listening to "garoche ta sacoche"

contract/best_contract.go

@@ -0,0 +1,79 @@
+package contract
+
+import (
+	"errors"
+	"strings"
+)
+
+type AcceptedContract struct {
+	Hash                  string
+	BlockCipher           string
+	BlockCipherMode       string
+	AsymetricCryptography string
+}
+
+func listContains(lst []string, elm string) bool {
+	for _, elm_ := range lst {
+		if elm == elm_ {
+			return true
+		}
+	}
+	return false
+}
+
+func joinAsError(msg []string) error {
+	if len(msg) > 0 {
+		return errors.New(strings.Join(msg, "\n"))
+	}
+	return nil
+}
+
+func getFirstItemInList1ThatIsAlsoInList2(lst1, lst2 []string) (string, error) {
+	for _, elm := range lst1 {
+		if listContains(lst2, elm) {
+			return elm, nil
+		}
+	}
+	return "", errors.New("no items in list1 is in list2")
+}
+
+func getBestBlockCipher(prvCtr *PrivateContract, pubCtr *PublicContract) (string, error) {
+	if b, err := getFirstItemInList1ThatIsAlsoInList2(pubCtr.AcceptedBlockCyphers, prvCtr.AcceptedBlockCyphers); err != nil {
+		return "", errors.New("cannot find a block cypher that satisfy both contracts")
+	} else {
+		return b, nil
+	}
+}
+
+func getBestBlockCipherMode(prvCtr *PrivateContract, pubCtr *PublicContract) (string, error) {
+	if m, err := getFirstItemInList1ThatIsAlsoInList2(pubCtr.AcceptedBlockCypherModes, prvCtr.AcceptedBlockCypherModes); err != nil {
+		return "", errors.New("cannot find a block cypher mode that satisfy both contracts")
+	} else {
+		return m, nil
+	}
+}
+
+func getBestHash(prvCtr *PrivateContract, pubCtr *PublicContract) (string, error) {
+	if h, err := getFirstItemInList1ThatIsAlsoInList2(pubCtr.AcceptedHashes, prvCtr.AcceptedHashes); err != nil {
+		return "", errors.New("cannot find a hash that satisfy both contracts")
+	} else {
+		return h, nil
+	}
+}
+
+func GetAcceptedContract(prvCtr *PrivateContract, pubCtr *PublicContract) (*AcceptedContract, error) {
+	ret := new(AcceptedContract)
+	errs := make([]string, 0, 4)
+	var err error
+	if ret.Hash, err = getBestHash(prvCtr, pubCtr); err != nil {
+		errs = append(errs, err.Error())
+	}
+	if ret.BlockCipher, err = getBestBlockCipher(prvCtr, pubCtr); err != nil {
+		errs = append(errs, err.Error())
+	}
+	if ret.BlockCipherMode, err = getBestBlockCipherMode(prvCtr, pubCtr); err != nil {
+		errs = append(errs, err.Error())
+	}
+
+	return ret, joinAsError(errs)
+}

contract/best_contract_test.go

@@ -0,0 +1,63 @@
+package contract
+
+import (
+	"testing"
+)
+
+func TestGetBestHash(t *testing.T) {
+	prvCtr := new(PrivateContract)
+	pubCtr := new(PublicContract)
+
+	pubCtr.AcceptedHashes = []string{"SHA384", "SHA256", "MD5"}
+	prvCtr.AcceptedHashes = []string{"SHA384", "SHA256"}
+	if h, err := getBestHash(prvCtr, pubCtr); err != nil {
+		t.Error(err)
+	} else if h != "SHA384" {
+		t.Error("bad choosen hash: ", h)
+	}
+	prvCtr.AcceptedHashes = []string{"SHA1", "MD4"}
+	if h, err := getBestHash(prvCtr, pubCtr); err == nil {
+		t.Error("should have an error here")
+	} else if h != "" {
+		t.Error("should not have choosen any hash function here")
+	}
+}
+
+func TestGetFirstItemInList1ThatIsAlsoInList2(t *testing.T) {
+	lst1 := []string{"a", "b", "c"}
+	lst2 := []string{"b", "c"}
+	if c, err := getFirstItemInList1ThatIsAlsoInList2(lst1, lst2); c != "b" || err != nil {
+		t.Fail()
+	}
+	lst2 = []string{"d", "e"}
+	if c, err := getFirstItemInList1ThatIsAlsoInList2(lst1, lst2); c != "" || err == nil {
+		t.Fail()
+	}
+}
+
+func TestGetAcceptedContract(t *testing.T) {
+	prvCtr := new(PrivateContract)
+	pubCtr := new(PublicContract)
+
+	pubCtr.AcceptedHashes = []string{"SHA384", "SHA256", "MD5"}
+	prvCtr.AcceptedHashes = []string{"SHA384", "SHA256"}
+
+	pubCtr.AcceptedBlockCyphers = []string{"aes", "des"}
+	prvCtr.AcceptedBlockCyphers = []string{"aes"}
+
+	pubCtr.AcceptedBlockCypherModes = []string{"ofb"}
+	prvCtr.AcceptedBlockCypherModes = []string{"ofb"}
+
+	ac, err := GetAcceptedContract(prvCtr, pubCtr)
+	if err != nil {
+		t.Error(err)
+		return
+	}
+	if ac.Hash != "SHA384" {
+		t.Error("bad hash")
+	}
+	if ac.BlockCipher != "aes" {
+		t.Error("bad block cipher")
+	}
+
+}

contract/public_contract.go

@@ -5,7 +5,8 @@ import (
 )
 
 type PublicContract struct {
-	AcceptedHashes      []string             `yaml:"accepted_hashes" json:"accepted_hashes"`
-	AcceptedBlockCypher []string             `yaml:"accepted_block_cypher" json:"accepted_block_cypher"`
-	RSAPublicKey        []*keys.RSAPublicKey `yaml:"rsa_public_key, omitempty" json:"rsa_public_key,omitempty"`
+	AcceptedHashes           []string             `yaml:"accepted_hashes" json:"accepted_hashes"`
+	AcceptedBlockCyphers     []string             `yaml:"accepted_block_cypher" json:"accepted_block_cypher"`
+	AcceptedBlockCypherModes []string             `yaml:"accepted_block_cypher_mode" json:"accepted_block_cypher_mode"`
+	RSAPublicKey             []*keys.RSAPublicKey `yaml:"rsa_public_key, omitempty" json:"rsa_public_key,omitempty"`
 }

contract/public_contract_test.go

@@ -36,9 +36,9 @@ func expectJson(c *PublicContract, jsonData string) error {
 
 func TestSimpleJsonification(t *testing.T) {
 	c := &PublicContract{
-		AcceptedHashes:      []string{"sha246"},
-		AcceptedBlockCypher: []string{"aes"},
-		RSAPublicKey:        []*keys.RSAPublicKey{&keys.RSAPublicKey{helper.B(12), 3}},
+		AcceptedHashes:       []string{"sha246"},
+		AcceptedBlockCyphers: []string{"aes"},
+		RSAPublicKey:         []*keys.RSAPublicKey{&keys.RSAPublicKey{helper.B(12), 3}},
 	}
 	if err := assertJSONMarshalling(c); err != nil {
 		t.Error(err)
@@ -47,9 +47,9 @@ func TestSimpleJsonification(t *testing.T) {
 
 func TestEmptyRSAPublicKey(t *testing.T) {
 	c := &PublicContract{
-		AcceptedHashes:      []string{"sha246"},
-		AcceptedBlockCypher: []string{"aes"},
-		RSAPublicKey:        []*keys.RSAPublicKey{&keys.RSAPublicKey{helper.B(12), 3}},
+		AcceptedHashes:       []string{"sha246"},
+		AcceptedBlockCyphers: []string{"aes"},
+		RSAPublicKey:         []*keys.RSAPublicKey{&keys.RSAPublicKey{helper.B(12), 3}},
 	}
 	jsonData := `{
 		"accepted_hashes": ["sha246"],