1 /* Copyright (C) 2015-2020 Open Information Security Foundation
2  *
3  * You can copy, redistribute or modify this Program under the terms of
4  * the GNU General Public License version 2 as published by the Free
5  * Software Foundation.
6  *
7  * This program is distributed in the hope that it will be useful,
8  * but WITHOUT ANY WARRANTY; without even the implied warranty of
9  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
10  * GNU General Public License for more details.
11  *
12  * You should have received a copy of the GNU General Public License
13  * version 2 along with this program; if not, write to the Free Software
14  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
15  * 02110-1301, USA.
16  */
17 
18 /**
19  * \file
20  *
21  * \author XXX Yourname <youremail@yourdomain>
22  *
23  * XXX Short description of the purpose of this keyword
24  */
25 
26 #include "suricata-common.h"
27 #include "util-unittest.h"
28 #include "util-byte.h"
29 
30 #include "detect-parse.h"
31 #include "detect-engine.h"
32 
33 #include "detect-template.h"
34 
35 /**
36  * \brief Regex for parsing our keyword options
37  */
38 #define PARSE_REGEX  "^\\s*([0-9]+)?\\s*,s*([0-9]+)?\\s*$"
39 static DetectParseRegex parse_regex;
40 
41 /* Prototypes of functions registered in DetectTemplateRegister below */
42 static int DetectTemplateMatch (DetectEngineThreadCtx *,
43         Packet *, const Signature *, const SigMatchCtx *);
44 static int DetectTemplateSetup (DetectEngineCtx *, Signature *, const char *);
45 static void DetectTemplateFree (DetectEngineCtx *, void *);
46 #ifdef UNITTESTS
47 static void DetectTemplateRegisterTests (void);
48 #endif
49 
50 /**
51  * \brief Registration function for template: keyword
52  *
53  * This function is called once in the 'lifetime' of the engine.
54  */
DetectTemplateRegister(void)55 void DetectTemplateRegister(void) {
56     /* keyword name: this is how the keyword is used in a rule */
57     sigmatch_table[DETECT_TEMPLATE].name = "template";
58     /* description: listed in "suricata --list-keywords=all" */
59     sigmatch_table[DETECT_TEMPLATE].desc = "give an introduction into how a detection module works";
60     /* link to further documentation of the keyword. Normally on the Suricata redmine/wiki */
61     sigmatch_table[DETECT_TEMPLATE].url = "https://redmine.openinfosecfoundation.org/projects/suricata/wiki/Suricata_Developers_Guide";
62     /* match function is called when the signature is inspected on a packet */
63     sigmatch_table[DETECT_TEMPLATE].Match = DetectTemplateMatch;
64     /* setup function is called during signature parsing, when the template
65      * keyword is encountered in the rule */
66     sigmatch_table[DETECT_TEMPLATE].Setup = DetectTemplateSetup;
67     /* free function is called when the detect engine is freed. Normally at
68      * shutdown, but also during rule reloads. */
69     sigmatch_table[DETECT_TEMPLATE].Free = DetectTemplateFree;
70 #ifdef UNITTESTS
71     /* registers unittests into the system */
72     sigmatch_table[DETECT_TEMPLATE].RegisterTests = DetectTemplateRegisterTests;
73 #endif
74     /* set up the PCRE for keyword parsing */
75     DetectSetupParseRegexes(PARSE_REGEX, &parse_regex);
76 }
77 
78 /**
79  * \brief This function is used to match TEMPLATE rule option on a packet
80  *
81  * \param t pointer to thread vars
82  * \param det_ctx pointer to the pattern matcher thread
83  * \param p pointer to the current packet
84  * \param m pointer to the sigmatch with context that we will cast into DetectTemplateData
85  *
86  * \retval 0 no match
87  * \retval 1 match
88  */
DetectTemplateMatch(DetectEngineThreadCtx * det_ctx,Packet * p,const Signature * s,const SigMatchCtx * ctx)89 static int DetectTemplateMatch (DetectEngineThreadCtx *det_ctx, Packet *p,
90                                 const Signature *s, const SigMatchCtx *ctx)
91 {
92     int ret = 0;
93     const DetectTemplateData *templated = (const DetectTemplateData *) ctx;
94 #if 0
95     if (PKT_IS_PSEUDOPKT(p)) {
96         /* fake pkt */
97     }
98 
99     if (PKT_IS_IPV4(p)) {
100         /* ipv4 pkt */
101     } else if (PKT_IS_IPV6(p)) {
102         /* ipv6 pkt */
103     } else {
104         SCLogDebug("packet is of not IPv4 or IPv6");
105         return ret;
106     }
107 #endif
108     /* packet payload access */
109     if (p->payload != NULL && p->payload_len > 0) {
110         if (templated->arg1 == p->payload[0] &&
111             templated->arg2 == p->payload[p->payload_len - 1])
112         {
113             ret = 1;
114         }
115     }
116 
117     return ret;
118 }
119 
120 /**
121  * \brief This function is used to parse template options passed via template: keyword
122  *
123  * \param templatestr Pointer to the user provided template options
124  *
125  * \retval templated pointer to DetectTemplateData on success
126  * \retval NULL on failure
127  */
DetectTemplateParse(const char * templatestr)128 static DetectTemplateData *DetectTemplateParse (const char *templatestr)
129 {
130     char arg1[4] = "";
131     char arg2[4] = "";
132     int ov[MAX_SUBSTRINGS];
133 
134     int ret = DetectParsePcreExec(&parse_regex, templatestr, 0, 0, ov, MAX_SUBSTRINGS);
135     if (ret != 3) {
136         SCLogError(SC_ERR_PCRE_MATCH, "parse error, ret %" PRId32 "", ret);
137         return NULL;
138     }
139 
140     ret = pcre_copy_substring((char *) templatestr, ov, MAX_SUBSTRINGS, 1, arg1, sizeof(arg1));
141     if (ret < 0) {
142         SCLogError(SC_ERR_PCRE_GET_SUBSTRING, "pcre_copy_substring failed");
143         return NULL;
144     }
145     SCLogDebug("Arg1 \"%s\"", arg1);
146 
147     ret = pcre_copy_substring((char *) templatestr, ov, MAX_SUBSTRINGS, 2, arg2, sizeof(arg2));
148     if (ret < 0) {
149         SCLogError(SC_ERR_PCRE_GET_SUBSTRING, "pcre_copy_substring failed");
150         return NULL;
151     }
152     SCLogDebug("Arg2 \"%s\"", arg2);
153 
154     DetectTemplateData *templated = SCMalloc(sizeof (DetectTemplateData));
155     if (unlikely(templated == NULL))
156         return NULL;
157 
158     if (ByteExtractStringUint8(&templated->arg1, 10, 0, (const char *)arg1) < 0) {
159         SCFree(templated);
160         return NULL;
161     }
162     if (ByteExtractStringUint8(&templated->arg2, 10, 0, (const char *)arg2) < 0) {
163         SCFree(templated);
164         return NULL;
165     }
166     return templated;
167 }
168 
169 /**
170  * \brief parse the options from the 'template' keyword in the rule into
171  *        the Signature data structure.
172  *
173  * \param de_ctx pointer to the Detection Engine Context
174  * \param s pointer to the Current Signature
175  * \param templatestr pointer to the user provided template options
176  *
177  * \retval 0 on Success
178  * \retval -1 on Failure
179  */
DetectTemplateSetup(DetectEngineCtx * de_ctx,Signature * s,const char * templatestr)180 static int DetectTemplateSetup (DetectEngineCtx *de_ctx, Signature *s, const char *templatestr)
181 {
182     DetectTemplateData *templated = DetectTemplateParse(templatestr);
183     if (templated == NULL)
184         return -1;
185 
186     SigMatch *sm = SigMatchAlloc();
187     if (sm == NULL) {
188         DetectTemplateFree(de_ctx, templated);
189         return -1;
190     }
191 
192     sm->type = DETECT_TEMPLATE;
193     sm->ctx = (void *)templated;
194 
195     SigMatchAppendSMToList(s, sm, DETECT_SM_LIST_MATCH);
196     s->flags |= SIG_FLAG_REQUIRE_PACKET;
197 
198     return 0;
199 }
200 
201 /**
202  * \brief this function will free memory associated with DetectTemplateData
203  *
204  * \param ptr pointer to DetectTemplateData
205  */
DetectTemplateFree(DetectEngineCtx * de_ctx,void * ptr)206 static void DetectTemplateFree(DetectEngineCtx *de_ctx, void *ptr)
207 {
208     DetectTemplateData *templated = (DetectTemplateData *)ptr;
209 
210     /* do more specific cleanup here, if needed */
211 
212     SCFree(templated);
213 }
214 
215 #ifdef UNITTESTS
216 #include "tests/detect-template.c"
217 #endif
218