detect/integers: nb index to match a specific number of times

For example
dns.rrtype: !A,nb>3
will match if we have more than 3 dns records which are not A

doc/userguide/rules/integer-keywords.rst

@@ -109,6 +109,7 @@ They expand the syntax of a single integer::
     any        Match with any index
     all        Match only if all indexes match
     all1       Match only if all and at least one indexes match
+    nb         Matches a number of times
     0>=        Match specific index
     0<         Match specific index with back to front indexing
     =========  ================================================
@@ -116,3 +117,9 @@ They expand the syntax of a single integer::
 The index ``all`` will match if there is no value.
 The index ``all1`` will not match if there is no value and behaves
 like ``all`` if there is at least one value.
+These keywords will wait for transaction completion to run, to
+be sure to have the final number of elements.
+
+The index ``nb`` accepts all comparison modes as integer keywords.
+For example ``nb>3`` will match only if more than 3 integers in the
+array match the value.

rust/src/detect/uint.rs

@@ -17,7 +17,7 @@
 
 use nom7::branch::alt;
 use nom7::bytes::complete::{is_a, tag, tag_no_case, take_while};
-use nom7::character::complete::{char, digit1, hex_digit1};
+use nom7::character::complete::{char, digit1, hex_digit1, i32 as nom_i32};
 use nom7::combinator::{all_consuming, map_opt, opt, value, verify};
 use nom7::error::{make_error, Error, ErrorKind};
 use nom7::Err;
@@ -26,7 +26,6 @@ use nom7::IResult;
 use super::EnumString;
 
 use std::ffi::{c_int, c_void, CStr};
-use std::str::FromStr;
 
 #[derive(PartialEq, Eq, Clone, Debug)]
 #[repr(u8)]
@@ -57,6 +56,7 @@ pub enum DetectUintIndex {
     All,
     All1,
     Index(i32),
+    NumberMatches(DetectUintData<u32>),
 }
 
 #[derive(Debug, PartialEq)]
@@ -65,16 +65,30 @@ pub struct DetectUintArrayData<T> {
     pub index: DetectUintIndex,
 }
 
+fn parse_uint_index_precise(s: &str) -> IResult<&str, DetectUintIndex> {
+    let (s, i32_index) = nom_i32(s)?;
+    Ok((s, DetectUintIndex::Index(i32_index)))
+}
+
+fn parse_uint_index_nb(s: &str) -> IResult<&str, DetectUintIndex> {
+    let (s, _) = tag("nb")(s)?;
+    let (s, du32) = detect_parse_uint::<u32>(s)?;
+    Ok((s, DetectUintIndex::NumberMatches(du32)))
+}
+
+fn parse_uint_index_val(s: &str) -> Option<DetectUintIndex> {
+    let (_s, arg1) = alt((parse_uint_index_precise, parse_uint_index_nb))(s).ok()?;
+    Some(arg1)
+}
+
 fn parse_uint_index(parts: &[&str]) -> Option<DetectUintIndex> {
     let index = if parts.len() == 2 {
         match parts[1] {
             "all" => DetectUintIndex::All,
             "all1" => DetectUintIndex::All1,
             "any" => DetectUintIndex::Any,
-            _ => {
-                let i32_index = i32::from_str(parts[1]).ok()?;
-                DetectUintIndex::Index(i32_index)
-            }
+            // not only a literal, but some numeric value
+            _ => return parse_uint_index_val(parts[1]),
         }
     } else {
         DetectUintIndex::Any
@@ -111,7 +125,7 @@ pub(crate) fn detect_parse_array_uint_enum<T1: DetectIntType, T2: EnumString<T1>
 pub(crate) fn detect_uint_match_at_index<T, U: DetectIntType>(
     array: &[T], ctx: &DetectUintArrayData<U>, get_value: impl Fn(&T) -> Option<U>, eof: bool,
 ) -> c_int {
-    match ctx.index {
+    match &ctx.index {
         DetectUintIndex::Any => {
             for response in array {
                 if let Some(code) = get_value(response) {
@@ -122,6 +136,28 @@ pub(crate) fn detect_uint_match_at_index<T, U: DetectIntType>(
             }
             return 0;
         }
+        DetectUintIndex::NumberMatches(du32) => {
+            if !eof {
+                match du32.mode {
+                    DetectUintMode::DetectUintModeGt | DetectUintMode::DetectUintModeGte => {}
+                    _ => {
+                        return 0;
+                    }
+                }
+            }
+            let mut nb = 0u32;
+            for response in array {
+                if let Some(code) = get_value(response) {
+                    if detect_match_uint::<U>(&ctx.du, code) {
+                        nb += 1;
+                    }
+                }
+            }
+            if detect_match_uint(du32, nb) {
+                return 1;
+            }
+            return 0;
+        }
         DetectUintIndex::All => {
             if !eof {
                 return 0;
@@ -154,11 +190,11 @@ pub(crate) fn detect_uint_match_at_index<T, U: DetectIntType>(
             return 0;
         }
         DetectUintIndex::Index(idx) => {
-            let index = if idx < 0 {
+            let index = if *idx < 0 {
                 // negative values for backward indexing.
                 ((array.len() as i32) + idx) as usize
             } else {
-                idx as usize
+                *idx as usize
             };
             if array.len() <= index {
                 return 0;