Dkim C Reference Documentation

Dkim

DomainKeys API for creating and verifying DKIM-Signature and DomainKey-Signature MIME (email) header fields. This API is included with the "Chilkat MIME" license. ("Chilkat MIME" may be referred to as "Chilkat S/MIME" on some chilkatsoft.com web pages. They are the same product.)

Create/Dispose

HCkDkim CkDkim_Create(void);

Creates an instance of the HCkDkim object and returns a handle (i.e. a "void *" pointer). The handle is passed in the 1st argument for the functions listed on this page.

void CkDkim_Dispose(HCkDkim handle);

Objects created by calling CkDkim_Create must be freed by calling this method. A memory leak occurs if a handle is not disposed by calling this function. Also, any handle returned by a Chilkat "C" function must also be freed by the application by calling the appropriate Dispose method, such as CkDkim_Dispose.

Callback Functions

Callback Functions are Introduced in Chilkat v9.5.0.56

void CkDkim_setAbortCheck(HCkHttp cHandle, BOOL (*fnAbortCheck)(void));

Provides the opportunity for a method call to be aborted. If TRUE is returned, the operation in progress is aborted. Return FALSE to allow the current method call to continue. This callback function is called periodically based on the value of the HeartbeatMs property. (If HeartbeatMs is 0, then no callbacks are made.) As an example, to make 5 AbortCheck callbacks per second, set the HeartbeatMs property equal to 200.

C Example using Callback Functions

void CkDkim_setPercentDone(HCkHttp cHandle, BOOL (*fnPercentDone)(int pctDone));

Provides the percentage completed for any method that involves network communications or time-consuming processing (assuming it is a method where a percentage completion can be measured). This callback is only called when it is possible to know a percentage completion, and when it makes sense to express the operation as a percentage completed. The pctDone argument will have a value from 1 to 100. For methods that complete very quickly, the number of PercentDone callbacks will vary, but the final callback should have a value of 100. For long running operations, no more than one callback per percentage point will occur (for example: 1, 2, 3, ... 98, 99, 100).

This callback counts as an AbortCheck callback, and takes the place of the AbortCheck event when it fires.

The return value indicates whether the method call should be aborted, or whether it should proceed. Return TRUE to abort, and FALSE to proceed.

void CkDkim_setProgressInfo(HCkHttp cHandle, void (*fnProgressInfo)(const char *name, const char *value));

This is a general callback that provides name/value information about what is happening at certain points during a method call. To see the information provided in ProgressInfo callbacks, if any, write code to handle this event and log the name/value pairs. Most are self-explanatory.

void CkDkim_setTaskCompleted(HCkHttp cHandle, void (*fnTaskCompleted)(HCkTask hTask));

Called in the background thread when an asynchronous task completes. (Note: When an async method is running, all callbacks are in the background thread.)

Properties

BOOL CkDkim_getAbortCurrent(HCkDkim cHandle);

void CkDkim_putAbortCurrent(HCkDkim cHandle, BOOL newVal);

Introduced in version 9.5.0.58

When set to TRUE, causes the currently running method to abort. Methods that always finish quickly (i.e.have no length file operations or network communications) are not affected. If no method is running, then this property is automatically reset to FALSE when the next method is called. When the abort occurs, this property is reset to FALSE. Both synchronous and asynchronous method calls can be aborted. (A synchronous method call could be aborted by setting this property from a separate thread.)

void CkDkim_getDebugLogFilePath(HCkDkim cHandle, HCkString retval);

void CkDkim_putDebugLogFilePath(HCkDkim cHandle, const char *newVal);

const char *CkDkim_debugLogFilePath(HCkDkim cHandle);

If set to a file path, causes each Chilkat method or property call to automatically append it's LastErrorText to the specified log file. The information is appended such that if a hang or crash occurs, it is possible to see the context in which the problem occurred, as well as a history of all Chilkat calls up to the point of the problem. The VerboseLogging property can be set to provide more detailed information.

This property is typically used for debugging the rare cases where a Chilkat method call hangs or generates an exception that halts program execution (i.e. crashes). A hang or crash should generally never happen. The typical causes of a hang are:

  1. a timeout related property was set to 0 to explicitly indicate that an infinite timeout is desired,
  2. the hang is actually a hang within an event callback (i.e. it is a hang within the application code), or
  3. there is an internal problem (bug) in the Chilkat code that causes the hang.

void CkDkim_getDkimAlg(HCkDkim cHandle, HCkString retval);

void CkDkim_putDkimAlg(HCkDkim cHandle, const char *newVal);

const char *CkDkim_dkimAlg(HCkDkim cHandle);

The signing algorithm to be used in creating the DKIM-Signature. Possible values are "rsa-sha256" and "rsa-sha1". The default value is "rsa-sha256".

int CkDkim_getDkimBodyLengthCount(HCkDkim cHandle);

void CkDkim_putDkimBodyLengthCount(HCkDkim cHandle, int newVal);

Optional body length count to set a maximum number of body bytes to be hashed when creating the DKIM-Signature field. The default value is 0, indicating that the entire body should be hashed.

void CkDkim_getDkimCanon(HCkDkim cHandle, HCkString retval);

void CkDkim_putDkimCanon(HCkDkim cHandle, const char *newVal);

const char *CkDkim_dkimCanon(HCkDkim cHandle);

Canonicalization algorithm to be used for both header and body when creating the DKIM-Signature. Possible values are "simple" and "relaxed". The default value is "relaxed".

void CkDkim_getDkimDomain(HCkDkim cHandle, HCkString retval);

void CkDkim_putDkimDomain(HCkDkim cHandle, const char *newVal);

const char *CkDkim_dkimDomain(HCkDkim cHandle);

The domain name of the signing domain when creating the DKIM-Signature.

void CkDkim_getDkimHeaders(HCkDkim cHandle, HCkString retval);

void CkDkim_putDkimHeaders(HCkDkim cHandle, const char *newVal);

const char *CkDkim_dkimHeaders(HCkDkim cHandle);

A colon-separated list of header field names that identify headers presented to the signing algorithm when creating the DKIM-Signature. The default value is: "mime-version:date:message-id:subject:from:to:content-type".

void CkDkim_getDkimSelector(HCkDkim cHandle, HCkString retval);

void CkDkim_putDkimSelector(HCkDkim cHandle, const char *newVal);

const char *CkDkim_dkimSelector(HCkDkim cHandle);

The selector to be used to form the DNS query for the public key. This property applies to creating a DKIM-Signature. For example, if the selector is "reykjavik" and the domain is "example-code.com", then the DNS query would be for "reykjavik._domainkey.example-code.com".

void CkDkim_getDomainKeyAlg(HCkDkim cHandle, HCkString retval);

void CkDkim_putDomainKeyAlg(HCkDkim cHandle, const char *newVal);

const char *CkDkim_domainKeyAlg(HCkDkim cHandle);

The signing algorithm to be used in creating the DomainKey-Signature. The only possible value is "rsa-sha1". The default value is "rsa-sha1".

void CkDkim_getDomainKeyCanon(HCkDkim cHandle, HCkString retval);

void CkDkim_putDomainKeyCanon(HCkDkim cHandle, const char *newVal);

const char *CkDkim_domainKeyCanon(HCkDkim cHandle);

Canonicalization algorithm to be used for when creating the DomainKey-Signature. Possible values are "simple" and "nofws". The default value is "nofws".

void CkDkim_getDomainKeyDomain(HCkDkim cHandle, HCkString retval);

void CkDkim_putDomainKeyDomain(HCkDkim cHandle, const char *newVal);

const char *CkDkim_domainKeyDomain(HCkDkim cHandle);

The domain name of the signing domain when creating the DomainKey-Signature.

void CkDkim_getDomainKeyHeaders(HCkDkim cHandle, HCkString retval);

void CkDkim_putDomainKeyHeaders(HCkDkim cHandle, const char *newVal);

const char *CkDkim_domainKeyHeaders(HCkDkim cHandle);

A colon-separated list of header field names that identify headers presented to the signing algorithm when creating the DomainKey-Signature. The default value is: "mime-version:date:message-id:subject:from:to:content-type".

void CkDkim_getDomainKeySelector(HCkDkim cHandle, HCkString retval);

void CkDkim_putDomainKeySelector(HCkDkim cHandle, const char *newVal);

const char *CkDkim_domainKeySelector(HCkDkim cHandle);

The selector to be used to form the DNS query for the public key. This property applies to creating a DomainKey-Signature. For example, if the selector is "reykjavik" and the domain is "example-code.com", then the DNS query would be for "reykjavik._domainkey.example-code.com".

int CkDkim_getHeartbeatMs(HCkDkim cHandle);

void CkDkim_putHeartbeatMs(HCkDkim cHandle, int newVal);

The number of milliseconds between each AbortCheck event callback. The AbortCheck callback allows an application to abort any method call prior to completion. If HeartbeatMs is 0 (the default), no AbortCheck event callbacks will fire.

void CkDkim_getLastErrorHtml(HCkDkim cHandle, HCkString retval);

const char *CkDkim_lastErrorHtml(HCkDkim cHandle);

Provides information in HTML format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.

void CkDkim_getLastErrorText(HCkDkim cHandle, HCkString retval);

const char *CkDkim_lastErrorText(HCkDkim cHandle);

Provides information in plain-text format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.

Concept of LastErrorText

LastErrorText Standard Information

void CkDkim_getLastErrorXml(HCkDkim cHandle, HCkString retval);

const char *CkDkim_lastErrorXml(HCkDkim cHandle);

Provides information in XML format about the last method/property called. If a method call returns a value indicating failure, or behaves unexpectedly, examine this property to get more information.

BOOL CkDkim_getLastMethodSuccess(HCkDkim cHandle);

void CkDkim_putLastMethodSuccess(HCkDkim cHandle, BOOL newVal);

Introduced in version 9.5.0.52

Indicate whether the last method call succeeded or failed. A value of TRUE indicates success, a value of FALSE indicates failure. This property is automatically set for method calls. It is not modified by property accesses. The property is automatically set to indicate success for the following types of method calls:

  • Any method that returns a string.
  • Any method returning a Chilkat object, binary bytes, or a date/time.
  • Any method returning a standard boolean status value where success = TRUE and failure = FALSE.
  • Any method returning an integer where failure is defined by a return value less than zero.

Note: Methods that do not fit the above requirements will always set this property equal to TRUE. For example, a method that returns no value (such as a "void" in C++) will technically always succeed.

BOOL CkDkim_getUtf8(HCkDkim cHandle);

void CkDkim_putUtf8(HCkDkim cHandle, BOOL newVal);

When set to TRUE, all "const char *" arguments are interpreted as utf-8 strings. If set to FALSE (the default), then "const char *" arguments are interpreted as ANSI strings. Also, when set to TRUE, and Chilkat method returning a "const char *" is returning the utf-8 representation. If set to FALSE, all "const char *" return values are ANSI strings.

BOOL CkDkim_getVerboseLogging(HCkDkim cHandle);

void CkDkim_putVerboseLogging(HCkDkim cHandle, BOOL newVal);

If set to TRUE, then the contents of LastErrorText (or LastErrorXml, or LastErrorHtml) may contain more verbose information. The default value is FALSE. Verbose logging should only be used for debugging. The potentially large quantity of logged information may adversely affect peformance.

void CkDkim_getVersion(HCkDkim cHandle, HCkString retval);

const char *CkDkim_version(HCkDkim cHandle);

Version of the component/library, such as "9.5.0.63"

Methods

BOOL CkDkim_AddDkimSignature(HCkDkim cHandle, HCkByteData mimeIn, HCkByteData outBytes);

This method is deprecated. It will be removed in a future version.

Constructs and prepends a DKIM-Signature header to the MIME. Prior to calling this method, your program must set both the DkimDomain and DkimSelector properties, and it must load a private key by calling LoadDkimPk or LoadDkimPkFile.

Note: This method is deprecated. Use the DkimSign method instead.

Returns TRUE for success, FALSE for failure.

Add DKIM-Signature Header to MIME / Email

Send DKIM Signed Email

BOOL CkDkim_AddDomainKeySignature(HCkDkim cHandle, HCkByteData mimeIn, HCkByteData outBytes);

This method is deprecated. It will be removed in a future version.

Constructs and prepends a DomainKey-Signature header to the MIME. Prior to calling this method, your program must set both the DomainKeyDomain and DomainKeySelector properties, and it must load a private key by calling LoadDomainKeyPk or LoadDomainKeyPkFile.

Note: This method is deprecated. Use the DomainKeySign method instead.

Returns TRUE for success, FALSE for failure.

Add DomainKey-Signature Header to MIME / Email

BOOL CkDkim_DkimSign(HCkDkim cHandle, HCkBinData mimeData);

Introduced in version 9.5.0.71

Constructs and prepends a DKIM-Signature header to the MIME passed in mimeData. Prior to calling this method, your program must set both the DkimDomain and DkimSelector properties, and it must load a private key by calling SetDkimPrivateKey.

Returns TRUE for success, FALSE for failure.

BOOL CkDkim_DkimVerify(HCkDkim cHandle, int sigIndex, HCkBinData mimeData);

Introduced in version 9.5.0.71

Verifies the Nth DKIM-Signature header in the mimeData. (In most cases, there is only one signature.) The 1st signature is at sigIndex 0.

Important: Many anti-virus programs, such as AVG, will modify the MIME of an email as it is received. This will cause DKIM signature verification to fail because the body of the MIME is modified.

Returns TRUE for success, FALSE for failure.

BOOL CkDkim_DomainKeySign(HCkDkim cHandle, HCkBinData mimeData);

Introduced in version 9.5.0.71

Constructs and prepends a DomainKey-Signature header to the MIME passed in mimeData. Prior to calling this method, your program must set both the DomainKeyDomain and DomainKeySelector properties, and it must load a private key by calling SetDomainKeyPrivateKey.

Returns TRUE for success, FALSE for failure.

BOOL CkDkim_DomainKeyVerify(HCkDkim cHandle, int sigIndex, HCkBinData mimeData);

Introduced in version 9.5.0.71

Verifies the Nth DomainKey-Signature header in the mimeData. (In most cases, there is only one signature.) The 1st signature is at sigIndex 0.

Important: Many anti-virus programs, such as AVG, will modify the MIME of an email as it is received. This will cause DomainKey signature verification to fail because the body of the MIME is modified.

Returns TRUE for success, FALSE for failure.

BOOL CkDkim_LoadDkimPk(HCkDkim cHandle, const char *privateKey, const char *optionalPassword);

This method is deprecated. It will be removed in a future version.

Loads an RSA private key to be used for creating a DKIM-Signature. Any valid RSA private key format that is not binary, such as PEM or XML, may be passed to this method. This method will automatically determine the format and parse it correctly. A password is only required if key is encrypted, such as for encrypted PEM.

Note: This method is deprecated. Use the SetDkimPrivateKey method instead.

Returns TRUE for success, FALSE for failure.

DKIM Signature using Windows Current User Certificate Store

BOOL CkDkim_LoadDkimPkBytes(HCkDkim cHandle, HCkByteData privateKeyDer, const char *optionalPassword);

This method is deprecated. It will be removed in a future version.

Loads an RSA private key to be used for creating a DKIM-Signature. Any valid RSA private key binary format, such as DER, may be passed to this method. This method will automatically determine the format and parse it correctly. A password is only required if key is encrypted.

Note: This method is deprecated. Use the SetDkimPrivateKey method instead.

Returns TRUE for success, FALSE for failure.

BOOL CkDkim_LoadDkimPkFile(HCkDkim cHandle, const char *privateKeyFilePath, const char *optionalPassword);

This method is deprecated. It will be removed in a future version.

Loads an RSA private key file to be used for creating a DKIM-Signature. The file name contains any valid RSA private key format, such as DER, PKCS8, PEM, XML, etc. This method will automatically determine the format and parse it correctly. A password is only required if key is encrypted, such as for encrypted PEM or encrypted PKCS8.

Note: This method is deprecated. Use the SetDkimPrivateKey method instead.

Returns TRUE for success, FALSE for failure.

BOOL CkDkim_LoadDomainKeyPk(HCkDkim cHandle, const char *privateKey, const char *optionalPassword);

This method is deprecated. It will be removed in a future version.

Loads an RSA private key to be used for creating a DomainKey-Signature. Any valid RSA private key format that is not binary, such as PEM or XML, may be passed to this method. This method will automatically determine the format and parse it correctly. A password is only required if key is encrypted, such as for encrypted PEM.

Note: This method is deprecated. Use the SetDomainKeyPrivateKey method instead.

Returns TRUE for success, FALSE for failure.

BOOL CkDkim_LoadDomainKeyPkBytes(HCkDkim cHandle, HCkByteData privateKeyDer, const char *optionalPassword);

This method is deprecated. It will be removed in a future version.

Loads an RSA private key to be used for creating a DomainKey-Signature. Any valid RSA private key binary format, such as DER, may be passed to this method. This method will automatically determine the format and parse it correctly. A password is only required if key is encrypted.

Note: This method is deprecated. Use the SetDomainKeyPrivateKey method instead.

Returns TRUE for success, FALSE for failure.

BOOL CkDkim_LoadDomainKeyPkFile(HCkDkim cHandle, const char *privateKeyFilePath, const char *optionalPassword);

This method is deprecated. It will be removed in a future version.

Loads an RSA private key file to be used for creating a DomainKey-Signature. The file name contains any valid RSA private key format, such as DER, PKCS8, PEM, XML, etc. This method will automatically determine the format and parse it correctly. A password is only required if key is encrypted, such as for encrypted PEM or encrypted PKCS8.

Note: This method is deprecated. Use the SetDomainKeyPrivateKey method instead.

Returns TRUE for success, FALSE for failure.

BOOL CkDkim_LoadPublicKey(HCkDkim cHandle, const char *selector, const char *domain, const char *publicKey);

Caches a public key to be used for verifying DKIM and DomainKey signatures for a given selector and domain. The publicKey is a string containing an RSA public key in any text format, such as XML, PEM, etc. This method will automatically detect the format and load the public key correctly. This method is useful for testing DKIM and DomainKey verification when your public key has not yet been installed in DNS.

Returns TRUE for success, FALSE for failure.

BOOL CkDkim_LoadPublicKeyFile(HCkDkim cHandle, const char *selector, const char *domain, const char *publicKeyFilepath);

Caches a public key to be used for verifying DKIM and DomainKey signatures for a given selector and domain. The publicKeyFilepath is a filepath of an RSA public key in any format. This method will automatically detect the format and load the public key correctly. This method is useful for testing DKIM and DomainKey verification when your public key has not yet been installed in DNS.

Returns TRUE for success, FALSE for failure.

int CkDkim_NumDkimSignatures(HCkDkim cHandle, HCkByteData mimeData);

Returns the number of DKIM-Signature header fields found in mimeData.

int CkDkim_NumDomainKeySignatures(HCkDkim cHandle, HCkByteData mimeData);

Returns the number of DomainKey-Signature header fields found in mimeData.

BOOL CkDkim_PrefetchPublicKey(HCkDkim cHandle, const char *selector, const char *domain);

Useful if your application is going to verify many emails from a single domain (or a few domains). This eliminates the need to do a DNS lookup to fetch the public key each time an email's DKIM or DomainKey signature is verified.

This method may be called multiple times -- once for each selector/domain to be pre-fetched. The verify methods (VerifyDkimSignature and VerifyDomainKeySignature) will use a pre-fetched key if the selector and domain match.

Returns TRUE for success, FALSE for failure.

HCkTask CkDkim_PrefetchPublicKeyAsync(HCkDkim cHandle, const char *selector, const char *domain);

Creates an asynchronous task to call the PrefetchPublicKey method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

Returns NULL on failure

How to Run an Asynchronous Task

BOOL CkDkim_SaveLastError(HCkDkim cHandle, const char *path);

Saves the last-error information (the contents of LastErrorXml) to an XML formatted file.

Returns TRUE for success, FALSE for failure.

BOOL CkDkim_SetDkimPrivateKey(HCkDkim cHandle, HCkPrivateKey privateKey);

Introduced in version 9.5.0.71

Sets the private key file to be used for creating a DKIM-Signature.

Returns TRUE for success, FALSE for failure.

BOOL CkDkim_SetDomainKeyPrivateKey(HCkDkim cHandle, HCkPrivateKey privateKey);

Introduced in version 9.5.0.71

Sets the private key file to be used for creating a DomainKey-Signature.

Returns TRUE for success, FALSE for failure.

BOOL CkDkim_UnlockComponent(HCkDkim cHandle, const char *unlockCode);

Unlocks the component allowing for the full functionality to be used. If this method unexpectedly returns FALSE, examine the contents of the LastErrorText property to determine the reason for failure.

Returns TRUE for success, FALSE for failure.

Diagnosing UnlockComponent Problems

UnlockComponent LastErrorText shows exact string passed to it.

Verify UnlockComponent Success w/ Purchased Unlock Code

LastErrorText Standard Information

BOOL CkDkim_VerifyDkimSignature(HCkDkim cHandle, int sigIndex, HCkByteData mimeData);

This method is deprecated. It will be removed in a future version.

Verifies the Nth DKIM-Signature header in the mimeData. (In most cases, there is only one signature.) The 1st signature is at sigIndex 0.

Important: Many anti-virus programs, such as AVG, will modify the MIME of an email as it is received. This will cause DKIM signature verification to fail because the body of the MIME is modified.

Note: This method is deprecated. Use the DkimVerify method instead.

Returns TRUE for success, FALSE for failure.

HCkTask CkDkim_VerifyDkimSignatureAsync(HCkDkim cHandle, int sigIndex, HCkByteData mimeData);

This method is deprecated. It will be removed in a future version.

Creates an asynchronous task to call the VerifyDkimSignature method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

Returns NULL on failure

How to Run an Asynchronous Task

BOOL CkDkim_VerifyDomainKeySignature(HCkDkim cHandle, int sigIndex, HCkByteData mimeData);

This method is deprecated. It will be removed in a future version.

Verifies the Nth DomainKey-Signature header in the mimeData. (In most cases, there is only one signature.) The 1st signature is at sigIndex 0.

Important: Many anti-virus programs, such as AVG, will modify the MIME of an email as it is received. This will cause DomainKey signature verification to fail because the body of the MIME is modified.

Note: This method is deprecated. Use the DomainKeyVerify method instead.

Returns TRUE for success, FALSE for failure.

HCkTask CkDkim_VerifyDomainKeySignatureAsync(HCkDkim cHandle, int sigIndex, HCkByteData mimeData);

This method is deprecated. It will be removed in a future version.

Creates an asynchronous task to call the VerifyDomainKeySignature method with the arguments provided. (Async methods are available starting in Chilkat v9.5.0.52.)

Returns NULL on failure

How to Run an Asynchronous Task