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verifiers: fix double close on pgp's sig file descriptor

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An error emerged as when I was testing the verifiers branch, so instead
of putting it in pgp prefix, the verifiers is used to reflect what the
patch is based on.

While running verify_detached, grub aborts with error.

verify_detached /@/.snapshots/1/snapshot/boot/grub/grub.cfg
/@/.snapshots/1/snapshot/boot/grub/grub.cfg.sig

alloc magic is broken at 0x7beea660: 0
Aborted. Press any key to exit.

The error is caused by sig file descriptor been closed twice, first time
in grub_verify_signature() to which it is passed as parameter. Second in
grub_cmd_verify_signature() or in whichever opens the sig file
descriptor. The second close is not consider as bug to me either, as in
common rule of what opens a file has to close it to avoid file
descriptor leakage.

After all the design of grub_verify_signature() makes it difficult to keep
a good trace on opened file descriptor from it's caller. Let's refine
the application interface to accept file path rather than descriptor, in
this way the caller doesn't have to care about closing the descriptor by
delegating it to grub_verify_signature() with full tracing to opened
file descriptor by itself.

Also making it clear that sig descriptor is not referenced in error
returning path of grub_verify_signature_init(), so it can be closed
directly by it's caller. This also makes delegating it to
grub_pubkey_close() infeasible to help in relieving file descriptor
leakage as it has to depend on uncertainty of ctxt fields in error
returning path.

Signed-off-by: Michael Chang <mchang@suse.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
This commit is contained in:
Michael Chang 2018-11-20 19:15:37 +08:00 committed by Daniel Kiper
parent 5c6f9bc156
commit e8b37e2c8d
2 changed files with 18 additions and 19 deletions
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35
grub-core/commands/pgp.c
View file

@ -495,13 +495,12 @@ grub_verify_signature_init (struct grub_pubkey_context *ctxt, grub_file_t sig)
grub_dprintf ("crypt", "alive\n");
ctxt->sig = sig;
ctxt->hash_context = grub_zalloc (ctxt->hash->contextsize);
if (!ctxt->hash_context)
return grub_errno;
ctxt->hash->init (ctxt->hash_context);
ctxt->sig = sig;
return GRUB_ERR_NONE;
}
@ -684,16 +683,26 @@ grub_pubkey_close (void *ctxt)
}
grub_err_t
grub_verify_signature (grub_file_t f, grub_file_t sig,
grub_verify_signature (grub_file_t f, const char *fsig,
struct grub_public_key *pkey)
{
grub_file_t sig;
grub_err_t err;
struct grub_pubkey_context ctxt;
grub_uint8_t *readbuf = NULL;
sig = grub_file_open (fsig,
GRUB_FILE_TYPE_SIGNATURE
| GRUB_FILE_TYPE_NO_DECOMPRESS);
if (!sig)
return grub_errno;
err = grub_verify_signature_init (&ctxt, sig);
if (err)
return err;
{
grub_file_close (sig);
return err;
}
readbuf = grub_zalloc (READBUF_SIZE);
if (!readbuf)
@ -807,7 +816,7 @@ static grub_err_t
grub_cmd_verify_signature (grub_extcmd_context_t ctxt,
int argc, char **args)
{
grub_file_t f = NULL, sig = NULL;
grub_file_t f = NULL;
grub_err_t err = GRUB_ERR_NONE;
struct grub_public_key *pk = NULL;
@ -845,19 +854,8 @@ grub_cmd_verify_signature (grub_extcmd_context_t ctxt,
goto fail;
}
sig = grub_file_open (args[1],
GRUB_FILE_TYPE_SIGNATURE
| GRUB_FILE_TYPE_NO_DECOMPRESS);
if (!sig)
{
err = grub_errno;
goto fail;
}
err = grub_verify_signature (f, sig, pk);
err = grub_verify_signature (f, args[1], pk);
fail:
if (sig)
grub_file_close (sig);
if (f)
grub_file_close (f);
if (pk)
@ -902,7 +900,8 @@ grub_pubkey_init (grub_file_t io, enum grub_file_type type __attribute__ ((unuse
err = grub_verify_signature_init (ctxt, sig);
if (err)
{
grub_pubkey_close (ctxt);
grub_free (ctxt);
grub_file_close (sig);
return err;
}
*context = ctxt;

2
include/grub/pubkey.h
View file

@ -25,7 +25,7 @@ struct grub_public_key *
grub_load_public_key (grub_file_t f);
grub_err_t
grub_verify_signature (grub_file_t f, grub_file_t sig,
grub_verify_signature (grub_file_t f, const char *fsig,
struct grub_public_key *pk);