On Fri, Nov 18, 2016 at 12:00:08PM +0000, Ignat Korchagin wrote:
> 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 <ig...@cloudflare.com>
> ---
> 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)
Please define some constants and use them properly...
> + l = *ptr++;
> + else if (*ptr < 255)
Ditto.
> + {
> + if (ptr + 1 >= sub + sub_len)
> + break;
> + l = (((ptr[0] & ~192) << GRUB_CHAR_BIT) | ptr[1]) + 192;
Ditto.
> + ptr += 2;
Ditto and below...
> + }
> + 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);
grub_zalloc()?
> + 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);
grub_zalloc()?
Daniel
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