util-lib: update dns_name_to_wire_format() to optionally generate DNSSEC canonical names

We'll need this later when putting together RR serializations to
checksum.

4 files changed, 18 insertions, 4 deletions

diff --git a/src/libsystemd-network/sd-dhcp-client.c b/src/libsystemd-network/sd-dhcp-client.c
index a03c8460a8..4521f8f0b1 100644
--- a/src/libsystemd-network/sd-dhcp-client.c
+++ b/src/libsystemd-network/sd-dhcp-client.c
@@ -554,7 +554,7 @@ static int client_append_fqdn_option(DHCPMessage *message, size_t optlen, size_t
         buffer[1] = 0;                 /* RCODE1 (deprecated) */
         buffer[2] = 0;                 /* RCODE2 (deprecated) */
 
-        r = dns_name_to_wire_format(fqdn, buffer + 3, sizeof(buffer) - 3);
+        r = dns_name_to_wire_format(fqdn, buffer + 3, sizeof(buffer) - 3, false);
         if (r > 0)
                 r = dhcp_option_append(message, optlen, optoffset, 0,
                                        DHCP_OPTION_FQDN, 3 + r, buffer);
diff --git a/src/shared/dns-domain.c b/src/shared/dns-domain.c
index 5ac8ad5b7a..429aa6d2cb 100644
--- a/src/shared/dns-domain.c
+++ b/src/shared/dns-domain.c
@@ -865,7 +865,7 @@ bool dns_name_is_single_label(const char *name) {
 }
 
 /* Encode a domain name according to RFC 1035 Section 3.1, without compression */
-int dns_name_to_wire_format(const char *domain, uint8_t *buffer, size_t len) {
+int dns_name_to_wire_format(const char *domain, uint8_t *buffer, size_t len, bool canonical) {
         uint8_t *label_length, *out;
         int r;
 
@@ -890,6 +890,20 @@ int dns_name_to_wire_format(const char *domain, uint8_t *buffer, size_t len) {
                 if (r < 0)
                         return r;
 
+                if (canonical) {
+                        size_t i;
+
+                        /* Optionally, output the name in DNSSEC
+                         * canonical format, as described in RFC 4034,
+                         * section 6.2. Or in other words: in
+                         * lower-case. */
+
+                        for (i = 0; i < (size_t) r; i++) {
+                                if (out[i] >= 'A' && out[i] <= 'Z')
+                                        out[i] = out[i] - 'A' + 'a';
+                        }
+                }
+
                 /* Fill label length, move forward */
                 *label_length = r;
                 out += r;
diff --git a/src/shared/dns-domain.h b/src/shared/dns-domain.h
index 44a9975541..17dab1da18 100644
--- a/src/shared/dns-domain.h
+++ b/src/shared/dns-domain.h
@@ -77,7 +77,7 @@ int dns_name_address(const char *p, int *family, union in_addr_union *a);
 bool dns_name_is_root(const char *name);
 bool dns_name_is_single_label(const char *name);
 
-int dns_name_to_wire_format(const char *domain, uint8_t *buffer, size_t len);
+int dns_name_to_wire_format(const char *domain, uint8_t *buffer, size_t len, bool canonical);
 
 bool dns_srv_type_is_valid(const char *name);
 bool dns_service_name_is_valid(const char *name);
diff --git a/src/test/test-dns-domain.c b/src/test/test-dns-domain.c
index 7f53a8cc56..de003e251c 100644
--- a/src/test/test-dns-domain.c
+++ b/src/test/test-dns-domain.c
@@ -56,7 +56,7 @@ static void test_dns_name_to_wire_format_one(const char *what, const char *expec
         uint8_t buffer[buffer_sz];
         int r;
 
-        r = dns_name_to_wire_format(what, buffer, buffer_sz);
+        r = dns_name_to_wire_format(what, buffer, buffer_sz, false);
         assert_se(r == ret);
 
         if (r < 0)