requires: add option to ignore unknown requirements

The new behavior in 8, and backported is to treat unknown requirements
as unsatisfied requirements.

For 7.0.8, add a configuration option, "ignore-unknown-requirements"
to completely ignore unknown requirements, effectively treating them
as available.

Ticket: OISF#7434

doc/userguide/upgrade.rst

@@ -37,8 +37,23 @@ dedicated new configuration.
 Upgrading to 7.0.7
 ------------------
 - Unknown requirements in the ``requires`` keyword will now be treated
-  as unmet requirements, causing the rule to not be loaded. See
-  :ref:`keyword_requires`.
+  as unsatisfied requirements, causing the rule to not be loaded. See
+  :ref:`keyword_requires`. To opt out of this change and to ignore
+  uknown requirements, effectively treating them as satified the
+  ``ignore-unknown-requirements`` configuration option can be used.
+
+  Command line example::
+
+    --set ignore-unknown-requirements=true
+
+  Or as a top-level configuration option in ``suricata.yaml``:
+
+  .. code-block:: yaml
+
+    default-rule-path: /var/lib/suricata/rules
+    rule-files:
+      - suricata.rules
+    ignore-unknown-requirements: true
 
 Upgrading 6.0 to 7.0
 --------------------

rust/src/detect/requires.rs

@@ -297,9 +297,9 @@ fn check_version(
 }
 
 fn check_requires(
-    requires: &Requires, suricata_version: &SuricataVersion,
+    requires: &Requires, suricata_version: &SuricataVersion, ignore_unknown: bool,
 ) -> Result<(), RequiresError> {
-    if !requires.unknown.is_empty() {
+    if !ignore_unknown && !requires.unknown.is_empty() {
         return Err(RequiresError::UnknownRequirement(
             requires.unknown.join(","),
         ));
@@ -453,7 +453,7 @@ pub unsafe extern "C" fn SCDetectRequiresStatusLog(
 #[no_mangle]
 pub unsafe extern "C" fn SCDetectCheckRequires(
     requires: *const c_char, suricata_version_string: *const c_char, errstr: *mut *const c_char,
-    status: &mut SCDetectRequiresStatus,
+    status: &mut SCDetectRequiresStatus, ignore_unknown: c_int,
 ) -> c_int {
     // First parse the running Suricata version.
     let suricata_version = match parse_suricata_version(CStr::from_ptr(suricata_version_string)) {
@@ -476,7 +476,9 @@ pub unsafe extern "C" fn SCDetectCheckRequires(
         }
     };
 
-    match check_requires(&requires, &suricata_version) {
+    let ignore_unknown = if ignore_unknown == 0 { false } else { true };
+
+    match check_requires(&requires, &suricata_version, ignore_unknown) {
         Ok(()) => 0,
         Err(err) => {
             match &err {
@@ -497,6 +499,7 @@ pub unsafe extern "C" fn SCDetectCheckRequires(
                 RequiresError::VersionGt => {
                     status.gt_count += 1;
                 }
+                RequiresError::UnknownRequirement(_) => {}
                 _ => {}
             }
             *errstr = err.c_errmsg();

src/detect-requires.c

@@ -20,6 +20,10 @@
 #include "detect-engine.h"
 #include "rust.h"
 
+/* Set to true if unknown requirements should be ingored. In Suricata
+ * 8, unknown requirements are treated as unsatisfied requirements. */
+static int g_ignore_unknown_requirements = 0;
+
 static int DetectRequiresSetup(DetectEngineCtx *de_ctx, Signature *s, const char *rawstr)
 {
     if (de_ctx->requirements == NULL) {
@@ -28,7 +32,7 @@ static int DetectRequiresSetup(DetectEngineCtx *de_ctx, Signature *s, const char
     }
 
     const char *errmsg = NULL;
-    int res = SCDetectCheckRequires(rawstr, PROG_VER, &errmsg, de_ctx->requirements);
+    int res = SCDetectCheckRequires(rawstr, PROG_VER, &errmsg, de_ctx->requirements, g_ignore_unknown_requirements);
     if (res == -1) {
         // The requires expression is bad, log an error.
         SCLogError("%s: %s", errmsg, rawstr);
@@ -43,6 +47,8 @@ static int DetectRequiresSetup(DetectEngineCtx *de_ctx, Signature *s, const char
 
 void DetectRequiresRegister(void)
 {
+    ConfGetBool("ignore-unknown-requirements", &g_ignore_unknown_requirements);
+
     sigmatch_table[DETECT_REQUIRES].name = "requires";
     sigmatch_table[DETECT_REQUIRES].desc = "require Suricata version or features";
     sigmatch_table[DETECT_REQUIRES].url = "/rules/meta-keywords.html#requires";