sign.go

Documentation: github.com/theupdateframework/go-tuf/sign

     1  package sign
     2  
     3  import (
     4  	"encoding/json"
     5  	"errors"
     6  
     7  	"github.com/secure-systems-lab/go-securesystemslib/cjson"
     8  	"github.com/theupdateframework/go-tuf/data"
     9  	"github.com/theupdateframework/go-tuf/pkg/keys"
    10  )
    11  
    12  const maxSignatures = 1024
    13  
    14  // MakeSignatures creates data.Signatures for canonical using signer k.
    15  //
    16  // There will be one data.Signature for each of k's IDs, each wih the same
    17  // signature data.
    18  func MakeSignatures(canonical []byte, k keys.Signer) ([]data.Signature, error) {
    19  	sigData, err := k.SignMessage(canonical)
    20  	if err != nil {
    21  		return nil, err
    22  	}
    23  
    24  	ids := k.PublicData().IDs()
    25  	signatures := make([]data.Signature, 0, len(ids))
    26  	for _, id := range ids {
    27  		signatures = append(signatures, data.Signature{
    28  			KeyID:     id,
    29  			Signature: sigData,
    30  		})
    31  	}
    32  
    33  	return signatures, nil
    34  }
    35  
    36  // Sign signs the to-be-signed part of s using the signer k.
    37  //
    38  // The new signature(s) (one for each of k's key IDs) are appended to
    39  // s.Signatures. Existing signatures for the Key IDs are replaced.
    40  func Sign(s *data.Signed, k keys.Signer) error {
    41  	canonical, err := cjson.EncodeCanonical(s.Signed)
    42  	if err != nil {
    43  		return err
    44  	}
    45  
    46  	size := len(s.Signatures)
    47  	if size > maxSignatures-1 {
    48  		return errors.New("value too large")
    49  	}
    50  	signatures := make([]data.Signature, 0, size+1)
    51  	for _, oldSig := range s.Signatures {
    52  		if !k.PublicData().ContainsID(oldSig.KeyID) {
    53  			signatures = append(signatures, oldSig)
    54  		}
    55  	}
    56  
    57  	newSigs, err := MakeSignatures(canonical, k)
    58  	if err != nil {
    59  		return err
    60  	}
    61  	signatures = append(signatures, newSigs...)
    62  
    63  	s.Signatures = signatures
    64  	return nil
    65  }
    66  
    67  func Marshal(v interface{}, keys ...keys.Signer) (*data.Signed, error) {
    68  	b, err := json.Marshal(v)
    69  	if err != nil {
    70  		return nil, err
    71  	}
    72  	s := &data.Signed{Signed: b, Signatures: make([]data.Signature, 0)}
    73  	for _, k := range keys {
    74  		if err := Sign(s, k); err != nil {
    75  			return nil, err
    76  		}
    77  
    78  	}
    79  	return s, nil
    80  }
    81
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