Imports of package pkcs7

PathSynopsis
crypto/x509Package x509 implements a subset of the X.509 standard.
crypto/x509/pkixPackage pkix contains shared, low level structures used for ASN.1 parsing and serialization of X.509 certificates, CRL and OCSP.
encoding/asn1Package asn1 implements parsing of DER-encoded ASN.1 data structures, as defined in ITU-T Rec X.690.
errorsPackage errors implements functions to manipulate errors.
github.com/cloudflare/cfssl/errorsPackage errors provides error types returned in CF SSL.