build: Add support for propagating RPM IMA signatures

docs/treefile.md

@@ -32,6 +32,9 @@ It supports the following parameters:
  * `selinux`: boolean, optional: Defaults to `true`.  If `false`, then
    no SELinux labeling will be performed on the server side.
 
+ * `ima`: boolean, optional: Defaults to `false`.  Propagate any
+   IMA signatures in input RPMs into the final OSTree commit.
+
  * `boot-location` (or `boot_location`): string, optional:
     There are 2 possible values:
     * "new": A misnomer, this value is no longer "new".  Kernel data

rust/src/lib.rs

@@ -534,6 +534,7 @@ pub mod ffi {
         fn get_documentation(&self) -> bool;
         fn get_recommends(&self) -> bool;
         fn get_selinux(&self) -> bool;
+        fn get_ima(&self) -> bool;
         fn get_releasever(&self) -> String;
         fn get_repo_metadata_target(&self) -> RepoMetadataTarget;
         fn rpmdb_backend_is_target(&self) -> bool;

rust/src/treefile.rs

@@ -404,6 +404,7 @@ fn treefile_merge(dest: &mut TreeComposeConfig, src: &mut TreeComposeConfig) {
         basearch,
         rojig,
         selinux,
+        ima,
         gpg_key,
         include,
         container,
@@ -1257,6 +1258,10 @@ impl Treefile {
         self.parsed.base.selinux.unwrap_or(true)
     }
 
+    pub(crate) fn get_ima(&self) -> bool {
+        self.parsed.base.ima.unwrap_or(false)
+    }
+
     pub(crate) fn get_releasever(&self) -> String {
         self.parsed
             .base
@@ -2277,6 +2282,8 @@ pub(crate) struct BaseComposeConfigFields {
     #[serde(skip_serializing_if = "Option::is_none")]
     pub(crate) selinux: Option<bool>,
     #[serde(skip_serializing_if = "Option::is_none")]
+    pub(crate) ima: Option<bool>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub(crate) gpg_key: Option<String>,
     #[serde(skip_serializing_if = "Option::is_none")]
     pub(crate) include: Option<Include>,

src/libpriv/rpmostree-core.cxx

@@ -2425,6 +2425,9 @@ start_async_import_one_package (RpmOstreeContext *self, DnfPackage *pkg, GCancel
   if (self->treefile_rs->get_readonly_executables ())
     flags |= RPMOSTREE_IMPORTER_FLAGS_RO_EXECUTABLES;
 
+  if (self->treefile_rs->get_ima ())
+    flags |= RPMOSTREE_IMPORTER_FLAGS_IMA;
+
   /* TODO - tweak the unpacker flags for containers */
   OstreeRepo *ostreerepo = get_pkgcache_repo (self);
   g_autoptr (RpmOstreeImporter) unpacker = rpmostree_importer_new_take_fd (

src/libpriv/rpmostree-core.h

@@ -40,6 +40,10 @@ G_BEGIN_DECLS
 #define RPMOSTREE_DIR_CACHE_SOLV "solv"
 #define RPMOSTREE_DIR_LOCK "lock"
 
+// Extended attribute used at build time.
+#define RPMOSTREE_USER_IMA "user.ima"
+#define RPMOSTREE_SYSTEM_IMA "security.ima"
+
 /* See http://lists.rpm.org/pipermail/rpm-maint/2017-October/006681.html */
 /* This is also defined on the Rust side. */
 #define RPMOSTREE_RPMDB_LOCATION "usr/share/rpm"

src/libpriv/rpmostree-importer.cxx

@@ -40,6 +40,7 @@
 #include <grp.h>
 #include <pwd.h>
 #include <rpm/rpmfi.h>
+#include <rpm/rpmfiles.h>
 #include <rpm/rpmlib.h>
 #include <rpm/rpmlog.h>
 #include <rpm/rpmts.h>
@@ -146,7 +147,7 @@ rpmostree_importer_read_metainfo (int fd, Header *out_header, gsize *out_cpio_of
 
   if (out_fi)
     {
-      ret_fi = rpmfiNew (ts, ret_header, RPMTAG_BASENAMES, (RPMFI_NOHEADER | RPMFI_FLAGS_INSTALL));
+      ret_fi = rpmfiNew (ts, ret_header, RPMTAG_BASENAMES, RPMFI_NOHEADER | RPMFI_FLAGS_QUERY);
       ret_fi = rpmfiInit (ret_fi, 0);
     }
 
@@ -159,6 +160,30 @@ rpmostree_importer_read_metainfo (int fd, Header *out_header, gsize *out_cpio_of
   return TRUE;
 }
 
+/*
+ * ima_heck_zero_hdr: Check the signature for a zero header
+ *
+ * Check whether the given signature has a header with all zeros
+ *
+ * Returns -1 in case the signature is too short to compare
+ * (invalid signature), 0 in case the header is not only zeroes,
+ * and 1 if it is only zeroes.
+ */
+static int
+ima_check_zero_hdr (const unsigned char *fsig, size_t siglen)
+{
+  /*
+   * Every signature has a header signature_v2_hdr as defined in
+   * Linux's (4.5) security/integrity/integtrity.h. The following
+   * 9 bytes represent this header in front of the signature.
+   */
+  static const uint8_t zero_hdr[] = { 0, 0, 0, 0, 0, 0, 0, 0, 0 };
+
+  if (siglen < sizeof (zero_hdr))
+    return -1;
+  return (memcmp (fsig, &zero_hdr, sizeof (zero_hdr)) == 0);
+}
+
 static void
 build_rpmfi_overrides (RpmOstreeImporter *self)
 {
@@ -179,10 +204,14 @@ build_rpmfi_overrides (RpmOstreeImporter *self)
       const char *fn = rpmfiFN (self->fi);
       rpmfileAttrs fattrs = rpmfiFFlags (self->fi);
 
+      size_t siglen = 0;
+      const unsigned char *fsig = rpmfiFSignature (self->fi, &siglen);
+      const bool have_ima = (siglen > 0 && fsig && (ima_check_zero_hdr (fsig, siglen) == 0));
+
       const gboolean user_is_root = (user == NULL || g_str_equal (user, "root"));
       const gboolean group_is_root = (group == NULL || g_str_equal (group, "root"));
       const gboolean fcaps_is_unset = (fcaps == NULL || fcaps[0] == '\0');
-      if (!(user_is_root && group_is_root && fcaps_is_unset))
+      if (!(user_is_root && group_is_root && fcaps_is_unset) || have_ima)
         {
           g_hash_table_insert (self->rpmfi_overrides, g_strdup (fn), GINT_TO_POINTER (i));
         }
@@ -249,7 +278,7 @@ rpmostree_importer_new_take_fd (int *fd, OstreeRepo *repo, DnfPackage *pkg,
 
 static void
 get_rpmfi_override (RpmOstreeImporter *self, const char *path, const char **out_user,
-                    const char **out_group, const char **out_fcaps)
+                    const char **out_group, const char **out_fcaps, GVariant **out_ima)
 {
   gpointer v;
 
@@ -266,6 +295,18 @@ get_rpmfi_override (RpmOstreeImporter *self, const char *path, const char **out_
     *out_group = rpmfiFGroup (self->fi);
   if (out_fcaps)
     *out_fcaps = rpmfiFCaps (self->fi);
+
+  if (out_ima)
+    {
+      size_t siglen;
+      const guint8 *fsig = rpmfiFSignature (self->fi, &siglen);
+      if (siglen > 0 && fsig && (ima_check_zero_hdr (fsig, siglen) == 0))
+        {
+          GVariant *ima_signature
+              = g_variant_new_fixed_array (G_VARIANT_TYPE_BYTE, fsig, siglen, 1);
+          *out_ima = g_variant_ref_sink (ima_signature);
+        }
+    }
 }
 
 static gboolean
@@ -461,7 +502,7 @@ compose_filter_cb (OstreeRepo *repo, const char *path, GFileInfo *file_info, gpo
       /* Lookup any rpmfi overrides (was parsed from the header) */
       const char *user = NULL;
       const char *group = NULL;
-      get_rpmfi_override (self, path, &user, &group, NULL);
+      get_rpmfi_override (self, path, &user, &group, NULL, NULL);
 
       auto entry = ROSCXX_VAL (
           tmpfiles_translate (path, *file_info, user ?: "root", group ?: "root"), error);
@@ -501,12 +542,25 @@ xattr_cb (OstreeRepo *repo, const char *path, GFileInfo *file_info, gpointer use
   auto self = static_cast<RpmOstreeImporter *> (user_data);
   const char *fcaps = NULL;
 
-  get_rpmfi_override (self, path, NULL, NULL, &fcaps);
+  GVariant *imasig = NULL;
+  const bool use_ima = self->flags & RPMOSTREE_IMPORTER_FLAGS_IMA;
+  get_rpmfi_override (self, path, NULL, NULL, &fcaps, use_ima ? &imasig : NULL);
 
+  g_auto (GVariantBuilder) builder;
+  g_variant_builder_init (&builder, G_VARIANT_TYPE ("a(ayay)"));
   if (fcaps != NULL && fcaps[0] != '\0')
-    return rpmostree_fcap_to_xattr_variant (fcaps);
+    {
+      g_autoptr (GVariant) fcaps_v = rpmostree_fcap_to_ostree_xattr (fcaps);
+      g_variant_builder_add_value (&builder, fcaps_v);
+    }
+
+  if (imasig)
+    {
+      g_variant_builder_add (&builder, "(@ay@ay)", g_variant_new_bytestring (RPMOSTREE_SYSTEM_IMA),
+                             imasig);
+    }
 
-  return NULL;
+  return g_variant_ref_sink (g_variant_builder_end (&builder));
 }
 
 /* Given a path in an RPM archive, possibly translate it for ostree convention. */

src/libpriv/rpmostree-importer.h

@@ -45,12 +45,14 @@ G_DEFINE_AUTOPTR_CLEANUP_FUNC (RpmOstreeImporter, g_object_unref)
  * ostree-compliant paths rather than erroring out
  * @RPMOSTREE_IMPORTER_FLAGS_NODOCS: Skip documentation files
  * @RPMOSTREE_IMPORTER_FLAGS_RO_EXECUTABLES: Make executable files readonly
+ * @RPMOSTREE_IMPORTER_FLAGS_IMA: Enable IMA
  */
 typedef enum
 {
   RPMOSTREE_IMPORTER_FLAGS_SKIP_EXTRANEOUS = (1 << 0),
   RPMOSTREE_IMPORTER_FLAGS_NODOCS = (1 << 1),
   RPMOSTREE_IMPORTER_FLAGS_RO_EXECUTABLES = (1 << 2),
+  RPMOSTREE_IMPORTER_FLAGS_IMA = (1 << 3),
 } RpmOstreeImporterFlags;
 
 RpmOstreeImporter *rpmostree_importer_new_take_fd (int *fd, OstreeRepo *repo, DnfPackage *pkg,

src/libpriv/rpmostree-postprocess.cxx

@@ -639,6 +639,36 @@ struct CommitThreadData
   GError **error;
 };
 
+// In unified core mode, we'll see user-mode checkout files.
+// What we want for now is to access the embedded xattr values
+// which (along with other canonical file metadata) have been serialized
+// into the `user.ostreemeta` extended attribute.  What we should
+// actually do is add nice support for this in core ostree, and also
+// automatically pick up file owner for example.  This would be a key
+// thing to unblock fully unprivileged builds.
+//
+// But for now, just slurp up the xattrs so we get IMA in particular.
+static void
+extend_ostree_xattrs (GVariantBuilder *builder, GVariant *vbytes)
+{
+  g_autoptr (GBytes) bytes = g_variant_get_data_as_bytes (vbytes);
+  g_autoptr (GVariant) filemeta = g_variant_ref_sink (
+      g_variant_new_from_bytes (OSTREE_FILEMETA_GVARIANT_FORMAT, bytes, false));
+  g_autoptr (GVariant) xattrs = g_variant_get_child_value (filemeta, 3);
+  g_autoptr (GVariantIter) viter = g_variant_iter_new (xattrs);
+  GVariant *key, *value;
+  while (g_variant_iter_loop (viter, "(@ay@ay)", &key, &value))
+    {
+      const char *attrkey = g_variant_get_bytestring (key);
+      // Don't try to add the SELinux label - that's handled by the full
+      // relabel we do, although in the future it may be interesting to
+      // try canonically relying on the labeled pkgcache.
+      if (g_str_equal (attrkey, "security.selinux"))
+        continue;
+      g_variant_builder_add (builder, "(@ay@ay)", key, value);
+    }
+}
+
 /* Filters out all xattrs that aren't accepted. */
 static GVariant *
 filter_xattrs_cb (OstreeRepo *repo, const char *relpath, GFileInfo *file_info, gpointer user_data)
@@ -651,20 +681,16 @@ filter_xattrs_cb (OstreeRepo *repo, const char *relpath, GFileInfo *file_info, g
   static const char *accepted_xattrs[] = {
     "security.capability", /* https://lwn.net/Articles/211883/ */
     "user.pax.flags",      /* https://github.com/projectatomic/rpm-ostree/issues/412 */
-    "user.ima"             /* will be replaced with security.ima */
+    RPMOSTREE_USER_IMA,    /* will be replaced with security.ima */
   };
   g_autoptr (GVariant) existing_xattrs = NULL;
-  g_autoptr (GVariantIter) viter = NULL;
   GError *local_error = NULL;
   GError **error = &local_error;
-  GVariant *key, *value;
-  GVariantBuilder builder;
 
+  // From here, ensure the path is relative
   if (relpath[0] == '/')
     relpath++;
 
-  g_variant_builder_init (&builder, G_VARIANT_TYPE ("a(ayay)"));
-
   if (!*relpath)
     {
       if (!glnx_fd_get_all_xattrs (rootfs_fd, &existing_xattrs, NULL, error))
@@ -682,19 +708,45 @@ filter_xattrs_cb (OstreeRepo *repo, const char *relpath, GFileInfo *file_info, g
       g_atomic_int_set (&tdata->percent, (gint)((100.0 * tdata->n_processed) / tdata->n_bytes));
     }
 
-  viter = g_variant_iter_new (existing_xattrs);
+  GVariantBuilder builder;
+  g_variant_builder_init (&builder, G_VARIANT_TYPE ("a(ayay)"));
 
-  while (g_variant_iter_loop (viter, "(@ay@ay)", &key, &value))
+  GVariantIter viter;
+  g_variant_iter_init (&viter, existing_xattrs);
+  // Look for the special user.ostreemeta xattr; if present then it wins
+  GVariant *key, *value;
+  while (g_variant_iter_loop (&viter, "(@ay@ay)", &key, &value))
     {
+      const char *attrkey = g_variant_get_bytestring (key);
+
+      // If it's the special bare-user xattr, then slurp out the embedded
+      // xattrs.
+      if (g_str_equal (attrkey, "user.ostreemeta"))
+        {
+          extend_ostree_xattrs (&builder, value);
+          return g_variant_ref_sink (g_variant_builder_end (&builder));
+        }
+    }
+
+  // Otherwise, find the physical xattrs; this happens in the unified core case.
+  g_variant_iter_init (&viter, existing_xattrs);
+  while (g_variant_iter_loop (&viter, "(@ay@ay)", &key, &value))
+    {
+      const char *attrkey = g_variant_get_bytestring (key);
+
       for (guint i = 0; i < G_N_ELEMENTS (accepted_xattrs); i++)
         {
           const char *validkey = accepted_xattrs[i];
-          const char *attrkey = g_variant_get_bytestring (key);
           if (g_str_equal (validkey, attrkey))
             {
-              if (g_str_equal (validkey, "user.ima"))
-                g_variant_builder_add (&builder, "(@ay@ay)",
-                                       g_variant_new_bytestring ("security.ima"), value);
+              // Translate user.ima to its final security.ima value.  This allows handling
+              // IMA outside of rpm-ostree, without needing IMA to be enabled on the
+              // "host" system.
+              if (g_str_equal (validkey, RPMOSTREE_USER_IMA))
+                {
+                  g_variant_builder_add (&builder, "(@ay@ay)",
+                                         g_variant_new_bytestring (RPMOSTREE_SYSTEM_IMA), value);
+                }
               else
                 g_variant_builder_add (&builder, "(@ay@ay)", key, value);
             }