hmac_functional#

Compute a keyed HMAC digest of the data arguments in one call.

Shared dispatcher for every hmac_sha* one-shot: 21 Perl-level names (7 algorithms × 3 encodings) all land here. The name selects both the underlying SHA algorithm and the output encoding:

hmac_sha1, hmac_sha256, … return the raw binary MAC.
hmac_sha1_hex, hmac_sha256_hex, … return the lowercase hex MAC.
hmac_sha1_base64, hmac_sha256_base64, … return the unpadded Base64 MAC.

Argument shape matches upstream: the last argument is the key, every preceding argument is message data (concatenated byte-wise). With a single argument the key is that argument and the message is empty. With no arguments both key and message are empty.

Synopsis#

use Digest::SHA qw(hmac_sha256_hex hmac_sha1_base64);
my $tag = hmac_sha256_hex($message, $key);
my $b64 = hmac_sha1_base64(@chunks, $key);

What you get back#

A plain scalar. The raw-binary form has the fixed length of the chosen algorithm’s digest (20 bytes for SHA-1, 32 for SHA-256, 64 for SHA-512, and so on). The _hex form is twice that length; the _base64 form is the unpadded Base64 encoding.

Examples#

use Digest::SHA qw(hmac_sha256_hex);
my $mac = hmac_sha256_hex("Hi There", "\x0b" x 20);

## b0344c61d8db38535ca8afceaf0bf12b881dc200c9833da726e9376c2e32cff7

use Digest::SHA qw(hmac_sha1_hex);

## Concatenated message: "Hello, " + "world!"

my $mac = hmac_sha1_hex("Hello, ", "world!", $shared_secret);

use Digest::SHA qw(hmac_sha512_base64);
my $cookie_tag = hmac_sha512_base64($cookie_body, $server_secret);

use Digest::SHA qw(hmac_sha256_hex);
my $tag = hmac_sha256_hex($key);   # one arg: key only, empty message

Edge cases#

Single-argument calls treat the sole argument as the key and hash an empty message. This matches upstream behaviour and is rarely what you want — pass message and key explicitly.
Keys longer than the algorithm’s block size are hashed down to digest size before use (standard HMAC key reduction).
Wide characters in either key or data croak with Wide character in subroutine entry.

Differences from upstream#

Fully compatible with upstream Digest::SHA 6.04.