[PATCH] verify: search keyid in hashed signature subpackets

[Ignat Korchagin]

Currently GRUB2 verify logic searches PGP keyid only in unhashed subpackets of 
PGP signature packet. As a result, signatures generated with GoLang openpgp 
package (https://godoc.org/golang.org/x/crypto/openpgp) could not be verified, 
because this package puts keyid in hashed subpackets and GRUB code never 
initializes the keyid variable, therefore is not able to find "verification 
key" with id 0x0.

diff --git a/grub-core/commands/verify.c b/grub-core/commands/verify.c
index 166d0aa..dde37c4 100644
--- a/grub-core/commands/verify.c
+++ b/grub-core/commands/verify.c
@@ -532,33 +532,15 @@
 
     hash->write (context, &v, sizeof (v));
     hash->write (context, &v4, sizeof (v4));
-    while (rem)
-      {
-       r = grub_file_read (sig, readbuf,
-                           rem < READBUF_SIZE ? rem : READBUF_SIZE);
-       if (r < 0)
-         goto fail;
-       if (r == 0)
-         break;
-       hash->write (context, readbuf, r);
-       rem -= r;
-      }
-    hash->write (context, &v, sizeof (v));
-    s = 0xff;
-    hash->write (context, &s, sizeof (s));
-    hash->write (context, &headlen, sizeof (headlen));
-    r = grub_file_read (sig, &unhashed_sub, sizeof (unhashed_sub));
-    if (r != sizeof (unhashed_sub))
+    if (rem > READBUF_SIZE)
+      goto fail;
+    r = grub_file_read (sig, readbuf, rem);
+    if (r != rem)
       goto fail;
     {
       grub_uint8_t *ptr;
       grub_uint32_t l;
-      rem = grub_be_to_cpu16 (unhashed_sub);
-      if (rem > READBUF_SIZE)
-       goto fail;
-      r = grub_file_read (sig, readbuf, rem);
-      if (r != rem)
-       goto fail;
+
       for (ptr = readbuf; ptr < readbuf + rem; ptr += l)
        {
          if (*ptr < 192)
@@ -581,6 +563,46 @@
            keyid = grub_get_unaligned64 (ptr + 1);
        }
     }
+    hash->write (context, readbuf, r);
+    hash->write (context, &v, sizeof (v));
+    s = 0xff;
+    hash->write (context, &s, sizeof (s));
+    hash->write (context, &headlen, sizeof (headlen));
+    r = grub_file_read (sig, &unhashed_sub, sizeof (unhashed_sub));
+    if (r != sizeof (unhashed_sub))
+      goto fail;
+    if (keyid == 0)
+      {
+        grub_uint8_t *ptr;
+        grub_uint32_t l;
+        rem = grub_be_to_cpu16 (unhashed_sub);
+        if (rem > READBUF_SIZE)
+         goto fail;
+        r = grub_file_read (sig, readbuf, rem);
+        if (r != rem)
+         goto fail;
+        for (ptr = readbuf; ptr < readbuf + rem; ptr += l)
+         {
+           if (*ptr < 192)
+             l = *ptr++;
+           else if (*ptr < 255)
+             {
+               if (ptr + 1 >= readbuf + rem)
+                 break;
+               l = (((ptr[0] & ~192) << GRUB_CHAR_BIT) | ptr[1]) + 192;
+               ptr += 2;
+             }
+           else
+             {
+               if (ptr + 5 >= readbuf + rem)
+                 break;
+               l = grub_be_to_cpu32 (grub_get_unaligned32 (ptr + 1));
+               ptr += 5;
+             }
+           if (*ptr == 0x10 && l >= 8)
+             keyid = grub_get_unaligned64 (ptr + 1);
+         }
+      }
 
     hash->final (context);