linux-kernel - Re: [PATCH 2/3] binfmt_elf: Verify signature of signed elf binary

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Message-ID: <CALLzPKYHUDj6gxz44_bOe1ggoeqZd2HaA3R34OXgHqGR9X7AcQ@mail.gmail.com>
Date:	Thu, 17 Jan 2013 19:01:40 +0200
From:	"Kasatkin, Dmitry" <dmitry.kasatkin@...el.com>
To:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc:	Vivek Goyal <vgoyal@...hat.com>, linux-kernel@...r.kernel.org,
	ebiederm@...ssion.com, pjones@...hat.com, hpa@...or.com,
	dhowells@...hat.com, jwboyer@...hat.com
Subject: Re: [PATCH 2/3] binfmt_elf: Verify signature of signed elf binary

commit f6bf2c4c0339dabac435f518bb1fcb617fdef8f1
Author: Dmitry Kasatkin <dmitry.kasatkin@...el.com>
Date:   Thu Jan 17 18:50:43 2013 +0200

    ima: lock down memory if binary is digitally signed

    This patch set a flag in the linux_binprm structure if binary is
    digitally signed. The flag is used to lock down memory when loading
    ELF binary.

    Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@...el.com>

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 0c42cdb..ba94d13 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -44,6 +44,8 @@
 #define user_siginfo_t siginfo_t
 #endif

+#define LSM_UNSAFE_DIGSIG	16
+
 static int load_elf_binary(struct linux_binprm *bprm);
 static int load_elf_library(struct file *);
 static unsigned long elf_map(struct file *, unsigned long, struct elf_phdr *,
@@ -788,6 +790,9 @@ static int load_elf_binary(struct linux_binprm *bprm)

 		elf_flags = MAP_PRIVATE | MAP_DENYWRITE | MAP_EXECUTABLE;

+		if (bprm->unsafe & LSM_UNSAFE_DIGSIG)
+			elf_flags |= MAP_LOCKED;
+
 		vaddr = elf_ppnt->p_vaddr;
 		if (loc->elf_ex.e_type == ET_EXEC || load_addr_set) {
 			elf_flags |= MAP_FIXED;
diff --git a/security/integrity/ima/ima_main.c
b/security/integrity/ima/ima_main.c
index b359fb5..50d9959 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -27,6 +27,8 @@

 #include "ima.h"

+#define LSM_UNSAFE_DIGSIG	16
+
 int ima_initialized;

 #ifdef CONFIG_IMA_APPRAISE
@@ -315,10 +317,19 @@ int ima_file_mmap(struct file *file, unsigned long prot)
  */
 int ima_bprm_check(struct linux_binprm *bprm)
 {
-	return process_measurement(bprm->file,
+	int err;
+	struct integrity_iint_cache *iint;
+
+	err = process_measurement(bprm->file,
 				 (strcmp(bprm->filename, bprm->interp) == 0) ?
 				 bprm->filename : bprm->interp,
 				 MAY_EXEC, BPRM_CHECK);
+
+	iint = integrity_iint_find(bprm->file->f_dentry->d_inode);
+	if (iint && (iint->flags & IMA_DIGSIG))
+		bprm->unsafe |= LSM_UNSAFE_DIGSIG;
+
+	return err;
 }

 /**
--
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