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From f9ccee5c4c6cb0d4197b08ebeb36c1dceffe82e8 Mon Sep 17 00:00:00 2001
From: Thorsten Kukuk <kukuk@suse.com>
Date: Thu, 14 Nov 2024 10:27:28 +0100
Subject: [PATCH] pam_access: rework resolving of tokens as hostname
* modules/pam_access/pam_access.c: separate resolving of IP addresses
from hostnames. Don't resolve TTYs or display variables as hostname
(#834).
Add "nodns" option to disallow resolving of tokens as hostname.
* modules/pam_access/pam_access.8.xml: document nodns option
* modules/pam_access/access.conf.5.xml: document that hostnames should
be written as FQHN.
Upstream-Status: Backport [https://github.com/linux-pam/linux-pam/commit/940747f88c16e029b69a74e80a2e94f65cb3e628]
CVE: CVE-2024-10963
Signed-off-by: Stanislav Vovk <stanislav.vovk@est.tech>
---
modules/pam_access/access.conf.5.xml | 4 ++
modules/pam_access/pam_access.8.xml | 46 ++++++++++++------
modules/pam_access/pam_access.c | 72 +++++++++++++++++++++++++++-
3 files changed, 105 insertions(+), 17 deletions(-)
diff --git a/modules/pam_access/access.conf.5.xml b/modules/pam_access/access.conf.5.xml
index ff1cb223..158fc7df 100644
--- a/modules/pam_access/access.conf.5.xml
+++ b/modules/pam_access/access.conf.5.xml
@@ -220,10 +220,14 @@
the fields they are ignored. However if the list separator is changed with the
<emphasis>listsep</emphasis> option, the spaces will become part of the actual
item and the line will be most probably ignored. For this reason, it is not
recommended to put spaces around the ':' characters.
</para>
+ <para>
+ Hostnames should be written as Fully-Qualified Host Name (FQHN) to avoid
+ confusion with device names or PAM service names.
+ </para>
</refsect1>
<refsect1 xml:id="access.conf-see_also">
<title>SEE ALSO</title>
<para>
diff --git a/modules/pam_access/pam_access.8.xml b/modules/pam_access/pam_access.8.xml
index 010e749e..1182c907 100644
--- a/modules/pam_access/pam_access.8.xml
+++ b/modules/pam_access/pam_access.8.xml
@@ -20,15 +20,18 @@
<cmdsynopsis xml:id="pam_access-cmdsynopsis" sepchar=" ">
<command>pam_access.so</command>
<arg choice="opt" rep="norepeat">
debug
</arg>
+ <arg choice="opt" rep="norepeat">
+ noaudit
+ </arg>
<arg choice="opt" rep="norepeat">
nodefgroup
</arg>
<arg choice="opt" rep="norepeat">
- noaudit
+ nodns
</arg>
<arg choice="opt" rep="norepeat">
accessfile=<replaceable>file</replaceable>
</arg>
<arg choice="opt" rep="norepeat">
@@ -127,10 +130,37 @@
Do not report logins from disallowed hosts and ttys to the audit subsystem.
</para>
</listitem>
</varlistentry>
+ <varlistentry>
+ <term>
+ nodefgroup
+ </term>
+ <listitem>
+ <para>
+ User tokens which are not enclosed in parentheses will not be
+ matched against the group database. The backwards compatible default is
+ to try the group database match even for tokens not enclosed
+ in parentheses.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>
+ nodns
+ </term>
+ <listitem>
+ <para>
+ Do not try to resolve tokens as hostnames, only IPv4 and IPv6
+ addresses will be resolved. Which means to allow login from a
+ remote host, the IP addresses need to be specified in <filename>access.conf</filename>.
+ </para>
+ </listitem>
+ </varlistentry>
+
<varlistentry>
<term>
fieldsep=separators
</term>
<listitem>
@@ -168,24 +198,10 @@
"Domain Admins" contain a space.
</para>
</listitem>
</varlistentry>
- <varlistentry>
- <term>
- nodefgroup
- </term>
- <listitem>
- <para>
- User tokens which are not enclosed in parentheses will not be
- matched against the group database. The backwards compatible default is
- to try the group database match even for tokens not enclosed
- in parentheses.
- </para>
- </listitem>
- </varlistentry>
-
</variablelist>
</refsect1>
<refsect1 xml:id="pam_access-types">
<title>MODULE TYPES PROVIDED</title>
diff --git a/modules/pam_access/pam_access.c b/modules/pam_access/pam_access.c
index f70b7e49..d06496c3 100644
--- a/modules/pam_access/pam_access.c
+++ b/modules/pam_access/pam_access.c
@@ -97,10 +97,11 @@ struct login_info {
const char *config_file;
const char *hostname;
int debug; /* Print debugging messages. */
int only_new_group_syntax; /* Only allow group entries of the form "(xyz)" */
int noaudit; /* Do not audit denials */
+ int nodns; /* Do not try to resolve tokens as hostnames */
const char *fs; /* field separator */
const char *sep; /* list-element separator */
int from_remote_host; /* If PAM_RHOST was used for from */
struct addrinfo *res; /* Cached DNS resolution of from */
int gai_rv; /* Cached retval of getaddrinfo */
@@ -148,10 +149,12 @@ parse_args(pam_handle_t *pamh, struct login_info *loginfo,
loginfo->debug = YES;
} else if (strcmp (argv[i], "nodefgroup") == 0) {
loginfo->only_new_group_syntax = YES;
} else if (strcmp (argv[i], "noaudit") == 0) {
loginfo->noaudit = YES;
+ } else if (strcmp (argv[i], "nodns") == 0) {
+ loginfo->nodns = YES;
} else {
pam_syslog(pamh, LOG_ERR, "unrecognized option [%s]", argv[i]);
}
}
@@ -730,11 +733,11 @@ remote_match (pam_handle_t *pamh, char *tok, struct login_info *item)
if (tok[0] == '.') { /* domain: match last fields */
if ((str_len = strlen(string)) > tok_len
&& strcasecmp(tok, string + str_len - tok_len) == 0)
return YES;
- } else if (tok[tok_len - 1] == '.') { /* internet network numbers (end with ".") */
+ } else if (tok[tok_len - 1] == '.') { /* internet network numbers/subnet (end with ".") */
struct addrinfo hint;
memset (&hint, '\0', sizeof (hint));
hint.ai_flags = AI_CANONNAME;
hint.ai_family = AF_INET;
@@ -805,10 +808,43 @@ string_match (pam_handle_t *pamh, const char *tok, const char *string,
}
return (NO);
}
+static int
+is_device (pam_handle_t *pamh, const char *tok)
+{
+ struct stat st;
+ const char *dev = "/dev/";
+ char *devname;
+
+ devname = malloc (strlen(dev) + strlen (tok) + 1);
+ if (devname == NULL) {
+ pam_syslog(pamh, LOG_ERR, "Cannot allocate memory for device name: %m");
+ /*
+ * We should return an error and abort, but pam_access has no good
+ * error handling.
+ */
+ return NO;
+ }
+
+ char *cp = stpcpy (devname, dev);
+ strcpy (cp, tok);
+
+ if (lstat(devname, &st) != 0)
+ {
+ free (devname);
+ return NO;
+ }
+ free (devname);
+
+ if (S_ISCHR(st.st_mode))
+ return YES;
+
+ return NO;
+}
+
/* network_netmask_match - match a string against one token
* where string is a hostname or ip (v4,v6) address and tok
* represents either a hostname, a single ip (v4,v6) address
* or a network/netmask
*/
@@ -866,14 +902,46 @@ network_netmask_match (pam_handle_t *pamh,
if (getaddrinfo (tok, NULL, NULL, &ai) != 0)
{
return NO;
}
}
+ else if (isipaddr(tok, NULL, NULL) == YES)
+ {
+ if (getaddrinfo (tok, NULL, NULL, &ai) != 0)
+ {
+ if (item->debug)
+ pam_syslog(pamh, LOG_DEBUG, "cannot resolve IP address \"%s\"", tok);
+
+ return NO;
+ }
+ netmask_ptr = NULL;
+ }
+ else if (item->nodns)
+ {
+ /* Only hostnames are left, which we would need to resolve via DNS */
+ return NO;
+ }
else
{
+ /* Bail out on X11 Display entries and ttys. */
+ if (tok[0] == ':')
+ {
+ if (item->debug)
+ pam_syslog (pamh, LOG_DEBUG,
+ "network_netmask_match: tok=%s is X11 display", tok);
+ return NO;
+ }
+ if (is_device (pamh, tok))
+ {
+ if (item->debug)
+ pam_syslog (pamh, LOG_DEBUG,
+ "network_netmask_match: tok=%s is a TTY", tok);
+ return NO;
+ }
+
/*
- * It is either an IP address or a hostname.
+ * It is most likely a hostname.
* Let getaddrinfo sort everything out
*/
if (getaddrinfo (tok, NULL, NULL, &ai) != 0)
{
pam_syslog(pamh, LOG_ERR, "cannot resolve hostname \"%s\"", tok);
--
2.43.5
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