CryptGetMessageSignerCount function (wincrypt.h)
The CryptGetMessageSignerCount function returns the number of signers of a signed message.
Note
This function may return a count of duplicate signers and therefore may not be sufficient to avert attacks. We recommend using the sid (SignerIdentifier) field from SignerInfo to identify duplicate signers in a message.
Syntax
LONG CryptGetMessageSignerCount(
[in] DWORD dwMsgEncodingType,
[in] const BYTE *pbSignedBlob,
[in] DWORD cbSignedBlob
);
Parameters
[in] dwMsgEncodingType
Specifies the encoding type used. It is always acceptable to specify both the certificate and message encoding types by combining them with a bitwise-OR operation as shown in the following example:
X509_ASN_ENCODING | PKCS_7_ASN_ENCODING
Currently defined encoding types are:
- X509_ASN_ENCODING
- PKCS_7_ASN_ENCODING
[in] pbSignedBlob
A pointer to a buffer containing the signed message.
[in] cbSignedBlob
The size, in bytes, of the signed message.
Return value
Returns the number of signers of a signed message, zero when there are no signers, and minus one (–1) for an error.
For extended error information, call GetLastError. The following error code is most commonly returned.
| Return code | Description |
|---|---|
|
Invalid message encoding type. Currently only PKCS_7_ASN_ENCODING is supported. |
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.
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client | Windows XP [desktop apps only] |
| Minimum supported server | Windows Server 2003 [desktop apps only] |
| Target Platform | Windows |
| Header | wincrypt.h |
| Library | Crypt32.lib |
| DLL | Crypt32.dll |