Messages in this thread | | | Date | Thu, 4 Nov 2021 09:52:35 -0700 | Subject | Re: [RFC PATCH v7 14/16] scripts: add boot policy generation program | From | Deven Bowers <> |
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On 11/3/2021 9:53 AM, Roberto Sassu wrote: >> From: Roberto Sassu [mailto:roberto.sassu@huawei.com] >> Sent: Wednesday, November 3, 2021 5:43 PM >>> From: deven.desai@linux.microsoft.com >>> [mailto:deven.desai@linux.microsoft.com] >>> From: Deven Bowers <deven.desai@linux.microsoft.com> >>> >>> Enables an IPE policy to be enforced from kernel start, enabling access >>> control based on trust from kernel startup. This is accomplished by >>> transforming an IPE policy indicated by CONFIG_IPE_BOOT_POLICY into a >>> c-string literal that is parsed at kernel startup as an unsigned policy. >>> >>> Signed-off-by: Deven Bowers <deven.desai@linux.microsoft.com> >>> --- >>> >>> Relevant changes since v6: >>> * Move patch 01/12 to [14/16] of the series >>> >>> --- >>> MAINTAINERS | 1 + >>> scripts/Makefile | 1 + >>> scripts/ipe/Makefile | 2 + >>> scripts/ipe/polgen/.gitignore | 1 + >>> scripts/ipe/polgen/Makefile | 6 ++ >>> scripts/ipe/polgen/polgen.c | 145 ++++++++++++++++++++++++++++++++++ >>> security/ipe/.gitignore | 1 + >>> security/ipe/Kconfig | 10 +++ >>> security/ipe/Makefile | 13 +++ >>> security/ipe/ctx.c | 18 +++++ >>> 10 files changed, 198 insertions(+) >>> create mode 100644 scripts/ipe/Makefile >>> create mode 100644 scripts/ipe/polgen/.gitignore >>> create mode 100644 scripts/ipe/polgen/Makefile >>> create mode 100644 scripts/ipe/polgen/polgen.c >>> create mode 100644 security/ipe/.gitignore >>> >>> diff --git a/MAINTAINERS b/MAINTAINERS >>> index f1e76f791d47..a84ca781199b 100644 >>> --- a/MAINTAINERS >>> +++ b/MAINTAINERS >>> @@ -9283,6 +9283,7 @@ INTEGRITY POLICY ENFORCEMENT (IPE) >>> M: Deven Bowers <deven.desai@linux.microsoft.com> >>> M: Fan Wu <wufan@linux.microsoft.com> >>> S: Supported >>> +F: scripts/ipe/ >>> F: security/ipe/ >>> >>> INTEL 810/815 FRAMEBUFFER DRIVER >>> diff --git a/scripts/Makefile b/scripts/Makefile >>> index 9adb6d247818..a31da6d57a36 100644 >>> --- a/scripts/Makefile >>> +++ b/scripts/Makefile >>> @@ -41,6 +41,7 @@ targets += module.lds >>> subdir-$(CONFIG_GCC_PLUGINS) += gcc-plugins >>> subdir-$(CONFIG_MODVERSIONS) += genksyms >>> subdir-$(CONFIG_SECURITY_SELINUX) += selinux >>> +subdir-$(CONFIG_SECURITY_IPE) += ipe >>> >>> # Let clean descend into subdirs >>> subdir- += basic dtc gdb kconfig mod >>> diff --git a/scripts/ipe/Makefile b/scripts/ipe/Makefile >>> new file mode 100644 >>> index 000000000000..e87553fbb8d6 >>> --- /dev/null >>> +++ b/scripts/ipe/Makefile >>> @@ -0,0 +1,2 @@ >>> +# SPDX-License-Identifier: GPL-2.0-only >>> +subdir-y := polgen >>> diff --git a/scripts/ipe/polgen/.gitignore b/scripts/ipe/polgen/.gitignore >>> new file mode 100644 >>> index 000000000000..80f32f25d200 >>> --- /dev/null >>> +++ b/scripts/ipe/polgen/.gitignore >>> @@ -0,0 +1 @@ >>> +polgen >>> diff --git a/scripts/ipe/polgen/Makefile b/scripts/ipe/polgen/Makefile >>> new file mode 100644 >>> index 000000000000..066060c22b4a >>> --- /dev/null >>> +++ b/scripts/ipe/polgen/Makefile >>> @@ -0,0 +1,6 @@ >>> +# SPDX-License-Identifier: GPL-2.0 >>> +hostprogs-always-y := polgen >>> +HOST_EXTRACFLAGS += \ >>> + -I$(srctree)/include \ >>> + -I$(srctree)/include/uapi \ >>> + >>> diff --git a/scripts/ipe/polgen/polgen.c b/scripts/ipe/polgen/polgen.c >>> new file mode 100644 >>> index 000000000000..73cf13e743f7 >>> --- /dev/null >>> +++ b/scripts/ipe/polgen/polgen.c >>> @@ -0,0 +1,145 @@ >>> +// SPDX-License-Identifier: GPL-2.0 >>> +/* >>> + * Copyright (C) Microsoft Corporation. All rights reserved. >>> + */ >>> + >>> +#include <stdlib.h> >>> +#include <stddef.h> >>> +#include <stdio.h> >>> +#include <unistd.h> >>> +#include <errno.h> >>> + >>> +static void usage(const char *const name) >>> +{ >>> + printf("Usage: %s OutputFile (PolicyFile)\n", name); >>> + exit(EINVAL); >>> +} >>> + >>> +static int policy_to_buffer(const char *pathname, char **buffer, size_t *size) >>> +{ >>> + int rc = 0; >>> + FILE *fd; >>> + char *lbuf; >>> + size_t fsize; >>> + size_t read; >>> + >>> + fd = fopen(pathname, "r"); >>> + if (!fd) { >>> + rc = errno; >>> + goto out; >>> + } >>> + >>> + fseek(fd, 0, SEEK_END); >>> + fsize = ftell(fd); >>> + rewind(fd); >>> + >>> + lbuf = malloc(fsize); >>> + if (!lbuf) { >>> + rc = ENOMEM; >>> + goto out_close; >>> + } >>> + >>> + read = fread((void *)lbuf, sizeof(*lbuf), fsize, fd); >>> + if (read != fsize) { >>> + rc = -1; >>> + goto out_free; >>> + } >>> + >>> + *buffer = lbuf; >>> + *size = fsize; >>> + fclose(fd); >>> + >>> + return rc; >>> + >>> +out_free: >>> + free(lbuf); >>> +out_close: >>> + fclose(fd); >>> +out: >>> + return rc; >>> +} >>> + >>> +static int write_boot_policy(const char *pathname, const char *buf, size_t >> size) >>> +{ >>> + int rc = 0; >>> + FILE *fd; >>> + size_t i; >>> + >>> + fd = fopen(pathname, "w"); >>> + if (!fd) { >>> + rc = errno; >>> + goto err; >>> + } >>> + >>> + fprintf(fd, "/* This file is automatically generated."); >>> + fprintf(fd, " Do not edit. */\n"); >>> + fprintf(fd, "#include <stddef.h>\n"); >>> + fprintf(fd, "\nextern const char *const ipe_boot_policy;\n\n"); >>> + fprintf(fd, "const char *const ipe_boot_policy =\n"); >>> + >>> + if (!buf || size == 0) { >>> + fprintf(fd, "\tNULL;\n"); >>> + fclose(fd); >>> + return 0; >>> + } >>> + >>> + fprintf(fd, "\t\""); >>> + >>> + for (i = 0; i < size; ++i) { >>> + switch (buf[i]) { >>> + case '"': >>> + fprintf(fd, "\\\""); >>> + break; >>> + case '\'': >>> + fprintf(fd, "'"); >>> + break; >>> + case '\n': >>> + fprintf(fd, "\\n\"\n\t\""); >>> + break; >>> + case '\\': >>> + fprintf(fd, "\\\\"); >>> + break; >>> + case '\t': >>> + fprintf(fd, "\\t"); >>> + break; >>> + case '\?': >>> + fprintf(fd, "\\?"); >>> + break; >>> + default: >>> + fprintf(fd, "%c", buf[i]); >>> + } >>> + } >>> + fprintf(fd, "\";\n"); >>> + fclose(fd); >>> + >>> + return 0; >>> + >>> +err: >>> + if (fd) >>> + fclose(fd); >>> + return rc; >>> +} >>> + >>> +int main(int argc, const char *const argv[]) >>> +{ >>> + int rc = 0; >>> + size_t len = 0; >>> + char *policy = NULL; >>> + >>> + if (argc < 2) >>> + usage(argv[0]); >>> + >>> + if (argc > 2) { >>> + rc = policy_to_buffer(argv[2], &policy, &len); >>> + if (rc != 0) >>> + goto cleanup; >>> + } >>> + >>> + rc = write_boot_policy(argv[1], policy, len); >>> +cleanup: >>> + if (policy) >>> + free(policy); >>> + if (rc != 0) >>> + perror("An error occurred during policy conversion: "); >>> + return rc; >>> +} >>> diff --git a/security/ipe/.gitignore b/security/ipe/.gitignore >>> new file mode 100644 >>> index 000000000000..eca22ad5ed22 >>> --- /dev/null >>> +++ b/security/ipe/.gitignore >>> @@ -0,0 +1 @@ >>> +boot-policy.c >>> \ No newline at end of file >>> diff --git a/security/ipe/Kconfig b/security/ipe/Kconfig >>> index fcf82a8152ec..39df680b67a2 100644 >>> --- a/security/ipe/Kconfig >>> +++ b/security/ipe/Kconfig >>> @@ -20,6 +20,16 @@ menuconfig SECURITY_IPE >>> >>> if SECURITY_IPE >>> >>> +config IPE_BOOT_POLICY >>> + string "Integrity policy to apply on system startup" >>> + help >>> + This option specifies a filepath to a IPE policy that is compiled >>> + into the kernel. This policy will be enforced until a policy update >>> + is deployed via the $securityfs/ipe/policies/$policy_name/active >>> + interface. >>> + >>> + If unsure, leave blank. >>> + >>> choice >>> prompt "Hash algorithm used in auditing policies" >>> default IPE_AUDIT_HASH_SHA1 >>> diff --git a/security/ipe/Makefile b/security/ipe/Makefile >>> index 1e7b2d7fcd9e..89fec670f954 100644 >>> --- a/security/ipe/Makefile >>> +++ b/security/ipe/Makefile >>> @@ -7,7 +7,18 @@ >>> >>> ccflags-y := -I$(srctree)/security/ipe/modules >>> >>> +quiet_cmd_polgen = IPE_POL $(2) >>> + cmd_polgen = scripts/ipe/polgen/polgen security/ipe/boot-policy.c $(2) >>> + >>> +$(eval $(call config_filename,IPE_BOOT_POLICY)) >>> + >>> +targets += boot-policy.c >>> + >>> +$(obj)/boot-policy.c: scripts/ipe/polgen/polgen >>> $(IPE_BOOT_POLICY_FILENAME) FORCE >>> + $(call if_changed,polgen,$(IPE_BOOT_POLICY_FILENAME)) >>> + >>> obj-$(CONFIG_SECURITY_IPE) += \ >>> + boot-policy.o \ >>> ctx.o \ >>> eval.o \ >>> fs.o \ >>> @@ -21,3 +32,5 @@ obj-$(CONFIG_SECURITY_IPE) += \ >>> policyfs.o \ >>> >>> obj-$(CONFIG_AUDIT) += audit.o >>> + >>> +clean-files := boot-policy.c \ >>> diff --git a/security/ipe/ctx.c b/security/ipe/ctx.c >>> index fc9b8e467bc9..879acf4ceac5 100644 >>> --- a/security/ipe/ctx.c >>> +++ b/security/ipe/ctx.c >>> @@ -15,6 +15,7 @@ >>> #include <linux/spinlock.h> >>> #include <linux/moduleparam.h> >>> >>> +extern const char *const ipe_boot_policy; >>> static bool success_audit; >>> static bool enforce = true; >>> >>> @@ -329,6 +330,7 @@ void ipe_put_ctx(struct ipe_context *ctx) >>> int __init ipe_init_ctx(void) >>> { >>> int rc = 0; >>> + struct ipe_policy *p = NULL; >>> struct ipe_context *lns = NULL; >>> >>> lns = create_ctx(); >>> @@ -342,10 +344,26 @@ int __init ipe_init_ctx(void) >>> WRITE_ONCE(lns->enforce, enforce); >>> spin_unlock(&lns->lock); >>> >>> + if (ipe_boot_policy) { >>> + p = ipe_new_policy(ipe_boot_policy, strlen(ipe_boot_policy), >>> + NULL, 0); >>> + if (IS_ERR(p)) { >>> + rc = PTR_ERR(lns); >> This should be: >> >> rc = PTR_ERR(p); >> >>> + goto err; >>> + } >>> + >>> + ipe_add_policy(lns, p); >>> + rc = ipe_set_active_pol(p); >>> + if (!rc) >> Here you need to set a non-zero value, so that ipe_init() >> does not enable the LSM. > Actually you probably should just check that rc is not zero > and goto err. > > Roberto > Yeah, I actually noticed these two mistakes myself fairly recently.
Changes will be applied in v8. > >> I would set to 1 a new global variable, like ipe_lsm_enabled, >> in ipe_init() just before security_add_hooks(). >> >> Then, I would add a check of this variable in ipe_init_securityfs() >> to avoid the kernel panic.
That's my plan.
-Deven
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