Create CVE-2017-11882.yar

https://github.com/Yara-Rules/rules/issues/280

CVE_Rules/CVE-2017-11882.yar

+rule potential_CVE_2017_11882
+{
+    meta:
+      author = "ReversingLabs"
+      reference = "https://www.reversinglabs.com/newsroom/news/reversinglabs-yara-rule-detects-cobalt-strike-payload-exploiting-cve-2017-11882.html"
+      
+    strings:
+        $docfilemagic = { D0 CF 11 E0 A1 B1 1A E1 }
+
+        $equation1 = "Equation Native" wide ascii
+        $equation2 = "Microsoft Equation 3.0" wide ascii
+
+        $mshta = "mshta"
+        $http  = "http://"
+        $https = "https://"
+        $cmd   = "cmd"
+        $pwsh  = "powershell"
+        $exe   = ".exe"
+
+        $address = { 12 0C 43 00 }
+
+    condition:
+        $docfilemagic at 0 and any of ($mshta, $http, $https, $cmd, $pwsh, $exe) and any of ($equation1, $equation2) and $address
+}
+
+rule rtf_cve2017_11882_ole : malicious exploit cve_2017_11882 {
+    meta:
+        author = "John Davison"
+        description = "Attempts to identify the exploit CVE 2017 11882"
+        reference = "https://embedi.com/blog/skeleton-closet-ms-office-vulnerability-you-didnt-know-about"
+        sample = "51cf2a6c0c1a29abca9fd13cb22421da"
+        score = 60
+        //file_name = "re:^stream_[0-9]+_[0-9]+.dat$"
+    strings:
+        $headers = { 1c 00 00 00 02 00 ?? ?? a9 00 00 00 ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? 03 01 01 03 ?? }
+        $font = { 0a 01 08 5a 5a } // <-- I think that 5a 5a is the trigger for the buffer overflow
+        //$code = /[\x01-\x7F]{44}/
+        $winexec = { 12 0c 43 00 }
+    condition:
+        all of them and @font > @headers and @winexec == @font + 5 + 44
+}
+
+// same as above but for RTF documents
+rule rtf_cve2017_11882 : malicious exploit cve_2017_1182 {
+    meta:
+        author = "John Davison"
+        description = "Attempts to identify the exploit CVE 2017 11882"
+        reference = "https://embedi.com/blog/skeleton-closet-ms-office-vulnerability-you-didnt-know-about"
+        sample = "51cf2a6c0c1a29abca9fd13cb22421da"
+        score = 60
+        //file_ext = "rtf"
+    strings:
+        $headers = { 31 63 30 30 30 30 30 30  30 32 30 30 ?? ?? ?? ??
+                     61 39 30 30 30 30 30 30  ?? ?? ?? ?? ?? ?? ?? ??
+                     ?? ?? ?? ?? ?? ?? ?? ??  ?? ?? ?? ?? ?? ?? ?? ??
+                     ?? ?? ?? ?? ?? ?? ?? ??  30 33 30 31 30 31 30 33
+                     ?? ?? }
+        $font = { 30 61 30 31 30 38 35 61  35 61 }
+        $winexec = { 31 32 30 63 34 33 30 30 }
+    condition:
+        all of them and @font > @headers and @winexec == @font + ((5 + 44) * 2)
+}