path: root/src/setup/efivars.c

/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/

/***
  This file is part of systemd.

  Copyright 2013 Lennart Poettering
  Copyright 2013 Kay Sievers

  systemd is free software; you can redistribute it and/or modify it
  under the terms of the GNU Lesser General Public License as published by
  the Free Software Foundation; either version 2.1 of the License, or
  (at your option) any later version.

  systemd is distributed in the hope that it will be useful, but
  WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public License
  along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/

#include <unistd.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <errno.h>
#include <assert.h>
#include <stdio.h>
#include <fcntl.h>
#include <string.h>
#include <stddef.h>
#include <dirent.h>
#include <ctype.h>

#include "efivars.h"

bool is_efi_boot(void) {
        return access("/sys/firmware/efi", F_OK) >= 0;
}

int read_flag(const char *varname) {
        int r;
        void *v;
        size_t s;
        uint8_t b;

        r = efi_get_variable(EFI_VENDOR_GLOBAL, varname, &v, &s);
        if (r < 0)
                return r;

        if (s != 1) {
                r = -EINVAL;
                goto finish;
        }

        b = *(uint8_t *)v;
        r = b > 0;
finish:
        free(v);
        return r;
}

int is_efi_secure_boot(void) {
        return read_flag("SecureBoot");
}

int is_efi_secure_boot_setup_mode(void) {
        return read_flag("SetupMode");
}

int efi_get_variable(
                const uint8_t vendor[16],
                const char *name,
                void **value,
                size_t *size) {

        int fd = -1;
        char *p = NULL;
        uint32_t a;
        ssize_t n;
        struct stat st;
        void *b;
        int r;

        assert(name);
        assert(value);
        assert(size);

        if (asprintf(&p,
                     "/sys/firmware/efi/efivars/%s-%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x",
                     name,
                     vendor[0], vendor[1], vendor[2], vendor[3], vendor[4], vendor[5], vendor[6], vendor[7],
                     vendor[8], vendor[9], vendor[10], vendor[11], vendor[12], vendor[13], vendor[14], vendor[15]) < 0)
                return -ENOMEM;

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

        if (fstat(fd, &st) < 0) {
                r = -errno;
                goto finish;
        }
        if (st.st_size < 4) {
                r = -EIO;
                goto finish;
        }
        if (st.st_size > 4*1024*1024 + 4) {
                r = -E2BIG;
                goto finish;
        }

        n = read(fd, &a, sizeof(a));
        if (n < 0) {
                r = errno;
                goto finish;
        }
        if (n != sizeof(a)) {
                r = -EIO;
                goto finish;
        }

        b = malloc(st.st_size - 4 + 2);
        if (!b) {
                r = -ENOMEM;
                goto finish;
        }

        n = read(fd, b, (size_t) st.st_size - 4);
        if (n < 0) {
                free(b);
                r = errno;
                goto finish;
        }
        if (n != (ssize_t) st.st_size - 4) {
                free(b);
                r = -EIO;
                goto finish;
        }

        /* Always NUL terminate (2 bytes, to protect UTF-16) */
        ((char*) b)[st.st_size - 4] = 0;
        ((char*) b)[st.st_size - 4 + 1] = 0;

        *value = b;
        *size = (size_t) st.st_size - 4;
        r = 0;

finish:
        if (fd >= 0)
                close(fd);
        free(p);
        return r;
}

int efi_set_variable(
                const uint8_t vendor[16],
                const char *name,
                const void *value,
                size_t size) {

        struct var {
                uint32_t attr;
                char buf[];
        } __attribute__((packed)) *buf = NULL;
        char *p = NULL;
        int fd = -1;
        int r;

        assert(vendor);
        assert(name);

        if (asprintf(&p,
                     "/sys/firmware/efi/efivars/%s-%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x",
                     name,
                     vendor[0], vendor[1], vendor[2], vendor[3], vendor[4], vendor[5], vendor[6], vendor[7],
                     vendor[8], vendor[9], vendor[10], vendor[11], vendor[12], vendor[13], vendor[14], vendor[15]) < 0)
                return -ENOMEM;

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

        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 = -errno;
                goto finish;
        }

        buf->attr = EFI_VARIABLE_NON_VOLATILE|EFI_VARIABLE_BOOTSERVICE_ACCESS|EFI_VARIABLE_RUNTIME_ACCESS;
        memcpy(buf->buf, value, size);

        r = write(fd, buf, sizeof(uint32_t) + size);
        if (r < 0) {
                r = -errno;
                goto finish;
        }

        if ((size_t)r != sizeof(uint32_t) + size) {
                r = -EIO;
                goto finish;
        }

finish:
        if (fd >= 0)
                close(fd);
        free(buf);
        free(p);
        return r;
}

int efi_get_variable_string(const uint8_t vendor[16], const char *name, char **p) {
        void *s = NULL;
        size_t ss;
        char *x;
        int r;

        r = efi_get_variable(vendor, name, &s, &ss);
        if (r < 0)
                return r;

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

        *p = x;
        return 0;
}

static size_t utf16_size(const uint16_t *s) {
        size_t l = 0;

        while (s[l] > 0)
                l++;

        return (l+1) * sizeof(uint16_t);
}

struct guid {
        uint32_t u1;
        uint16_t u2;
        uint16_t u3;
        uint8_t u4[8];
} __attribute__((packed));

static void efi_guid_to_id128(const void *guid, uint8_t *bytes) {
        const struct guid *uuid = guid;

        bytes[0] = (uuid->u1 >> 24) & 0xff;
        bytes[1] = (uuid->u1 >> 16) & 0xff;
        bytes[2] = (uuid->u1 >> 8) & 0xff;
        bytes[3] = (uuid->u1) & 0xff;
        bytes[4] = (uuid->u2 >> 8) & 0xff;
        bytes[5] = (uuid->u2) & 0xff;
        bytes[6] = (uuid->u3 >> 8) & 0xff;
        bytes[7] = (uuid->u3) & 0xff;
        memcpy(bytes+8, uuid->u4, sizeof(uuid->u4));
}

static void id128_to_efi_guid(const uint8_t *bytes, void *guid) {
        struct guid *uuid = guid;

        uuid->u1 = bytes[0] << 24 | bytes[1] << 16 | bytes[2] << 8 | bytes[3];
        uuid->u2 = bytes[4] << 8 | bytes[5];
        uuid->u3 = bytes[6] << 8 | bytes[7];
        memcpy(uuid->u4, bytes+8, sizeof(uuid->u4));
}

char *tilt_backslashes(char *s) {
        char *p;

        for (p = s; *p; p++)
                if (*p == '\\')
                        *p = '/';

        return s;
}

uint16_t *tilt_slashes(uint16_t *s) {
        uint16_t *p;

        for (p = s; *p; p++)
                if (*p == '/')
                        *p = '\\';

        return s;
}

#define LOAD_OPTION_ACTIVE            0x00000001
#define MEDIA_DEVICE_PATH                   0x04
#define MEDIA_HARDDRIVE_DP                  0x01
#define MEDIA_FILEPATH_DP                   0x04
#define SIGNATURE_TYPE_GUID                 0x02
#define MBR_TYPE_EFI_PARTITION_TABLE_HEADER 0x02
#define END_DEVICE_PATH_TYPE                0x7f
#define END_ENTIRE_DEVICE_PATH_SUBTYPE      0xff

struct boot_option {
        uint32_t attr;
        uint16_t path_len;
        uint16_t title[];
} __attribute__((packed));

struct drive_path {
        uint32_t part_nr;
        uint64_t part_start;
        uint64_t part_size;
        char signature[16];
        uint8_t mbr_type;
        uint8_t signature_type;
} __attribute__((packed));

struct device_path {
        uint8_t type;
        uint8_t sub_type;
        uint16_t length;
        union {
                uint16_t path[0];
                struct drive_path drive;
        };
} __attribute__((packed));

int efi_get_boot_option(uint16_t id, char **title, uint8_t part_uuid[16], char **path) {
        char boot_id[9];
        uint8_t *buf = NULL;
        size_t l;
        struct boot_option *header;
        size_t title_size;
        char *s = NULL;
        char *p = NULL;
        uint8_t p_uuid[16] = "";
        int err;

        snprintf(boot_id, sizeof(boot_id), "Boot%04X", id);
        err = efi_get_variable(EFI_VENDOR_GLOBAL, boot_id, (void **) &buf, &l);
        if (err < 0)
                return err;
        if (l < sizeof(struct boot_option)) {
                err = -ENOENT;
                goto err;
        }

        header = (struct boot_option *) buf;
        title_size = utf16_size(header->title);
        if (title_size > l - offsetof(struct boot_option, title)) {
                err = -EINVAL;
                goto err;
        }

        s = utf16_to_utf8(header->title, title_size);
        if (!s) {
                err = -ENOMEM;
                goto err;
        }

        if (header->path_len > 0) {
                uint8_t *dbuf;
                size_t dnext;

                dbuf = buf + offsetof(struct boot_option, title) + title_size;
                dnext = 0;
                while (dnext < header->path_len) {
                        struct device_path *dpath;

                        dpath = (struct device_path *)(dbuf + dnext);
                        if (dpath->length < 4)
                                break;

                        /* Type 0x7F – End of Hardware Device Path, Sub-Type 0xFF – End Entire Device Path */
                        if (dpath->type == END_DEVICE_PATH_TYPE && dpath->sub_type == END_ENTIRE_DEVICE_PATH_SUBTYPE)
                                break;

                        dnext += dpath->length;

                        if (dpath->type != MEDIA_DEVICE_PATH)
                                continue;

                        if (dpath->sub_type == MEDIA_HARDDRIVE_DP) {
                                /* GPT Partition Table */
                                if (dpath->drive.mbr_type != MBR_TYPE_EFI_PARTITION_TABLE_HEADER)
                                        continue;

                                if (dpath->drive.signature_type != SIGNATURE_TYPE_GUID)
                                        continue;

                                efi_guid_to_id128(dpath->drive.signature, p_uuid);
                                continue;
                        }

                        if (dpath->sub_type == MEDIA_FILEPATH_DP) {
                                p = utf16_to_utf8(dpath->path, dpath->length-4);
                                tilt_backslashes(p);
                                continue;
                        }
                }
        }

        if (title)
                *title = s;
        else
                free(s);

        if (part_uuid)
                memcpy(part_uuid, p_uuid, 16);

        if (path)
                *path = p;
        else
                free(p);

        free(buf);
        return 0;
err:
        free(s);
        free(p);
        free(buf);
        return err;
}

static void to_utf16(uint16_t *dest, const char *src) {
        int i;

        for (i = 0; src[i] != '\0'; i++)
                dest[i] = src[i];
        dest[i] = '\0';
}

int efi_add_boot_option(uint16_t id, const char *title,
                        uint32_t part, uint64_t pstart, uint64_t psize,
                        const uint8_t part_uuid[16],
                        const char *path) {
        char boot_id[9];
        char *buf;
        size_t size;
        size_t title_len;
        size_t path_len;
        struct boot_option *option;
        struct device_path *devicep;
        int err;

        title_len = (strlen(title)+1) * 2;
        path_len = (strlen(path)+1) * 2;

        buf = calloc(sizeof(struct boot_option) + title_len +
                     sizeof(struct drive_path) +
                     sizeof(struct device_path) + path_len, 1);
        if (!buf) {
                err = -ENOMEM;
                goto finish;
        }

        /* header */
        option = (struct boot_option *)buf;
        option->attr = LOAD_OPTION_ACTIVE;
        option->path_len = offsetof(struct device_path, drive) + sizeof(struct drive_path) +
                           offsetof(struct device_path, path) + path_len +
                           offsetof(struct device_path, path);
        to_utf16(option->title, title);
        size = offsetof(struct boot_option, title) + title_len;

        /* partition info */
        devicep = (struct device_path *)(buf + size);
        devicep->type = MEDIA_DEVICE_PATH;
        devicep->sub_type = MEDIA_HARDDRIVE_DP;
        devicep->length = offsetof(struct device_path, drive) + sizeof(struct drive_path);
        devicep->drive.part_nr = part;
        devicep->drive.part_start = pstart;
        devicep->drive.part_size =  psize;
        devicep->drive.signature_type = SIGNATURE_TYPE_GUID;
        devicep->drive.mbr_type = MBR_TYPE_EFI_PARTITION_TABLE_HEADER;
        id128_to_efi_guid(part_uuid, devicep->drive.signature);
        size += devicep->length;

        /* path to loader */
        devicep = (struct device_path *)(buf + size);
        devicep->type = MEDIA_DEVICE_PATH;
        devicep->sub_type = MEDIA_FILEPATH_DP;
        devicep->length = offsetof(struct device_path, path) + path_len;
        to_utf16(devicep->path, path);
        tilt_slashes(devicep->path);
        size += devicep->length;

        /* end of path */
        devicep = (struct device_path *)(buf + size);
        devicep->type = END_DEVICE_PATH_TYPE;
        devicep->sub_type = END_ENTIRE_DEVICE_PATH_SUBTYPE;
        devicep->length = offsetof(struct device_path, path);
        size += devicep->length;

        snprintf(boot_id, sizeof(boot_id), "Boot%04X", id);
        err = efi_set_variable(EFI_VENDOR_GLOBAL, boot_id, buf, size);

finish:
        free(buf);
        return err;
}

int efi_remove_boot_option(uint16_t id) {
        char boot_id[9];

        snprintf(boot_id, sizeof(boot_id), "Boot%04X", id);
        return efi_set_variable(EFI_VENDOR_GLOBAL, boot_id, NULL, 0);
}

int efi_get_boot_order(uint16_t **order) {
        void *buf;
        size_t l;
        int r;

        r = efi_get_variable(EFI_VENDOR_GLOBAL, "BootOrder", &buf, &l);
        if (r < 0)
                return r;

        if (l <= 0) {
                free(buf);
                return -ENOENT;
        }

        if ((l % sizeof(uint16_t) > 0)) {
                free(buf);
                return -EINVAL;
        }

        *order = buf;
        return (int) (l / sizeof(uint16_t));
}

int efi_set_boot_order(uint16_t *order, size_t n) {
        return efi_set_variable(EFI_VENDOR_GLOBAL, "BootOrder", order, n * sizeof(uint16_t));
}

static int boot_id_hex(const char s[4]) {
        int i;
        int id = 0;

        for (i = 0; i < 4; i++)
                if (s[i] >= '0' && s[i] <= '9')
                        id |= (s[i] - '0') << (3 - i) * 4;
                else if (s[i] >= 'A' && s[i] <= 'F')
                        id |= (s[i] - 'A' + 10) << (3 - i) * 4;
                else
                        return -1;

        return id;
}

static int cmp_uint16(const void *_a, const void *_b) {
        const uint16_t *a = _a, *b = _b;

        return (int)*a - (int)*b;
}

int efi_get_boot_options(uint16_t **options) {
        DIR *dir;
        struct dirent *de;
        uint16_t *list = NULL;
        int count = 0;

        assert(options);

        dir = opendir("/sys/firmware/efi/efivars/");
        if (!dir)
                return -errno;

        while ((de = readdir(dir))) {
                int id;
                uint16_t *t;

                if (strncmp(de->d_name, "Boot", 4) != 0)
                        continue;

                if (strlen(de->d_name) != 45)
                        continue;

                if (strcmp(de->d_name + 8, "-8be4df61-93ca-11d2-aa0d-00e098032b8c") != 0)
                        continue;

                id = boot_id_hex(de->d_name + 4);
                if (id < 0)
                        continue;

                t = realloc(list, (count + 1) * sizeof(uint16_t));
                if (!t) {
                        free(list);
                        closedir(dir);
                        return -ENOMEM;
                }
                list = t;

                list[count++] = id;
        }

        closedir(dir);
        qsort(list, count, sizeof(uint16_t), cmp_uint16);
        *options = list;

        return count;
}

char *utf16_to_utf8(const void *s, size_t length) {
        char *r;
        const uint8_t *f;
        uint8_t *t;

        r = malloc((length*3+1)/2 + 1);
        if (!r)
                return NULL;

        t = (uint8_t*) r;

        for (f = s; f < (const uint8_t*) s + length; f += 2) {
                uint16_t c;

                c = (f[1] << 8) | f[0];

                if (c == 0) {
                        *t = 0;
                        return r;
                } else if (c < 0x80) {
                        *(t++) = (uint8_t) c;
                } else if (c < 0x800) {
                        *(t++) = (uint8_t) (0xc0 | (c >> 6));
                        *(t++) = (uint8_t) (0x80 | (c & 0x3f));
                } else {
                        *(t++) = (uint8_t) (0xe0 | (c >> 12));
                        *(t++) = (uint8_t) (0x80 | ((c >> 6) & 0x3f));
                        *(t++) = (uint8_t) (0x80 | (c & 0x3f));
                }
        }

        *t = 0;

        return r;
}