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Update annotations of sgx_sealed_data_t and sgx_aes_gcm_data_t (#639) #640

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Update annotations of sgx_sealed_data_t and sgx_aes_gcm_data_t (#639) #640

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12 changes: 6 additions & 6 deletions common/inc/sgx_tseal.h
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Original file line number Diff line number Diff line change
Expand Up @@ -47,18 +47,18 @@

typedef struct _aes_gcm_data_t
{
uint32_t payload_size; /* 0: Size of the payload which includes both the encrypted data and the optional additional MAC text */
uint8_t reserved[12]; /* 4: Reserved bits */
uint32_t payload_size; /* 0: Size of the payload which includes the encrypted data: payload[] */
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The payload[] includes encrypted data and the optional additional authenticated data if users seal data with a plaintext (for example, sgx_seal_data() is called with p_additional_MACtext not NULL). So I suppose the previous annotation is correct.

uint8_t reserved[SGX_SEAL_IV_SIZE]; /* 4: Reserved bits used as iv */
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Although the value of the used IV in tseal library is the same as this reserved bits array, but they are indeed different buffers. This reserved array is actually to make the structure 16byte aligned.

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See the sample code, it's used as IV:
https://github.com/intel/linux-sgx/blob/master/SampleCode/LocalAttestation/EnclaveInitiator/EnclaveMessageExchange.cpp#L199
https://github.com/intel/linux-sgx/blob/master/SampleCode/LocalAttestation/EnclaveInitiator/EnclaveMessageExchange.cpp#L207

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OK. Thanks for the explanation. This usage may not be aligned with the initial design of the structure. But the functionality is correct.

uint8_t payload_tag[SGX_SEAL_TAG_SIZE]; /* 16: AES-GMAC of the plain text, payload, and the sizes */
uint8_t payload[]; /* 32: The payload data which includes the encrypted data followed by the optional additional MAC text */
uint8_t payload[]; /* 32: The payload data which includes the encrypted data followed by payload_tag */
} sgx_aes_gcm_data_t;

typedef struct _sealed_data_t
{
sgx_key_request_t key_request; /* 00: The key request used to obtain the sealing key */
uint32_t plain_text_offset; /* 64: Offset within aes_data.playload to the start of the optional additional MAC text */
uint8_t reserved[12]; /* 68: Reserved bits */
sgx_aes_gcm_data_t aes_data; /* 80: Data structure holding the AES/GCM related data */
uint32_t plain_text_offset; /* 512: Offset within aes_data.playload to the start of the optional additional MAC text */
uint8_t reserved[12]; /* 516: Reserved bits */
sgx_aes_gcm_data_t aes_data; /* 528: Data structure holding the AES/GCM related data */
} sgx_sealed_data_t;

#ifdef __cplusplus
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