Replace fmt.Errorf with custom error types in pkg/gen/caps

Author: xaionaro@dx.center

pkg/gen/caps/err_capability_conflict.go

@@ -0,0 +1,17 @@
+package caps
+
+// ErrCapabilityConflict is returned when capability flags violate
+// the mutual-dependency or exclusivity rules defined in the SPDM spec.
+type ErrCapabilityConflict struct {
+	Msg string
+}
+
+// Error implements the error interface.
+func (e *ErrCapabilityConflict) Error() string {
+	return e.Msg
+}
+
+// Unwrap implements the errors unwrapping interface.
+func (e *ErrCapabilityConflict) Unwrap() error {
+	return nil
+}

pkg/gen/caps/validate.go

@@ -1,7 +1,5 @@
 package caps
 
-import "fmt"
-
 // ValidateResponderCaps checks that responder capability flags satisfy
 // the mandatory dependencies defined in DSP0274 Section 10.4, Table 15.
 func ValidateResponderCaps(c ResponderCaps) error {
@@ -20,19 +18,19 @@ func validateResponderSessionCaps(c ResponderCaps) error {
 	// ENCRYPT_CAP and MAC_CAP must both be set or both clear.
 	if hasEncrypt != hasMAC {
 		if hasEncrypt {
-			return fmt.Errorf("ENCRYPT_CAP requires MAC_CAP to also be set")
+			return &ErrCapabilityConflict{Msg: "ENCRYPT_CAP requires MAC_CAP to also be set"}
 		}
-		return fmt.Errorf("MAC_CAP requires ENCRYPT_CAP to also be set")
+		return &ErrCapabilityConflict{Msg: "MAC_CAP requires ENCRYPT_CAP to also be set"}
 	}
 
 	// If ENCRYPT_CAP or MAC_CAP is set, KEY_EX_CAP or PSK_CAP must be set.
 	if (hasEncrypt || hasMAC) && !c.HasKeyExCap() && !c.HasPSKCap() {
-		return fmt.Errorf("ENCRYPT_CAP/MAC_CAP require KEY_EX_CAP or PSK_CAP")
+		return &ErrCapabilityConflict{Msg: "ENCRYPT_CAP/MAC_CAP require KEY_EX_CAP or PSK_CAP"}
 	}
 
 	// MEAS_FRESH_CAP requires MEAS_CAP (NoSig or Sig).
 	if c.HasMeasFreshCap() && !c.HasMeasCap() {
-		return fmt.Errorf("MEAS_FRESH_CAP requires MEAS_CAP")
+		return &ErrCapabilityConflict{Msg: "MEAS_FRESH_CAP requires MEAS_CAP"}
 	}
 
 	return nil
@@ -44,24 +42,24 @@ func validateResponderSessionCaps(c ResponderCaps) error {
 func validateResponderAuthCaps(c ResponderCaps) error {
 	// CERT_CAP and PUB_KEY_ID_CAP are mutually exclusive.
 	if c.HasCertCap() && c.HasPubKeyIDCap() {
-		return fmt.Errorf("CERT_CAP and PUB_KEY_ID_CAP are mutually exclusive")
+		return &ErrCapabilityConflict{Msg: "CERT_CAP and PUB_KEY_ID_CAP are mutually exclusive"}
 	}
 
 	// CHAL_CAP requires CERT_CAP or PUB_KEY_ID_CAP.
 	if c.HasChalCap() && !c.HasCertCap() && !c.HasPubKeyIDCap() {
-		return fmt.Errorf("CHAL_CAP requires CERT_CAP or PUB_KEY_ID_CAP")
+		return &ErrCapabilityConflict{Msg: "CHAL_CAP requires CERT_CAP or PUB_KEY_ID_CAP"}
 	}
 
 	hasKeyEx := c.HasKeyExCap()
 
 	// MUT_AUTH_CAP requires KEY_EX_CAP or PSK_CAP.
 	if c.HasMutAuthCap() && !hasKeyEx && !c.HasPSKCap() {
-		return fmt.Errorf("MUT_AUTH_CAP requires KEY_EX_CAP or PSK_CAP")
+		return &ErrCapabilityConflict{Msg: "MUT_AUTH_CAP requires KEY_EX_CAP or PSK_CAP"}
 	}
 
 	// HANDSHAKE_IN_THE_CLEAR_CAP requires KEY_EX_CAP.
 	if c.HasHandshakeInTheClearCap() && !hasKeyEx {
-		return fmt.Errorf("HANDSHAKE_IN_THE_CLEAR_CAP requires KEY_EX_CAP")
+		return &ErrCapabilityConflict{Msg: "HANDSHAKE_IN_THE_CLEAR_CAP requires KEY_EX_CAP"}
 	}
 
 	return nil
@@ -85,14 +83,14 @@ func validateRequesterSessionCaps(c RequesterCaps) error {
 	// ENCRYPT_CAP and MAC_CAP must both be set or both clear.
 	if hasEncrypt != hasMAC {
 		if hasEncrypt {
-			return fmt.Errorf("ENCRYPT_CAP requires MAC_CAP to also be set")
+			return &ErrCapabilityConflict{Msg: "ENCRYPT_CAP requires MAC_CAP to also be set"}
 		}
-		return fmt.Errorf("MAC_CAP requires ENCRYPT_CAP to also be set")
+		return &ErrCapabilityConflict{Msg: "MAC_CAP requires ENCRYPT_CAP to also be set"}
 	}
 
 	// If ENCRYPT_CAP or MAC_CAP is set, KEY_EX_CAP or PSK_CAP must be set.
 	if (hasEncrypt || hasMAC) && !c.HasKeyExCap() && !c.HasPSKCap() {
-		return fmt.Errorf("ENCRYPT_CAP/MAC_CAP require KEY_EX_CAP or PSK_CAP")
+		return &ErrCapabilityConflict{Msg: "ENCRYPT_CAP/MAC_CAP require KEY_EX_CAP or PSK_CAP"}
 	}
 
 	return nil
@@ -104,24 +102,24 @@ func validateRequesterSessionCaps(c RequesterCaps) error {
 func validateRequesterAuthCaps(c RequesterCaps) error {
 	// CERT_CAP and PUB_KEY_ID_CAP are mutually exclusive.
 	if c.HasCertCap() && c.HasPubKeyIDCap() {
-		return fmt.Errorf("CERT_CAP and PUB_KEY_ID_CAP are mutually exclusive")
+		return &ErrCapabilityConflict{Msg: "CERT_CAP and PUB_KEY_ID_CAP are mutually exclusive"}
 	}
 
 	// CHAL_CAP requires CERT_CAP or PUB_KEY_ID_CAP.
 	if c.HasChalCap() && !c.HasCertCap() && !c.HasPubKeyIDCap() {
-		return fmt.Errorf("CHAL_CAP requires CERT_CAP or PUB_KEY_ID_CAP")
+		return &ErrCapabilityConflict{Msg: "CHAL_CAP requires CERT_CAP or PUB_KEY_ID_CAP"}
 	}
 
 	hasKeyEx := c.HasKeyExCap()
 
 	// MUT_AUTH_CAP requires KEY_EX_CAP or PSK_CAP.
 	if c.HasMutAuthCap() && !hasKeyEx && !c.HasPSKCap() {
-		return fmt.Errorf("MUT_AUTH_CAP requires KEY_EX_CAP or PSK_CAP")
+		return &ErrCapabilityConflict{Msg: "MUT_AUTH_CAP requires KEY_EX_CAP or PSK_CAP"}
 	}
 
 	// HANDSHAKE_IN_THE_CLEAR_CAP requires KEY_EX_CAP.
 	if c.HasHandshakeInTheClearCap() && !hasKeyEx {
-		return fmt.Errorf("HANDSHAKE_IN_THE_CLEAR_CAP requires KEY_EX_CAP")
+		return &ErrCapabilityConflict{Msg: "HANDSHAKE_IN_THE_CLEAR_CAP requires KEY_EX_CAP"}
 	}
 
 	return nil