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Merge pull request bottlerocket-os#3416 from bcressey/resolved-to-par…
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…se-domains

support non-standard DHCP Option 15 in EC2
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bcressey authored Sep 6, 2023
2 parents 87a7d3f + b7d0b8f commit 8812c57
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Original file line number Diff line number Diff line change
@@ -0,0 +1,131 @@
From 4c79d11d6888944f251681003a7b8b41606e108b Mon Sep 17 00:00:00 2001
From: Ben Cressey <[email protected]>
Date: Sat, 2 Sep 2023 16:19:22 +0000
Subject: [PATCH] sd-dhcp-lease: parse multiple domains in option 15

Non-compliant DHCP servers may pass through multiple domain names in
Option 15, separated by a space character. This is then normalized
into "032" by systemd-networkd, which effectively synthesizes a new
domain name that doesn't match any of the expected ones.

DHCP also supports Option 119 which specifies a compression scheme to
avoid repeating any shared suffixes of the domain names. This option
doesn't support space-separated domains either, so working around the
problem isn't as straightforward as treating an Option 15 payload as
a 119 payload instead.

Deal with this by splitting the Option 15 payload on spaces first,
before normalizing the individual domain names. If multiple domains
are found, use them as the list of search domains unless Option 119
is also present.

Signed-off-by: Ben Cressey <[email protected]>
---
src/libsystemd-network/sd-dhcp-lease.c | 69 +++++++++++++++++++++-----
1 file changed, 56 insertions(+), 13 deletions(-)

diff --git a/src/libsystemd-network/sd-dhcp-lease.c b/src/libsystemd-network/sd-dhcp-lease.c
index b14ad57..263e97e 100644
--- a/src/libsystemd-network/sd-dhcp-lease.c
+++ b/src/libsystemd-network/sd-dhcp-lease.c
@@ -401,34 +401,70 @@ static int lease_parse_string(const uint8_t *option, size_t len, char **ret) {
return 0;
}

-static int lease_parse_domain(const uint8_t *option, size_t len, char **ret) {
- _cleanup_free_ char *name = NULL, *normalized = NULL;
+static int lease_parse_domain_list(const uint8_t *option, size_t len, char ***ret) {
+ _cleanup_free_ char *parsed = NULL;
+ _cleanup_strv_free_ char **names = NULL, **normalized_names = NULL;
int r;

assert(option);
assert(ret);

- r = lease_parse_string(option, len, &name);
+ r = lease_parse_string(option, len, &parsed);
if (r < 0)
return r;
- if (!name) {
- *ret = mfree(*ret);
+
+ if (!parsed)
return 0;
+
+ names = strv_split(parsed, " ");
+ if (!names)
+ return -ENOMEM;
+
+ STRV_FOREACH(name, names) {
+ _cleanup_free_ char *normalized = NULL;
+
+ r = dns_name_normalize(*name, 0, &normalized);
+ if (r < 0)
+ return r;
+
+ if (is_localhost(normalized))
+ return -EINVAL;
+
+ if (dns_name_is_root(normalized))
+ return -EINVAL;
+
+ r = strv_extend(&normalized_names, normalized);
+ if (r < 0)
+ return r;
}

- r = dns_name_normalize(name, 0, &normalized);
+ strv_free_and_replace(*ret, normalized_names);
+ return 0;
+}
+
+static int lease_parse_domain(const uint8_t *option, size_t len, char **ret) {
+ _cleanup_strv_free_ char **names = NULL;
+ size_t n;
+ int r;
+
+ assert(option);
+ assert(ret);
+
+ r = lease_parse_domain_list(option, len, &names);
if (r < 0)
return r;

- if (is_localhost(normalized))
- return -EINVAL;
-
- if (dns_name_is_root(normalized))
- return -EINVAL;
+ n = strv_length(names);
+ if (n == 0) {
+ *ret = mfree(*ret);
+ return 0;
+ }

- free_and_replace(*ret, normalized);
+ r = free_and_strdup(ret, names[0]);
+ if (r < 0)
+ return r;

- return 0;
+ return n;
}

static int lease_parse_in_addrs(const uint8_t *option, size_t len, struct in_addr **ret, size_t *n_ret) {
@@ -725,6 +761,13 @@ int dhcp_lease_parse_options(uint8_t code, uint8_t len, const void *option, void
return 0;
}

+ if (r <= 1 || !strv_isempty(lease->search_domains))
+ break;
+
+ r = lease_parse_domain_list(option, len, &lease->search_domains);
+ if (r < 0)
+ log_debug_errno(r, "Failed to parse Domain Search List, ignoring: %m");
+
break;

case SD_DHCP_OPTION_DOMAIN_SEARCH:
--
2.40.1

4 changes: 4 additions & 0 deletions packages/systemd/systemd.spec
Original file line number Diff line number Diff line change
Expand Up @@ -57,6 +57,10 @@ Patch9011: 9011-systemd-networkd-Conditionalize-hostnamed-timezoned-.patch
# as a kernel command line parameter to override.
Patch9012: 9012-core-mount-increase-mount-rate-limit-burst-to-25.patch

# Local patch to work around a potentially non-compliant Option 15 in the DHCP
# lease in EC2.
Patch9013: 9013-sd-dhcp-lease-parse-multiple-domains-in-option-15.patch

BuildRequires: gperf
BuildRequires: intltool
BuildRequires: meson
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