From: Tianjia Zhang <[email protected]>
Q1 and Q2 are numbers with *maximum* length of 384 bytes. If the calculated
length of Q1 and Q2 is less than 384 bytes, things will go wrong.
E.g. if Q2 is 383 bytes, then
1. The bytes of q2 are copied to sigstruct->q2 in calc_q1q2().
2. The entire sigstruct->q2 is reversed, which results it being
256 * Q2, given that the last byte of sigstruct->q2 is added
to before the bytes given by calc_q1q2().
Either change in key or measurement can trigger the bug. E.g. an unmeasured
heap could cause a devastating change in Q1 or Q2.
Reverse exactly the bytes of Q1 and Q2 in calc_q1q2() before returning to
the caller.
Fixes: dedde2634570 ("selftests/sgx: Trigger the reclaimer in the selftests")
Link: https://lore.kernel.org/linux-sgx/[email protected]/
Signed-off-by: Tianjia Zhang <[email protected]>
Signed-off-by: Jarkko Sakkinen <[email protected]>
---
The original patch did a bad job explaining the code change but it
turned out making sense. I wrote a new description.
v2:
- Added a fixes tag.
tools/testing/selftests/sgx/sigstruct.c | 41 +++++++++++++------------
1 file changed, 21 insertions(+), 20 deletions(-)
diff --git a/tools/testing/selftests/sgx/sigstruct.c b/tools/testing/selftests/sgx/sigstruct.c
index dee7a3d6c5a5..92bbc5a15c39 100644
--- a/tools/testing/selftests/sgx/sigstruct.c
+++ b/tools/testing/selftests/sgx/sigstruct.c
@@ -55,10 +55,27 @@ static bool alloc_q1q2_ctx(const uint8_t *s, const uint8_t *m,
return true;
}
+static void reverse_bytes(void *data, int length)
+{
+ int i = 0;
+ int j = length - 1;
+ uint8_t temp;
+ uint8_t *ptr = data;
+
+ while (i < j) {
+ temp = ptr[i];
+ ptr[i] = ptr[j];
+ ptr[j] = temp;
+ i++;
+ j--;
+ }
+}
+
static bool calc_q1q2(const uint8_t *s, const uint8_t *m, uint8_t *q1,
uint8_t *q2)
{
struct q1q2_ctx ctx;
+ int len;
if (!alloc_q1q2_ctx(s, m, &ctx)) {
fprintf(stderr, "Not enough memory for Q1Q2 calculation\n");
@@ -89,8 +106,10 @@ static bool calc_q1q2(const uint8_t *s, const uint8_t *m, uint8_t *q1,
goto out;
}
- BN_bn2bin(ctx.q1, q1);
- BN_bn2bin(ctx.q2, q2);
+ len = BN_bn2bin(ctx.q1, q1);
+ reverse_bytes(q1, len);
+ len = BN_bn2bin(ctx.q2, q2);
+ reverse_bytes(q2, len);
free_q1q2_ctx(&ctx);
return true;
@@ -152,22 +171,6 @@ static RSA *gen_sign_key(void)
return key;
}
-static void reverse_bytes(void *data, int length)
-{
- int i = 0;
- int j = length - 1;
- uint8_t temp;
- uint8_t *ptr = data;
-
- while (i < j) {
- temp = ptr[i];
- ptr[i] = ptr[j];
- ptr[j] = temp;
- i++;
- j--;
- }
-}
-
enum mrtags {
MRECREATE = 0x0045544145524345,
MREADD = 0x0000000044444145,
@@ -367,8 +370,6 @@ bool encl_measure(struct encl *encl)
/* BE -> LE */
reverse_bytes(sigstruct->signature, SGX_MODULUS_SIZE);
reverse_bytes(sigstruct->modulus, SGX_MODULUS_SIZE);
- reverse_bytes(sigstruct->q1, SGX_MODULUS_SIZE);
- reverse_bytes(sigstruct->q2, SGX_MODULUS_SIZE);
EVP_MD_CTX_destroy(ctx);
RSA_free(key);
--
2.32.0
On Mon, Jul 05, 2021 at 08:09:21AM +0300, Jarkko Sakkinen wrote:
> From: Tianjia Zhang <[email protected]>
>
> Q1 and Q2 are numbers with *maximum* length of 384 bytes. If the calculated
> length of Q1 and Q2 is less than 384 bytes, things will go wrong.
>
> E.g. if Q2 is 383 bytes, then
>
> 1. The bytes of q2 are copied to sigstruct->q2 in calc_q1q2().
> 2. The entire sigstruct->q2 is reversed, which results it being
> 256 * Q2, given that the last byte of sigstruct->q2 is added
> to before the bytes given by calc_q1q2().
>
> Either change in key or measurement can trigger the bug. E.g. an unmeasured
> heap could cause a devastating change in Q1 or Q2.
>
> Reverse exactly the bytes of Q1 and Q2 in calc_q1q2() before returning to
> the caller.
>
> Fixes: dedde2634570 ("selftests/sgx: Trigger the reclaimer in the selftests")
Oops :-(
Was meant to be
Fixes: 2adcba79e69d ("selftests/x86: Add a selftest for SGX")
/Jarkko
On 7/4/21 11:09 PM, Jarkko Sakkinen wrote:
> From: Tianjia Zhang <[email protected]>
>
> Q1 and Q2 are numbers with *maximum* length of 384 bytes. If the calculated
> length of Q1 and Q2 is less than 384 bytes, things will go wrong.
>
> E.g. if Q2 is 383 bytes, then
>
> 1. The bytes of q2 are copied to sigstruct->q2 in calc_q1q2().
> 2. The entire sigstruct->q2 is reversed, which results it being
> 256 * Q2, given that the last byte of sigstruct->q2 is added
> to before the bytes given by calc_q1q2().
>
> Either change in key or measurement can trigger the bug. E.g. an unmeasured
> heap could cause a devastating change in Q1 or Q2.
>
> Reverse exactly the bytes of Q1 and Q2 in calc_q1q2() before returning to
> the caller.
>
> Fixes: dedde2634570 ("selftests/sgx: Trigger the reclaimer in the selftests")
> Link: https://lore.kernel.org/linux-sgx/[email protected]/
> Signed-off-by: Tianjia Zhang <[email protected]>
> Signed-off-by: Jarkko Sakkinen <[email protected]>
> ---
> The original patch did a bad job explaining the code change but it
> turned out making sense. I wrote a new description.
>
> v2:
> - Added a fixes tag.
> tools/testing/selftests/sgx/sigstruct.c | 41 +++++++++++++------------
> 1 file changed, 21 insertions(+), 20 deletions(-)
>
> diff --git a/tools/testing/selftests/sgx/sigstruct.c b/tools/testing/selftests/sgx/sigstruct.c
> index dee7a3d6c5a5..92bbc5a15c39 100644
> --- a/tools/testing/selftests/sgx/sigstruct.c
> +++ b/tools/testing/selftests/sgx/sigstruct.c
> @@ -55,10 +55,27 @@ static bool alloc_q1q2_ctx(const uint8_t *s, const uint8_t *m,
> return true;
> }
>
> +static void reverse_bytes(void *data, int length)
> +{
> + int i = 0;
> + int j = length - 1;
> + uint8_t temp;
> + uint8_t *ptr = data;
> +
> + while (i < j) {
> + temp = ptr[i];
> + ptr[i] = ptr[j];
> + ptr[j] = temp;
> + i++;
> + j--;
> + }
> +}
I was just about apply this one and noticed this reverse_bytes().
Aren't there byteswap functions you could call instead of writing
your own?
thanks,
-- Shuah
On Fri, Jul 23, 2021 at 01:53:06PM -0600, Shuah Khan wrote:
> On 7/4/21 11:09 PM, Jarkko Sakkinen wrote:
> > From: Tianjia Zhang <[email protected]>
> >
> > Q1 and Q2 are numbers with *maximum* length of 384 bytes. If the calculated
> > length of Q1 and Q2 is less than 384 bytes, things will go wrong.
> >
> > E.g. if Q2 is 383 bytes, then
> >
> > 1. The bytes of q2 are copied to sigstruct->q2 in calc_q1q2().
> > 2. The entire sigstruct->q2 is reversed, which results it being
> > 256 * Q2, given that the last byte of sigstruct->q2 is added
> > to before the bytes given by calc_q1q2().
> >
> > Either change in key or measurement can trigger the bug. E.g. an unmeasured
> > heap could cause a devastating change in Q1 or Q2.
> >
> > Reverse exactly the bytes of Q1 and Q2 in calc_q1q2() before returning to
> > the caller.
> >
> > Fixes: dedde2634570 ("selftests/sgx: Trigger the reclaimer in the selftests")
> > Link: https://lore.kernel.org/linux-sgx/[email protected]/
> > Signed-off-by: Tianjia Zhang <[email protected]>
> > Signed-off-by: Jarkko Sakkinen <[email protected]>
> > ---
> > The original patch did a bad job explaining the code change but it
> > turned out making sense. I wrote a new description.
> >
> > v2:
> > - Added a fixes tag.
> > tools/testing/selftests/sgx/sigstruct.c | 41 +++++++++++++------------
> > 1 file changed, 21 insertions(+), 20 deletions(-)
> >
> > diff --git a/tools/testing/selftests/sgx/sigstruct.c b/tools/testing/selftests/sgx/sigstruct.c
> > index dee7a3d6c5a5..92bbc5a15c39 100644
> > --- a/tools/testing/selftests/sgx/sigstruct.c
> > +++ b/tools/testing/selftests/sgx/sigstruct.c
> > @@ -55,10 +55,27 @@ static bool alloc_q1q2_ctx(const uint8_t *s, const uint8_t *m,
> > return true;
> > }
> > +static void reverse_bytes(void *data, int length)
> > +{
> > + int i = 0;
> > + int j = length - 1;
> > + uint8_t temp;
> > + uint8_t *ptr = data;
> > +
> > + while (i < j) {
> > + temp = ptr[i];
> > + ptr[i] = ptr[j];
> > + ptr[j] = temp;
> > + i++;
> > + j--;
> > + }
> > +}
>
> I was just about apply this one and noticed this reverse_bytes().
> Aren't there byteswap functions you could call instead of writing
> your own?
Sorry for latency, just came from two week leave.
glibc does provide bswap for 16, 32, 64 bit numbers but nothing better.
I have no idea if libssl has such function. Since the test code already
uses this function, and it works, and it's not a newly added function in
this patch, I would consider keeping it.
> thanks,
> -- Shuah
/Jarkko
On 7/26/21 9:12 PM, Jarkko Sakkinen wrote:
> On Fri, Jul 23, 2021 at 01:53:06PM -0600, Shuah Khan wrote:
>> On 7/4/21 11:09 PM, Jarkko Sakkinen wrote:
>>> From: Tianjia Zhang <[email protected]>
>>>
>>> Q1 and Q2 are numbers with *maximum* length of 384 bytes. If the calculated
>>> length of Q1 and Q2 is less than 384 bytes, things will go wrong.
>>>
>>> E.g. if Q2 is 383 bytes, then
>>>
>>> 1. The bytes of q2 are copied to sigstruct->q2 in calc_q1q2().
>>> 2. The entire sigstruct->q2 is reversed, which results it being
>>> 256 * Q2, given that the last byte of sigstruct->q2 is added
>>> to before the bytes given by calc_q1q2().
>>>
>>> Either change in key or measurement can trigger the bug. E.g. an unmeasured
>>> heap could cause a devastating change in Q1 or Q2.
>>>
>>> Reverse exactly the bytes of Q1 and Q2 in calc_q1q2() before returning to
>>> the caller.
>>>
>>> Fixes: dedde2634570 ("selftests/sgx: Trigger the reclaimer in the selftests")
>>> Link: https://lore.kernel.org/linux-sgx/[email protected]/
>>> Signed-off-by: Tianjia Zhang <[email protected]>
>>> Signed-off-by: Jarkko Sakkinen <[email protected]>
>>> ---
>>> The original patch did a bad job explaining the code change but it
>>> turned out making sense. I wrote a new description.
>>>
>>> v2:
>>> - Added a fixes tag.
>>> tools/testing/selftests/sgx/sigstruct.c | 41 +++++++++++++------------
>>> 1 file changed, 21 insertions(+), 20 deletions(-)
>>>
>>> diff --git a/tools/testing/selftests/sgx/sigstruct.c b/tools/testing/selftests/sgx/sigstruct.c
>>> index dee7a3d6c5a5..92bbc5a15c39 100644
>>> --- a/tools/testing/selftests/sgx/sigstruct.c
>>> +++ b/tools/testing/selftests/sgx/sigstruct.c
>>> @@ -55,10 +55,27 @@ static bool alloc_q1q2_ctx(const uint8_t *s, const uint8_t *m,
>>> return true;
>>> }
>>> +static void reverse_bytes(void *data, int length)
>>> +{
>>> + int i = 0;
>>> + int j = length - 1;
>>> + uint8_t temp;
>>> + uint8_t *ptr = data;
>>> +
>>> + while (i < j) {
>>> + temp = ptr[i];
>>> + ptr[i] = ptr[j];
>>> + ptr[j] = temp;
>>> + i++;
>>> + j--;
>>> + }
>>> +}
>>
>> I was just about apply this one and noticed this reverse_bytes().
>> Aren't there byteswap functions you could call instead of writing
>> your own?
>
> Sorry for latency, just came from two week leave.
>
> glibc does provide bswap for 16, 32, 64 bit numbers but nothing better.
>
> I have no idea if libssl has such function. Since the test code already
> uses this function, and it works, and it's not a newly added function in
> this patch, I would consider keeping it.
>
I will queue this up since it is fixing an important problem.
Let's look into if this can be replaced with a lib call when
you do cleanups perhaps for the next release.
thanks,
-- Shuah
On Thu, Jul 29, 2021 at 03:33:10PM -0600, Shuah Khan wrote:
> On 7/26/21 9:12 PM, Jarkko Sakkinen wrote:
> > On Fri, Jul 23, 2021 at 01:53:06PM -0600, Shuah Khan wrote:
> > > On 7/4/21 11:09 PM, Jarkko Sakkinen wrote:
> > > > From: Tianjia Zhang <[email protected]>
> > > >
> > > > Q1 and Q2 are numbers with *maximum* length of 384 bytes. If the calculated
> > > > length of Q1 and Q2 is less than 384 bytes, things will go wrong.
> > > >
> > > > E.g. if Q2 is 383 bytes, then
> > > >
> > > > 1. The bytes of q2 are copied to sigstruct->q2 in calc_q1q2().
> > > > 2. The entire sigstruct->q2 is reversed, which results it being
> > > > 256 * Q2, given that the last byte of sigstruct->q2 is added
> > > > to before the bytes given by calc_q1q2().
> > > >
> > > > Either change in key or measurement can trigger the bug. E.g. an unmeasured
> > > > heap could cause a devastating change in Q1 or Q2.
> > > >
> > > > Reverse exactly the bytes of Q1 and Q2 in calc_q1q2() before returning to
> > > > the caller.
> > > >
> > > > Fixes: dedde2634570 ("selftests/sgx: Trigger the reclaimer in the selftests")
> > > > Link: https://lore.kernel.org/linux-sgx/[email protected]/
> > > > Signed-off-by: Tianjia Zhang <[email protected]>
> > > > Signed-off-by: Jarkko Sakkinen <[email protected]>
> > > > ---
> > > > The original patch did a bad job explaining the code change but it
> > > > turned out making sense. I wrote a new description.
> > > >
> > > > v2:
> > > > - Added a fixes tag.
> > > > tools/testing/selftests/sgx/sigstruct.c | 41 +++++++++++++------------
> > > > 1 file changed, 21 insertions(+), 20 deletions(-)
> > > >
> > > > diff --git a/tools/testing/selftests/sgx/sigstruct.c b/tools/testing/selftests/sgx/sigstruct.c
> > > > index dee7a3d6c5a5..92bbc5a15c39 100644
> > > > --- a/tools/testing/selftests/sgx/sigstruct.c
> > > > +++ b/tools/testing/selftests/sgx/sigstruct.c
> > > > @@ -55,10 +55,27 @@ static bool alloc_q1q2_ctx(const uint8_t *s, const uint8_t *m,
> > > > return true;
> > > > }
> > > > +static void reverse_bytes(void *data, int length)
> > > > +{
> > > > + int i = 0;
> > > > + int j = length - 1;
> > > > + uint8_t temp;
> > > > + uint8_t *ptr = data;
> > > > +
> > > > + while (i < j) {
> > > > + temp = ptr[i];
> > > > + ptr[i] = ptr[j];
> > > > + ptr[j] = temp;
> > > > + i++;
> > > > + j--;
> > > > + }
> > > > +}
> > >
> > > I was just about apply this one and noticed this reverse_bytes().
> > > Aren't there byteswap functions you could call instead of writing
> > > your own?
> >
> > Sorry for latency, just came from two week leave.
> >
> > glibc does provide bswap for 16, 32, 64 bit numbers but nothing better.
> > I have no idea if libssl has such function. Since the test code already
> > uses this function, and it works, and it's not a newly added function in
> > this patch, I would consider keeping it.
>
> I will queue this up since it is fixing an important problem.
> Let's look into if this can be replaced with a lib call when
> you do cleanups perhaps for the next release.
Thank you.
/Jarkko