pcrlock: Record predictions at start of component range

Currently pcrlock won't predict PCR values that would be present at the start
of the requested location range (unless there are no events for that PCR in the
location range). This means predictions for the default range 760:940, which is
intended to start just after entering the initrd, are not actually possible to
fulfill until after the initrd is exited (or possibly even later, depending on
what other events are recorded).

Fix this by recording predictions immediately prior to processing components
after the start point.

Fixes #39946

diff --git a/src/pcrlock/pcrlock.c b/src/pcrlock/pcrlock.c
index a02846e785dbd581d9d94e003f33d4ffa56e6a25..ab97c1a754e30a3b092df76edc6ba7d1a9e05689 100644 (file)
--- a/src/pcrlock/pcrlock.c
+++ b/src/pcrlock/pcrlock.c
@@ -4004,8 +4004,7 @@ static int pcr_prediction_add_result(
                 Tpm2PCRPrediction *context,
                 Tpm2PCRPredictionResult *result,
                 uint32_t pcr,
-                const char *path,
-                size_t offset) {
+                const char *path) {
 
         _cleanup_free_ Tpm2PCRPredictionResult *copy = NULL;
         int r;
@@ -4040,18 +4039,11 @@ static const EVP_MD* evp_from_tpm2_alg(uint16_t alg) {
 }
 
 static int event_log_component_variant_calculate(
-                Tpm2PCRPrediction *context,
                 Tpm2PCRPredictionResult *result,
-                EventLogComponent *component,
                 EventLogComponentVariant *variant,
-                uint32_t pcr,
-                const char *path) {
+                uint32_t pcr) {
 
-        int r;
-
-        assert(context);
         assert(result);
-        assert(component);
         assert(variant);
 
         FOREACH_ARRAY(rr, variant->records, variant->n_records) {
@@ -4107,13 +4099,6 @@ static int event_log_component_variant_calculate(
 
                         assert(l == (unsigned) sz);
                 }
-
-                /* This is a valid result once we hit the start location */
-                if (arg_location_start && strcmp(component->id, arg_location_start) >= 0) {
-                        r = pcr_prediction_add_result(context, result, pcr, path, rr - variant->records);
-                        if (r < 0)
-                                return r;
-                }
         }
 
         return 0;
@@ -4137,7 +4122,7 @@ static int event_log_predict_pcrs(
         /* Check if we reached the end of the components, generate a result, and backtrack */
         if (component_index >= el->n_components ||
             (arg_location_end && strcmp(el->components[component_index]->id, arg_location_end) > 0)) {
-                r = pcr_prediction_add_result(context, parent_result, pcr, path, /* offset= */ 0);
+                r = pcr_prediction_add_result(context, parent_result, pcr, path);
                 if (r < 0)
                         return r;
 
@@ -4146,6 +4131,13 @@ static int event_log_predict_pcrs(
 
         component = ASSERT_PTR(el->components[component_index]);
 
+        /* Check if we are just about to process a component after start, if so record a result and continue. */
+        if (arg_location_start && strcmp(component->id, arg_location_start) > 0) {
+                r = pcr_prediction_add_result(context, parent_result, pcr, path);
+                if (r < 0)
+                        return r;
+        }
+
         FOREACH_ARRAY(ii, component->variants, component->n_variants) {
                 _cleanup_free_ Tpm2PCRPredictionResult *result = NULL;
                 EventLogComponentVariant *variant = *ii;
@@ -4169,12 +4161,9 @@ static int event_log_predict_pcrs(
                         return log_oom();
 
                 r = event_log_component_variant_calculate(
-                                context,
                                 result,
-                                component,
                                 variant,
-                                pcr,
-                                subpath);
+                                pcr);
                 if (r < 0)
                         return r;