# dkim_get_sigsubstring()

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SYNOPSIS

    #include <dkim.h>
    DKIM_STAT dkim_get_sigsubstring(
    	DKIM *dkim,
    	DKIM_SIGINFO *sig,
            char *buf,
            size_t *buflen
    );

Retrieve a minimal substring of the actual signature (i.e. the "b=" tag value) from a specified signature, of sufficient length to identify this signature uniquely from others.

DESCRIPTION

Called When | `dkim_getsig()` is called after `dkim_eom()` when `dkim` is a verifying handle, i.e. one returned by an earlier call to `dkim_verify()`.

ARGUMENTS

Argument | Description
--- | ---
dkim | Message-specific handle, returned by `dkim_sign()`.
sig | Signature-specific handle, retrieved by a prior call to `dkim_getsiglist()`.
buf | Pointer to a buffer that should receive a minimal unique substring of the digital signature portion of `sig`.
buflen | The address of an integer that should contain the number of bytes available at `buf` and will be updated to contain the number of bytes needed to produce a minimal substring.

NOTES

- No fewer than eight bytes will be requested. If two or more signatures have the same initial byte sequences in "b=" tags, larger lengths will be required, theoretically requiring as much as the entire signature.
- If the size of `buf` is too small to contain the minimal substring of `sig`, `DKIM_STAT_NORESOURCE` is returned, `buflen` will be updated to indicate the minimal number of bytes required, and `buf` will be unchanged.
- The string written to `buf` will be NULL-terminated unless the provided buffer is exactly the right size to contain the output.

Copyright (c) 2005, 2007 Sendmail, Inc. and its suppliers. All rights reserved.
Copyright (c) 2010, 2011, The OpenDKIM Project. All rights reserved.
By using this file, you agree to the terms and conditions set forth in the respective licenses.