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zipl: secure boot - verify load address

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To ensure that only verified code is executed the stage 3 loader has
to check if the load psw points to an address that has previously been
verified by the machine loader.

If secure boot is enabled the IPL process will only continue if the
verification was successful.

Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
Acked-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>
This commit is contained in:
Stefan Haberland
2019-04-15 17:51:26 +02:00
committed by Jan Höppner
parent 7e7a77675d
commit 331b54d573
4 changed files with 227 additions and 2 deletions
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zipl/boot/stage3.c
+81 -2
View File
@@ -12,6 +12,15 @@
#include "libc.h"
#include "s390.h"
#include "stage3.h"
#include "error.h"
#define for_each_rb_entry(entry, rb) \
for (entry = rb->entries; \
(void *) entry + sizeof(*entry) <= (void *) rb + rb->len; \
entry++)
static const char *msg_sipl_inval = "Secure boot failure: invalid load address";
static const char *msg_sipl_unverified = "Secure boot failure: unverified load address";
static unsigned char ebc_037[256] = {
/* 0x00 NUL SOH STX ETX *SEL HT *RNL DEL */
@@ -192,6 +201,64 @@ start_kernel(void)
: [psw] "a" (psw) );
}
unsigned int
is_verified_address(unsigned long image_addr)
{
struct ipl_rb_component_entry *comp;
struct ipl_rb_components *comps;
struct ipl_pl_hdr *pl_hdr;
struct ipl_rl_hdr *rl_hdr;
struct ipl_rb_hdr *rb_hdr;
unsigned long tmp;
void *rl_end;
/*
* There is an IPL report, to find it load the pointer to the
* IPL parameter information block from lowcore and skip past
* the IPL parameter list, then align the address to a double
* word boundary.
*/
tmp = (unsigned long) S390_lowcore.ipl_parmblock_ptr;
pl_hdr = (struct ipl_pl_hdr *) tmp;
tmp = (tmp + pl_hdr->len + 7) & -8UL;
rl_hdr = (struct ipl_rl_hdr *) tmp;
/* Walk through the IPL report blocks in the IPL Report list */
comps = NULL;
rl_end = (void *) rl_hdr + rl_hdr->len;
rb_hdr = (void *) rl_hdr + sizeof(*rl_hdr);
while ((void *) rb_hdr + sizeof(*rb_hdr) < rl_end &&
(void *) rb_hdr + rb_hdr->len <= rl_end) {
switch (rb_hdr->rbt) {
case IPL_RBT_COMPONENTS:
comps = (struct ipl_rb_components *) rb_hdr;
break;
default:
break;
}
rb_hdr = (void *) rb_hdr + rb_hdr->len;
}
for_each_rb_entry(comp, comps) {
if (image_addr == comp->addr &&
comp->flags & IPL_RB_COMPONENT_FLAG_SIGNED &&
comp->flags & IPL_RB_COMPONENT_FLAG_VERIFIED)
return 1;
}
return 0;
}
unsigned int
secure_boot_enabled()
{
struct ipl_pl_hdr *pl_hdr;
unsigned long tmp;
tmp = (unsigned long) S390_lowcore.ipl_parmblock_ptr;
pl_hdr = (struct ipl_pl_hdr *) tmp;
return pl_hdr->flags & IPL_FLAG_SECURE;
}
void start(void)
{
unsigned int subchannel_id;
@@ -200,8 +267,20 @@ void start(void)
unsigned int begin = 0, end = 0, length = 0;
/*
* Relocate the kernel image to its actual load address while stripping
* away the kernel IPL header to not overwrite the stage3 loader.
* IPL process is secure we have to use default IPL values and
* check if the psw jump address is within at the start of a
* verified component. If it is not IPL is aborted.
*/
if (secure_boot_enabled()) {
if (_image_addr != DEFAULT_IMAGE_ADDR ||
_load_psw != DEFAULT_PSW_LOAD)
panic(ESECUREBOOT, "%s", msg_sipl_inval);
if (!is_verified_address(_load_psw & PSW_ADDR_MASK))
panic(ESECUREBOOT, "%s", msg_sipl_unverified);
}
/*
* cut the kernel header
*/
memmove((void *)_image_addr,
(void *)_image_addr + KERNEL_HEADER_SIZE,