dnsmasq: CVE-2017-15107

* CVE-2017-15107
A vulnerability was found in Dnsmasq's implementation of DNSSEC.
Wildcard synthesized NSEC records could be improperly interpreted
to prove the non-existence of hostnames that actually exist.

Affects dnsmasq <= 2.78

CVE: CVE-2017-15107
Ref: https://access.redhat.com/security/cve/cve-2017-15107
Signed-off-by: Sinan Kaya <okaya@kernel.org>
Signed-off-by: Armin Kuster <akuster808@gmail.com>

2 files changed, 264 insertions, 0 deletions

diff --git a/meta-networking/recipes-support/dnsmasq/dnsmasq_2.78.bb b/meta-networking/recipes-support/dnsmasq/dnsmasq_2.78.bb
index 4d1dc6e69e..d2465f82d6 100644
--- a/meta-networking/recipes-support/dnsmasq/dnsmasq_2.78.bb
+++ b/meta-networking/recipes-support/dnsmasq/dnsmasq_2.78.bb
@@ -2,6 +2,7 @@ require dnsmasq.inc
 
 SRC_URI += "\
     file://lua.patch \
+    file://CVE-2017-15107.patch \
 "
 
 SRC_URI[dnsmasq-2.78.md5sum] = "3bb97f264c73853f802bf70610150788"
diff --git a/meta-networking/recipes-support/dnsmasq/files/CVE-2017-15107.patch b/meta-networking/recipes-support/dnsmasq/files/CVE-2017-15107.patch
new file mode 100644
index 0000000000..701101bcba
--- /dev/null
+++ b/meta-networking/recipes-support/dnsmasq/files/CVE-2017-15107.patch
@@ -0,0 +1,263 @@
+From 5a56e1b78a753d3295564daddc9ce389cc69fd68 Mon Sep 17 00:00:00 2001
+From: Simon Kelley <simon@thekelleys.org.uk>
+Date: Fri, 19 Jan 2018 12:26:08 +0000
+Subject: [PATCH] DNSSEC fix for wildcard NSEC records. CVE-2017-15107 applies.
+
+It's OK for NSEC records to be expanded from wildcards,
+but in that case, the proof of non-existence is only valid
+starting at the wildcard name, *.<domain> NOT the name expanded
+from the wildcard. Without this check it's possible for an
+attacker to craft an NSEC which wrongly proves non-existence
+in a domain which includes a wildcard for NSEC.
+
+Upstream-Status: Backport [http://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=commit;h=4fe6744a220eddd3f1749b40cac3dfc510787de6]
+CVE: CVE-2017-15107
+Signed-off-by: Sinan Kaya <okaya@kernel.org>
+---
+ CHANGELOG    |  44 +++++++++++++++++++
+ src/dnssec.c | 117 +++++++++++++++++++++++++++++++++++++++++++++------
+ 2 files changed, 147 insertions(+), 14 deletions(-)
+
+diff --git a/CHANGELOG b/CHANGELOG
+index 075fe1a6..5226dce8 100644
+--- a/CHANGELOG
++++ b/CHANGELOG
+@@ -1,3 +1,47 @@
++version 2.79
++       Fix parsing of CNAME arguments, which are confused by extra spaces.
++       Thanks to Diego Aguirre for spotting the bug.
++
++       Where available, use IP_UNICAST_IF or IPV6_UNICAST_IF to bind
++       upstream servers to an interface, rather than SO_BINDTODEVICE.
++       Thanks to Beniamino Galvani for the patch.
++
++       Always return a SERVFAIL answer to DNS queries without the
++       recursion desired bit set, UNLESS acting as an authoritative
++       DNS server. This avoids a potential route to cache snooping.
++
++       Add support for Ed25519 signatures in DNSSEC validation.
++
++       No longer support RSA/MD5 signatures in DNSSEC validation,
++       since these are not secure. This behaviour is mandated in
++       RFC-6944.
++
++       Fix incorrect error exit code from dhcp_release6 utility.
++       Thanks Gaudenz Steinlin for the bug report.
++
++       Use SIGINT (instead of overloading SIGHUP) to turn on DNSSEC
++       time validation when --dnssec-no-timecheck is in use.
++       Note that this is an incompatible change from earlier releases.
++
++       Allow more than one --bridge-interface option to refer to an
++       interface, so that we can use
++       --bridge-interface=int1,alias1
++       --bridge-interface=int1,alias2
++       as an alternative to
++       --bridge-interface=int1,alias1,alias2
++       Thanks to Neil Jerram for work on this.
++
++       Fix for DNSSEC with wildcard-derived NSEC records.
++       It's OK for NSEC records to be expanded from wildcards,
++       but in that case, the proof of non-existence is only valid
++       starting at the wildcard name, *.<domain> NOT the name expanded
++       from the wildcard. Without this check it's possible for an
++       attacker to craft an NSEC which wrongly proves non-existence.
++       Thanks to Ralph Dolmans for finding this, and co-ordinating 
++       the vulnerability tracking and fix release.
++       CVE-2017-15107 applies.
++
++
+ version 2.78
+         Fix logic of appending ".<layer>" to PXE basename. Thanks to Chris
+        Novakovic for the patch.
+diff --git a/src/dnssec.c b/src/dnssec.c
+index a74d01ab..1417be56 100644
+--- a/src/dnssec.c
++++ b/src/dnssec.c
+@@ -424,15 +424,17 @@ static void from_wire(char *name)
+ static int count_labels(char *name)
+ {
+   int i;
+-
++  char *p;
++  
+   if (*name == 0)
+     return 0;
+ 
+-  for (i = 0; *name; name++)
+-    if (*name == '.')
++  for (p = name, i = 0; *p; p++)
++    if (*p == '.')
+       i++;
+ 
+-  return i+1;
++  /* Don't count empty first label. */
++  return *name == '.' ? i : i+1;
+ }
+ 
+ /* Implement RFC1982 wrapped compare for 32-bit numbers */
+@@ -1405,8 +1407,8 @@ static int hostname_cmp(const char *a, const char *b)
+     }
+ }
+ 
+-static int prove_non_existence_nsec(struct dns_header *header, size_t plen, unsigned char **nsecs, int nsec_count,
+-                                   char *workspace1, char *workspace2, char *name, int type, int *nons)
++static int prove_non_existence_nsec(struct dns_header *header, size_t plen, unsigned char **nsecs, unsigned char **labels, int nsec_count,
++                                   char *workspace1_in, char *workspace2, char *name, int type, int *nons)
+ {
+   int i, rc, rdlen;
+   unsigned char *p, *psave;
+@@ -1419,6 +1421,9 @@ static int prove_non_existence_nsec(struct dns_header *header, size_t plen, unsi
+   /* Find NSEC record that proves name doesn't exist */
+   for (i = 0; i < nsec_count; i++)
+     {
++      char *workspace1 = workspace1_in;
++      int sig_labels, name_labels;
++
+       p = nsecs[i];
+       if (!extract_name(header, plen, &p, workspace1, 1, 10))
+        return 0;
+@@ -1427,7 +1432,27 @@ static int prove_non_existence_nsec(struct dns_header *header, size_t plen, unsi
+       psave = p;
+       if (!extract_name(header, plen, &p, workspace2, 1, 10))
+        return 0;
+-      
++
++      /* If NSEC comes from wildcard expansion, use original wildcard
++        as name for computation. */
++      sig_labels = *labels[i];
++      name_labels = count_labels(workspace1);
++
++      if (sig_labels < name_labels)
++       {
++         int k;
++         for (k = name_labels - sig_labels; k != 0; k--)
++           {
++             while (*workspace1 != '.' && *workspace1 != 0)
++               workspace1++;
++             if (k != 1 && *workspace1 == '.')
++               workspace1++;
++           }
++         
++         workspace1--;
++         *workspace1 = '*';
++       }
++         
+       rc = hostname_cmp(workspace1, name);
+       
+       if (rc == 0)
+@@ -1825,24 +1850,26 @@ static int prove_non_existence_nsec3(struct dns_header *header, size_t plen, uns
+ 
+ static int prove_non_existence(struct dns_header *header, size_t plen, char *keyname, char *name, int qtype, int qclass, char *wildname, int *nons)
+ {
+-  static unsigned char **nsecset = NULL;
+-  static int nsecset_sz = 0;
++  static unsigned char **nsecset = NULL, **rrsig_labels = NULL;
++  static int nsecset_sz = 0, rrsig_labels_sz = 0;
+   
+   int type_found = 0;
+-  unsigned char *p = skip_questions(header, plen);
++  unsigned char *auth_start, *p = skip_questions(header, plen);
+   int type, class, rdlen, i, nsecs_found;
+   
+   /* Move to NS section */
+   if (!p || !(p = skip_section(p, ntohs(header->ancount), header, plen)))
+     return 0;
++
++  auth_start = p;
+   
+   for (nsecs_found = 0, i = ntohs(header->nscount); i != 0; i--)
+     {
+       unsigned char *pstart = p;
+       
+-      if (!(p = skip_name(p, header, plen, 10)))
++      if (!extract_name(header, plen, &p, daemon->workspacename, 1, 10))
+        return 0;
+-      
++         
+       GETSHORT(type, p); 
+       GETSHORT(class, p);
+       p += 4; /* TTL */
+@@ -1859,7 +1886,69 @@ static int prove_non_existence(struct dns_header *header, size_t plen, char *key
+          if (!expand_workspace(&nsecset, &nsecset_sz, nsecs_found))
+            return 0; 
+          
+-         nsecset[nsecs_found++] = pstart;
++         if (type == T_NSEC)
++           {
++             /* If we're looking for NSECs, find the corresponding SIGs, to 
++                extract the labels value, which we need in case the NSECs
++                are the result of wildcard expansion.
++                Note that the NSEC may not have been validated yet
++                so if there are multiple SIGs, make sure the label value
++                is the same in all, to avoid be duped by a rogue one.
++                If there are no SIGs, that's an error */
++             unsigned char *p1 = auth_start;
++             int res, j, rdlen1, type1, class1;
++             
++             if (!expand_workspace(&rrsig_labels, &rrsig_labels_sz, nsecs_found))
++               return 0;
++             
++             rrsig_labels[nsecs_found] = NULL;
++             
++             for (j = ntohs(header->nscount); j != 0; j--)
++               {
++                 if (!(res = extract_name(header, plen, &p1, daemon->workspacename, 0, 10)))
++                   return 0;
++
++                  GETSHORT(type1, p1); 
++                  GETSHORT(class1, p1);
++                  p1 += 4; /* TTL */
++                  GETSHORT(rdlen1, p1);
++
++                  if (!CHECK_LEN(header, p1, plen, rdlen1))
++                    return 0;
++                  
++                  if (res == 1 && class1 == qclass && type1 == T_RRSIG)
++                    {
++                      int type_covered;
++                      unsigned char *psav = p1;
++                      
++                      if (rdlen < 18)
++                        return 0; /* bad packet */
++
++                      GETSHORT(type_covered, p1);
++
++                      if (type_covered == T_NSEC)
++                        {
++                          p1++; /* algo */
++                          
++                          /* labels field must be the same in every SIG we find. */
++                          if (!rrsig_labels[nsecs_found])
++                            rrsig_labels[nsecs_found] = p1;
++                          else if (*rrsig_labels[nsecs_found] != *p1) /* algo */
++                            return 0;
++                          }
++                      p1 = psav;
++                    }
++                  
++                  if (!ADD_RDLEN(header, p1, plen, rdlen1))
++                    return 0;
++               }
++
++             /* Must have found at least one sig. */
++             if (!rrsig_labels[nsecs_found])
++               return 0;
++           }
++
++         nsecset[nsecs_found++] = pstart;   
+        }
+       
+       if (!ADD_RDLEN(header, p, plen, rdlen))
+@@ -1867,7 +1956,7 @@ static int prove_non_existence(struct dns_header *header, size_t plen, char *key
+     }
+   
+   if (type_found == T_NSEC)
+-    return prove_non_existence_nsec(header, plen, nsecset, nsecs_found, daemon->workspacename, keyname, name, qtype, nons);
++    return prove_non_existence_nsec(header, plen, nsecset, rrsig_labels, nsecs_found, daemon->workspacename, keyname, name, qtype, nons);
+   else if (type_found == T_NSEC3)
+     return prove_non_existence_nsec3(header, plen, nsecset, nsecs_found, daemon->workspacename, keyname, name, qtype, wildname, nons);
+   else
+-- 
+2.19.0
+