The Microsoft compiler cannot handle multiple const modifiers
for the same type. It is also unhappy with the output pointer
parameter being declared const.
This change introduces new typedefs and cast of the dlsym() return
type to prevent warnings.
Change-Id: Ia92645efab8d2ec6745339a6f47c690782ae730a
Rename common_plugin_ftable to krb5_plugin_common_ftable.
Create lib/krb5/common_plugin.h to include the structure and typedef.
The common_plugin.h header is now included by ccache_plugin.h
along with a prototype for the required ccache_ops_plugin_load()
function.
Change-Id: I2b27d6d0f5cf0544482c3f01784fef945e12e8d8
As with the krb5plugin_an2ln_ftable_desc, krb5plugin_db_ftable_desc,
and krb5plugin_kuserok_ftable_desc the function pointers in
common_plugin_ftable_desc must be annotated with KRB5_LIB_CALL.
Change-Id: Ia7ea78743ee9eb8c7f6b648063852ca91a360d2c
Only fallback to loading the plugin function table directly if
if the initialization function is not exported. Failing a
consistency check should not permit falling back to a potentially
incompatible function table.
Change-Id: Ic753ed9a090aef6073853f7309f0f8f0f29d0aa9
Anonymous PKINIT tickets discard the realm information used to locate the
issuing AS. Store the issuing realm in the credentials cache in order to locate
a KDC which can renew them.
When generating KRB5SignedPath in the AS, use the reply client name rather than
the one from the request, so validation will work correctly in the TGS.
even if tgt used an enctype with a different checksum.
Per [MS-SFU] 2.2.1 PA-FOR-USER the checksum is always
HMAC_MD5, and that's what Windows and MIT clients send.
In heimdal both the client and kdc use instead the
checksum of the tgt, and therefore work with each other
but windows and MIT clients fail against heimdal KDC.
Both Windows and MIT KDC would allow any keyed checksum
to be used so Heimdal client work fine against it.
Change Heimdal KDC to allow HMAC_MD5 even for non RC4
based tgt in order to support per-spec clients.
Signed-off-by: Isaac Boukris <iboukris@gmail.com>
Before committing to a PKCS#11 mechanism, check that it can provide the
required encryption or digest services by validating the flags returned by
C_GetMechanismInfo().
Commit bdcd7d2f moved the KRB5_ANON_MATCH_xxx preprocessor symbols to krb5.h,
but did not remove the originals from krb5_locl.h. This commit removes them.
The combination of 8740528b24
("Windows-compatible sentinel socket type and value") and
d497d7e4a7 ("krb5_sendto_kdc:
failover for multiple AAAA/A RRs on one domain") broke
all the send to kdc loop on Windows. rk_socket_t is
a HANDLE and rk_INVALID_SOCKET is the max value. Therefore,
no valid socket will be larger and all communications
will fail.
Change-Id: I3464f78d67b19f14050ad7a01738fb32bac99385
_krb5_principal_is_anonymous() is used outside lib/krb5 and
therefore it needs to be properly exported and its flag macros
need to be in a public header: krb5.h not krb5_locl.h.
Including krb5_locl.h from within kuser_locl.h for instance
results in build failures on Solaris.
This change renames the function and makes it part of the public
api.
Change-Id: I130d1698b10bdbd150b95e8c7d32dfc362889ce6
RFC8062 Section 7 requires verification of the PA-PKINIT-KX key excahnge
when anonymous PKINIT is used. Failure to do so can permit an active
attacker to become a man-in-the-middle.
Introduced by a1ef548600. First tagged
release Heimdal 1.4.0.
CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N (4.8)
Change-Id: I6cc1c0c24985936468af08693839ac6c3edda133
Signed-off-by: Jeffrey Altman <jaltman@auristor.com>
Approved-by: Jeffrey Altman <jaltman@auritor.com>
S4U2Self is an extension to Kerberos used in Active Directory to allow
a service to request a kerberos ticket to itself from the Kerberos Key
Distribution Center (KDC) for a non-Kerberos authenticated user
(principal in Kerboros parlance). This is useful to allow internal
code paths to be standardized around Kerberos.
S4U2Proxy (constrained-delegation) is an extension of this mechanism
allowing this impersonation to a second service over the network. It
allows a privileged server that obtained a S4U2Self ticket to itself
to then assert the identity of that principal to a second service and
present itself as that principal to get services from the second
service.
There is a flaw in Samba's AD DC in the Heimdal KDC. When the Heimdal
KDC checks the checksum that is placed on the S4U2Self packet by the
server to protect the requested principal against modification, it
does not confirm that the checksum algorithm that protects the user
name (principal) in the request is keyed. This allows a
man-in-the-middle attacker who can intercept the request to the KDC to
modify the packet by replacing the user name (principal) in the
request with any desired user name (principal) that exists in the KDC
and replace the checksum protecting that name with a CRC32 checksum
(which requires no prior knowledge to compute).
This would allow a S4U2Self ticket requested on behalf of user name
(principal) user@EXAMPLE.COM to any service to be changed to a
S4U2Self ticket with a user name (principal) of
Administrator@EXAMPLE.COM. This ticket would then contain the PAC of
the modified user name (principal).
==================
CVSSv3 calculation
==================
CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H (7.5)
=========================
Workaround and Mitigation
=========================
If server does not take privileged actions based on Kerberos tickets
obtained by S4U2Self nor obtains Kerberos tickets via further
S4U2Proxy requests then this issue cannot be exploited.
Note that the path to an exploit is not generic, the KDC is not harmed
by the malicious checksum, it is the client service requesting the
ticket being mislead, because it trusted the KDC to return the correct
ticket and PAC.
It is out of scope for Samba to describe all of the possible tool
chains that might be vulnerable. Here are two examples of possible
exploits in order to explain the issue more clearly.
1). SFU2Self might be used by a web service authenticating an end user
via OAuth, Shibboleth, or other protocols to obtain a S4U2Self
Kerberos service ticket for use by any Kerberos service principal the
web service has a keytab for. One example is acquiring an AFS token
by requesting an afs/cell@REALM service ticket for a client via
SFU2Self. With this exploit an organization that deploys a KDC built
from Heimdal (be it Heimdal directly or vendor versions such as found
in Samba) is vulnerable to privilege escalation attacks.
2). If a server authenticates users using X509 certificates, and then
uses S4U2Self to obtain a Kerberos service ticket on behalf of the
user (principal) in order to authorize access to local resources, a
man-in-the-middle attacker could allow a non-privilaged user to access
privilaged resources being protected by the server, or privilaged
resources being protected by a second server, if the first server uses
the S4U2Proxy extension in order to get a new Kerberos service ticket
to obtain access to the second server.
In both these scenarios under conditions allowing man-in-the-middle
active network protocol manipulation, a malicious user could
authenticate using the non-Kerborized credentials of an unprivileged
user, and then elevate its privileges by intercepting the packet from
the server to the KDC and changing the requested user name (principal).
The only Samba clients that use S4U2Self are:
- the "net ads kerberos pac dump" (debugging) tool.
- the CIFS proxy in the deprecated/developer-only NTVFS file
server. Note this code is not compiled or enabled by default.
In particular, winbindd does *not* use S4U2Self.
Finally, MIT Kerberos and so therefore the experimental MIT KDC backend
for Samba AD is understood not to be impacted.
===============
Further Reading
===============
There is more detail on and a description of the protocols in
[MS-SFU]: Kerberos Protocol Extensions: Service for User and Constrained
Delegation Protocol
https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-sfu/
=======
Credits
=======
Originally reported by Isaac Boukris and Andrew Bartlett of the Samba
Team and Catalyst.
Patches provided by Isaac Boukris.
Advisory written by Andrew Bartlett of the Samba Team and Catalyst,
with contributions from Isaac Boukris, Jeffrey Altman and Jeremy
Allison.
BUG: https://bugzilla.samba.org/show_bug.cgi?id=13685
Change-Id: I4ac69ebf0503eb999a7d497a2c30fe4d293a8cc8
Signed-off-by: Isaac Boukris <iboukris@gmail.com>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Signed-off-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Jeffrey Altman <jaltman@auristor.com>
Signed-off-by: Jeffrey Altman <jaltman@auristor.com>
We found that the libraries behaviour when dealing with domains with
more than one entry in them is slightly suboptimal. The situation
was
kdc1 IN A 1.2.3.4
kdc1 IN AAAA ff02::1
I.e. a single hostmame with both IPv6 and IPv4 addresses. When we
run krb5_sendto_kdc on a box with only IPv4 addresses, there is a
3s delay before it fails back to the IPv4 address. This is because
the library sets the 2nd address on each hostname to be 3s in the
future and each additional one another 3s.
We change wait_response() s.t. if one is able to make progress, we
iterate over the list of hosts and move them all 1s forward. We
also modify submit_request() to skip hosts if host_connect() fails.
Add macros to give symbolic names to the flags which can be passed to
krb5_get_init_creds_opt_set_pkinit(). Reserve flags for BTMM and not validating
KDC anchors.
Add _krb5_principal_is_anonymous() private API for checking if a principal is
anonymous or not. The third argument determines whether to match authenticated
anonymous, unauthenticated anonymous, or both types of principal.
Allow non-anonymous tickets to be used to obtain an anonymous service ticket,
by setting the anonymous KDC option. Do not include Win2K PAC in anonymous
service tickets. Validate anonymous flags per RFC 8062.
RFC8062 section 4.1 allows clients with long-term KDC keys to set the anonymous
flag; in this case their identity is authenticated but the returned ticket
contains the anonymous principal name as the client name.
kdc: allow authenticated anonymous PKINIT
The KDC PKINIT code conflated the checks for authenticated and unauthenticated
anonymous by only looking at the anonymous KDC request option.
The utility function _kdc_make_anonymous_principalname() previously returned a
principal of "anonymous" rather than "WELLKNOWN/ANONYMOUS", as specified by
RFC8062. This is not used by the AS-REQ code.
The PAC will typically contain information that may reveal the identity of a
principal. Do not include it for anonymous requests, at least until such time
as the PAC plugin API supports indicating that the request was anonymous.
RFC 8062 states that if the client in the AS request is anonymous, the
anonymous KDC option must be set in the request; otherwise, KDC_ERR_BADOPTION
must be returned. We were previously returning KDC_ERR_C_PRINCIPAL_UNKNOWN.
95eb83c424 ("roken: Add roken_get_username() and friends")
failed to copy the username C-String NUL terminator. As a result
a "DOMAIN\user" is returned as "userIN\user".
Change-Id: I10027e4eef18364074eecf385fa9fab1ae68dbe7
Modern OpenSSL no longer has the 2038 year restriction. Update the
certs to last 500 years rather than 10 years.
Modern crypto requirements suggest a stronger key strength than 1024.
Update to use a minimum of 4096.
Fix executable bit on gen-req.sh
We choose a semantic for the file offset during truncate operations
which is to leave the offset as is unless it is off the end of the
file in which case we pull it back in to the end. We update fd and
stdio handling to match the {,e}mem behaviour.
The rk_UNCONST macro exists because neither __DECONST nor uintptr_t
are available on all platforms (for example, AIX).
Change-Id: Ie36f0dd7a9ce454d411761ee4dbd6fc1f7c6692c
b10ad7eb57
("roken: strtoll.c negation is a no-op on unsigned integer")
broke strtoll() by failing to assign 'ret' in the success case.
Change-Id: I30535d83a2bef305140f1a6bd1ed2eeba23db9b9
strtoull() returns an unsigned long long. However, then the input
string represents a negative number the return value is supposed to
be the unsigned representation of the negative value. Before applying
the negation the value must be cast to (long long).
Change-Id: Icf9e75400ff736819b1f7e0e6fb3c8abd707a23a
strtoll() returns a signed long long not an unsigned long long.
When applying the negation for negatives the value must be cast
from unsigned to signed and then stored in a signed variable
before returning it.
Change-Id: If568afd2509d27c7bf206ca59d32ca150cb34857
__declspec not _declspec
Include "err.h" not <err.h>
Include "roken.h" before "err.h"
Indent "#if" as "# if" within roken.h.in when CPP rules must be copied
into the generated "roken.h".
Correct verr() attribute to be ROKEN_LIB_NORETURN_FUNCTION.
Change-Id: I4289ecaba4a097175b4a5a1cde529b59038c72e3
