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- Fix CVE-2024-8508, unbounded name compression could lead to denial of
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@gthess
gthess committed Oct 3, 2024
1 parent 01883fb commit b7c61d7
Showing 1 changed file with 46 additions and 31 deletions.
77 changes: 46 additions & 31 deletions util/data/msgencode.c
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Original file line number Diff line number Diff line change
Expand Up @@ -62,6 +62,10 @@
#define RETVAL_TRUNC -4
/** return code that means all is peachy keen. Equal to DNS rcode NOERROR */
#define RETVAL_OK 0
/** Max compressions we are willing to perform; more than that will result
* in semi-compressed messages, or truncated even on TCP for huge messages, to
* avoid locking the CPU for long */
#define MAX_COMPRESSION_PER_MESSAGE 120

/**
* Data structure to help domain name compression in outgoing messages.
Expand Down Expand Up @@ -284,15 +288,17 @@ write_compressed_dname(sldns_buffer* pkt, uint8_t* dname, int labs,

/** compress owner name of RR, return RETVAL_OUTMEM RETVAL_TRUNC */
static int
compress_owner(struct ub_packed_rrset_key* key, sldns_buffer* pkt,
struct regional* region, struct compress_tree_node** tree,
size_t owner_pos, uint16_t* owner_ptr, int owner_labs)
compress_owner(struct ub_packed_rrset_key* key, sldns_buffer* pkt,
struct regional* region, struct compress_tree_node** tree,
size_t owner_pos, uint16_t* owner_ptr, int owner_labs,
size_t* compress_count)
{
struct compress_tree_node* p;
struct compress_tree_node** insertpt = NULL;
if(!*owner_ptr) {
/* compress first time dname */
if((p = compress_tree_lookup(tree, key->rk.dname,
if(*compress_count < MAX_COMPRESSION_PER_MESSAGE &&
(p = compress_tree_lookup(tree, key->rk.dname,
owner_labs, &insertpt))) {
if(p->labs == owner_labs)
/* avoid ptr chains, since some software is
Expand All @@ -301,6 +307,7 @@ compress_owner(struct ub_packed_rrset_key* key, sldns_buffer* pkt,
if(!write_compressed_dname(pkt, key->rk.dname,
owner_labs, p))
return RETVAL_TRUNC;
(*compress_count)++;
/* check if typeclass+4 ttl + rdatalen is available */
if(sldns_buffer_remaining(pkt) < 4+4+2)
return RETVAL_TRUNC;
Expand All @@ -313,7 +320,8 @@ compress_owner(struct ub_packed_rrset_key* key, sldns_buffer* pkt,
if(owner_pos <= PTR_MAX_OFFSET)
*owner_ptr = htons(PTR_CREATE(owner_pos));
}
if(!compress_tree_store(key->rk.dname, owner_labs,
if(*compress_count < MAX_COMPRESSION_PER_MESSAGE &&
!compress_tree_store(key->rk.dname, owner_labs,
owner_pos, region, p, insertpt))
return RETVAL_OUTMEM;
} else {
Expand All @@ -333,20 +341,24 @@ compress_owner(struct ub_packed_rrset_key* key, sldns_buffer* pkt,

/** compress any domain name to the packet, return RETVAL_* */
static int
compress_any_dname(uint8_t* dname, sldns_buffer* pkt, int labs,
struct regional* region, struct compress_tree_node** tree)
compress_any_dname(uint8_t* dname, sldns_buffer* pkt, int labs,
struct regional* region, struct compress_tree_node** tree,
size_t* compress_count)
{
struct compress_tree_node* p;
struct compress_tree_node** insertpt = NULL;
size_t pos = sldns_buffer_position(pkt);
if((p = compress_tree_lookup(tree, dname, labs, &insertpt))) {
if(*compress_count < MAX_COMPRESSION_PER_MESSAGE &&
(p = compress_tree_lookup(tree, dname, labs, &insertpt))) {
if(!write_compressed_dname(pkt, dname, labs, p))
return RETVAL_TRUNC;
(*compress_count)++;
} else {
if(!dname_buffer_write(pkt, dname))
return RETVAL_TRUNC;
}
if(!compress_tree_store(dname, labs, pos, region, p, insertpt))
if(*compress_count < MAX_COMPRESSION_PER_MESSAGE &&
!compress_tree_store(dname, labs, pos, region, p, insertpt))
return RETVAL_OUTMEM;
return RETVAL_OK;
}
Expand All @@ -364,9 +376,9 @@ type_rdata_compressable(struct ub_packed_rrset_key* key)

/** compress domain names in rdata, return RETVAL_* */
static int
compress_rdata(sldns_buffer* pkt, uint8_t* rdata, size_t todolen,
struct regional* region, struct compress_tree_node** tree,
const sldns_rr_descriptor* desc)
compress_rdata(sldns_buffer* pkt, uint8_t* rdata, size_t todolen,
struct regional* region, struct compress_tree_node** tree,
const sldns_rr_descriptor* desc, size_t* compress_count)
{
int labs, r, rdf = 0;
size_t dname_len, len, pos = sldns_buffer_position(pkt);
Expand All @@ -380,8 +392,8 @@ compress_rdata(sldns_buffer* pkt, uint8_t* rdata, size_t todolen,
switch(desc->_wireformat[rdf]) {
case LDNS_RDF_TYPE_DNAME:
labs = dname_count_size_labels(rdata, &dname_len);
if((r=compress_any_dname(rdata, pkt, labs, region,
tree)) != RETVAL_OK)
if((r=compress_any_dname(rdata, pkt, labs, region,
tree, compress_count)) != RETVAL_OK)
return r;
rdata += dname_len;
todolen -= dname_len;
Expand Down Expand Up @@ -449,7 +461,8 @@ static int
packed_rrset_encode(struct ub_packed_rrset_key* key, sldns_buffer* pkt,
uint16_t* num_rrs, time_t timenow, struct regional* region,
int do_data, int do_sig, struct compress_tree_node** tree,
sldns_pkt_section s, uint16_t qtype, int dnssec, size_t rr_offset)
sldns_pkt_section s, uint16_t qtype, int dnssec, size_t rr_offset,
size_t* compress_count)
{
size_t i, j, owner_pos;
int r, owner_labs;
Expand Down Expand Up @@ -477,9 +490,9 @@ packed_rrset_encode(struct ub_packed_rrset_key* key, sldns_buffer* pkt,
for(i=0; i<data->count; i++) {
/* rrset roundrobin */
j = (i + rr_offset) % data->count;
if((r=compress_owner(key, pkt, region, tree,
owner_pos, &owner_ptr, owner_labs))
!= RETVAL_OK)
if((r=compress_owner(key, pkt, region, tree,
owner_pos, &owner_ptr, owner_labs,
compress_count)) != RETVAL_OK)
return r;
sldns_buffer_write(pkt, &key->rk.type, 2);
sldns_buffer_write(pkt, &key->rk.rrset_class, 2);
Expand All @@ -489,8 +502,8 @@ packed_rrset_encode(struct ub_packed_rrset_key* key, sldns_buffer* pkt,
else sldns_buffer_write_u32(pkt, data->rr_ttl[j]-adjust);
if(c) {
if((r=compress_rdata(pkt, data->rr_data[j],
data->rr_len[j], region, tree, c))
!= RETVAL_OK)
data->rr_len[j], region, tree, c,
compress_count)) != RETVAL_OK)
return r;
} else {
if(sldns_buffer_remaining(pkt) < data->rr_len[j])
Expand All @@ -510,9 +523,9 @@ packed_rrset_encode(struct ub_packed_rrset_key* key, sldns_buffer* pkt,
return RETVAL_TRUNC;
sldns_buffer_write(pkt, &owner_ptr, 2);
} else {
if((r=compress_any_dname(key->rk.dname,
pkt, owner_labs, region, tree))
!= RETVAL_OK)
if((r=compress_any_dname(key->rk.dname,
pkt, owner_labs, region, tree,
compress_count)) != RETVAL_OK)
return r;
if(sldns_buffer_remaining(pkt) <
4+4+data->rr_len[i])
Expand Down Expand Up @@ -544,7 +557,8 @@ static int
insert_section(struct reply_info* rep, size_t num_rrsets, uint16_t* num_rrs,
sldns_buffer* pkt, size_t rrsets_before, time_t timenow,
struct regional* region, struct compress_tree_node** tree,
sldns_pkt_section s, uint16_t qtype, int dnssec, size_t rr_offset)
sldns_pkt_section s, uint16_t qtype, int dnssec, size_t rr_offset,
size_t* compress_count)
{
int r;
size_t i, setstart;
Expand All @@ -560,7 +574,7 @@ insert_section(struct reply_info* rep, size_t num_rrsets, uint16_t* num_rrs,
setstart = sldns_buffer_position(pkt);
if((r=packed_rrset_encode(rep->rrsets[rrsets_before+i],
pkt, num_rrs, timenow, region, 1, 1, tree,
s, qtype, dnssec, rr_offset))
s, qtype, dnssec, rr_offset, compress_count))
!= RETVAL_OK) {
/* Bad, but if due to size must set TC bit */
/* trim off the rrset neatly. */
Expand All @@ -573,7 +587,7 @@ insert_section(struct reply_info* rep, size_t num_rrsets, uint16_t* num_rrs,
setstart = sldns_buffer_position(pkt);
if((r=packed_rrset_encode(rep->rrsets[rrsets_before+i],
pkt, num_rrs, timenow, region, 1, 0, tree,
s, qtype, dnssec, rr_offset))
s, qtype, dnssec, rr_offset, compress_count))
!= RETVAL_OK) {
sldns_buffer_set_position(pkt, setstart);
return r;
Expand All @@ -584,7 +598,7 @@ insert_section(struct reply_info* rep, size_t num_rrsets, uint16_t* num_rrs,
setstart = sldns_buffer_position(pkt);
if((r=packed_rrset_encode(rep->rrsets[rrsets_before+i],
pkt, num_rrs, timenow, region, 0, 1, tree,
s, qtype, dnssec, rr_offset))
s, qtype, dnssec, rr_offset, compress_count))
!= RETVAL_OK) {
sldns_buffer_set_position(pkt, setstart);
return r;
Expand Down Expand Up @@ -677,6 +691,7 @@ reply_info_encode(struct query_info* qinfo, struct reply_info* rep,
struct compress_tree_node* tree = 0;
int r;
size_t rr_offset;
size_t compress_count=0;

sldns_buffer_clear(buffer);
if(udpsize < sldns_buffer_limit(buffer))
Expand Down Expand Up @@ -723,7 +738,7 @@ reply_info_encode(struct query_info* qinfo, struct reply_info* rep,
arep.rrsets = &qinfo->local_alias->rrset;
if((r=insert_section(&arep, 1, &ancount, buffer, 0,
timezero, region, &tree, LDNS_SECTION_ANSWER,
qinfo->qtype, dnssec, rr_offset)) != RETVAL_OK) {
qinfo->qtype, dnssec, rr_offset, &compress_count)) != RETVAL_OK) {
if(r == RETVAL_TRUNC) {
/* create truncated message */
sldns_buffer_write_u16_at(buffer, 6, ancount);
Expand All @@ -738,7 +753,7 @@ reply_info_encode(struct query_info* qinfo, struct reply_info* rep,
/* insert answer section */
if((r=insert_section(rep, rep->an_numrrsets, &ancount, buffer,
0, timenow, region, &tree, LDNS_SECTION_ANSWER, qinfo->qtype,
dnssec, rr_offset)) != RETVAL_OK) {
dnssec, rr_offset, &compress_count)) != RETVAL_OK) {
if(r == RETVAL_TRUNC) {
/* create truncated message */
sldns_buffer_write_u16_at(buffer, 6, ancount);
Expand All @@ -756,7 +771,7 @@ reply_info_encode(struct query_info* qinfo, struct reply_info* rep,
if((r=insert_section(rep, rep->ns_numrrsets, &nscount, buffer,
rep->an_numrrsets, timenow, region, &tree,
LDNS_SECTION_AUTHORITY, qinfo->qtype,
dnssec, rr_offset)) != RETVAL_OK) {
dnssec, rr_offset, &compress_count)) != RETVAL_OK) {
if(r == RETVAL_TRUNC) {
/* create truncated message */
sldns_buffer_write_u16_at(buffer, 8, nscount);
Expand All @@ -773,7 +788,7 @@ reply_info_encode(struct query_info* qinfo, struct reply_info* rep,
if((r=insert_section(rep, rep->ar_numrrsets, &arcount, buffer,
rep->an_numrrsets + rep->ns_numrrsets, timenow, region,
&tree, LDNS_SECTION_ADDITIONAL, qinfo->qtype,
dnssec, rr_offset)) != RETVAL_OK) {
dnssec, rr_offset, &compress_count)) != RETVAL_OK) {
if(r == RETVAL_TRUNC) {
/* no need to set TC bit, this is the additional */
sldns_buffer_write_u16_at(buffer, 10, arcount);
Expand Down

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