From: Vitaly Chikunov <vt@altlinux.org>
To: Mimi Zohar <zohar@linux.vnet.ibm.com>,
Dmitry Kasatkin <dmitry.kasatkin@gmail.com>,
linux-integrity@vger.kernel.org
Subject: Re: [PATCH 1/3] ima-avm-utils: Fix hash buffer overflow in verify_evm
Date: Mon, 26 Nov 2018 16:45:59 +0300 [thread overview]
Message-ID: <20181126134559.rkgdsjbvx2226bw2@sole.flsd.net> (raw)
In-Reply-To: <20181126043953.1126-1-vt@altlinux.org>
Excuse me, typo in the commit name, supposed to be
ima-evm-utils: Fix hash buffer overflow in verify_evm
of course.
On Mon, Nov 26, 2018 at 07:39:51AM +0300, Vitaly Chikunov wrote:
> Commit ae1319eeabd6 ("Remove hardcoding of SHA1 in EVM signatures")
> introduces overflow of 20 byte buffer on the stack while calculating evm
> hash. Also, invalid hash length is passed to the underlying verification
> function. This prevents any non-SHA1 hashes from being properly
> validated using evmctl.
>
> Signed-off-by: Vitaly Chikunov <vt@altlinux.org>
> ---
> src/evmctl.c | 13 ++++++++-----
> 1 file changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/src/evmctl.c b/src/evmctl.c
> index 1b46d58..94d7ab1 100644
> --- a/src/evmctl.c
> +++ b/src/evmctl.c
> @@ -55,6 +55,7 @@
> #include <keyutils.h>
> #include <ctype.h>
> #include <termios.h>
> +#include <assert.h>
>
> #include <openssl/sha.h>
> #include <openssl/pem.h>
> @@ -760,13 +761,15 @@ static int cmd_sign_evm(struct command *cmd)
>
> static int verify_evm(const char *file)
> {
> - unsigned char hash[20];
> + unsigned char hash[64];
> unsigned char sig[1024];
> + int mdlen;
> int len;
>
> - len = calc_evm_hash(file, hash);
> - if (len <= 1)
> - return len;
> + mdlen = calc_evm_hash(file, hash);
> + assert(mdlen <= sizeof(hash));
> + if (mdlen <= 1)
> + return mdlen;
>
> len = lgetxattr(file, "security.evm", sig, sizeof(sig));
> if (len < 0) {
> @@ -779,7 +782,7 @@ static int verify_evm(const char *file)
> return -1;
> }
>
> - return verify_hash(file, hash, sizeof(hash), sig + 1, len - 1);
> + return verify_hash(file, hash, mdlen, sig + 1, len - 1);
> }
>
> static int cmd_verify_evm(struct command *cmd)
> --
> 2.11.0
next prev parent reply other threads:[~2018-11-26 13:46 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-26 4:39 [PATCH 1/3] ima-avm-utils: Fix hash buffer overflow in verify_evm Vitaly Chikunov
2018-11-26 4:39 ` [PATCH 2/3] ima-evm-utils: Add --xattr-user option for testing Vitaly Chikunov
2018-11-27 11:55 ` Mimi Zohar
2018-11-26 4:39 ` [PATCH 3/3] ima-evm-utils: Allow to use Streebog hash function Vitaly Chikunov
2018-11-27 11:56 ` Mimi Zohar
2018-11-27 13:08 ` Vitaly Chikunov
2018-11-27 13:33 ` Mimi Zohar
2018-11-26 13:45 ` Vitaly Chikunov [this message]
2018-11-27 11:52 ` [PATCH 1/3] ima-avm-utils: Fix hash buffer overflow in verify_evm Mimi Zohar
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