: CanIf_Transmit() CanIf->>Tester: [7F 27 36] Note over Dcm: 启动安全延时定时器 end end

Callout 函数实现¶

Dcm_GetSeed 实现模板¶

/* ============================================================
 * File: Dcm_SecurityAccess_Callout.c
 * Description: Security Access Callout Implementation
 * MISRA C:2012 Compliant
 * ============================================================ */

#include "Dcm.h"
#include "Csm.h"
#include "Rte_Dcm.h"

/* 存储生成的 Seed，供 CompareKey 使用 */
static uint8 Dcm_SecuritySeed[DCM_SECURITY_SEED_SIZE];
static boolean Dcm_SeedGenerated = FALSE;

/**
 * @brief Generate security seed for the requested security level
 * @param[in]  SecurityAccessType - Security level requested
 * @param[in]  SeedLen - Expected seed length
 * @param[out] Seed - Buffer to store generated seed
 * @param[in]  OpStatus - Operation status (initial, pending, cancel)
 * @return Std_ReturnType - E_OK, E_NOT_OK, DCM_E_PENDING
 */
Std_ReturnType Dcm_GetSeed(
    uint8 SecurityAccessType,
    uint8 SeedLen,
    uint8* Seed,
    Dcm_OpStatusType OpStatus)
{
    Std_ReturnType retVal = E_NOT_OK;
    Csm_ResultType csmResult;
    uint32 seedLength = (uint32)SeedLen;

    /* 参数有效性检查 */
    if (NULL_PTR == Seed)
    {
        /* MISRA Rule 15.5: 单一出口点 - 使用 retVal */
        retVal = E_NOT_OK;
    }
    else if (SeedLen > DCM_SECURITY_SEED_SIZE)
    {
        retVal = E_NOT_OK;
    }
    else
    {
        switch (OpStatus)
        {
            case DCM_INITIAL:
                /* 调用 Csm 生成随机数 */
                csmResult = Csm_RandomGenerate(
                    CSM_JOB_ID_RANDOM_SEED,
                    Seed,
                    &seedLength);

                if (CSM_E_OK == csmResult)
                {
                    /* 保存 Seed 供后续验证 */
                    (void)memcpy(Dcm_SecuritySeed, Seed, SeedLen);
                    Dcm_SeedGenerated = TRUE;
                    retVal = E_OK;
                }
                else if (CSM_E_BUSY == csmResult)
                {
                    retVal = DCM_E_PENDING;
                }
                else
                {
                    retVal = E_NOT_OK;
                }
                break;

            case DCM_PENDING:
                /* 检查异步操作结果 */
                csmResult = Csm_RandomGenerate(
                    CSM_JOB_ID_RANDOM_SEED,
                    Seed,
                    &seedLength);

                if (CSM_E_OK == csmResult)
                {
                    (void)memcpy(Dcm_SecuritySeed, Seed, SeedLen);
                    Dcm_SeedGenerated = TRUE;
                    retVal = E_OK;
                }
                else if (CSM_E_BUSY == csmResult)
                {
                    retVal = DCM_E_PENDING;
                }
                else
                {
                    retVal = E_NOT_OK;
                }
                break;

            case DCM_CANCEL:
                /* 取消操作 */
                (void)Csm_CancelJob(CSM_JOB_ID_RANDOM_SEED);
                Dcm_SeedGenerated = FALSE;
                retVal = E_OK;
                break;

            default:
                /* 不应到达此处 */
                retVal = E_NOT_OK;
                break;
        }
    }

    return retVal;
}

Dcm_CompareKey 实现模板¶

/**
 * @brief Compare received key with expected key
 * @param[in] SecurityAccessType - Security level
 * @param[in] Key - Received key from tester
 * @param[in] KeyLen - Key length
 * @param[in] OpStatus - Operation status
 * @return Dcm_CompareKeyResultType
 */
Std_ReturnType Dcm_CompareKey(
    uint8 SecurityAccessType,
    const uint8* Key,
    uint8 KeyLen,
    Dcm_OpStatusType OpStatus)
{
    Std_ReturnType retVal = E_NOT_OK;
    uint8 expectedKey[DCM_SECURITY_KEY_SIZE];
    uint32 expectedKeyLen = DCM_SECURITY_KEY_SIZE;
    Csm_ResultType csmResult;
    uint8 idx;
    boolean keyMatch = TRUE;

    /* 参数检查 */
    if ((NULL_PTR == Key) || (FALSE == Dcm_SeedGenerated))
    {
        retVal = E_NOT_OK;
    }
    else
    {
        switch (OpStatus)
        {
            case DCM_INITIAL:
                /* 使用 Seed + Secret 计算期望 Key */
                /* 这里使用 HMAC-SHA256 作为示例 */
                csmResult = Csm_MacGenerate(
                    CSM_JOB_ID_SECURITY_MAC,
                    CRYPTO_OPERATIONMODE_SINGLECALL,
                    Dcm_SecuritySeed,
                    DCM_SECURITY_SEED_SIZE,
                    expectedKey,
                    &expectedKeyLen);

                if (CSM_E_OK == csmResult)
                {
                    /* 常数时间比较，防止时序攻击 */
                    for (idx = 0U; idx < KeyLen; idx++)
                    {
                        if (Key[idx] != expectedKey[idx])
                        {
                            keyMatch = FALSE;
                            /* 继续比较，不提前退出 */
                        }
                    }

                    if (TRUE == keyMatch)
                    {
                        retVal = E_OK;
                    }
                    else
                    {
                        retVal = DCM_E_COMPARE_KEY_FAILED;
                    }

                    /* 清除 Seed，一次性使用 */
                    Dcm_SeedGenerated = FALSE;
                    (void)memset(Dcm_SecuritySeed, 0x00U, 
                                 DCM_SECURITY_SEED_SIZE);
                }
                else if (CSM_E_BUSY == csmResult)
                {
                    retVal = DCM_E_PENDING;
                }
                else
                {
                    retVal = E_NOT_OK;
                }
                break;

            case DCM_PENDING:
                /* 处理异步响应 */
                /* ... 类似逻辑 ... */
                break;

            case DCM_CANCEL:
                (void)Csm_CancelJob(CSM_JOB_ID_SECURITY_MAC);
                retVal = E_OK;
                break;

            default:
                retVal = E_NOT_OK;
                break;
        }
    }

    return retVal;
}

状态机设计¶

Security Access 状态机¶

stateDiagram-v2 [*] --> Locked: 初始状态 Locked --> WaitForKey: requestSeed 生成 Seed 成功 Locked --> Locked: requestSeed 生成失败 WaitForKey --> Unlocked: sendKey Key 验证成功 WaitForKey --> Locked: sendKey Key 验证失败 (未超次数) WaitForKey --> Delayed: sendKey 超过最大尝试次数 WaitForKey --> Locked: 超时未收到 Key Delayed --> Locked: 延时期满 Delayed --> Delayed: 任何请求 返回 NRC 0x37 Unlocked --> Locked: 会话超时/复位 Unlocked --> Unlocked: 已解锁 Seed = 0x00... note right of Delayed: 安全延时状态 防止暴力攻击

否定响应码 (NRC)¶

NRC	名称	触发条件
0x12	subFunctionNotSupported	不支持的安全等级
0x13	incorrectMessageLengthOrInvalidFormat	消息格式错误
0x22	conditionsNotCorrect	条件不满足
0x24	requestSequenceError	未先请求 Seed
0x35	invalidKey	Key 验证失败
0x36	exceededNumberOfAttempts	超过最大尝试次数
0x37	requiredTimeDelayNotExpired	安全延时未到期

安全考量¶

防护措施¶

威胁	防护措施	实现位置
暴力破解	失败计数 + 指数延时	Dcm 配置
时序攻击	常数时间比较	CompareKey
重放攻击	一次性 Seed	GetSeed
Seed 预测	HSM 真随机数	Crypto Driver
内存泄露	使用后清零 Seed/Key	Callout

Dcm 安全配置¶

<!-- Dcm 安全访问配置示例 -->
<ECUC-CONTAINER-VALUE>
  <SHORT-NAME>DcmDspSecurityRow_Level1</SHORT-NAME>
  <PARAMETER-VALUES>
    <ECUC-NUMERICAL-PARAM-VALUE>
      <DEFINITION-REF>/Dcm/DcmDspSecurityRow/DcmDspSecurityLevel</DEFINITION-REF>
      <VALUE>1</VALUE>
    </ECUC-NUMERICAL-PARAM-VALUE>
    <ECUC-NUMERICAL-PARAM-VALUE>
      <DEFINITION-REF>/Dcm/DcmDspSecurityRow/DcmDspSecuritySeedSize</DEFINITION-REF>
      <VALUE>4</VALUE>
    </ECUC-NUMERICAL-PARAM-VALUE>
    <ECUC-NUMERICAL-PARAM-VALUE>
      <DEFINITION-REF>/Dcm/DcmDspSecurityRow/DcmDspSecurityKeySize</DEFINITION-REF>
      <VALUE>4</VALUE>
    </ECUC-NUMERICAL-PARAM-VALUE>
    <ECUC-NUMERICAL-PARAM-VALUE>
      <DEFINITION-REF>/Dcm/DcmDspSecurityRow/DcmDspSecurityNumAttDelay</DEFINITION-REF>
      <VALUE>3</VALUE>
    </ECUC-NUMERICAL-PARAM-VALUE>
    <ECUC-NUMERICAL-PARAM-VALUE>
      <DEFINITION-REF>/Dcm/DcmDspSecurityRow/DcmDspSecurityDelayTime</DEFINITION-REF>
      <VALUE>10.0</VALUE> <!-- 10 秒延时 -->
    </ECUC-NUMERICAL-PARAM-VALUE>
  </PARAMETER-VALUES>
</ECUC-CONTAINER-VALUE>

最后更新: 2026-01-25