attributes.go

Documentation: github.com/sassoftware/relic/lib/pkcs7

     1  //
     2  // Copyright (c) SAS Institute Inc.
     3  //
     4  // Licensed under the Apache License, Version 2.0 (the "License");
     5  // you may not use this file except in compliance with the License.
     6  // You may obtain a copy of the License at
     7  //
     8  //     http://www.apache.org/licenses/LICENSE-2.0
     9  //
    10  // Unless required by applicable law or agreed to in writing, software
    11  // distributed under the License is distributed on an "AS IS" BASIS,
    12  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  // See the License for the specific language governing permissions and
    14  // limitations under the License.
    15  //
    16  
    17  package pkcs7
    18  
    19  import (
    20  	"encoding/asn1"
    21  	"fmt"
    22  )
    23  
    24  type ErrNoAttribute struct {
    25  	ID asn1.ObjectIdentifier
    26  }
    27  
    28  func (e ErrNoAttribute) Error() string {
    29  	return fmt.Sprintf("attribute not found: %s", e.ID)
    30  }
    31  
    32  // marshal authenticated attributes for digesting
    33  func (l *AttributeList) Bytes() ([]byte, error) {
    34  	// needs an explicit SET OF tag but not the class-specific tag from the
    35  	// original struct. see RFC 2315 9.3, 2nd paragraph
    36  	encoded, err := asn1.Marshal(struct {
    37  		A []Attribute `asn1:"set"`
    38  	}{A: *l})
    39  	if err != nil {
    40  		return nil, err
    41  	}
    42  	var raw asn1.RawValue
    43  	if _, err := asn1.Unmarshal(encoded, &raw); err != nil {
    44  		return nil, err
    45  	}
    46  	return raw.Bytes, nil
    47  }
    48  
    49  // unmarshal a single attribute, if it exists
    50  func (l *AttributeList) GetOne(oid asn1.ObjectIdentifier, dest interface{}) error {
    51  	for _, raw := range *l {
    52  		if !raw.Type.Equal(oid) {
    53  			continue
    54  		}
    55  		rest, err := asn1.Unmarshal(raw.Values.Bytes, dest)
    56  		if err != nil {
    57  			return err
    58  		} else if len(rest) != 0 {
    59  			return fmt.Errorf("attribute %s: expected one, found multiple", oid)
    60  		} else {
    61  			return nil
    62  		}
    63  	}
    64  	return ErrNoAttribute{oid}
    65  }
    66  
    67  // create or append to an attribute
    68  func (l *AttributeList) Add(oid asn1.ObjectIdentifier, obj interface{}) error {
    69  	value, err := asn1.Marshal(obj)
    70  	if err != nil {
    71  		return err
    72  	}
    73  	for _, attr := range *l {
    74  		if attr.Type.Equal(oid) {
    75  			attr.Values.Bytes = append(attr.Values.Bytes, value...)
    76  			return nil
    77  		}
    78  	}
    79  	*l = append(*l, Attribute{
    80  		Type: oid,
    81  		Values: asn1.RawValue{
    82  			Class:      asn1.ClassUniversal,
    83  			Tag:        asn1.TagSet,
    84  			IsCompound: true,
    85  			Bytes:      value,
    86  		}})
    87  	return nil
    88  }
    89
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