Add ostree=aboot for signed Android Boot Images

Some kernel images are delivered in a signed kernel + cmdline +
initramfs + dtb blob. When this is added to the commit server side, only
after this do you know what the cmdline is, this creates a recursion
issue. To avoid this, in the case where we have ostree=aboot karg
set, do the bls parsing in the initramfs instead, so we can take
advantage of existing bls logic.

src/switchroot/ostree-mount-util.h

@@ -21,17 +21,19 @@
 #ifndef __OSTREE_MOUNT_UTIL_H_
 #define __OSTREE_MOUNT_UTIL_H_
 
+#include <dirent.h>
 #include <err.h>
+#include <fcntl.h>
+#include <stdbool.h>
+#include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #include <sys/statvfs.h>
-#include <stdio.h>
 #include <unistd.h>
-#include <fcntl.h>
-#include <string.h>
-#include <stdbool.h>
 
 #define INITRAMFS_MOUNT_VAR "/run/ostree/initramfs-mount-var"
 #define _OSTREE_SYSROOT_READONLY_STAMP "/run/ostree-sysroot-ro.stamp"
+#define ABOOT_KARG "aboot"
 
 static inline int
 path_is_on_readonly_fs (const char *path)
@@ -72,6 +74,26 @@ read_proc_cmdline (void)
   return cmdline;
 }
 
+static inline void
+free_char (char **to_free)
+{
+  free (*to_free);
+}
+
+static inline void
+close_dir (DIR **dir)
+{
+  if (*dir)
+    closedir (*dir);
+}
+
+static inline void
+close_file (FILE **f)
+{
+  if (*f)
+    fclose (*f);
+}
+
 static inline char *
 read_proc_cmdline_ostree (void)
 {
@@ -106,6 +128,133 @@ read_proc_cmdline_ostree (void)
   return ret;
 }
 
+static inline void
+cpy_and_null (char **dest, char **src)
+{
+  *dest = *src;
+  *src = NULL;
+}
+
+/* If the key matches the start of the line, copy line to out
+ */
+static inline bool
+cpy_if_key_match (char **line, const char *key, char **out)
+{
+  /* There should only be one of each key per BLS file, so check for NULL, we
+   * should only parse the first occurance of a key, if there's two, it's a
+   * malformed BLS file
+   */
+  if (!*out && strstr (*line, key) == *line)
+    {
+      cpy_and_null (out, line);
+      return true;
+    }
+
+  return false;
+}
+
+/* On completion version and options will be set to new values if the version
+ * is more recent. Will loop line through line on the passed in open FILE.
+ */
+static inline void
+copy_if_higher_version (FILE *f, char **version, char **options)
+{
+  char __attribute__ ((cleanup (free_char))) *line = NULL;
+  char __attribute__ ((cleanup (free_char))) *version_local = NULL;
+  char __attribute__ ((cleanup (free_char))) *options_local = NULL;
+  /* Note getline() will reuse the previous buffer when not zero */
+  for (size_t len = 0; getline (&line, &len, f) != -1;)
+    {
+      /* This is an awful hack to avoid depending on GLib in the
+       * initramfs right now.
+       */
+      if (cpy_if_key_match (&line, "version ", &version_local))
+        {
+          if (options_local)
+            break;
+        }
+      else if (cpy_if_key_match (&line, "options ", &options_local))
+        {
+          if (version_local)
+            break;
+        }
+    }
+
+  /* The case where we have no version set yet */
+  if (!*version
+      || strverscmp (version_local + sizeof ("version"), (*version) + sizeof ("version")) > 0)
+    {
+      cpy_and_null (version, &version_local);
+      cpy_and_null (options, &options_local);
+    }
+
+  return;
+}
+
+static inline char *
+parse_ostree_from_options (const char *options)
+{
+  if (options)
+    {
+      options += sizeof ("options");
+      char *start_of_ostree = strstr (options, "ostree=");
+      if (start_of_ostree > options)
+        {
+          start_of_ostree += sizeof ("ostree");
+          /* trim everything to the right */
+          strtok (start_of_ostree, " \t\r\n");
+          return strdup (start_of_ostree);
+        }
+    }
+
+  return strdup ("");
+}
+
+/* This function is for boot arrangements where it is not possible to use a
+ * karg/cmdline, this is the case when the cmdline is part of the signed
+ * boot image, alternatively this function takes the karg from the bls entry
+ * which will have the correct ostree= karg set. This bls entry is not parsed
+ * from the bootloader but from the initramfs instead.
+ */
+static inline char *
+bls_parser_get_ostree_option (const char *sysroot)
+{
+  char out[PATH_MAX] = "";
+  int written = snprintf (out, PATH_MAX, "%s/boot/loader/entries", sysroot);
+  DIR __attribute__ ((cleanup (close_dir))) *dir = opendir (out);
+  if (!dir)
+    {
+      fprintf (stderr, "opendir(\"%s\") failed with %d\n", out, errno);
+      return strdup ("");
+    }
+
+  char __attribute__ ((cleanup (free_char))) *version = NULL;
+  char __attribute__ ((cleanup (free_char))) *options = NULL;
+  for (struct dirent *ent = 0; (ent = readdir (dir));)
+    {
+      if (ent->d_name[0] == '.')
+        continue;
+
+      const size_t d_name_len = strlen (ent->d_name);
+      if (d_name_len < sizeof (".conf")
+          || strcmp (ent->d_name + d_name_len - sizeof (".conf") + 1, ".conf"))
+        continue;
+
+      snprintf (out + written, PATH_MAX - written, "/%s", ent->d_name);
+
+      FILE __attribute__ ((cleanup (close_file))) *f = fopen (out, "r");
+      if (!f)
+        {
+          fprintf (stderr, "fopen(\"%s\", \"r\") failed with %d\n", out, errno);
+          continue;
+        }
+
+      copy_if_higher_version (f, &version, &options);
+    }
+
+  return parse_ostree_from_options (options);
+}
+
 /* This is an API for other projects to determine whether or not the
  * currently running system is ostree-controlled.
  */

src/switchroot/ostree-prepare-root.c

@@ -124,9 +124,13 @@ resolve_deploy_path (const char * root_mountpoint)
 {
   char destpath[PATH_MAX];
   struct stat stbuf;
-  char *ostree_target, *deploy_path;
+  char __attribute__ ((cleanup (free_char))) *ostree_target;
+  char *deploy_path;
 
   ostree_target = read_proc_cmdline_ostree ();
+  if (!strcmp (ostree_target, ABOOT_KARG))
+    ostree_target = bls_parser_get_ostree_option (root_mountpoint);
+
   if (!ostree_target)
     errx (EXIT_FAILURE, "No OSTree target; expected ostree=/ostree/boot.N/...");
 

src/switchroot/ostree-system-generator.c

@@ -62,7 +62,10 @@ main(int argc, char *argv[])
    * exit so that we don't error, but at the same time work where switchroot
    * is PID 1 (and so hasn't created /run/ostree-booted).
    */
-  char *ostree_cmdline = read_proc_cmdline_ostree ();
+  char __attribute__ ((cleanup (free_char))) *ostree_cmdline = read_proc_cmdline_ostree ();
+  if (!strcmp (ostree_cmdline, ABOOT_KARG))
+    ostree_cmdline = bls_parser_get_ostree_option ("/sysroot");
+
   if (!ostree_cmdline)
     exit (EXIT_SUCCESS);