[PATCH] verify: search keyid in hashed signature subpackets (repost)

[Ignat Korchagin]

Reposting this, as requested by Daniel and rebasing on current tree.

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.

Signed-off-by: Ignat Korchagin <address@hidden>
---
 grub-core/commands/verify.c | 115 +++++++++++++++++++++++++++++---------------
 1 file changed, 76 insertions(+), 39 deletions(-)

diff --git a/grub-core/commands/verify.c b/grub-core/commands/verify.c
index 67cb1c7..1b628b2 100644
--- a/grub-core/commands/verify.c
+++ b/grub-core/commands/verify.c
@@ -445,6 +445,38 @@ rsa_pad (gcry_mpi_t *hmpi, grub_uint8_t *hval,
   return ret;
 }
 
+static grub_uint64_t
+grub_subpacket_keyid_search (const grub_uint8_t * sub, grub_ssize_t sub_len)
+{
+  const grub_uint8_t *ptr;
+  grub_uint32_t l;
+  grub_uint64_t keyid = 0;
+
+  for (ptr = sub; ptr < sub + sub_len; ptr += l)
+    {
+      if (*ptr < 192)
+        l = *ptr++;
+      else if (*ptr < 255)
+        {
+          if (ptr + 1 >= sub + sub_len)
+            break;
+          l = (((ptr[0] & ~192) << GRUB_CHAR_BIT) | ptr[1]) + 192;
+          ptr += 2;
+        }
+      else
+        {
+          if (ptr + 5 >= sub + sub_len)
+            break;
+          l = grub_be_to_cpu32 (grub_get_unaligned32 (ptr + 1));
+          ptr += 5;
+        }
+      if (*ptr == 0x10 && l >= 8)
+        keyid = grub_get_unaligned64 (ptr + 1);
+    }
+
+  return keyid;
+}
+
 static grub_err_t
 grub_verify_signature_real (char *buf, grub_size_t size,
                            grub_file_t f, grub_file_t sig,
@@ -529,20 +561,31 @@ grub_verify_signature_real (char *buf, grub_size_t size,
            break;
          hash->write (context, readbuf, r);
        }
+    grub_free (readbuf);
+
+    readbuf = grub_malloc (rem);
+    if (!readbuf)
+      goto fail;
 
     hash->write (context, &v, sizeof (v));
     hash->write (context, &v4, sizeof (v4));
-    while (rem)
+
+    r = 0;
+    while (r < rem)
       {
-       r = grub_file_read (sig, readbuf,
-                           rem < READBUF_SIZE ? rem : READBUF_SIZE);
-       if (r < 0)
-         goto fail;
-       if (r == 0)
+        grub_ssize_t rr = grub_file_read (sig, readbuf + r, rem - r);
+        if (rr < 0)
+          goto fail;
+        if (rr == 0)
          break;
-       hash->write (context, readbuf, r);
-       rem -= r;
+        r += rr;
       }
+    if (r != rem)
+      goto fail;
+    hash->write (context, readbuf, rem);
+    keyid = grub_subpacket_keyid_search (readbuf, rem);
+    grub_free (readbuf);
+
     hash->write (context, &v, sizeof (v));
     s = 0xff;
     hash->write (context, &s, sizeof (s));
@@ -550,40 +593,34 @@ grub_verify_signature_real (char *buf, grub_size_t size,
     r = grub_file_read (sig, &unhashed_sub, sizeof (unhashed_sub));
     if (r != sizeof (unhashed_sub))
       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)
-           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);
-       }
-    }
+    rem = grub_be_to_cpu16 (unhashed_sub);
+    readbuf = grub_malloc (rem);
+    if (!readbuf)
+      goto fail;
+
+    r = 0;
+    while (r < rem)
+      {
+        grub_ssize_t rr = grub_file_read (sig, readbuf + r, rem - r);
+        if (rr < 0)
+          goto fail;
+        if (rr == 0)
+          break;
+        r += rr;
+      }
+    if (r != rem)
+      goto fail;
+
+    if (keyid == 0)
+      keyid = grub_subpacket_keyid_search (readbuf, rem);
+    grub_free (readbuf);
 
     hash->final (context);
 
+    readbuf = grub_zalloc (READBUF_SIZE);
+    if (!readbuf)
+      goto fail;
+
     grub_dprintf ("crypt", "alive\n");
 
     hval = hash->read (context);
-- 
2.1.4