From eaad892c513806801e3d2055788fa202372b3f15 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>
Date: Fri, 21 Aug 2020 17:21:04 +0200
Subject: [PATCH] shared/seccomp-util: added functionality to make list of
 filtred syscalls

While at it, start removing the "seccomp_" prefix from our
own functions. It is used by libseccomp.

(cherry picked from commit 000c05207d68658b76af9e1caf9aa3a4e3fa697b)

Related: #2040247
---
 src/nspawn/nspawn-seccomp.c |  9 +++++++--
 src/shared/seccomp-util.c   | 39 ++++++++++++++++++++++++++++++-------
 src/shared/seccomp-util.h   |  8 +++++++-
 3 files changed, 46 insertions(+), 10 deletions(-)

diff --git a/src/nspawn/nspawn-seccomp.c b/src/nspawn/nspawn-seccomp.c
index 17abfcec26..2b4a65e875 100644
--- a/src/nspawn/nspawn-seccomp.c
+++ b/src/nspawn/nspawn-seccomp.c
@@ -148,13 +148,18 @@ static int seccomp_add_default_syscall_filter(
                 if (whitelist[i].capability != 0 && (cap_list_retain & (1ULL << whitelist[i].capability)) == 0)
                         continue;
 
-                r = seccomp_add_syscall_filter_item(ctx, whitelist[i].name, SCMP_ACT_ALLOW, syscall_blacklist, false);
+                r = seccomp_add_syscall_filter_item(ctx,
+                                                    whitelist[i].name,
+                                                    SCMP_ACT_ALLOW,
+                                                    syscall_blacklist,
+                                                    false,
+                                                    NULL);
                 if (r < 0)
                         return log_error_errno(r, "Failed to add syscall filter item %s: %m", whitelist[i].name);
         }
 
         STRV_FOREACH(p, syscall_whitelist) {
-                r = seccomp_add_syscall_filter_item(ctx, *p, SCMP_ACT_ALLOW, syscall_blacklist, false);
+                r = seccomp_add_syscall_filter_item(ctx, *p, SCMP_ACT_ALLOW, syscall_blacklist, false, NULL);
                 if (r < 0)
                         log_warning_errno(r, "Failed to add rule for system call %s on %s, ignoring: %m",
                                           *p, seccomp_arch_to_string(arch));
diff --git a/src/shared/seccomp-util.c b/src/shared/seccomp-util.c
index 710a734715..56075d92e0 100644
--- a/src/shared/seccomp-util.c
+++ b/src/shared/seccomp-util.c
@@ -874,15 +874,31 @@ const SyscallFilterSet *syscall_filter_set_find(const char *name) {
         return NULL;
 }
 
-static int seccomp_add_syscall_filter_set(scmp_filter_ctx seccomp, const SyscallFilterSet *set, uint32_t action, char **exclude, bool log_missing);
+static int add_syscall_filter_set(
+                scmp_filter_ctx seccomp,
+                const SyscallFilterSet *set,
+                uint32_t action,
+                char **exclude,
+                bool log_missing,
+                char ***added);
+
+int seccomp_add_syscall_filter_item(
+                scmp_filter_ctx *seccomp,
+                const char *name,
+                uint32_t action,
+                char **exclude,
+                bool log_missing,
+                char ***added) {
 
-int seccomp_add_syscall_filter_item(scmp_filter_ctx *seccomp, const char *name, uint32_t action, char **exclude, bool log_missing) {
         assert(seccomp);
         assert(name);
 
         if (strv_contains(exclude, name))
                 return 0;
 
+        /* Any syscalls that are handled are added to the *added strv. The pointer
+         * must be either NULL or point to a valid pre-initialized possibly-empty strv. */
+
         if (name[0] == '@') {
                 const SyscallFilterSet *other;
 
@@ -892,7 +908,7 @@ int seccomp_add_syscall_filter_item(scmp_filter_ctx *seccomp, const char *name,
                         return -EINVAL;
                 }
 
-                return seccomp_add_syscall_filter_set(seccomp, other, action, exclude, log_missing);
+                return add_syscall_filter_set(seccomp, other, action, exclude, log_missing, added);
 
         } else {
                 int id, r;
@@ -916,25 +932,34 @@ int seccomp_add_syscall_filter_item(scmp_filter_ctx *seccomp, const char *name,
                                 return r;
                 }
 
+                if (added) {
+                        r = strv_extend(added, name);
+                        if (r < 0)
+                                return r;
+                }
+
                 return 0;
         }
 }
 
-static int seccomp_add_syscall_filter_set(
+static int add_syscall_filter_set(
                 scmp_filter_ctx seccomp,
                 const SyscallFilterSet *set,
                 uint32_t action,
                 char **exclude,
-                bool log_missing) {
+                bool log_missing,
+                char ***added) {
 
         const char *sys;
         int r;
 
+        /* Any syscalls that are handled are added to the *added strv. It needs to be initialized. */
+
         assert(seccomp);
         assert(set);
 
         NULSTR_FOREACH(sys, set->value) {
-                r = seccomp_add_syscall_filter_item(seccomp, sys, action, exclude, log_missing);
+                r = seccomp_add_syscall_filter_item(seccomp, sys, action, exclude, log_missing, added);
                 if (r < 0)
                         return r;
         }
@@ -960,7 +985,7 @@ int seccomp_load_syscall_filter_set(uint32_t default_action, const SyscallFilter
                 if (r < 0)
                         return r;
 
-                r = seccomp_add_syscall_filter_set(seccomp, set, action, NULL, log_missing);
+                r = add_syscall_filter_set(seccomp, set, action, NULL, log_missing, NULL);
                 if (r < 0)
                         return log_debug_errno(r, "Failed to add filter set: %m");
 
diff --git a/src/shared/seccomp-util.h b/src/shared/seccomp-util.h
index 541ba1e067..291b2bffe0 100644
--- a/src/shared/seccomp-util.h
+++ b/src/shared/seccomp-util.h
@@ -59,7 +59,13 @@ const SyscallFilterSet *syscall_filter_set_find(const char *name);
 
 int seccomp_filter_set_add(Hashmap *s, bool b, const SyscallFilterSet *set);
 
-int seccomp_add_syscall_filter_item(scmp_filter_ctx *ctx, const char *name, uint32_t action, char **exclude, bool log_missing);
+int seccomp_add_syscall_filter_item(
+                scmp_filter_ctx *ctx,
+                const char *name,
+                uint32_t action,
+                char **exclude,
+                bool log_missing,
+                char ***added);
 
 int seccomp_load_syscall_filter_set(uint32_t default_action, const SyscallFilterSet *set, uint32_t action, bool log_missing);
 int seccomp_load_syscall_filter_set_raw(uint32_t default_action, Hashmap* set, uint32_t action, bool log_missing);