[thirdparty/systemd.git] / src / basic / efivars.c

/* SPDX-License-Identifier: LGPL-2.1-or-later */

#include <fcntl.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <time.h>
#include <unistd.h>

#include "alloc-util.h"
#include "chattr-util.h"
#include "efivars.h"
#include "fd-util.h"
#include "io-util.h"
#include "log.h"
#include "memory-util.h"
#include "string-util.h"
#include "time-util.h"
#include "utf8.h"
#include "virt.h"

#if ENABLE_EFI

/* Reads from efivarfs sometimes fail with EINTR. Retry that many times. */
#define EFI_N_RETRIES_NO_DELAY 20
#define EFI_N_RETRIES_TOTAL 25
#define EFI_RETRY_DELAY (50 * USEC_PER_MSEC)

int efi_get_variable(
                const char *variable,
                uint32_t *ret_attribute,
                void **ret_value,
                size_t *ret_size) {

        _cleanup_close_ int fd = -EBADF;
        _cleanup_free_ void *buf = NULL;
        struct stat st;
        usec_t begin = 0; /* Unnecessary initialization to appease gcc */
        uint32_t a;
        ssize_t n;

        assert(variable);

        const char *p = strjoina("/sys/firmware/efi/efivars/", variable);

        if (!ret_value && !ret_size && !ret_attribute) {
                /* If caller is not interested in anything, just check if the variable exists and is
                 * readable. */
                if (access(p, R_OK) < 0)
                        return -errno;

                return 0;
        }

        if (DEBUG_LOGGING) {
                log_debug("Reading EFI variable %s.", p);
                begin = now(CLOCK_MONOTONIC);
        }

        fd = open(p, O_RDONLY|O_NOCTTY|O_CLOEXEC);
        if (fd < 0)
                return log_debug_errno(errno, "open(\"%s\") failed: %m", p);

        if (fstat(fd, &st) < 0)
                return log_debug_errno(errno, "fstat(\"%s\") failed: %m", p);
        if (st.st_size < 4)
                return log_debug_errno(SYNTHETIC_ERRNO(ENODATA), "EFI variable %s is shorter than 4 bytes, refusing.", p);
        if (st.st_size > 4*1024*1024 + 4)
                return log_debug_errno(SYNTHETIC_ERRNO(E2BIG), "EFI variable %s is ridiculously large, refusing.", p);

        if (ret_value || ret_attribute) {
                /* The kernel ratelimits reads from the efivarfs because EFI is inefficient, and we'll
                 * occasionally fail with EINTR here. A slowdown is better than a failure for us, so
                 * retry a few times and eventually fail with -EBUSY.
                 *
                 * See https://github.com/torvalds/linux/blob/master/fs/efivarfs/file.c#L75
                 * and
                 * https://github.com/torvalds/linux/commit/bef3efbeb897b56867e271cdbc5f8adaacaeb9cd.
                 */
                for (unsigned try = 0;; try++) {
                        n = read(fd, &a, sizeof(a));
                        if (n >= 0)
                                break;
                        log_debug_errno(errno, "Reading from \"%s\" failed: %m", p);
                        if (errno != EINTR)
                                return -errno;
                        if (try >= EFI_N_RETRIES_TOTAL)
                                return -EBUSY;

                        if (try >= EFI_N_RETRIES_NO_DELAY)
                                (void) usleep_safe(EFI_RETRY_DELAY);
                }

                /* Unfortunately kernel reports EOF if there's an inconsistency between efivarfs var list
                 * and what's actually stored in firmware, c.f. #34304. A zero size env var is not allowed in
                 * efi and hence the variable doesn't really exist in the backing store as long as it is zero
                 * sized, and the kernel calls this "uncommitted". Hence we translate EOF back to ENOENT here,
                 * as with kernel behavior before
                 * https://github.com/torvalds/linux/commit/3fab70c165795431f00ddf9be8b84ddd07bd1f8f
                 *
                 * If the kernel changes behaviour (to flush dentries on resume), we can drop
                 * this at some point in the future. But note that the commit is 11
                 * years old at this point so we'll need to deal with the current behaviour for
                 * a long time.
                 */
                if (n == 0)
                        return log_debug_errno(SYNTHETIC_ERRNO(ENOENT),
                                               "EFI variable %s is uncommitted", p);

                if (n != sizeof(a))
                        return log_debug_errno(SYNTHETIC_ERRNO(EIO),
                                               "Read %zi bytes from EFI variable %s, expected %zu.",  n, p, sizeof(a));
        }

        if (ret_value) {
                buf = malloc(st.st_size - 4 + 3);
                if (!buf)
                        return -ENOMEM;

                n = read(fd, buf, (size_t) st.st_size - 4);
                if (n < 0)
                        return log_debug_errno(errno, "Failed to read value of EFI variable %s: %m", p);
                assert(n <= st.st_size - 4);

                /* Always NUL-terminate (3 bytes, to properly protect UTF-16, even if truncated in the middle
                 * of a character) */
                ((char*) buf)[n] = 0;
                ((char*) buf)[n + 1] = 0;
                ((char*) buf)[n + 2] = 0;
        } else
                /* Assume that the reported size is accurate */
                n = st.st_size - 4;

        if (DEBUG_LOGGING) {
                usec_t end = now(CLOCK_MONOTONIC);
                if (end > begin + EFI_RETRY_DELAY)
                        log_debug("Detected slow EFI variable read access on %s: %s",
                                  variable, FORMAT_TIMESPAN(end - begin, 1));
        }

        /* Note that efivarfs interestingly doesn't require ftruncate() to update an existing EFI variable
         * with a smaller value. */

        if (ret_attribute)
                *ret_attribute = a;

        if (ret_value)
                *ret_value = TAKE_PTR(buf);

        if (ret_size)
                *ret_size = n;

        return 0;
}

int efi_get_variable_string(const char *variable, char **ret) {
        _cleanup_free_ void *s = NULL;
        size_t ss = 0;
        char *x;
        int r;

        assert(variable);

        r = efi_get_variable(variable, NULL, &s, &ss);
        if (r < 0)
                return r;

        x = utf16_to_utf8(s, ss);
        if (!x)
                return -ENOMEM;

        if (ret)
                *ret = x;

        return 0;
}

int efi_get_variable_path(const char *variable, char **ret) {
        int r;

        assert(variable);

        r = efi_get_variable_string(variable, ret);
        if (r < 0)
                return r;

        if (ret)
                efi_tilt_backslashes(*ret);

        return r;
}

static int efi_verify_variable(const char *variable, uint32_t attr, const void *value, size_t size) {
        _cleanup_free_ void *buf = NULL;
        size_t n;
        uint32_t a;
        int r;

        assert(variable);
        assert(value || size == 0);

        r = efi_get_variable(variable, &a, &buf, &n);
        if (r < 0)
                return r;

        return a == attr && memcmp_nn(buf, n, value, size) == 0;
}

int efi_set_variable(const char *variable, const void *value, size_t size) {
        static const uint32_t attr = EFI_VARIABLE_NON_VOLATILE|EFI_VARIABLE_BOOTSERVICE_ACCESS|EFI_VARIABLE_RUNTIME_ACCESS;

        struct var {
                uint32_t attr;
                char buf[];
        } _packed_ * _cleanup_free_ buf = NULL;
        _cleanup_close_ int fd = -EBADF;
        bool saved_flags_valid = false;
        unsigned saved_flags;
        int r;

        assert(variable);
        assert(value || size == 0);

        /* size 0 means removal, empty variable would not be enough for that */
        if (size > 0 && efi_verify_variable(variable, attr, value, size) > 0) {
                log_debug("Variable '%s' is already in wanted state, skipping write.", variable);
                return 0;
        }

        const char *p = strjoina("/sys/firmware/efi/efivars/", variable);

        /* Newer efivarfs protects variables that are not in an allow list with FS_IMMUTABLE_FL by default,
         * to protect them for accidental removal and modification. We are not changing these variables
         * accidentally however, hence let's unset the bit first. */

        r = chattr_full(AT_FDCWD, p,
                        /* value = */ 0,
                        /* mask = */ FS_IMMUTABLE_FL,
                        /* ret_previous = */ &saved_flags,
                        /* ret_final = */ NULL,
                        /* flags = */ 0);
        if (r < 0 && r != -ENOENT)
                log_debug_errno(r, "Failed to drop FS_IMMUTABLE_FL flag from '%s', ignoring: %m", p);

        saved_flags_valid = r >= 0;

        if (size == 0) {
                if (unlink(p) < 0) {
                        r = -errno;
                        goto finish;
                }

                return 0;
        }

        fd = open(p, O_WRONLY|O_CREAT|O_NOCTTY|O_CLOEXEC, 0644);
        if (fd < 0) {
                r = -errno;
                goto finish;
        }

        buf = malloc(sizeof(uint32_t) + size);
        if (!buf) {
                r = -ENOMEM;
                goto finish;
        }

        buf->attr = attr;
        memcpy(buf->buf, value, size);

        r = loop_write(fd, buf, sizeof(uint32_t) + size);
        if (r < 0)
                goto finish;

        /* For some reason efivarfs doesn't update mtime automatically. Let's do it manually then. This is
         * useful for processes that cache EFI variables to detect when changes occurred. */
        if (futimens(fd, /* times = */ NULL) < 0)
                log_debug_errno(errno, "Failed to update mtime/atime on %s, ignoring: %m", p);

        r = 0;

finish:
        if (saved_flags_valid) {
                int q;

                /* Restore the original flags field, just in case */
                if (fd < 0)
                        q = chattr_path(p, saved_flags, FS_IMMUTABLE_FL);
                else
                        q = chattr_fd(fd, saved_flags, FS_IMMUTABLE_FL);
                if (q < 0)
                        log_debug_errno(q, "Failed to restore FS_IMMUTABLE_FL on '%s', ignoring: %m", p);
        }

        return r;
}

int efi_set_variable_string(const char *variable, const char *value) {
        _cleanup_free_ char16_t *u16 = NULL;

        u16 = utf8_to_utf16(value, SIZE_MAX);
        if (!u16)
                return -ENOMEM;

        return efi_set_variable(variable, u16, (char16_strlen(u16) + 1) * sizeof(char16_t));
}

bool is_efi_boot(void) {
        static int cache = -1;

        if (cache < 0) {
                if (detect_container() > 0)
                        cache = false;
                else {
                        cache = access("/sys/firmware/efi/", F_OK) >= 0;
                        if (!cache && errno != ENOENT)
                                log_debug_errno(errno, "Unable to test whether /sys/firmware/efi/ exists, assuming EFI not available: %m");
                }
        }

        return cache;
}

static int read_flag(const char *variable) {
        _cleanup_free_ void *v = NULL;
        uint8_t b;
        size_t s;
        int r;

        if (!is_efi_boot()) /* If this is not an EFI boot, assume the queried flags are zero */
                return 0;

        r = efi_get_variable(variable, NULL, &v, &s);
        if (r < 0)
                return r;

        if (s != 1)
                return -EINVAL;

        b = *(uint8_t *)v;
        return !!b;
}

bool is_efi_secure_boot(void) {
        static int cache = -1;
        int r;

        if (cache < 0) {
                r = read_flag(EFI_GLOBAL_VARIABLE_STR("SecureBoot"));
                if (r == -ENOENT)
                        cache = false;
                else if (r < 0)
                        log_debug_errno(r, "Error reading SecureBoot EFI variable, assuming not in SecureBoot mode: %m");
                else
                        cache = r;
        }

        return cache > 0;
}

SecureBootMode efi_get_secure_boot_mode(void) {
        static SecureBootMode cache = _SECURE_BOOT_INVALID;

        if (cache != _SECURE_BOOT_INVALID)
                return cache;

        int secure = read_flag(EFI_GLOBAL_VARIABLE_STR("SecureBoot"));
        if (secure < 0) {
                if (secure != -ENOENT)
                        log_debug_errno(secure, "Error reading SecureBoot EFI variable, assuming not in SecureBoot mode: %m");

                return (cache = SECURE_BOOT_UNSUPPORTED);
        }

        /* We can assume false for all these if they are abscent (AuditMode and
         * DeployedMode may not exist on older firmware). */
        int audit    = read_flag(EFI_GLOBAL_VARIABLE_STR("AuditMode"));
        int deployed = read_flag(EFI_GLOBAL_VARIABLE_STR("DeployedMode"));
        int setup    = read_flag(EFI_GLOBAL_VARIABLE_STR("SetupMode"));
        log_debug("Secure boot variables: SecureBoot=%d AuditMode=%d DeployedMode=%d SetupMode=%d",
                  secure, audit, deployed, setup);

        return (cache = decode_secure_boot_mode(secure, audit > 0, deployed > 0, setup > 0));
}
#endif

char *efi_tilt_backslashes(char *s) {
        return string_replace_char(s, '\\', '/');
}
Commit	Line	Data
	1	/* SPDX-License-Identifier: LGPL-2.1-or-later */
	2
	3	#include <fcntl.h>
	4	#include <stdlib.h>
	5	#include <sys/stat.h>
	6	#include <time.h>
	7	#include <unistd.h>
	8
	9	#include "alloc-util.h"
	10	#include "chattr-util.h"
	11	#include "efivars.h"
	12	#include "fd-util.h"
	13	#include "io-util.h"
	14	#include "log.h"
	15	#include "memory-util.h"
	16	#include "string-util.h"
	17	#include "time-util.h"
	18	#include "utf8.h"
	19	#include "virt.h"
	20
	21	#if ENABLE_EFI
	22
	23	/* Reads from efivarfs sometimes fail with EINTR. Retry that many times. */
	24	#define EFI_N_RETRIES_NO_DELAY 20
	25	#define EFI_N_RETRIES_TOTAL 25
	26	#define EFI_RETRY_DELAY (50 * USEC_PER_MSEC)
	27
	28	int efi_get_variable(
	29	const char *variable,
	30	uint32_t *ret_attribute,
	31	void **ret_value,
	32	size_t *ret_size) {
	33
	34	_cleanup_close_ int fd = -EBADF;
	35	_cleanup_free_ void *buf = NULL;
	36	struct stat st;
	37	usec_t begin = 0; /* Unnecessary initialization to appease gcc */
	38	uint32_t a;
	39	ssize_t n;
	40
	41	assert(variable);
	42
	43	const char *p = strjoina("/sys/firmware/efi/efivars/", variable);
	44
	45	if (!ret_value && !ret_size && !ret_attribute) {
	46	/* If caller is not interested in anything, just check if the variable exists and is
	47	* readable. */
	48	if (access(p, R_OK) < 0)
	49	return -errno;
	50
	51	return 0;
	52	}
	53
	54	if (DEBUG_LOGGING) {
	55	log_debug("Reading EFI variable %s.", p);
	56	begin = now(CLOCK_MONOTONIC);
	57	}
	58
	59	fd = open(p, O_RDONLY\|O_NOCTTY\|O_CLOEXEC);
	60	if (fd < 0)
	61	return log_debug_errno(errno, "open(\"%s\") failed: %m", p);
	62
	63	if (fstat(fd, &st) < 0)
	64	return log_debug_errno(errno, "fstat(\"%s\") failed: %m", p);
	65	if (st.st_size < 4)
	66	return log_debug_errno(SYNTHETIC_ERRNO(ENODATA), "EFI variable %s is shorter than 4 bytes, refusing.", p);
	67	if (st.st_size > 410241024 + 4)
	68	return log_debug_errno(SYNTHETIC_ERRNO(E2BIG), "EFI variable %s is ridiculously large, refusing.", p);
	69
	70	if (ret_value \|\| ret_attribute) {
	71	/* The kernel ratelimits reads from the efivarfs because EFI is inefficient, and we'll
	72	* occasionally fail with EINTR here. A slowdown is better than a failure for us, so
	73	* retry a few times and eventually fail with -EBUSY.
	74	*
	75	* See https://github.com/torvalds/linux/blob/master/fs/efivarfs/file.c#L75
	76	* and
	77	* https://github.com/torvalds/linux/commit/bef3efbeb897b56867e271cdbc5f8adaacaeb9cd.
	78	*/
	79	for (unsigned try = 0;; try++) {
	80	n = read(fd, &a, sizeof(a));
	81	if (n >= 0)
	82	break;
	83	log_debug_errno(errno, "Reading from \"%s\" failed: %m", p);
	84	if (errno != EINTR)
	85	return -errno;
	86	if (try >= EFI_N_RETRIES_TOTAL)
	87	return -EBUSY;
	88
	89	if (try >= EFI_N_RETRIES_NO_DELAY)
	90	(void) usleep_safe(EFI_RETRY_DELAY);
	91	}
	92
	93	/* Unfortunately kernel reports EOF if there's an inconsistency between efivarfs var list
	94	* and what's actually stored in firmware, c.f. #34304. A zero size env var is not allowed in
	95	* efi and hence the variable doesn't really exist in the backing store as long as it is zero
	96	* sized, and the kernel calls this "uncommitted". Hence we translate EOF back to ENOENT here,
	97	* as with kernel behavior before
	98	* https://github.com/torvalds/linux/commit/3fab70c165795431f00ddf9be8b84ddd07bd1f8f
	99	*
	100	* If the kernel changes behaviour (to flush dentries on resume), we can drop
	101	* this at some point in the future. But note that the commit is 11
	102	* years old at this point so we'll need to deal with the current behaviour for
	103	* a long time.
	104	*/
	105	if (n == 0)
	106	return log_debug_errno(SYNTHETIC_ERRNO(ENOENT),
	107	"EFI variable %s is uncommitted", p);
	108
	109	if (n != sizeof(a))
	110	return log_debug_errno(SYNTHETIC_ERRNO(EIO),
	111	"Read %zi bytes from EFI variable %s, expected %zu.", n, p, sizeof(a));
	112	}
	113
	114	if (ret_value) {
	115	buf = malloc(st.st_size - 4 + 3);
	116	if (!buf)
	117	return -ENOMEM;
	118
	119	n = read(fd, buf, (size_t) st.st_size - 4);
	120	if (n < 0)
	121	return log_debug_errno(errno, "Failed to read value of EFI variable %s: %m", p);
	122	assert(n <= st.st_size - 4);
	123
	124	/* Always NUL-terminate (3 bytes, to properly protect UTF-16, even if truncated in the middle
	125	* of a character) */
	126	((char*) buf)[n] = 0;
	127	((char*) buf)[n + 1] = 0;
	128	((char*) buf)[n + 2] = 0;
	129	} else
	130	/* Assume that the reported size is accurate */
	131	n = st.st_size - 4;
	132
	133	if (DEBUG_LOGGING) {
	134	usec_t end = now(CLOCK_MONOTONIC);
	135	if (end > begin + EFI_RETRY_DELAY)
	136	log_debug("Detected slow EFI variable read access on %s: %s",
	137	variable, FORMAT_TIMESPAN(end - begin, 1));
	138	}
	139
	140	/* Note that efivarfs interestingly doesn't require ftruncate() to update an existing EFI variable
	141	* with a smaller value. */
	142
	143	if (ret_attribute)
	144	*ret_attribute = a;
	145
	146	if (ret_value)
	147	*ret_value = TAKE_PTR(buf);
	148
	149	if (ret_size)
	150	*ret_size = n;
	151
	152	return 0;
	153	}
	154
	155	int efi_get_variable_string(const char variable, char *ret) {
	156	_cleanup_free_ void *s = NULL;
	157	size_t ss = 0;
	158	char *x;
	159	int r;
	160
	161	assert(variable);
	162
	163	r = efi_get_variable(variable, NULL, &s, &ss);
	164	if (r < 0)
	165	return r;
	166
	167	x = utf16_to_utf8(s, ss);
	168	if (!x)
	169	return -ENOMEM;
	170
	171	if (ret)
	172	*ret = x;
	173
	174	return 0;
	175	}
	176
	177	int efi_get_variable_path(const char variable, char *ret) {
	178	int r;
	179
	180	assert(variable);
	181
	182	r = efi_get_variable_string(variable, ret);
	183	if (r < 0)
	184	return r;
	185
	186	if (ret)
	187	efi_tilt_backslashes(*ret);
	188
	189	return r;
	190	}
	191
	192	static int efi_verify_variable(const char variable, uint32_t attr, const void value, size_t size) {
	193	_cleanup_free_ void *buf = NULL;
	194	size_t n;
	195	uint32_t a;
	196	int r;
	197
	198	assert(variable);
	199	assert(value \|\| size == 0);
	200
	201	r = efi_get_variable(variable, &a, &buf, &n);
	202	if (r < 0)
	203	return r;
	204
	205	return a == attr && memcmp_nn(buf, n, value, size) == 0;
	206	}
	207
	208	int efi_set_variable(const char variable, const void value, size_t size) {
	209	static const uint32_t attr = EFI_VARIABLE_NON_VOLATILE\|EFI_VARIABLE_BOOTSERVICE_ACCESS\|EFI_VARIABLE_RUNTIME_ACCESS;
	210
	211	struct var {
	212	uint32_t attr;
	213	char buf[];
	214	} _packed_ * _cleanup_free_ buf = NULL;
	215	_cleanup_close_ int fd = -EBADF;
	216	bool saved_flags_valid = false;
	217	unsigned saved_flags;
	218	int r;
	219
	220	assert(variable);
	221	assert(value \|\| size == 0);
	222
	223	/* size 0 means removal, empty variable would not be enough for that */
	224	if (size > 0 && efi_verify_variable(variable, attr, value, size) > 0) {
	225	log_debug("Variable '%s' is already in wanted state, skipping write.", variable);
	226	return 0;
	227	}
	228
	229	const char *p = strjoina("/sys/firmware/efi/efivars/", variable);
	230
	231	/* Newer efivarfs protects variables that are not in an allow list with FS_IMMUTABLE_FL by default,
	232	* to protect them for accidental removal and modification. We are not changing these variables
	233	* accidentally however, hence let's unset the bit first. */
	234
	235	r = chattr_full(AT_FDCWD, p,
	236	/* value = */ 0,
	237	/* mask = */ FS_IMMUTABLE_FL,
	238	/* ret_previous = */ &saved_flags,
	239	/* ret_final = */ NULL,
	240	/* flags = */ 0);
	241	if (r < 0 && r != -ENOENT)
	242	log_debug_errno(r, "Failed to drop FS_IMMUTABLE_FL flag from '%s', ignoring: %m", p);
	243
	244	saved_flags_valid = r >= 0;
	245
	246	if (size == 0) {
	247	if (unlink(p) < 0) {
	248	r = -errno;
	249	goto finish;
	250	}
	251
	252	return 0;
	253	}
	254
	255	fd = open(p, O_WRONLY\|O_CREAT\|O_NOCTTY\|O_CLOEXEC, 0644);
	256	if (fd < 0) {
	257	r = -errno;
	258	goto finish;
	259	}
	260
	261	buf = malloc(sizeof(uint32_t) + size);
	262	if (!buf) {
	263	r = -ENOMEM;
	264	goto finish;
	265	}
	266
	267	buf->attr = attr;
	268	memcpy(buf->buf, value, size);
	269
	270	r = loop_write(fd, buf, sizeof(uint32_t) + size);
	271	if (r < 0)
	272	goto finish;
	273
	274	/* For some reason efivarfs doesn't update mtime automatically. Let's do it manually then. This is
	275	* useful for processes that cache EFI variables to detect when changes occurred. */
	276	if (futimens(fd, /* times = */ NULL) < 0)
	277	log_debug_errno(errno, "Failed to update mtime/atime on %s, ignoring: %m", p);
	278
	279	r = 0;
	280
	281	finish:
	282	if (saved_flags_valid) {
	283	int q;
	284
	285	/* Restore the original flags field, just in case */
	286	if (fd < 0)
	287	q = chattr_path(p, saved_flags, FS_IMMUTABLE_FL);
	288	else
	289	q = chattr_fd(fd, saved_flags, FS_IMMUTABLE_FL);
	290	if (q < 0)
	291	log_debug_errno(q, "Failed to restore FS_IMMUTABLE_FL on '%s', ignoring: %m", p);
	292	}
	293
	294	return r;
	295	}
	296
	297	int efi_set_variable_string(const char variable, const char value) {
	298	_cleanup_free_ char16_t *u16 = NULL;
	299
	300	u16 = utf8_to_utf16(value, SIZE_MAX);
	301	if (!u16)
	302	return -ENOMEM;
	303
	304	return efi_set_variable(variable, u16, (char16_strlen(u16) + 1) * sizeof(char16_t));
	305	}
	306
	307	bool is_efi_boot(void) {
	308	static int cache = -1;
	309
	310	if (cache < 0) {
	311	if (detect_container() > 0)
	312	cache = false;
	313	else {
	314	cache = access("/sys/firmware/efi/", F_OK) >= 0;
	315	if (!cache && errno != ENOENT)
	316	log_debug_errno(errno, "Unable to test whether /sys/firmware/efi/ exists, assuming EFI not available: %m");
	317	}
	318	}
	319
	320	return cache;
	321	}
	322
	323	static int read_flag(const char *variable) {
	324	_cleanup_free_ void *v = NULL;
	325	uint8_t b;
	326	size_t s;
	327	int r;
	328
	329	if (!is_efi_boot()) /* If this is not an EFI boot, assume the queried flags are zero */
	330	return 0;
	331
	332	r = efi_get_variable(variable, NULL, &v, &s);
	333	if (r < 0)
	334	return r;
	335
	336	if (s != 1)
	337	return -EINVAL;
	338
	339	b = (uint8_t )v;
	340	return !!b;
	341	}
	342
	343	bool is_efi_secure_boot(void) {
	344	static int cache = -1;
	345	int r;
	346
	347	if (cache < 0) {
	348	r = read_flag(EFI_GLOBAL_VARIABLE_STR("SecureBoot"));
	349	if (r == -ENOENT)
	350	cache = false;
	351	else if (r < 0)
	352	log_debug_errno(r, "Error reading SecureBoot EFI variable, assuming not in SecureBoot mode: %m");
	353	else
	354	cache = r;
	355	}
	356
	357	return cache > 0;
	358	}
	359
	360	SecureBootMode efi_get_secure_boot_mode(void) {
	361	static SecureBootMode cache = _SECURE_BOOT_INVALID;
	362
	363	if (cache != _SECURE_BOOT_INVALID)
	364	return cache;
	365
	366	int secure = read_flag(EFI_GLOBAL_VARIABLE_STR("SecureBoot"));
	367	if (secure < 0) {
	368	if (secure != -ENOENT)
	369	log_debug_errno(secure, "Error reading SecureBoot EFI variable, assuming not in SecureBoot mode: %m");
	370
	371	return (cache = SECURE_BOOT_UNSUPPORTED);
	372	}
	373
	374	/* We can assume false for all these if they are abscent (AuditMode and
	375	* DeployedMode may not exist on older firmware). */
	376	int audit = read_flag(EFI_GLOBAL_VARIABLE_STR("AuditMode"));
	377	int deployed = read_flag(EFI_GLOBAL_VARIABLE_STR("DeployedMode"));
	378	int setup = read_flag(EFI_GLOBAL_VARIABLE_STR("SetupMode"));
	379	log_debug("Secure boot variables: SecureBoot=%d AuditMode=%d DeployedMode=%d SetupMode=%d",
	380	secure, audit, deployed, setup);
	381
	382	return (cache = decode_secure_boot_mode(secure, audit > 0, deployed > 0, setup > 0));
	383	}
	384	#endif
	385
	386	char efi_tilt_backslashes(char s) {
	387	return string_replace_char(s, '\\', '/');
	388	}