ANDROID: dm: android-verity: use default verity public key

If the dm-android-verity target does not provide a default
key try using the default public key from the system keyring.
The defualt verity keyid is passed as a kernel command line
argument veritykeyid=.

The order of the dm-android-verity params have been reversed
to facilitate the change.

Old format example:
dm="system none ro,0 1 android-verity Android:#7e4333f9bba00adfe0ede979e28ed1920492b40f /dev/mmcblk0p43"

New formats supported:
dm="system none ro,0 1 android-verity /dev/mmcblk0p43 Android:#7e4333f9bba00adfe0ede979e28ed1920492b40f"

(or)

dm="system none ro,0 1 android-verity /dev/mmcblk0p43"
when veritykeyid= is set in the kernel command line.

BUG: 28384658
Signed-off-by: Badhri Jagan Sridharan <Badhri@google.com>
Change-Id: I506c89b053d835ab579e703eef2bc1f8487250de
(cherry picked from commit c5c74d0327729f35b576564976885596c6d0e7fb)

diff --git a/drivers/md/dm-android-verity.c b/drivers/md/dm-android-verity.c
index 00275a986d037d68d66f50ab6c41f8de979707c2..097fb2b1de891795a69424c3d3fe947e6f0cb2f9 100644 (file)
--- a/drivers/md/dm-android-verity.c
+++ b/drivers/md/dm-android-verity.c
@@ -43,6 +43,7 @@
 
 static char verifiedbootstate[VERITY_COMMANDLINE_PARAM_LENGTH];
 static char veritymode[VERITY_COMMANDLINE_PARAM_LENGTH];
+static char veritykeyid[VERITY_DEFAULT_KEY_ID_LENGTH];
 
 static bool target_added;
 static bool verity_enabled = true;
@@ -79,6 +80,19 @@ static int __init verity_mode_param(char *line)
 
 __setup("androidboot.veritymode=", verity_mode_param);
 
+static int __init verity_keyid_param(char *line)
+{
+       strlcpy(veritykeyid, line, sizeof(veritykeyid));
+       return 1;
+}
+
+__setup("veritykeyid=", verity_keyid_param);
+
+static inline bool default_verity_key_id(void)
+{
+       return veritykeyid[0] != '\0';
+}
+
 static int table_extract_mpi_array(struct public_key_signature *pks,
                                const void *data, size_t len)
 {
@@ -608,7 +622,7 @@ static int android_verity_ctr(struct dm_target *ti, unsigned argc, char **argv)
        dev_t uninitialized_var(dev);
        struct android_metadata *uninitialized_var(metadata);
        int err = 0, i, mode;
-       char *key_id, *table_ptr, dummy,
+       char *key_id, *table_ptr, dummy, *target_device,
        *verity_table_args[VERITY_TABLE_ARGS + 2 + VERITY_TABLE_OPT_FEC_ARGS];
        /* One for specifying number of opt args and one for mode */
        sector_t data_sectors;
@@ -619,24 +633,34 @@ static int android_verity_ctr(struct dm_target *ti, unsigned argc, char **argv)
        char buf[FEC_ARG_LENGTH], *buf_ptr;
        unsigned long long tmpll;
 
-       if (argc != 2) {
+       if (argc == 1) {
+               /* Use the default keyid */
+               if (default_verity_key_id())
+                       key_id = veritykeyid;
+               else {
+                       DMERR("veritykeyid= is not set");
+                       handle_error();
+                       return -EINVAL;
+               }
+       } else if (argc == 2)
+               key_id = argv[1];
+       else {
                DMERR("Incorrect number of arguments");
                handle_error();
                return -EINVAL;
        }
 
-       /* should come as one of the arguments for the verity target */
-       key_id = argv[0];
-       strreplace(argv[0], '#', ' ');
+       strreplace(key_id, '#', ' ');
+       target_device = argv[0];
 
-       dev = name_to_dev_t(argv[1]);
+       dev = name_to_dev_t(target_device);
        if (!dev) {
-               DMERR("no dev found for %s", argv[1]);
+               DMERR("no dev found for %s", target_device);
                handle_error();
                return -EINVAL;
        }
 
-       DMINFO("key:%s dev:%s", argv[0], argv[1]);
+       DMINFO("key:%s dev:%s", key_id, target_device);
 
        if (extract_fec_header(dev, &fec, &ecc)) {
                DMERR("Error while extracting fec header");
@@ -734,30 +758,33 @@ static int android_verity_ctr(struct dm_target *ti, unsigned argc, char **argv)
 
        /* Setup linear target and free */
        if (!verity_enabled) {
-               err = add_as_linear_device(ti, argv[1]);
+               err = add_as_linear_device(ti, target_device);
                goto free_metadata;
        }
 
        /*substitute data_dev and hash_dev*/
-       verity_table_args[1] = argv[1];
-       verity_table_args[2] = argv[1];
+       verity_table_args[1] = target_device;
+       verity_table_args[2] = target_device;
 
        mode = verity_mode();
 
        if (ecc.valid && IS_BUILTIN(CONFIG_DM_VERITY_FEC)) {
                if (mode) {
                        err = snprintf(buf, FEC_ARG_LENGTH,
-                       "%u %s " VERITY_TABLE_OPT_FEC_FORMAT,
-                       1 + VERITY_TABLE_OPT_FEC_ARGS,
-                       mode == DM_VERITY_MODE_RESTART ?
-                       VERITY_TABLE_OPT_RESTART : VERITY_TABLE_OPT_LOGGING,
-                       argv[1], ecc.start / FEC_BLOCK_SIZE, ecc.blocks,
-                       ecc.roots);
+                               "%u %s " VERITY_TABLE_OPT_FEC_FORMAT,
+                               1 + VERITY_TABLE_OPT_FEC_ARGS,
+                               mode == DM_VERITY_MODE_RESTART ?
+                                       VERITY_TABLE_OPT_RESTART :
+                                       VERITY_TABLE_OPT_LOGGING,
+                               target_device,
+                               ecc.start / FEC_BLOCK_SIZE, ecc.blocks,
+                               ecc.roots);
                } else {
                        err = snprintf(buf, FEC_ARG_LENGTH,
-                       "%u " VERITY_TABLE_OPT_FEC_FORMAT,
-                       VERITY_TABLE_OPT_FEC_ARGS, argv[1],
-                       ecc.start / FEC_BLOCK_SIZE, ecc.blocks, ecc.roots);
+                               "%u " VERITY_TABLE_OPT_FEC_FORMAT,
+                               VERITY_TABLE_OPT_FEC_ARGS, target_device,
+                               ecc.start / FEC_BLOCK_SIZE, ecc.blocks,
+                               ecc.roots);
                }
        } else if (mode) {
                err = snprintf(buf, FEC_ARG_LENGTH,

diff --git a/drivers/md/dm-android-verity.h b/drivers/md/dm-android-verity.h
index efb7965248968c79d65764396c0ac49bc8f22261..43655ee0f813fb6d6e87c8892e8d8495801d094b 100644 (file)
--- a/drivers/md/dm-android-verity.h
+++ b/drivers/md/dm-android-verity.h
@@ -27,6 +27,22 @@
 #define VERITY_TABLE_ARGS 10
 #define VERITY_COMMANDLINE_PARAM_LENGTH 20
 
+/*
+ * <subject>:<sha1-id> is the format for the identifier.
+ * subject can either be the Common Name(CN) + Organization Name(O) or
+ * just the CN if the it is prefixed with O
+ * From https://tools.ietf.org/html/rfc5280#appendix-A
+ * ub-organization-name-length INTEGER ::= 64
+ * ub-common-name-length INTEGER ::= 64
+ *
+ * http://lxr.free-electrons.com/source/crypto/asymmetric_keys/x509_cert_parser.c?v=3.9#L278
+ * ctx->o_size + 2 + ctx->cn_size + 1
+ * + 41 characters for ":" and sha1 id
+ * 64 + 2 + 64 + 1 + 1 + 40 (172)
+ * setting VERITY_DEFAULT_KEY_ID_LENGTH to 200 characters.
+ */
+#define VERITY_DEFAULT_KEY_ID_LENGTH 200
+
 #define FEC_MAGIC 0xFECFECFE
 #define FEC_BLOCK_SIZE (4 * 1024)
 #define FEC_VERSION 0