1 files changed, 253 insertions, 0 deletions
diff --git a/src/detect-krb5-errcode.c b/src/detect-krb5-errcode.c
new file mode 100644
index 0000000..30c516f
--- /dev/null
+++ b/src/detect-krb5-errcode.c
@@ -0,0 +1,253 @@
+/* Copyright (C) 2018-2020 Open Information Security Foundation
+ *
+ * You can copy, redistribute or modify this Program under the terms of
+ * the GNU General Public License version 2 as published by the Free
+ * Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * version 2 along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+/**
+ * \file
+ *
+ * \author Pierre Chifflier <chifflier@wzdftpd.net>
+ */
+
+#include "suricata-common.h"
+#include "util-unittest.h"
+#include "util-byte.h"
+
+#include "detect-parse.h"
+#include "detect-engine.h"
+
+#include "detect-krb5-errcode.h"
+
+#include "app-layer-krb5.h"
+#include "rust.h"
+
+/**
+ * \brief Regex for parsing our keyword options
+ */
+#define PARSE_REGEX  "^\\s*([A-z0-9\\.]+|\"[A-z0-9_\\.]+\")\\s*$"
+static DetectParseRegex parse_regex;
+
+/* Prototypes of functions registered in DetectKrb5ErrCodeRegister below */
+static int DetectKrb5ErrCodeMatch (DetectEngineThreadCtx *, Flow *,
+                                   uint8_t, void *, void *, const Signature *,
+                                   const SigMatchCtx *);
+static int DetectKrb5ErrCodeSetup (DetectEngineCtx *, Signature *, const char *);
+static void DetectKrb5ErrCodeFree (DetectEngineCtx *, void *);
+#ifdef UNITTESTS
+static void DetectKrb5ErrCodeRegisterTests (void);
+#endif
+
+static int g_krb5_err_code_list_id = 0;
+
+/**
+ * \brief Registration function for krb5_err_code: keyword
+ *
+ * This function is called once in the 'lifetime' of the engine.
+ */
+void DetectKrb5ErrCodeRegister(void)
+{
+    sigmatch_table[DETECT_AL_KRB5_ERRCODE].name = "krb5_err_code";
+    sigmatch_table[DETECT_AL_KRB5_ERRCODE].desc = "match Kerberos 5 error code";
+    sigmatch_table[DETECT_AL_KRB5_ERRCODE].url = "/rules/kerberos-keywords.html#krb5-err-code";
+    sigmatch_table[DETECT_AL_KRB5_ERRCODE].Match = NULL;
+    sigmatch_table[DETECT_AL_KRB5_ERRCODE].AppLayerTxMatch = DetectKrb5ErrCodeMatch;
+    sigmatch_table[DETECT_AL_KRB5_ERRCODE].Setup = DetectKrb5ErrCodeSetup;
+    sigmatch_table[DETECT_AL_KRB5_ERRCODE].Free = DetectKrb5ErrCodeFree;
+#ifdef UNITTESTS
+    sigmatch_table[DETECT_AL_KRB5_ERRCODE].RegisterTests = DetectKrb5ErrCodeRegisterTests;
+#endif
+
+    DetectAppLayerInspectEngineRegister2("krb5_err_code", ALPROTO_KRB5, SIG_FLAG_TOSERVER, 0,
+            DetectEngineInspectGenericList, NULL);
+
+    DetectAppLayerInspectEngineRegister2("krb5_err_code", ALPROTO_KRB5, SIG_FLAG_TOCLIENT, 0,
+            DetectEngineInspectGenericList, NULL);
+
+    /* set up the PCRE for keyword parsing */
+    DetectSetupParseRegexes(PARSE_REGEX, &parse_regex);
+
+    g_krb5_err_code_list_id = DetectBufferTypeRegister("krb5_err_code");
+    SCLogDebug("g_krb5_err_code_list_id %d", g_krb5_err_code_list_id);
+}
+
+/**
+ * \brief This function is used to match KRB5 rule option on a packet
+ *
+ * \param t pointer to thread vars
+ * \param det_ctx pointer to the pattern matcher thread
+ * \param p pointer to the current packet
+ * \param m pointer to the sigmatch with context that we will cast into DetectKrb5Data
+ *
+ * \retval 0 no match
+ * \retval 1 match
+ */
+static int DetectKrb5ErrCodeMatch (DetectEngineThreadCtx *det_ctx,
+                                   Flow *f, uint8_t flags, void *state,
+                                   void *txv, const Signature *s,
+                                   const SigMatchCtx *ctx)
+{
+    int32_t err_code;
+    int ret;
+    const DetectKrb5ErrCodeData *dd = (const DetectKrb5ErrCodeData *)ctx;
+
+    SCEnter();
+
+    ret = rs_krb5_tx_get_errcode(txv, &err_code);
+    if (ret != 0)
+        SCReturnInt(0);
+
+    if (dd->err_code == err_code)
+        SCReturnInt(1);
+
+    SCReturnInt(0);
+}
+
+/**
+ * \brief This function is used to parse options passed via krb5_errcode: keyword
+ *
+ * \param krb5str Pointer to the user provided krb5_err_code options
+ *
+ * \retval krb5d pointer to DetectKrb5Data on success
+ * \retval NULL on failure
+ */
+static DetectKrb5ErrCodeData *DetectKrb5ErrCodeParse (const char *krb5str)
+{
+    DetectKrb5ErrCodeData *krb5d = NULL;
+    char arg1[4] = "";
+    int res = 0;
+    size_t pcre2len;
+
+    pcre2_match_data *match = NULL;
+    int ret = DetectParsePcreExec(&parse_regex, &match, krb5str, 0, 0);
+    if (ret != 2) {
+        SCLogError("parse error, ret %" PRId32 "", ret);
+        goto error;
+    }
+
+    pcre2len = sizeof(arg1);
+    res = pcre2_substring_copy_bynumber(match, 1, (PCRE2_UCHAR8 *)arg1, &pcre2len);
+    if (res < 0) {
+        SCLogError("pcre2_substring_copy_bynumber failed");
+        goto error;
+    }
+
+    krb5d = SCMalloc(sizeof (DetectKrb5ErrCodeData));
+    if (unlikely(krb5d == NULL))
+        goto error;
+    if (StringParseInt32(&krb5d->err_code, 10, 0,
+                         (const char *)arg1) < 0) {
+        goto error;
+    }
+    pcre2_match_data_free(match);
+    return krb5d;
+
+error:
+    if (match) {
+        pcre2_match_data_free(match);
+    }
+    if (krb5d)
+        SCFree(krb5d);
+    return NULL;
+}
+
+/**
+ * \brief parse the options from the 'krb5_err_code' keyword in the rule into
+ *        the Signature data structure.
+ *
+ * \param de_ctx pointer to the Detection Engine Context
+ * \param s pointer to the Current Signature
+ * \param krb5str pointer to the user provided options
+ *
+ * \retval 0 on Success
+ * \retval -1 on Failure
+ */
+static int DetectKrb5ErrCodeSetup (DetectEngineCtx *de_ctx, Signature *s, const char *krb5str)
+{
+    DetectKrb5ErrCodeData *krb5d = NULL;
+    SigMatch *sm = NULL;
+
+    if (DetectSignatureSetAppProto(s, ALPROTO_KRB5) != 0)
+        return -1;
+
+    krb5d = DetectKrb5ErrCodeParse(krb5str);
+    if (krb5d == NULL)
+        goto error;
+
+    sm = SigMatchAlloc();
+    if (sm == NULL)
+        goto error;
+
+    sm->type = DETECT_AL_KRB5_ERRCODE;
+    sm->ctx = (void *)krb5d;
+
+    SigMatchAppendSMToList(s, sm, g_krb5_err_code_list_id);
+
+    return 0;
+
+error:
+    if (krb5d != NULL)
+        DetectKrb5ErrCodeFree(de_ctx, krb5d);
+    if (sm != NULL)
+        SCFree(sm);
+    return -1;
+}
+
+/**
+ * \brief this function will free memory associated with DetectKrb5Data
+ *
+ * \param ptr pointer to DetectKrb5Data
+ */
+static void DetectKrb5ErrCodeFree(DetectEngineCtx *de_ctx, void *ptr) {
+    DetectKrb5ErrCodeData *krb5d = (DetectKrb5ErrCodeData *)ptr;
+
+    SCFree(krb5d);
+}
+
+#ifdef UNITTESTS
+/**
+ * \test description of the test
+ */
+
+static int DetectKrb5ErrCodeParseTest01 (void)
+{
+    DetectKrb5ErrCodeData *krb5d = DetectKrb5ErrCodeParse("10");
+    FAIL_IF_NULL(krb5d);
+    FAIL_IF(!(krb5d->err_code == 10));
+    DetectKrb5ErrCodeFree(NULL, krb5d);
+    PASS;
+}
+
+static int DetectKrb5ErrCodeSignatureTest01 (void)
+{
+    DetectEngineCtx *de_ctx = DetectEngineCtxInit();
+    FAIL_IF_NULL(de_ctx);
+
+    Signature *sig = DetectEngineAppendSig(de_ctx, "alert krb5 any any -> any any (krb5_err_code:10; sid:1; rev:1;)");
+    FAIL_IF_NULL(sig);
+
+    DetectEngineCtxFree(de_ctx);
+    PASS;
+}
+
+/**
+ * \brief this function registers unit tests for DetectKrb5ErrCode
+ */
+static void DetectKrb5ErrCodeRegisterTests(void)
+{
+    UtRegisterTest("DetectKrb5ErrCodeParseTest01", DetectKrb5ErrCodeParseTest01);
+    UtRegisterTest("DetectKrb5ErrCodeSignatureTest01",
+                   DetectKrb5ErrCodeSignatureTest01);
+}
+#endif /* UNITTESTS */