CryptRetrieveObjectByUrlA function (wincrypt.h)
The CryptRetrieveObjectByUrl function retrieves the public key infrastructure (PKI) object from a location specified by a URL.
These remote objects are in encoded format and are retrieved in a "context" form.
Syntax
BOOL CryptRetrieveObjectByUrlA(
[in] LPCSTR pszUrl,
[in] LPCSTR pszObjectOid,
[in] DWORD dwRetrievalFlags,
[in] DWORD dwTimeout,
[out] LPVOID *ppvObject,
[in] HCRYPTASYNC hAsyncRetrieve,
[in, optional] PCRYPT_CREDENTIALS pCredentials,
[in, optional] LPVOID pvVerify,
[in] PCRYPT_RETRIEVE_AUX_INFO pAuxInfo
);
Parameters
[in] pszUrl
The address of a PKI object to be retrieved. The following schemes are supported:
- ldap (Lightweight Directory Access Protocol)
- http
- https (certificate revocation list (CRL) or online certificate status protocol (OCSP) retrievals only)
- file
[in] pszObjectOid
The address of a null-terminated ANSI string that identifies the type of object to retrieve. This can be one of the following values.
| Value | Meaning |
|---|---|
|
Retrieve one or more data BLOBs. The encoded bits are returned in an array of BLOBs. ppvObject is the address of a CRYPT_BLOB_ARRAY structure pointer that receives the BLOB array. When this structure is no longer needed, you must free it by passing the address of this structure to the CryptMemFree function. |
|
Retrieve one or more certificates.
If a single object is being retrieved, ppvObject is the address of a CERT_CONTEXT structure pointer that receives the context. When this context is no longer needed, you must free it by passing the CERT_CONTEXT structure pointer to the CertFreeCertificateContext function. If multiple objects are being retrieved, ppvObject is the address of an HCERTSTORE variable that receives the handle of a store that contains the certificates. When this store is no longer needed, you must close it by passing this handle to the CertCloseStore function. |
|
Retrieve one or more certificate revocation lists (CRLs).
If a single object is being retrieved, ppvObject is the address of a CRL_CONTEXT structure pointer that receives the context. When this context is no longer needed, you must free it by passing the CRL_CONTEXT structure pointer to the CertFreeCRLContext function. If multiple objects are being retrieved, ppvObject is the address of an HCERTSTORE variable that receives the handle of a store that contains the CRLs. When this store is no longer needed, you must close it by passing this handle to the CertCloseStore function. |
|
Retrieve one or more certificate trust lists (CTLs).
If a single object is being retrieved, ppvObject is the address of a CTL_CONTEXT structure pointer that receives the context. When this context is no longer needed, you must free it by passing the CTL_CONTEXT structure pointer to the CertFreeCTLContext function. If multiple objects are being retrieved, ppvObject is the address of an HCERTSTORE variable that receives the handle of a store that contains the CTLs. When this store is no longer needed, you must close it by passing this handle to the CertCloseStore function. |
|
ppvObject is the address of an HCERTSTORE variable that receives the handle of a store that contains the objects from the message. When this store is no longer needed, you must close it by passing this handle to the CertCloseStore function. |
|
ppvObject is the address of an HCERTSTORE variable that receives the handle of a store that contains the objects. When this store is no longer needed, you must close it by passing this handle to the CertCloseStore function. |
|
ppvObject is the address of a pointer to a CRYPT_BLOB_ARRAY structure. |
[in] dwRetrievalFlags
Determines whether to use the cached URL or a URL retrieved from the wire URL. The form in which objects are returned is determined by the value of pszObjectOid.
| Value | Meaning |
|---|---|
|
Validates the content retrieved by a wire URL before writing the URL to the cache.
The default provider does not support the HTTPS protocol for AIA retrievals. |
|
This value is not supported. |
|
Retrieves the encoded bits from the URL cache only. Do not use the wire to retrieve the URL. |
|
Does not store the retrieved encoded bits to the URL cache. If this flag is not set, the retrieved URL is cached. |
|
Uses the POST method instead of the default GET method for HTTP retrievals.
In a POST URL, additional binary data and header strings are appended to the base URL in the following format: BaseURL/OptionalURLEscaped&Base64EncodedAdditionalData?OptionalAdditionalHTTPHeaders The following example shows the additional binary data delimited by the last slash mark (/) and a Content-Type header delimited by a question mark (?) appended to a base URL.
When this flag is set, the CryptRetrieveObjectByUrl function parses the URL by using the last slash mark (/) and question mark (?) delimiters. The string, which is delimited by a slash mark (/), contains an unescaped URL (that is, a plain text URL without escape characters or escape sequences) and Base64 data decoded into binary form before being passed to the WinHttpSendRequest function as the lpOptional parameter. The string delimited by a question mark (?) is passed to the WinHttpSendRequest function as the pwszHeaders parameter. |
|
Performs A-Record-only DNS lookup on the supplied host string, preventing the generation of false DNS queries when resolving host names. This flag should be used when passing a host name as opposed to a domain name. |
|
Retrieves the entry index and attribute name for each LDAP object. The beginning of each returned BLOB contains the following ANSI string:
"entry index in decimal\0attribute name\0" When this flag is set, pszObjectOid must be NULL so that a BLOB is returned. This flag only applies to the ldap scheme. |
|
Fails if the LDAP search scope is not set to base in the URL. Use with LDAP only. |
|
Digitally signs all of the LDAP traffic to and from a server by using the Kerberos authentication protocol. This feature provides integrity required by some applications. |
|
Inhibits automatic authentication handling. |
|
Enables a conditional HTTP URL retrieval. When this flag is set, for a conditional retrieval that returns HTTP_STATUS_NOT_MODIFIED, CryptRetrieveObjectByUrl returns TRUE and ppvObject is set to NULL. If pAuxInfo is not NULL, dwHttpStatusCode is set to HTTP_STATUS_NOT_MODIFIED. Otherwise, ppvObject is updated for a successful retrieval. |
|
Keeps track of offline failures and delays before hitting the wire on subsequent retrievals. This value is for wire retrieval only. |
|
Enables proxy cache retrieval of an object. If a proxy cache was not explicitly bypassed, fProxyCacheRetrieval is set to TRUE in pAuxInfo. This value only applies to HTTP URL retrievals. |
|
Retrieves multiple objects if available. All objects must be of a homogeneous object type as determined by the value of pszObjectOid, unless the object identifier (OID) value is CONTEXT_OID_CAPI2_ANY. |
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Tags the URL as exempt from being flushed from the cache. For more information, see STICKY_CACHE_ENTRY in INTERNET_CACHE_ENTRY_INFO. |
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Acquires signature verification on the context created. In this case pszObjectOid must be non-NULL and pvVerify points to the signer certificate context. |
|
This flag is not implemented. Do not use it. |
|
Retrieves the encoded bits from the wire only. Does not use the URL cache. |
[in] dwTimeout
Specifies the maximum number of milliseconds to wait for retrieval. If a value of zero is specified, this function does not time out. This parameter is not used if the URL scheme is file:///.
[out] ppvObject
The address of a pointer to the returned object. The return type can be one of the supported types shown in pszObjectOid.
[in] hAsyncRetrieve
This parameter is reserved and must be set to NULL.
[in, optional] pCredentials
This parameter is not used.
[in, optional] pvVerify
A pointer to a verification object. This object is a function of the dwRetrievalFlags parameter. It can be NULL to indicate that the caller is not interested in getting the certificate context or index of the signer if dwRetrievalFlags is CRYPT_VERIFY_CONTEXT_SIGNATURE.
[in] pAuxInfo
An optional pointer to a CRYPT_RETRIEVE_AUX_INFO structure. If not NULL and if the cbSize member of the structure is set, this parameter returns the time of the last successful wire retrieval.
Return value
If the function succeeds, the return value is nonzero (TRUE).
If the function fails, the return value is zero (FALSE).
Remarks
The remote object retrieval manager exposes two provider models. One is the Scheme Provider model that allows for installable protocol providers as defined by the URL scheme, that is, ldap, http, ftp, or file. The scheme provider entry point is the same as the CryptRetrieveObjectByUrl function; however, the *ppvObject returned is always a counted array of encoded bits (one per object retrieved).
The second provider model is the Context Provider model that allows for installable creators of the context handles (objects) based on the retrieved encoded bits. These are dispatched based on the object identifier (OID) specified in the call to CryptRetrieveObjectByUrl.
Individual PKI objects such as certificates, trusts lists, revocation lists, PKCS #7 messages, and multiple homogeneous objects can be retrieved. Starting with Windows Vista with Service Pack 1 (SP1) and Windows Server 2008, security of "http:" and "ldap:" retrievals have been hardened. This function supports "http:" and "ldap:" URL schemes as well as newly defined schemes.
Windows XP: "ftp:" is not supported for network retrieval.
Note
The wincrypt.h header defines CryptRetrieveObjectByUrl as an alias that automatically selects the ANSI or Unicode version of this function based on the definition of the UNICODE preprocessor constant. Mixing usage of the encoding-neutral alias with code that is not encoding-neutral can lead to mismatches that result in compilation or runtime errors. For more information, see Conventions for Function Prototypes.
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 | Cryptnet.lib |
| DLL | Cryptnet.dll |