forked from osmocom/wireshark
packet-kerberos: try to verify the PAC checksums and display the used keys
This makes it much easier to analyze how PAC signing is supposed to work with trusted domains. Change-Id: I9993e5d92b7efee5aa91cd0e2005787f7d384444 Signed-off-by: Stefan Metzmacher <metze@samba.org> Reviewed-on: https://code.wireshark.org/review/35704 Petri-Dish: Anders Broman <a.broman58@gmail.com> Tested-by: Petri Dish Buildbot Reviewed-by: Anders Broman <a.broman58@gmail.com>osmith/wip
Stefan Metzmacher
Anders Broman
parent
23a6fab52e
commit
d9aab840a7
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@ -54,6 +54,7 @@
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#include <wsutil/wsgcrypt.h>
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#include <wsutil/file_util.h>
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#include <wsutil/str_util.h>
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#include <wsutil/pint.h>
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#include "packet-kerberos.h"
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#include "packet-netbios.h"
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#include "packet-tcp.h"
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@ -295,6 +296,22 @@ static void used_encryption_key(proto_tree *tree, packet_info *pinfo,
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ek->keyvalue[2] & 0xFF, ek->keyvalue[3] & 0xFF);
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}
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#ifdef HAVE_MIT_KERBEROS
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static void used_signing_key(proto_tree *tree, packet_info *pinfo,
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enc_key_t *ek, tvbuff_t *tvb,
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krb5_cksumtype checksum,
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const char *reason)
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{
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proto_tree_add_expert_format(tree, pinfo, &ei_kerberos_decrypted_keytype,
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tvb, 0, 0,
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"%s checksum %d keytype %d in frame %u "
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"using %s (%02x%02x%02x%02x...)",
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reason, checksum, ek->keytype, pinfo->fd->num, ek->key_origin,
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ek->keyvalue[0] & 0xFF, ek->keyvalue[1] & 0xFF,
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ek->keyvalue[2] & 0xFF, ek->keyvalue[3] & 0xFF);
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}
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#endif /* HAVE_MIT_KERBEROS */
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#endif /* HAVE_HEIMDAL_KERBEROS || HAVE_MIT_KERBEROS */
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#if defined(HAVE_MIT_KERBEROS)
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@ -443,6 +460,101 @@ decrypt_krb5_data(proto_tree *tree _U_, packet_info *pinfo,
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}
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USES_APPLE_RST
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extern krb5_error_code
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krb5int_c_mandatory_cksumtype(krb5_context, krb5_enctype, krb5_cksumtype *);
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static void
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verify_krb5_pac(proto_tree *tree _U_, asn1_ctx_t *actx, tvbuff_t *pactvb)
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{
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krb5_error_code ret;
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enc_key_t *ek = NULL;;
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krb5_data checksum_data = {0,0,NULL};
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krb5_cksumtype server_checksum = 0;
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krb5_cksumtype kdc_checksum = 0;
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int length = tvb_captured_length(pactvb);
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const guint8 *pacbuffer = NULL;
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krb5_pac pac;
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/* don't do anything if we are not attempting to decrypt data */
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if(!krb_decrypt || length < 1){
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return;
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}
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/* make sure we have all the data we need */
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if (tvb_captured_length(pactvb) < tvb_reported_length(pactvb)) {
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return;
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}
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pacbuffer = tvb_get_ptr(pactvb, 0, length);
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ret = krb5_pac_parse(krb5_ctx, pacbuffer, length, &pac);
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if (ret != 0) {
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proto_tree_add_expert_format(tree, actx->pinfo, &ei_kerberos_decrypted_keytype,
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pactvb, 0, 0,
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"Failed to parse PAC buffer %d in frame %u",
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ret, actx->pinfo->fd->num);
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return;
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}
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ret = krb5_pac_get_buffer(krb5_ctx, pac, KRB5_PAC_SERVER_CHECKSUM,
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&checksum_data);
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if (ret == 0) {
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server_checksum = pletoh32(checksum_data.data);
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krb5_free_data_contents(krb5_ctx, &checksum_data);
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};
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ret = krb5_pac_get_buffer(krb5_ctx, pac, KRB5_PAC_PRIVSVR_CHECKSUM,
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&checksum_data);
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if (ret == 0) {
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kdc_checksum = pletoh32(checksum_data.data);
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krb5_free_data_contents(krb5_ctx, &checksum_data);
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};
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read_keytab_file_from_preferences();
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for(ek=enc_key_list;ek;ek=ek->next){
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krb5_keyblock keyblock;
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krb5_cksumtype checksumtype = 0;
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if (server_checksum == 0 && kdc_checksum == 0) {
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break;
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}
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ret = krb5int_c_mandatory_cksumtype(krb5_ctx, ek->keytype,
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&checksumtype);
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if (ret != 0) {
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continue;
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}
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keyblock.magic = KV5M_KEYBLOCK;
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keyblock.enctype = ek->keytype;
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keyblock.length = ek->keylength;
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keyblock.contents = (guint8 *)ek->keyvalue;
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if (checksumtype == server_checksum) {
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ret = krb5_pac_verify(krb5_ctx, pac, 0, NULL,
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&keyblock, NULL);
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if (ret == 0) {
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used_signing_key(tree, actx->pinfo, ek, pactvb,
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server_checksum, "Verified Server");
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server_checksum = 0;
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}
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}
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if (checksumtype == kdc_checksum) {
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ret = krb5_pac_verify(krb5_ctx, pac, 0, NULL,
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NULL, &keyblock);
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if (ret == 0) {
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used_signing_key(tree, actx->pinfo, ek, pactvb,
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kdc_checksum, "Verified KDC");
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kdc_checksum = 0;
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}
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}
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}
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krb5_pac_free(krb5_ctx, pac);
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}
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#elif defined(HAVE_HEIMDAL_KERBEROS)
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static krb5_context krb5_ctx;
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@ -1897,6 +2009,10 @@ dissect_krb5_AD_WIN2K_PAC(gboolean implicit_tag _U_, tvbuff_t *tvb, int offset,
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guint32 version;
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guint32 i;
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#ifdef HAVE_MIT_KERBEROS
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verify_krb5_pac(tree, actx, tvb);
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#endif
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/* first in the PAC structure comes the number of entries */
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entries=tvb_get_letohl(tvb, offset);
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proto_tree_add_uint(tree, hf_krb_w2k_pac_entries, tvb, offset, 4, entries);
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@ -62,6 +62,7 @@
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#include <wsutil/wsgcrypt.h>
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#include <wsutil/file_util.h>
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#include <wsutil/str_util.h>
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#include <wsutil/pint.h>
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#include "packet-kerberos.h"
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#include "packet-netbios.h"
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#include "packet-tcp.h"
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@ -387,7 +388,7 @@ static int hf_kerberos_PAC_OPTIONS_FLAGS_forward_to_full_dc = -1;
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static int hf_kerberos_PAC_OPTIONS_FLAGS_resource_based_constrained_delegation = -1;
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/*--- End of included file: packet-kerberos-hf.c ---*/
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#line 173 "./asn1/kerberos/packet-kerberos-template.c"
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#line 174 "./asn1/kerberos/packet-kerberos-template.c"
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/* Initialize the subtree pointers */
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static gint ett_kerberos = -1;
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@ -475,7 +476,7 @@ static gint ett_kerberos_PA_FX_FAST_REPLY = -1;
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static gint ett_kerberos_KrbFastArmoredRep = -1;
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/*--- End of included file: packet-kerberos-ett.c ---*/
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#line 187 "./asn1/kerberos/packet-kerberos-template.c"
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#line 188 "./asn1/kerberos/packet-kerberos-template.c"
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static expert_field ei_kerberos_decrypted_keytype = EI_INIT;
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static expert_field ei_kerberos_address = EI_INIT;
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@ -503,7 +504,7 @@ static gboolean gbl_do_col_info;
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#define KERBEROS_ADDR_TYPE_IPV6 24
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/*--- End of included file: packet-kerberos-val.h ---*/
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#line 199 "./asn1/kerberos/packet-kerberos-template.c"
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#line 200 "./asn1/kerberos/packet-kerberos-template.c"
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static void
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call_kerberos_callbacks(packet_info *pinfo, proto_tree *tree, tvbuff_t *tvb, int tag, kerberos_callbacks *cb)
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@ -598,11 +599,27 @@ static void used_encryption_key(proto_tree *tree, packet_info *pinfo,
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cryptotvb, 0, 0,
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"Decrypted keytype %d usage %d in frame %u "
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"using %s (%02x%02x%02x%02x...)",
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ek->keytype, pinfo->fd->num, usage, ek->key_origin,
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ek->keytype, usage, pinfo->fd->num, ek->key_origin,
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ek->keyvalue[0] & 0xFF, ek->keyvalue[1] & 0xFF,
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ek->keyvalue[2] & 0xFF, ek->keyvalue[3] & 0xFF);
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}
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#ifdef HAVE_MIT_KERBEROS
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static void used_signing_key(proto_tree *tree, packet_info *pinfo,
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enc_key_t *ek, tvbuff_t *tvb,
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krb5_cksumtype checksum,
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const char *reason)
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{
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proto_tree_add_expert_format(tree, pinfo, &ei_kerberos_decrypted_keytype,
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tvb, 0, 0,
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"%s checksum %d keytype %d in frame %u "
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"using %s (%02x%02x%02x%02x...)",
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reason, checksum, ek->keytype, pinfo->fd->num, ek->key_origin,
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ek->keyvalue[0] & 0xFF, ek->keyvalue[1] & 0xFF,
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ek->keyvalue[2] & 0xFF, ek->keyvalue[3] & 0xFF);
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}
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#endif /* HAVE_MIT_KERBEROS */
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#endif /* HAVE_HEIMDAL_KERBEROS || HAVE_MIT_KERBEROS */
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#if defined(HAVE_MIT_KERBEROS)
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@ -751,6 +768,101 @@ decrypt_krb5_data(proto_tree *tree _U_, packet_info *pinfo,
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}
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USES_APPLE_RST
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extern krb5_error_code
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krb5int_c_mandatory_cksumtype(krb5_context, krb5_enctype, krb5_cksumtype *);
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static void
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verify_krb5_pac(proto_tree *tree _U_, asn1_ctx_t *actx, tvbuff_t *pactvb)
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{
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krb5_error_code ret;
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enc_key_t *ek = NULL;;
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krb5_data checksum_data = {0,0,NULL};
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krb5_cksumtype server_checksum = 0;
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krb5_cksumtype kdc_checksum = 0;
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int length = tvb_captured_length(pactvb);
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const guint8 *pacbuffer = NULL;
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krb5_pac pac;
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/* don't do anything if we are not attempting to decrypt data */
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if(!krb_decrypt || length < 1){
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return;
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}
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/* make sure we have all the data we need */
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if (tvb_captured_length(pactvb) < tvb_reported_length(pactvb)) {
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return;
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}
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pacbuffer = tvb_get_ptr(pactvb, 0, length);
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ret = krb5_pac_parse(krb5_ctx, pacbuffer, length, &pac);
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if (ret != 0) {
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proto_tree_add_expert_format(tree, actx->pinfo, &ei_kerberos_decrypted_keytype,
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pactvb, 0, 0,
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"Failed to parse PAC buffer %d in frame %u",
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ret, actx->pinfo->fd->num);
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return;
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}
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ret = krb5_pac_get_buffer(krb5_ctx, pac, KRB5_PAC_SERVER_CHECKSUM,
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&checksum_data);
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if (ret == 0) {
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server_checksum = pletoh32(checksum_data.data);
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krb5_free_data_contents(krb5_ctx, &checksum_data);
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};
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ret = krb5_pac_get_buffer(krb5_ctx, pac, KRB5_PAC_PRIVSVR_CHECKSUM,
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&checksum_data);
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if (ret == 0) {
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kdc_checksum = pletoh32(checksum_data.data);
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krb5_free_data_contents(krb5_ctx, &checksum_data);
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};
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read_keytab_file_from_preferences();
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for(ek=enc_key_list;ek;ek=ek->next){
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krb5_keyblock keyblock;
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krb5_cksumtype checksumtype = 0;
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if (server_checksum == 0 && kdc_checksum == 0) {
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break;
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}
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ret = krb5int_c_mandatory_cksumtype(krb5_ctx, ek->keytype,
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&checksumtype);
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if (ret != 0) {
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continue;
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}
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keyblock.magic = KV5M_KEYBLOCK;
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keyblock.enctype = ek->keytype;
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keyblock.length = ek->keylength;
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keyblock.contents = (guint8 *)ek->keyvalue;
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if (checksumtype == server_checksum) {
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ret = krb5_pac_verify(krb5_ctx, pac, 0, NULL,
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&keyblock, NULL);
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if (ret == 0) {
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used_signing_key(tree, actx->pinfo, ek, pactvb,
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server_checksum, "Verified Server");
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server_checksum = 0;
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}
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}
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if (checksumtype == kdc_checksum) {
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ret = krb5_pac_verify(krb5_ctx, pac, 0, NULL,
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NULL, &keyblock);
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if (ret == 0) {
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used_signing_key(tree, actx->pinfo, ek, pactvb,
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kdc_checksum, "Verified KDC");
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kdc_checksum = 0;
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}
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}
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}
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krb5_pac_free(krb5_ctx, pac);
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}
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#elif defined(HAVE_HEIMDAL_KERBEROS)
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static krb5_context krb5_ctx;
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@ -2205,6 +2317,10 @@ dissect_krb5_AD_WIN2K_PAC(gboolean implicit_tag _U_, tvbuff_t *tvb, int offset,
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guint32 version;
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guint32 i;
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#ifdef HAVE_MIT_KERBEROS
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verify_krb5_pac(tree, actx, tvb);
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#endif
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/* first in the PAC structure comes the number of entries */
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entries=tvb_get_letohl(tvb, offset);
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proto_tree_add_uint(tree, hf_krb_w2k_pac_entries, tvb, offset, 4, entries);
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@ -4657,7 +4773,7 @@ dissect_kerberos_EncryptedChallenge(gboolean implicit_tag _U_, tvbuff_t *tvb _U_
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/*--- End of included file: packet-kerberos-fn.c ---*/
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#line 1918 "./asn1/kerberos/packet-kerberos-template.c"
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#line 2034 "./asn1/kerberos/packet-kerberos-template.c"
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/* Make wrappers around exported functions for now */
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int
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@ -5865,7 +5981,7 @@ void proto_register_kerberos(void) {
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NULL, HFILL }},
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/*--- End of included file: packet-kerberos-hfarr.c ---*/
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#line 2305 "./asn1/kerberos/packet-kerberos-template.c"
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#line 2421 "./asn1/kerberos/packet-kerberos-template.c"
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};
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/* List of subtrees */
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@ -5955,7 +6071,7 @@ void proto_register_kerberos(void) {
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&ett_kerberos_KrbFastArmoredRep,
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/*--- End of included file: packet-kerberos-ettarr.c ---*/
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#line 2321 "./asn1/kerberos/packet-kerberos-template.c"
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#line 2437 "./asn1/kerberos/packet-kerberos-template.c"
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};
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static ei_register_info ei[] = {
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