Brad Bishop | 757e94a | 2018-09-07 18:58:51 +0000 | [diff] [blame] | 1 | From 5a56e1b78a753d3295564daddc9ce389cc69fd68 Mon Sep 17 00:00:00 2001 |
| 2 | From: Simon Kelley <simon@thekelleys.org.uk> |
| 3 | Date: Fri, 19 Jan 2018 12:26:08 +0000 |
| 4 | Subject: [PATCH] DNSSEC fix for wildcard NSEC records. CVE-2017-15107 applies. |
| 5 | |
| 6 | It's OK for NSEC records to be expanded from wildcards, |
| 7 | but in that case, the proof of non-existence is only valid |
| 8 | starting at the wildcard name, *.<domain> NOT the name expanded |
| 9 | from the wildcard. Without this check it's possible for an |
| 10 | attacker to craft an NSEC which wrongly proves non-existence |
| 11 | in a domain which includes a wildcard for NSEC. |
| 12 | |
| 13 | Upstream-Status: Backport [http://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=commit;h=4fe6744a220eddd3f1749b40cac3dfc510787de6] |
| 14 | CVE: CVE-2017-15107 |
| 15 | Signed-off-by: Sinan Kaya <okaya@kernel.org> |
| 16 | --- |
| 17 | CHANGELOG | 44 +++++++++++++++++++ |
| 18 | src/dnssec.c | 117 +++++++++++++++++++++++++++++++++++++++++++++------ |
| 19 | 2 files changed, 147 insertions(+), 14 deletions(-) |
| 20 | |
| 21 | diff --git a/CHANGELOG b/CHANGELOG |
| 22 | index 075fe1a6..5226dce8 100644 |
| 23 | --- a/CHANGELOG |
| 24 | +++ b/CHANGELOG |
| 25 | @@ -1,3 +1,47 @@ |
| 26 | +version 2.79 |
| 27 | + Fix parsing of CNAME arguments, which are confused by extra spaces. |
| 28 | + Thanks to Diego Aguirre for spotting the bug. |
| 29 | + |
| 30 | + Where available, use IP_UNICAST_IF or IPV6_UNICAST_IF to bind |
| 31 | + upstream servers to an interface, rather than SO_BINDTODEVICE. |
| 32 | + Thanks to Beniamino Galvani for the patch. |
| 33 | + |
| 34 | + Always return a SERVFAIL answer to DNS queries without the |
| 35 | + recursion desired bit set, UNLESS acting as an authoritative |
| 36 | + DNS server. This avoids a potential route to cache snooping. |
| 37 | + |
| 38 | + Add support for Ed25519 signatures in DNSSEC validation. |
| 39 | + |
| 40 | + No longer support RSA/MD5 signatures in DNSSEC validation, |
| 41 | + since these are not secure. This behaviour is mandated in |
| 42 | + RFC-6944. |
| 43 | + |
| 44 | + Fix incorrect error exit code from dhcp_release6 utility. |
| 45 | + Thanks Gaudenz Steinlin for the bug report. |
| 46 | + |
| 47 | + Use SIGINT (instead of overloading SIGHUP) to turn on DNSSEC |
| 48 | + time validation when --dnssec-no-timecheck is in use. |
| 49 | + Note that this is an incompatible change from earlier releases. |
| 50 | + |
| 51 | + Allow more than one --bridge-interface option to refer to an |
| 52 | + interface, so that we can use |
| 53 | + --bridge-interface=int1,alias1 |
| 54 | + --bridge-interface=int1,alias2 |
| 55 | + as an alternative to |
| 56 | + --bridge-interface=int1,alias1,alias2 |
| 57 | + Thanks to Neil Jerram for work on this. |
| 58 | + |
| 59 | + Fix for DNSSEC with wildcard-derived NSEC records. |
| 60 | + It's OK for NSEC records to be expanded from wildcards, |
| 61 | + but in that case, the proof of non-existence is only valid |
| 62 | + starting at the wildcard name, *.<domain> NOT the name expanded |
| 63 | + from the wildcard. Without this check it's possible for an |
| 64 | + attacker to craft an NSEC which wrongly proves non-existence. |
| 65 | + Thanks to Ralph Dolmans for finding this, and co-ordinating |
| 66 | + the vulnerability tracking and fix release. |
| 67 | + CVE-2017-15107 applies. |
| 68 | + |
| 69 | + |
| 70 | version 2.78 |
| 71 | Fix logic of appending ".<layer>" to PXE basename. Thanks to Chris |
| 72 | Novakovic for the patch. |
| 73 | diff --git a/src/dnssec.c b/src/dnssec.c |
| 74 | index a74d01ab..1417be56 100644 |
| 75 | --- a/src/dnssec.c |
| 76 | +++ b/src/dnssec.c |
| 77 | @@ -424,15 +424,17 @@ static void from_wire(char *name) |
| 78 | static int count_labels(char *name) |
| 79 | { |
| 80 | int i; |
| 81 | - |
| 82 | + char *p; |
| 83 | + |
| 84 | if (*name == 0) |
| 85 | return 0; |
| 86 | |
| 87 | - for (i = 0; *name; name++) |
| 88 | - if (*name == '.') |
| 89 | + for (p = name, i = 0; *p; p++) |
| 90 | + if (*p == '.') |
| 91 | i++; |
| 92 | |
| 93 | - return i+1; |
| 94 | + /* Don't count empty first label. */ |
| 95 | + return *name == '.' ? i : i+1; |
| 96 | } |
| 97 | |
| 98 | /* Implement RFC1982 wrapped compare for 32-bit numbers */ |
| 99 | @@ -1405,8 +1407,8 @@ static int hostname_cmp(const char *a, const char *b) |
| 100 | } |
| 101 | } |
| 102 | |
| 103 | -static int prove_non_existence_nsec(struct dns_header *header, size_t plen, unsigned char **nsecs, int nsec_count, |
| 104 | - char *workspace1, char *workspace2, char *name, int type, int *nons) |
| 105 | +static int prove_non_existence_nsec(struct dns_header *header, size_t plen, unsigned char **nsecs, unsigned char **labels, int nsec_count, |
| 106 | + char *workspace1_in, char *workspace2, char *name, int type, int *nons) |
| 107 | { |
| 108 | int i, rc, rdlen; |
| 109 | unsigned char *p, *psave; |
| 110 | @@ -1419,6 +1421,9 @@ static int prove_non_existence_nsec(struct dns_header *header, size_t plen, unsi |
| 111 | /* Find NSEC record that proves name doesn't exist */ |
| 112 | for (i = 0; i < nsec_count; i++) |
| 113 | { |
| 114 | + char *workspace1 = workspace1_in; |
| 115 | + int sig_labels, name_labels; |
| 116 | + |
| 117 | p = nsecs[i]; |
| 118 | if (!extract_name(header, plen, &p, workspace1, 1, 10)) |
| 119 | return 0; |
| 120 | @@ -1427,7 +1432,27 @@ static int prove_non_existence_nsec(struct dns_header *header, size_t plen, unsi |
| 121 | psave = p; |
| 122 | if (!extract_name(header, plen, &p, workspace2, 1, 10)) |
| 123 | return 0; |
| 124 | - |
| 125 | + |
| 126 | + /* If NSEC comes from wildcard expansion, use original wildcard |
| 127 | + as name for computation. */ |
| 128 | + sig_labels = *labels[i]; |
| 129 | + name_labels = count_labels(workspace1); |
| 130 | + |
| 131 | + if (sig_labels < name_labels) |
| 132 | + { |
| 133 | + int k; |
| 134 | + for (k = name_labels - sig_labels; k != 0; k--) |
| 135 | + { |
| 136 | + while (*workspace1 != '.' && *workspace1 != 0) |
| 137 | + workspace1++; |
| 138 | + if (k != 1 && *workspace1 == '.') |
| 139 | + workspace1++; |
| 140 | + } |
| 141 | + |
| 142 | + workspace1--; |
| 143 | + *workspace1 = '*'; |
| 144 | + } |
| 145 | + |
| 146 | rc = hostname_cmp(workspace1, name); |
| 147 | |
| 148 | if (rc == 0) |
| 149 | @@ -1825,24 +1850,26 @@ static int prove_non_existence_nsec3(struct dns_header *header, size_t plen, uns |
| 150 | |
| 151 | static int prove_non_existence(struct dns_header *header, size_t plen, char *keyname, char *name, int qtype, int qclass, char *wildname, int *nons) |
| 152 | { |
| 153 | - static unsigned char **nsecset = NULL; |
| 154 | - static int nsecset_sz = 0; |
| 155 | + static unsigned char **nsecset = NULL, **rrsig_labels = NULL; |
| 156 | + static int nsecset_sz = 0, rrsig_labels_sz = 0; |
| 157 | |
| 158 | int type_found = 0; |
| 159 | - unsigned char *p = skip_questions(header, plen); |
| 160 | + unsigned char *auth_start, *p = skip_questions(header, plen); |
| 161 | int type, class, rdlen, i, nsecs_found; |
| 162 | |
| 163 | /* Move to NS section */ |
| 164 | if (!p || !(p = skip_section(p, ntohs(header->ancount), header, plen))) |
| 165 | return 0; |
| 166 | + |
| 167 | + auth_start = p; |
| 168 | |
| 169 | for (nsecs_found = 0, i = ntohs(header->nscount); i != 0; i--) |
| 170 | { |
| 171 | unsigned char *pstart = p; |
| 172 | |
| 173 | - if (!(p = skip_name(p, header, plen, 10))) |
| 174 | + if (!extract_name(header, plen, &p, daemon->workspacename, 1, 10)) |
| 175 | return 0; |
| 176 | - |
| 177 | + |
| 178 | GETSHORT(type, p); |
| 179 | GETSHORT(class, p); |
| 180 | p += 4; /* TTL */ |
| 181 | @@ -1859,7 +1886,69 @@ static int prove_non_existence(struct dns_header *header, size_t plen, char *key |
| 182 | if (!expand_workspace(&nsecset, &nsecset_sz, nsecs_found)) |
| 183 | return 0; |
| 184 | |
| 185 | - nsecset[nsecs_found++] = pstart; |
| 186 | + if (type == T_NSEC) |
| 187 | + { |
| 188 | + /* If we're looking for NSECs, find the corresponding SIGs, to |
| 189 | + extract the labels value, which we need in case the NSECs |
| 190 | + are the result of wildcard expansion. |
| 191 | + Note that the NSEC may not have been validated yet |
| 192 | + so if there are multiple SIGs, make sure the label value |
| 193 | + is the same in all, to avoid be duped by a rogue one. |
| 194 | + If there are no SIGs, that's an error */ |
| 195 | + unsigned char *p1 = auth_start; |
| 196 | + int res, j, rdlen1, type1, class1; |
| 197 | + |
| 198 | + if (!expand_workspace(&rrsig_labels, &rrsig_labels_sz, nsecs_found)) |
| 199 | + return 0; |
| 200 | + |
| 201 | + rrsig_labels[nsecs_found] = NULL; |
| 202 | + |
| 203 | + for (j = ntohs(header->nscount); j != 0; j--) |
| 204 | + { |
| 205 | + if (!(res = extract_name(header, plen, &p1, daemon->workspacename, 0, 10))) |
| 206 | + return 0; |
| 207 | + |
| 208 | + GETSHORT(type1, p1); |
| 209 | + GETSHORT(class1, p1); |
| 210 | + p1 += 4; /* TTL */ |
| 211 | + GETSHORT(rdlen1, p1); |
| 212 | + |
| 213 | + if (!CHECK_LEN(header, p1, plen, rdlen1)) |
| 214 | + return 0; |
| 215 | + |
| 216 | + if (res == 1 && class1 == qclass && type1 == T_RRSIG) |
| 217 | + { |
| 218 | + int type_covered; |
| 219 | + unsigned char *psav = p1; |
| 220 | + |
| 221 | + if (rdlen < 18) |
| 222 | + return 0; /* bad packet */ |
| 223 | + |
| 224 | + GETSHORT(type_covered, p1); |
| 225 | + |
| 226 | + if (type_covered == T_NSEC) |
| 227 | + { |
| 228 | + p1++; /* algo */ |
| 229 | + |
| 230 | + /* labels field must be the same in every SIG we find. */ |
| 231 | + if (!rrsig_labels[nsecs_found]) |
| 232 | + rrsig_labels[nsecs_found] = p1; |
| 233 | + else if (*rrsig_labels[nsecs_found] != *p1) /* algo */ |
| 234 | + return 0; |
| 235 | + } |
| 236 | + p1 = psav; |
| 237 | + } |
| 238 | + |
| 239 | + if (!ADD_RDLEN(header, p1, plen, rdlen1)) |
| 240 | + return 0; |
| 241 | + } |
| 242 | + |
| 243 | + /* Must have found at least one sig. */ |
| 244 | + if (!rrsig_labels[nsecs_found]) |
| 245 | + return 0; |
| 246 | + } |
| 247 | + |
| 248 | + nsecset[nsecs_found++] = pstart; |
| 249 | } |
| 250 | |
| 251 | if (!ADD_RDLEN(header, p, plen, rdlen)) |
| 252 | @@ -1867,7 +1956,7 @@ static int prove_non_existence(struct dns_header *header, size_t plen, char *key |
| 253 | } |
| 254 | |
| 255 | if (type_found == T_NSEC) |
| 256 | - return prove_non_existence_nsec(header, plen, nsecset, nsecs_found, daemon->workspacename, keyname, name, qtype, nons); |
| 257 | + return prove_non_existence_nsec(header, plen, nsecset, rrsig_labels, nsecs_found, daemon->workspacename, keyname, name, qtype, nons); |
| 258 | else if (type_found == T_NSEC3) |
| 259 | return prove_non_existence_nsec3(header, plen, nsecset, nsecs_found, daemon->workspacename, keyname, name, qtype, wildname, nons); |
| 260 | else |
| 261 | -- |
| 262 | 2.19.0 |
| 263 | |