From cc293c8466625bf8d238fc41d26db169a126e21b Mon Sep 17 00:00:00 2001 From: Mimi Zohar Date: Fri, 22 Mar 2024 14:50:36 -0400 Subject: [PATCH] ima: define an init_module critical data record The init_module syscall loads an ELF image into kernel space without measuring the buffer containing the ELF image. To close this kernel module integrity gap, define a new critical-data record which includes the hash of the ELF image. Instead of including the buffer data in the IMA measurement list, include the hash of the buffer data to avoid large IMA measurement list records. The buffer data hash would be the same value as the finit_module syscall file hash. To enable measuring the init_module buffer and other critical data from boot, define "ima_policy=critical_data" on the boot command line. Since builtin policies are not persistent, a custom IMA policy must include the rule as well: measure func=CRITICAL_DATA label=modules To verify the template data hash value, first convert the buffer data hash to binary: grep "init_module" \ /sys/kernel/security/integrity/ima/ascii_runtime_measurements | \ tail -1 | cut -d' ' -f 6 | xxd -r -p | sha256sum Reported-by: Ken Goldman Reviewed-by: Jarkko Sakkinen Signed-off-by: Mimi Zohar --- security/integrity/ima/ima_main.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c index c84e8c55333d..4b4348d681a6 100644 --- a/security/integrity/ima/ima_main.c +++ b/security/integrity/ima/ima_main.c @@ -902,6 +902,13 @@ static int ima_post_load_data(char *buf, loff_t size, return 0; } + /* + * Measure the init_module syscall buffer containing the ELF image. + */ + if (load_id == LOADING_MODULE) + ima_measure_critical_data("modules", "init_module", + buf, size, true, NULL, 0); + return 0; }