Options¶

Every algorithm choice and every relaxation is made per call through these structs. Their zero values select the defaults listed here. Construct them with field names, because new fields may be added, as the Compatibility policy describes.

SignerInfoConfig¶

Passed to AddSigner, AddSignerChain and SignWithoutAttr. SignWithoutAttr ignores it.

Field	Type	Default	Meaning
`ExtraSignedAttributes`	`[]Attribute`	none	Signed attributes added after content-type, message-digest and signing-time
`ExtraUnsignedAttributes`	`[]Attribute`	none	Attributes outside the signature
`SigningTime`	`time.Time`	the current time	Value of the signing-time attribute, stored in UTC

Attribute has a Type (an asn1.ObjectIdentifier) and a Value that encoding/asn1 must be able to encode.

SignedData settings¶

Two methods on SignedData apply to the signers added after the call:

Method	Default	Meaning
`SetDigestAlgorithm(oid)`	`OIDDigestAlgorithmSHA256`	Digest of the content and the signed attributes
`SetEncryptionAlgorithm(oid)`	derived from the key and the digest	Signature algorithm identifier. For RSA keys `OIDEncryptionAlgorithmRSA` is also accepted. Any other value must equal the derived one

VerifyOptions¶

Passed to Verify.

Field	Type	Default	Meaning
`Roots`	`*x509.CertPool`	nil, no chain check	Trust anchors for the signer certificate chains
`Intermediates`	`[]*x509.Certificate`	none	Certificates that may complete a chain, in addition to those in the message
`SignerCertificates`	`[]*x509.Certificate`	none	Signer certificates for messages that do not carry them
`CurrentTime`	`time.Time`	the current time	Time at which chains are checked
`VerifyAtSigningTime`	`bool`	false	Check chains at the signing-time attribute when `CurrentTime` is zero
`KeyUsages`	`[]x509.ExtKeyUsage`	any usage	Extended key usages to accept. The chain must allow at least one of them
`AllowMD5`	`bool`	false	Accept signers that use the MD5 digest

Intermediates, CurrentTime, VerifyAtSigningTime and KeyUsages matter only when Roots is set. Verification explains each check.

EncryptOptions¶

Passed to Encrypt and EncryptUsingPSK.

Field	Type	Default	Meaning
`ContentEncryption`	`ContentEncryptionAlgorithm`	`AES128CBC`	Content cipher
`KeyEncryption`	`KeyEncryptionAlgorithm`	`RSAPKCS1v15`	Key transport for each recipient. `EncryptUsingPSK` ignores it
`OAEPHash`	`crypto.Hash`	`crypto.SHA256`	RSAES-OAEP hash and MGF1 hash. Used only with `RSAOAEP`

OAEPHash accepts crypto.SHA1, crypto.SHA224, crypto.SHA256, crypto.SHA384 and crypto.SHA512. Another value fails with ErrUnsupportedKeyEncryptionHash.

DecryptOptions¶

Passed to Decrypt and DecryptUsingPSK.

Field	Type	Default	Meaning
`ContentEncryptionAlgorithms`	`[]ContentEncryptionAlgorithm`	`DefaultContentDecryptionAlgorithms`	Content ciphers to accept

DefaultContentDecryptionAlgorithms is AES128CBC, AES192CBC, AES256CBC and DESEDE3CBC. A non-empty list replaces it, so add the defaults to the list when extending it, as Encryption and decryption shows. The key transport is read from the message and needs no option.

DefaultContentDecryptionAlgorithms is an exported variable that every Decrypt and DecryptUsingPSK call reads. Do not modify it. Pass ContentEncryptionAlgorithms instead.

ParseOptions¶

Passed to ParseWithOptions. Parse uses the zero value.

Field	Type	Default	Meaning
`LegacyCertificateParser`	`bool`	false	When `crypto/x509` refuses a certificate because its authority key identifier is marked critical, parse every certificate of the message again with a copy of the Go 1.23 parser

PKCS7.Hasher¶

A parsed message has a Hasher field. When it is set, Verify calls its Hash(crypto.Hash, io.Reader) ([]byte, error) method to compute the content digest that the message-digest attribute is compared with. It is nil by default, which uses the standard library hash.