1DNSSEC-CDS(8) BIND 9 DNSSEC-CDS(8)
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6 dnssec-cds - change DS records for a child zone based on CDS/CDNSKEY
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9 dnssec-cds [-a alg...] [-c class] [-D] {-d dsset-file} {-f child-file}
10 [-i**[extension]] [-s** start-time] [-T ttl] [-u] [-v level] [-V] {do‐
11 main}
12
14 The dnssec-cds command changes DS records at a delegation point based
15 on CDS or CDNSKEY records published in the child zone. If both CDS and
16 CDNSKEY records are present in the child zone, the CDS is preferred.
17 This enables a child zone to inform its parent of upcoming changes to
18 its key-signing keys (KSKs); by polling periodically with dnssec-cds,
19 the parent can keep the DS records up-to-date and enable automatic
20 rolling of KSKs.
21 Two input files are required. The -f child-file option specifies a file
23 containing the child's CDS and/or CDNSKEY records, plus RRSIG and
24 DNSKEY records so that they can be authenticated. The -d path option
25 specifies the location of a file containing the current DS records. For
26 example, this could be a dsset- file generated by dnssec-signzone, or
27 the output of dnssec-dsfromkey, or the output of a previous run of
28 dnssec-cds.
29 The dnssec-cds command uses special DNSSEC validation logic specified
31 by RFC 7344. It requires that the CDS and/or CDNSKEY records be validly
32 signed by a key represented in the existing DS records. This is typi‐
33 cally the pre-existing KSK.
34 For protection against replay attacks, the signatures on the child
36 records must not be older than they were on a previous run of
37 dnssec-cds. Their age is obtained from the modification time of the ds‐
38 set- file, or from the -s option.
39 To protect against breaking the delegation, dnssec-cds ensures that the
41 DNSKEY RRset can be verified by every key algorithm in the new DS
42 RRset, and that the same set of keys are covered by every DS digest
43 type.
44 By default, replacement DS records are written to the standard output;
46 with the -i option the input file is overwritten in place. The replace‐
47 ment DS records are the same as the existing records, when no change is
48 required. The output can be empty if the CDS/CDNSKEY records specify
49 that the child zone wants to be insecure.
50 WARNING:
52 Be careful not to delete the DS records when dnssec-cds fails!
53 Alternatively, dnssec-cds -u writes an nsupdate script to the standard
55 output. The -u and -i options can be used together to maintain a dsset-
56 file as well as emit an nsupdate script.
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59 -a algorithm
60 This option specifies a digest algorithm to use when converting
61 CDNSKEY records to DS records. This option can be repeated, so
62 that multiple DS records are created for each CDNSKEY record.
63 This option has no effect when using CDS records.
64 The algorithm must be one of SHA-1, SHA-256, or SHA-384. These
66 values are case-insensitive, and the hyphen may be omitted. If
67 no algorithm is specified, the default is SHA-256.
68 -c class
70 This option specifies the DNS class of the zones.
71 -D This option generates DS records from CDNSKEY records if both
73 CDS and CDNSKEY records are present in the child zone. By de‐
74 fault CDS records are preferred.
75 -d path
77 This specifies the location of the parent DS records. The path
78 can be the name of a file containing the DS records; if it is a
79 directory, dnssec-cds looks for a dsset- file for the domain in‐
80 side the directory.
81 To protect against replay attacks, child records are rejected if
83 they were signed earlier than the modification time of the ds‐
84 set- file. This can be adjusted with the -s option.
85 -f child-file
87 This option specifies the file containing the child's CDS and/or
88 CDNSKEY records, plus its DNSKEY records and the covering RRSIG
89 records, so that they can be authenticated.
90 The examples below describe how to generate this file.
92 -iextension
94 This option updates the dsset- file in place, instead of writing
95 DS records to the standard output.
96 There must be no space between the -i and the extension. If no
98 extension is provided, the old dsset- is discarded. If an exten‐
99 sion is present, a backup of the old dsset- file is kept with
100 the extension appended to its filename.
101 To protect against replay attacks, the modification time of the
103 dsset- file is set to match the signature inception time of the
104 child records, provided that it is later than the file's current
105 modification time.
106 -s start-time
108 This option specifies the date and time after which RRSIG
109 records become acceptable. This can be either an absolute or a
110 relative time. An absolute start time is indicated by a number
111 in YYYYMMDDHHMMSS notation; 20170827133700 denotes 13:37:00 UTC
112 on August 27th, 2017. A time relative to the dsset- file is in‐
113 dicated with -N, which is N seconds before the file modification
114 time. A time relative to the current time is indicated with
115 now+N.
116 If no start-time is specified, the modification time of the ds‐
118 set- file is used.
119 -T ttl This option specifies a TTL to be used for new DS records. If
121 not specified, the default is the TTL of the old DS records. If
122 they had no explicit TTL, the new DS records also have no ex‐
123 plicit TTL.
124 -u This option writes an nsupdate script to the standard output,
126 instead of printing the new DS reords. The output is empty if no
127 change is needed.
128 Note: The TTL of new records needs to be specified: it can be
130 done in the original dsset- file, with the -T option, or using
131 the nsupdate ttl command.
132 -V This option prints version information.
134 -v level
136 This option sets the debugging level. Level 1 is intended to be
137 usefully verbose for general users; higher levels are intended
138 for developers.
139 domain This indicates the name of the delegation point/child zone apex.
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143 The dnssec-cds command exits 0 on success, or non-zero if an error oc‐
144 curred.
145 If successful, the DS records may or may not need to be changed.
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149 Before running dnssec-signzone, ensure that the delegations are
150 up-to-date by running dnssec-cds on every dsset- file.
151 To fetch the child records required by dnssec-cds, invoke dig as in the
153 script below. It is acceptable if the dig fails, since dnssec-cds per‐
154 forms all the necessary checking.
155 for f in dsset-*
157 do
158 d=${f#dsset-}
159 dig +dnssec +noall +answer $d DNSKEY $d CDNSKEY $d CDS |
160 dnssec-cds -i -f /dev/stdin -d $f $d
161 done
162 When the parent zone is automatically signed by named, dnssec-cds can
164 be used with nsupdate to maintain a delegation as follows. The dsset-
165 file allows the script to avoid having to fetch and validate the parent
166 DS records, and it maintains the replay attack protection time.
167 dig +dnssec +noall +answer $d DNSKEY $d CDNSKEY $d CDS |
169 dnssec-cds -u -i -f /dev/stdin -d $f $d |
170 nsupdate -l
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173 dig(1), dnssec-settime(8), dnssec-signzone(8), nsupdate(1), BIND 9 Ad‐
174 ministrator Reference Manual, RFC 7344.
175
177 Internet Systems Consortium
178
180 2021, Internet Systems Consortium
1819.16.16-RH DNSSEC-CDS(8)