From: Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>
Date: Fri, 14 May 2021 15:03:30 +0000 (+0200)
Subject: resolved: use narrower types for label counts in rr
X-Git-Tag: v249-rc1~203^2~5
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=98e80bf9d2f069e58283a74a6cfd8bf69578af31;p=thirdparty%2Fsystemd.git

resolved: use narrower types for label counts in rr

Order will be adjusted later to remove holes.
---

diff --git a/src/resolve/resolved-dns-dnssec.c b/src/resolve/resolved-dns-dnssec.c
index e191badad5b..70d7837a3a8 100644
--- a/src/resolve/resolved-dns-dnssec.c
+++ b/src/resolve/resolved-dns-dnssec.c
@@ -483,14 +483,14 @@ static int dnssec_rrsig_prepare(DnsResourceRecord *rrsig) {
         const char *name;
         int r;
 
-        /* Checks whether the specified RRSIG RR is somewhat valid, and initializes the .n_skip_labels_source and
-         * .n_skip_labels_signer fields so that we can use them later on. */
+        /* Checks whether the specified RRSIG RR is somewhat valid, and initializes the .n_skip_labels_source
+         * and .n_skip_labels_signer fields so that we can use them later on. */
 
         assert(rrsig);
         assert(rrsig->key->type == DNS_TYPE_RRSIG);
 
         /* Check if this RRSIG RR is already prepared */
-        if (rrsig->n_skip_labels_source != UINT_MAX)
+        if (rrsig->n_skip_labels_source != UINT8_MAX)
                 return 0;
 
         if (rrsig->rrsig.inception > rrsig->rrsig.expiration)
@@ -523,6 +523,7 @@ static int dnssec_rrsig_prepare(DnsResourceRecord *rrsig) {
         if (r == 0)
                 return -EINVAL;
 
+        assert(n_key_labels < UINT8_MAX); /* UINT8_MAX/-1 means unsigned. */
         rrsig->n_skip_labels_source = n_key_labels - rrsig->rrsig.labels;
         rrsig->n_skip_labels_signer = n_key_labels - n_signer_labels;
 
@@ -1291,10 +1292,10 @@ static int nsec3_is_good(DnsResourceRecord *rr, DnsResourceRecord *nsec3) {
 
         /* Ignore NSEC3 RRs generated from wildcards. If these NSEC3 RRs weren't correctly signed we can't make this
          * check (since rr->n_skip_labels_source is -1), but that's OK, as we won't trust them anyway in that case. */
-        if (!IN_SET(rr->n_skip_labels_source, 0, UINT_MAX))
+        if (!IN_SET(rr->n_skip_labels_source, 0, UINT8_MAX))
                 return 0;
         /* Ignore NSEC3 RRs that are located anywhere else than one label below the zone */
-        if (!IN_SET(rr->n_skip_labels_signer, 1, UINT_MAX))
+        if (!IN_SET(rr->n_skip_labels_signer, 1, UINT8_MAX))
                 return 0;
 
         if (!nsec3)
diff --git a/src/resolve/resolved-dns-rr.c b/src/resolve/resolved-dns-rr.c
index 0493faee6b9..e493c32158f 100644
--- a/src/resolve/resolved-dns-rr.c
+++ b/src/resolve/resolved-dns-rr.c
@@ -381,8 +381,8 @@ DnsResourceRecord* dns_resource_record_new(DnsResourceKey *key) {
                 .n_ref = 1,
                 .key = dns_resource_key_ref(key),
                 .expiry = USEC_INFINITY,
-                .n_skip_labels_signer = UINT_MAX,
-                .n_skip_labels_source = UINT_MAX,
+                .n_skip_labels_signer = UINT8_MAX,
+                .n_skip_labels_source = UINT8_MAX,
         };
 
         return rr;
@@ -1258,7 +1258,7 @@ int dns_resource_record_signer(DnsResourceRecord *rr, const char **ret) {
 
         /* Returns the RRset's signer, if it is known. */
 
-        if (rr->n_skip_labels_signer == UINT_MAX)
+        if (rr->n_skip_labels_signer == UINT8_MAX)
                 return -ENODATA;
 
         n = dns_resource_key_name(rr->key);
@@ -1281,7 +1281,7 @@ int dns_resource_record_source(DnsResourceRecord *rr, const char **ret) {
 
         /* Returns the RRset's synthesizing source, if it is known. */
 
-        if (rr->n_skip_labels_source == UINT_MAX)
+        if (rr->n_skip_labels_source == UINT8_MAX)
                 return -ENODATA;
 
         n = dns_resource_key_name(rr->key);
@@ -1315,7 +1315,7 @@ int dns_resource_record_is_synthetic(DnsResourceRecord *rr) {
 
         /* Returns > 0 if the RR is generated from a wildcard, and is not the asterisk name itself */
 
-        if (rr->n_skip_labels_source == UINT_MAX)
+        if (rr->n_skip_labels_source == UINT8_MAX)
                 return -ENODATA;
 
         if (rr->n_skip_labels_source == 0)
diff --git a/src/resolve/resolved-dns-rr.h b/src/resolve/resolved-dns-rr.h
index 43bbcb30735..10c05dd9c30 100644
--- a/src/resolve/resolved-dns-rr.h
+++ b/src/resolve/resolved-dns-rr.h
@@ -4,6 +4,7 @@
 #include <netinet/in.h>
 
 #include "bitmap.h"
+#include "dns-def.h"
 #include "dns-type.h"
 #include "hashmap.h"
 #include "in-addr-util.h"
@@ -98,9 +99,9 @@ struct DnsResourceRecord {
         usec_t expiry; /* RRSIG signature expiry */
 
         /* How many labels to strip to determine "signer" of the RRSIG (aka, the zone). -1 if not signed. */
-        unsigned n_skip_labels_signer;
+        uint8_t n_skip_labels_signer;
         /* How many labels to strip to determine "synthesizing source" of this RR, i.e. the wildcard's immediate parent. -1 if not signed. */
-        unsigned n_skip_labels_source;
+        uint8_t n_skip_labels_source;
 
         bool unparsable:1;
 
@@ -245,6 +246,9 @@ struct DnsResourceRecord {
         };
 };
 
+/* We use uint8_t for label counts above, and UINT8_MAX/-1 has special meaning. */
+assert_cc(DNS_N_LABELS_MAX < UINT8_MAX);
+
 static inline const void* DNS_RESOURCE_RECORD_RDATA(const DnsResourceRecord *rr) {
         if (!rr)
                 return NULL;