resolve: unify memdup() code when parsing RRs

Let's make dns_packet_read_public_key() more generic by renaming it to
dns_packet_read_memdup() (which more accurately describes what it
does...). Then, patch all cases where we memdup() RR data to use this
new call.

This specifically checks for zero-length objects, and handles them
gracefully. It will set zero length payload fields as a result.

Special care should be taken to ensure that any code using this call
can handle the returned allocated field to be NULL if the size is
specified as 0!

1 files changed, 3 insertions, 3 deletions

diff --git a/src/resolve/resolved-dns-rr.c b/src/resolve/resolved-dns-rr.c
index 859b3f7339..e489688b85 100644
--- a/src/resolve/resolved-dns-rr.c
+++ b/src/resolve/resolved-dns-rr.c
@@ -776,7 +776,7 @@ int dns_resource_record_to_string(const DnsResourceRecord *rr, char **ret) {
         case DNS_TYPE_NSEC3: {
                 _cleanup_free_ char *salt = NULL, *hash = NULL;
 
-                if (rr->nsec3.salt_size) {
+                if (rr->nsec3.salt_size > 0) {
                         salt = hexmem(rr->nsec3.salt, rr->nsec3.salt_size);
                         if (!salt)
                                 return -ENOMEM;
@@ -795,7 +795,7 @@ int dns_resource_record_to_string(const DnsResourceRecord *rr, char **ret) {
                              rr->nsec3.algorithm,
                              rr->nsec3.flags,
                              rr->nsec3.iterations,
-                             rr->nsec3.salt_size ? salt : "-",
+                             rr->nsec3.salt_size > 0 ? salt : "-",
                              hash,
                              t);
                 if (r < 0)
@@ -809,7 +809,7 @@ int dns_resource_record_to_string(const DnsResourceRecord *rr, char **ret) {
                 if (!t)
                         return -ENOMEM;
 
-                r = asprintf(&s, "%s \\# %"PRIu8" %s", k, rr->generic.size, t);
+                r = asprintf(&s, "%s \\# %zu %s", k, rr->generic.size, t);
                 if (r < 0)
                         return -ENOMEM;
                 break;