detect: add email.cc keyword

email.cc matches on MIME EMAIL Carbon Copy
This keyword maps to the EVE field email.cc[]
It is a sticky buffer
Supports prefiltering

Ticket: #7588

doc/userguide/rules/email-keywords.rst

@@ -74,3 +74,27 @@ Example of a signature that would alert if a packet contains the MIME field ``to
 .. container:: example-rule
 
   alert smtp any any -> any any (msg:"Test mime email to"; :example-rule-emphasis:`email.to; content:"172.16.92.2@linuxbox";` sid:1;)
+
+email.cc
+--------
+
+Matches the MIME ``Cc`` field of an email.
+
+Comparison is case-sensitive.
+
+Syntax::
+
+ email.cc; content:"<content to match against>";
+
+``email.cc`` is a 'sticky buffer' and can be used as a ``fast_pattern``.
+
+This keyword maps to the EVE field ``email.cc[]``
+
+Example
+^^^^^^^
+
+Example of a signature that would alert if a packet contains the MIME field ``cc`` with the value ``Emily <emily.roberts@example.com>, Ava <ava.johnson@example.com>, Sophia Wilson <sophia.wilson@example.com>``
+
+.. container:: example-rule
+
+  alert smtp any any -> any any (msg:"Test mime email cc"; :example-rule-emphasis:`email.cc; content:"Emily <emily.roberts@example.com>, Ava <ava.johnson@example.com>, Sophia Wilson <sophia.wilson@example.com>";` sid:1;)

doc/userguide/rules/multi-buffer-matching.rst

@@ -47,7 +47,7 @@ Example rule:
 
 The above rule will alert on a single dns query containing
 "example.net" or "example.domain.net" since the rule content
-matches are within a single ``dns.query`` buffer and all 
+matches are within a single ``dns.query`` buffer and all
 content match requirements of the rule are met.
 
 
@@ -65,7 +65,7 @@ Using our example from above, the first query is for example.net
 which matches content:"example"; but does not match content:".com";
 
 The second query is for something.com which would match on the
-content:".com"; but not the content:"example"; 
+content:".com"; but not the content:"example";
 
 So with the Suricata behavior prior to Suricata 7, the signature
 would not fire in this case since both content conditions will

rust/src/mime/detect.rs

@@ -20,6 +20,8 @@ use super::smtp::MimeStateSMTP;
 use std::ffi::CStr;
 use std::ptr;
 
+/// Intermediary function used in detect-email.c to access data from the MimeStateSMTP structure.
+/// The hname parameter determines which data will be returned.
 #[no_mangle]
 pub unsafe extern "C" fn SCDetectMimeEmailGetData(
     ctx: &MimeStateSMTP, buffer: *mut *const u8, buffer_len: *mut u32,

src/detect-email.c

@@ -25,6 +25,7 @@
 static int g_mime_email_from_buffer_id = 0;
 static int g_mime_email_subject_buffer_id = 0;
 static int g_mime_email_to_buffer_id = 0;
+static int g_mime_email_cc_buffer_id = 0;
 
 static int DetectMimeEmailFromSetup(DetectEngineCtx *de_ctx, Signature *s, const char *arg)
 {
@@ -131,6 +132,40 @@ static InspectionBuffer *GetMimeEmailToData(DetectEngineThreadCtx *det_ctx,
     return buffer;
 }
 
+static int DetectMimeEmailCcSetup(DetectEngineCtx *de_ctx, Signature *s, const char *arg)
+{
+    if (DetectBufferSetActiveList(de_ctx, s, g_mime_email_cc_buffer_id) < 0)
+        return -1;
+
+    if (DetectSignatureSetAppProto(s, ALPROTO_SMTP) < 0)
+        return -1;
+
+    return 0;
+}
+
+static InspectionBuffer *GetMimeEmailCcData(DetectEngineThreadCtx *det_ctx,
+        const DetectEngineTransforms *transforms, Flow *f, const uint8_t _flow_flags, void *txv,
+        const int list_id)
+{
+    InspectionBuffer *buffer = InspectionBufferGet(det_ctx, list_id);
+    if (buffer->inspect == NULL) {
+        SMTPTransaction *tx = (SMTPTransaction *)txv;
+
+        const uint8_t *b_email_cc = NULL;
+        uint32_t b_email_cc_len = 0;
+
+        if (tx->mime_state == NULL)
+            return NULL;
+
+        if (SCDetectMimeEmailGetData(tx->mime_state, &b_email_cc, &b_email_cc_len, "cc") != 1)
+            return NULL;
+
+        InspectionBufferSetup(det_ctx, list_id, buffer, b_email_cc, b_email_cc_len);
+        InspectionBufferApplyTransforms(buffer, transforms);
+    }
+    return buffer;
+}
+
 void DetectEmailRegister(void)
 {
     SCSigTableElmt kw = { 0 };
@@ -167,4 +202,15 @@ void DetectEmailRegister(void)
             DetectHelperBufferMpmRegister("email.to", "MIME EMAIL TO", ALPROTO_SMTP, false,
                     true, // to server
                     GetMimeEmailToData);
+
+    kw.name = "email.cc";
+    kw.desc = "'Cc' field from an email";
+    kw.url = "/rules/email-keywords.html#email.cc";
+    kw.Setup = (int (*)(void *, void *, const char *))DetectMimeEmailCcSetup;
+    kw.flags = SIGMATCH_NOOPT | SIGMATCH_INFO_STICKY_BUFFER;
+    DetectHelperKeywordRegister(&kw);
+    g_mime_email_cc_buffer_id =
+            DetectHelperBufferMpmRegister("email.cc", "MIME EMAIL CC", ALPROTO_SMTP, false,
+                    true, // to server
+                    GetMimeEmailCcData);
 }