pki: Print and document the name constraint type for DNS or email constraints

As email constraints may be for a specific host, it is not clear from the
name itself if it is a DNS or email constraint.

src/pki/commands/print.c

@@ -65,6 +65,22 @@ static void print_key(private_key_t *key)
 	}
 }
 
+/**
+ * Get a prefix for a named constraint identity type
+ */
+static char* get_type_pfx(identification_t *id)
+{
+	switch (id->get_type(id))
+	{
+		case ID_RFC822_ADDR:
+			return "email:";
+		case ID_FQDN:
+			return "dns:";
+		default:
+			return "";
+	}
+}
+
 /**
  * Print X509 specific certificate information
  */
@@ -202,7 +218,7 @@ static void print_x509(x509_t *x509)
 			printf("Permitted NameConstraints:\n");
 			first = FALSE;
 		}
-		printf("           %Y\n", id);
+		printf("           %s%Y\n", get_type_pfx(id), id);
 	}
 	enumerator->destroy(enumerator);
 	first = TRUE;
@@ -214,7 +230,7 @@ static void print_x509(x509_t *x509)
 			printf("Excluded NameConstraints:\n");
 			first = FALSE;
 		}
-		printf("           %Y\n", id);
+		printf("           %s%Y\n", get_type_pfx(id), id);
 	}
 	enumerator->destroy(enumerator);
 

src/pki/man/pki---issue.1.in

@@ -147,10 +147,22 @@ times.
 Set path length constraint.
 .TP
 .BI "\-n, \-\-nc-permitted " name
-Add permitted NameConstraint extension to certificate.
+Add permitted NameConstraint extension to certificate. For DNS or email
+constraints, the identity type is not always detectable by the given name. Use
+the
+.B dns:
+or
+.B email:
+prefix to force a constraint type.
 .TP
 .BI "\-N, \-\-nc-excluded " name
-Add excluded NameConstraint extension to certificate.
+Add excluded NameConstraint extension to certificate. For DNS or email
+constraints, the identity type is not always detectable by the given name. Use
+the
+.B dns:
+or
+.B email:
+prefix to force a constraint type.
 .TP
 .BI "\-M, \-\-policy-mapping " issuer-oid:subject-oid
 Add policyMapping from issuer to subject OID.

src/pki/man/pki---self.1.in

@@ -127,10 +127,22 @@ times.
 Set path length constraint.
 .TP
 .BI "\-n, \-\-nc-permitted " name
-Add permitted NameConstraint extension to certificate.
+Add permitted NameConstraint extension to certificate. For DNS or email
+constraints, the identity type is not always detectable by the given name. Use
+the
+.B dns:
+or
+.B email:
+prefix to force a constraint type.
 .TP
 .BI "\-N, \-\-nc-excluded " name
-Add excluded NameConstraint extension to certificate.
+Add excluded NameConstraint extension to certificate. For DNS or email
+constraints, the identity type is not always detectable by the given name. Use
+the
+.B dns:
+or
+.B email:
+prefix to force a constraint type.
 .TP
 .BI "\-M, \-\-policy-mapping " issuer-oid:subject-oid
 Add policyMapping from issuer to subject OID.