CryptVerifyMessageSignature (Compact 2013)

3/28/2014

This function verifies a signed message's signature.

Syntax

BOOL WINAPI CryptVerifyMessageSignature(
        __in PCRYPT_VERIFY_MESSAGE_PARA pVerifyPara,
        __in DWORD dwSignerIndex,
        __in const BYTE *pbSignedBlob,
        __in DWORD cbSignedBlob,
        __out BYTE *pbDecoded,
        __inout DWORD *pcbDecoded,
        __out_opt PCCERT_CONTEXT *ppSignerCert
);

Parameters

• pVerifyPara
  [in] Pointer to a CRYPT_VERIFY_MESSAGE_PARA structure that contains verification parameters.

• dwSignerIndex
  [in] Index of the signature you want. There can be more than one signature. CryptVerifyMessageSignature can be called repeatedly, incrementing dwSignerIndex each time. Set this parameter to zero for the first signer, or if there is only one signer. If the function returns FALSE, and GetLastError returns CRYPT_E_NO_SIGNER, the previous call processed the last signer of the message.

• pbSignedBlob
  [in] Pointer to a buffer that contains the signed message.

• cbSignedBlob
  [in] Size, in bytes, of the signed message buffer.

• pbDecoded
  [out] Pointer to a buffer to receive the decoded message.

  This parameter can be NULL if the decoded message is not needed for additional processing or to set the size of the message for memory allocation purposes. For more information, see Retrieving Data of Unknown Length.

• pcbDecoded
  [in, out] Pointer to a DWORD value that specifies the size, in bytes, of the pbDecoded buffer. When the function returns, this DWORD contains the size, in bytes, of the decoded message. The decoded message will not be returned if this parameter is NULL.

  Note

  When processing the data returned, applications must use the actual size of the data returned. The actual size can be slightly smaller than the size of the buffer specified on input. (On input, buffer sizes are usually specified large enough to ensure that the largest possible output data will fit in the buffer.) On output, the variable pointed to by this parameter is updated to reflect the actual size of the data copied to the buffer.

• ppSignerCert
  [out, optional] The address of a CERT_CONTEXT structure pointer that receives the certificate of the signer. When you have finished using this structure, free it by passing this pointer to the CertFreeCertificateContext function. This parameter can be NULL if the signer's certificate is not needed.

Return Value

If the function succeeds, the function returns nonzero. Nonzero does not necessarily mean that the signature was verified. In the case of a detached message, the variable pointed to by pcbDecoded will contain zero. In this case, this function will return nonzero, but the signature is not verified. To verify the signature of a detached message, use the CryptVerifyDetachedMessageSignature function.

If the function was not successful, it returns zero. For extended error information, call GetLastError.

The following table shows the error codes most commonly returned by the GetLastError function.

If the function fails, GetLastError may return an Abstract Syntax Notation One (ASN.1) encoding/decoding error. For information about these errors, see ASN.1 Encoding/Decoding Return Values.

Remarks

This function should not be used to verify the signature of a detached message. You should use the CryptVerifyDetachedMessageSignature function to verify the signature of a detached message.

For a verified signer and message, ppSignerCert is updated with the CERT_CONTEXT of the signer. It must be freed by calling CertFreeCertificateContext. Otherwise, ppSignerCert is set to NULL.

For a message that contains only certificates and certificate revocation lists (CRLs), pcbDecoded is set to NULL.

Requirements

See Also

Reference

Certificates Functions