Adding upstream version 252.22.upstream/252.22upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 531 insertions, 0 deletions

diff --git a/src/core/bpf-devices.c b/src/core/bpf-devices.c
new file mode 100644
index 0000000..3af9e78
--- /dev/null
+++ b/src/core/bpf-devices.c
@@ -0,0 +1,531 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <fnmatch.h>
+#include <linux/bpf_insn.h>
+
+#include "bpf-devices.h"
+#include "bpf-program.h"
+#include "devnum-util.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "nulstr-util.h"
+#include "parse-util.h"
+#include "path-util.h"
+#include "stdio-util.h"
+#include "string-util.h"
+
+#define PASS_JUMP_OFF 4096
+
+static int bpf_access_type(const char *acc) {
+        int r = 0;
+
+        assert(acc);
+
+        for (; *acc; acc++)
+                switch (*acc) {
+                case 'r':
+                        r |= BPF_DEVCG_ACC_READ;
+                        break;
+                case 'w':
+                        r |= BPF_DEVCG_ACC_WRITE;
+                        break;
+                case 'm':
+                        r |= BPF_DEVCG_ACC_MKNOD;
+                        break;
+                default:
+                        return -EINVAL;
+                }
+
+        return r;
+}
+
+static int bpf_prog_allow_list_device(
+                BPFProgram *prog,
+                char type,
+                int major,
+                int minor,
+                const char *acc) {
+
+        int r, access;
+
+        assert(prog);
+        assert(acc);
+
+        log_trace("%s: %c %d:%d %s", __func__, type, major, minor, acc);
+
+        access = bpf_access_type(acc);
+        if (access <= 0)
+                return -EINVAL;
+
+        assert(IN_SET(type, 'b', 'c'));
+        const int bpf_type = type == 'c' ? BPF_DEVCG_DEV_CHAR : BPF_DEVCG_DEV_BLOCK;
+
+        const struct bpf_insn insn[] = {
+                BPF_MOV32_REG(BPF_REG_1, BPF_REG_3),
+                BPF_ALU32_IMM(BPF_AND, BPF_REG_1, access),
+                BPF_JMP_REG(BPF_JNE, BPF_REG_1, BPF_REG_3, 4), /* compare access type */
+
+                BPF_JMP_IMM(BPF_JNE, BPF_REG_2, bpf_type, 3),  /* compare device type */
+                BPF_JMP_IMM(BPF_JNE, BPF_REG_4, major, 2),     /* compare major */
+                BPF_JMP_IMM(BPF_JNE, BPF_REG_5, minor, 1),     /* compare minor */
+                BPF_JMP_A(PASS_JUMP_OFF),                      /* jump to PASS */
+        };
+
+        if (FLAGS_SET(access, BPF_DEVCG_ACC_READ | BPF_DEVCG_ACC_WRITE | BPF_DEVCG_ACC_MKNOD))
+                r = bpf_program_add_instructions(prog, insn + 3, ELEMENTSOF(insn) - 3);
+        else
+                r = bpf_program_add_instructions(prog, insn, ELEMENTSOF(insn));
+        if (r < 0)
+                log_error_errno(r, "Extending device control BPF program failed: %m");
+
+        return r;
+}
+
+static int bpf_prog_allow_list_major(
+                BPFProgram *prog,
+                char type,
+                int major,
+                const char *acc) {
+
+        int r, access;
+
+        assert(prog);
+        assert(acc);
+
+        log_trace("%s: %c %d:* %s", __func__, type, major, acc);
+
+        access = bpf_access_type(acc);
+        if (access <= 0)
+                return -EINVAL;
+
+        assert(IN_SET(type, 'b', 'c'));
+        const int bpf_type = type == 'c' ? BPF_DEVCG_DEV_CHAR : BPF_DEVCG_DEV_BLOCK;
+
+        const struct bpf_insn insn[] = {
+                BPF_MOV32_REG(BPF_REG_1, BPF_REG_3),
+                BPF_ALU32_IMM(BPF_AND, BPF_REG_1, access),
+                BPF_JMP_REG(BPF_JNE, BPF_REG_1, BPF_REG_3, 3), /* compare access type */
+
+                BPF_JMP_IMM(BPF_JNE, BPF_REG_2, bpf_type, 2),  /* compare device type */
+                BPF_JMP_IMM(BPF_JNE, BPF_REG_4, major, 1),     /* compare major */
+                BPF_JMP_A(PASS_JUMP_OFF),                      /* jump to PASS */
+        };
+
+        if (FLAGS_SET(access, BPF_DEVCG_ACC_READ | BPF_DEVCG_ACC_WRITE | BPF_DEVCG_ACC_MKNOD))
+                r = bpf_program_add_instructions(prog, insn + 3, ELEMENTSOF(insn) - 3);
+        else
+                r = bpf_program_add_instructions(prog, insn, ELEMENTSOF(insn));
+        if (r < 0)
+                log_error_errno(r, "Extending device control BPF program failed: %m");
+
+        return r;
+}
+
+static int bpf_prog_allow_list_class(
+                BPFProgram *prog,
+                char type,
+                const char *acc) {
+
+        int r, access;
+
+        assert(prog);
+        assert(acc);
+
+        log_trace("%s: %c *:* %s", __func__, type, acc);
+
+        access = bpf_access_type(acc);
+        if (access <= 0)
+                return -EINVAL;
+
+        assert(IN_SET(type, 'b', 'c'));
+        const int bpf_type = type == 'c' ? BPF_DEVCG_DEV_CHAR : BPF_DEVCG_DEV_BLOCK;
+
+        const struct bpf_insn insn[] = {
+                BPF_MOV32_REG(BPF_REG_1, BPF_REG_3),
+                BPF_ALU32_IMM(BPF_AND, BPF_REG_1, access),
+                BPF_JMP_REG(BPF_JNE, BPF_REG_1, BPF_REG_3, 2), /* compare access type */
+
+                BPF_JMP_IMM(BPF_JNE, BPF_REG_2, bpf_type, 1), /* compare device type */
+                BPF_JMP_A(PASS_JUMP_OFF),                     /* jump to PASS */
+        };
+
+        if (FLAGS_SET(access, BPF_DEVCG_ACC_READ | BPF_DEVCG_ACC_WRITE | BPF_DEVCG_ACC_MKNOD))
+                r = bpf_program_add_instructions(prog, insn + 3, ELEMENTSOF(insn) - 3);
+        else
+                r = bpf_program_add_instructions(prog, insn, ELEMENTSOF(insn));
+        if (r < 0)
+                log_error_errno(r, "Extending device control BPF program failed: %m");
+
+        return r;
+}
+
+int bpf_devices_cgroup_init(
+                BPFProgram **ret,
+                CGroupDevicePolicy policy,
+                bool allow_list) {
+
+        const struct bpf_insn pre_insn[] = {
+                /* load device type to r2 */
+                BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1,
+                            offsetof(struct bpf_cgroup_dev_ctx, access_type)),
+                BPF_ALU32_IMM(BPF_AND, BPF_REG_2, 0xFFFF),
+
+                /* load access type to r3 */
+                BPF_LDX_MEM(BPF_W, BPF_REG_3, BPF_REG_1,
+                            offsetof(struct bpf_cgroup_dev_ctx, access_type)),
+                BPF_ALU32_IMM(BPF_RSH, BPF_REG_3, 16),
+
+                /* load major number to r4 */
+                BPF_LDX_MEM(BPF_W, BPF_REG_4, BPF_REG_1,
+                            offsetof(struct bpf_cgroup_dev_ctx, major)),
+
+                /* load minor number to r5 */
+                BPF_LDX_MEM(BPF_W, BPF_REG_5, BPF_REG_1,
+                            offsetof(struct bpf_cgroup_dev_ctx, minor)),
+        };
+
+        _cleanup_(bpf_program_freep) BPFProgram *prog = NULL;
+        int r;
+
+        assert(ret);
+
+        if (policy == CGROUP_DEVICE_POLICY_AUTO && !allow_list)
+                return 0;
+
+        r = bpf_program_new(BPF_PROG_TYPE_CGROUP_DEVICE, "sd_devices", &prog);
+        if (r < 0)
+                return log_error_errno(r, "Loading device control BPF program failed: %m");
+
+        if (policy == CGROUP_DEVICE_POLICY_CLOSED || allow_list) {
+                r = bpf_program_add_instructions(prog, pre_insn, ELEMENTSOF(pre_insn));
+                if (r < 0)
+                        return log_error_errno(r, "Extending device control BPF program failed: %m");
+        }
+
+        *ret = TAKE_PTR(prog);
+
+        return 0;
+}
+
+int bpf_devices_apply_policy(
+                BPFProgram **prog,
+                CGroupDevicePolicy policy,
+                bool allow_list,
+                const char *cgroup_path,
+                BPFProgram **prog_installed) {
+
+        _cleanup_free_ char *controller_path = NULL;
+        int r;
+
+        /* This will assign *prog_installed if everything goes well. */
+
+        assert(prog);
+        if (!*prog)
+                goto finish;
+
+        const bool deny_everything = policy == CGROUP_DEVICE_POLICY_STRICT && !allow_list;
+
+        const struct bpf_insn post_insn[] = {
+                /* return DENY */
+                BPF_MOV64_IMM(BPF_REG_0, 0),
+                BPF_JMP_A(1),
+        };
+
+        const struct bpf_insn exit_insn[] = {
+                /* finally return DENY if deny_everything else ALLOW */
+                BPF_MOV64_IMM(BPF_REG_0, deny_everything ? 0 : 1),
+                BPF_EXIT_INSN()
+        };
+
+        if (!deny_everything) {
+                r = bpf_program_add_instructions(*prog, post_insn, ELEMENTSOF(post_insn));
+                if (r < 0)
+                        return log_error_errno(r, "Extending device control BPF program failed: %m");
+
+                /* Fixup PASS_JUMP_OFF jump offsets. */
+                for (size_t off = 0; off < (*prog)->n_instructions; off++) {
+                        struct bpf_insn *ins = &((*prog)->instructions[off]);
+
+                        if (ins->code == (BPF_JMP | BPF_JA) && ins->off == PASS_JUMP_OFF)
+                                ins->off = (*prog)->n_instructions - off - 1;
+                }
+        }
+
+        r = bpf_program_add_instructions(*prog, exit_insn, ELEMENTSOF(exit_insn));
+        if (r < 0)
+                return log_error_errno(r, "Extending device control BPF program failed: %m");
+
+        r = cg_get_path(SYSTEMD_CGROUP_CONTROLLER, cgroup_path, NULL, &controller_path);
+        if (r < 0)
+                return log_error_errno(r, "Failed to determine cgroup path: %m");
+
+        r = bpf_program_cgroup_attach(*prog, BPF_CGROUP_DEVICE, controller_path, BPF_F_ALLOW_MULTI);
+        if (r < 0)
+                return log_error_errno(r, "Attaching device control BPF program to cgroup %s failed: %m",
+                                       empty_to_root(cgroup_path));
+
+ finish:
+        /* Unref the old BPF program (which will implicitly detach it) right before attaching the new program. */
+        if (prog_installed) {
+                bpf_program_free(*prog_installed);
+                *prog_installed = TAKE_PTR(*prog);
+        }
+        return 0;
+}
+
+int bpf_devices_supported(void) {
+        const struct bpf_insn trivial[] = {
+                BPF_MOV64_IMM(BPF_REG_0, 1),
+                BPF_EXIT_INSN()
+        };
+
+        _cleanup_(bpf_program_freep) BPFProgram *program = NULL;
+        static int supported = -1;
+        int r;
+
+        /* Checks whether BPF device controller is supported. For this, we check five things:
+         *
+         * a) whether we are privileged
+         * b) whether the unified hierarchy is being used
+         * c) the BPF implementation in the kernel supports BPF_PROG_TYPE_CGROUP_DEVICE programs, which we require
+         */
+
+        if (supported >= 0)
+                return supported;
+
+        if (geteuid() != 0) {
+                log_debug("Not enough privileges, BPF device control is not supported.");
+                return supported = 0;
+        }
+
+        r = cg_unified_controller(SYSTEMD_CGROUP_CONTROLLER);
+        if (r < 0)
+                return log_error_errno(r, "Can't determine whether the unified hierarchy is used: %m");
+        if (r == 0) {
+                log_debug("Not running with unified cgroups, BPF device control is not supported.");
+                return supported = 0;
+        }
+
+        r = bpf_program_new(BPF_PROG_TYPE_CGROUP_DEVICE, "sd_devices", &program);
+        if (r < 0) {
+                log_debug_errno(r, "Can't allocate CGROUP DEVICE BPF program, BPF device control is not supported: %m");
+                return supported = 0;
+        }
+
+        r = bpf_program_add_instructions(program, trivial, ELEMENTSOF(trivial));
+        if (r < 0) {
+                log_debug_errno(r, "Can't add trivial instructions to CGROUP DEVICE BPF program, BPF device control is not supported: %m");
+                return supported = 0;
+        }
+
+        r = bpf_program_load_kernel(program, NULL, 0);
+        if (r < 0) {
+                log_debug_errno(r, "Can't load kernel CGROUP DEVICE BPF program, BPF device control is not supported: %m");
+                return supported = 0;
+        }
+
+        return supported = 1;
+}
+
+static int allow_list_device_pattern(
+                BPFProgram *prog,
+                const char *path,
+                char type,
+                const unsigned *maj,
+                const unsigned *min,
+                const char *acc) {
+
+        assert(IN_SET(type, 'b', 'c'));
+
+        if (cg_all_unified() > 0) {
+                if (!prog)
+                        return 0;
+
+                if (maj && min)
+                        return bpf_prog_allow_list_device(prog, type, *maj, *min, acc);
+                else if (maj)
+                        return bpf_prog_allow_list_major(prog, type, *maj, acc);
+                else
+                        return bpf_prog_allow_list_class(prog, type, acc);
+
+        } else {
+                char buf[2+DECIMAL_STR_MAX(unsigned)*2+2+4];
+                int r;
+
+                if (maj && min)
+                        xsprintf(buf, "%c %u:%u %s", type, *maj, *min, acc);
+                else if (maj)
+                        xsprintf(buf, "%c %u:* %s", type, *maj, acc);
+                else
+                        xsprintf(buf, "%c *:* %s", type, acc);
+
+                /* Changing the devices list of a populated cgroup might result in EINVAL, hence ignore
+                 * EINVAL here. */
+
+                r = cg_set_attribute("devices", path, "devices.allow", buf);
+                if (r < 0)
+                        log_full_errno(IN_SET(r, -ENOENT, -EROFS, -EINVAL, -EACCES, -EPERM) ? LOG_DEBUG : LOG_WARNING,
+                                       r, "Failed to set devices.allow on %s: %m", path);
+
+                return r;
+        }
+}
+
+int bpf_devices_allow_list_device(
+                BPFProgram *prog,
+                const char *path,
+                const char *node,
+                const char *acc) {
+
+        mode_t mode;
+        dev_t rdev;
+        int r;
+
+        assert(path);
+        assert(acc);
+        assert(strlen(acc) <= 3);
+
+        log_trace("%s: %s %s", __func__, node, acc);
+
+        /* Some special handling for /dev/block/%u:%u, /dev/char/%u:%u, /run/systemd/inaccessible/chr and
+         * /run/systemd/inaccessible/blk paths. Instead of stat()ing these we parse out the major/minor directly. This
+         * means clients can use these path without the device node actually around */
+        r = device_path_parse_major_minor(node, &mode, &rdev);
+        if (r < 0) {
+                if (r != -ENODEV)
+                        return log_warning_errno(r, "Couldn't parse major/minor from device path '%s': %m", node);
+
+                struct stat st;
+                if (stat(node, &st) < 0)
+                        return log_warning_errno(errno, "Couldn't stat device %s: %m", node);
+
+                if (!S_ISCHR(st.st_mode) && !S_ISBLK(st.st_mode))
+                        return log_warning_errno(SYNTHETIC_ERRNO(ENODEV), "%s is not a device.", node);
+
+                mode = st.st_mode;
+                rdev = (dev_t) st.st_rdev;
+        }
+
+        unsigned maj = major(rdev), min = minor(rdev);
+        return allow_list_device_pattern(prog, path, S_ISCHR(mode) ? 'c' : 'b', &maj, &min, acc);
+}
+
+int bpf_devices_allow_list_major(
+                BPFProgram *prog,
+                const char *path,
+                const char *name,
+                char type,
+                const char *acc) {
+
+        unsigned maj;
+        int r;
+
+        assert(path);
+        assert(acc);
+        assert(IN_SET(type, 'b', 'c'));
+
+        if (streq(name, "*"))
+                /* If the name is a wildcard, then apply this list to all devices of this type */
+                return allow_list_device_pattern(prog, path, type, NULL, NULL, acc);
+
+        if (safe_atou(name, &maj) >= 0 && DEVICE_MAJOR_VALID(maj))
+                /* The name is numeric and suitable as major. In that case, let's take its major, and create
+                 * the entry directly. */
+                return allow_list_device_pattern(prog, path, type, &maj, NULL, acc);
+
+        _cleanup_fclose_ FILE *f = NULL;
+        bool good = false, any = false;
+
+        f = fopen("/proc/devices", "re");
+        if (!f)
+                return log_warning_errno(errno, "Cannot open /proc/devices to resolve %s: %m", name);
+
+        for (;;) {
+                _cleanup_free_ char *line = NULL;
+                char *w, *p;
+
+                r = read_line(f, LONG_LINE_MAX, &line);
+                if (r < 0)
+                        return log_warning_errno(r, "Failed to read /proc/devices: %m");
+                if (r == 0)
+                        break;
+
+                if (type == 'c' && streq(line, "Character devices:")) {
+                        good = true;
+                        continue;
+                }
+
+                if (type == 'b' && streq(line, "Block devices:")) {
+                        good = true;
+                        continue;
+                }
+
+                if (isempty(line)) {
+                        good = false;
+                        continue;
+                }
+
+                if (!good)
+                        continue;
+
+                p = strstrip(line);
+
+                w = strpbrk(p, WHITESPACE);
+                if (!w)
+                        continue;
+                *w = 0;
+
+                r = safe_atou(p, &maj);
+                if (r < 0)
+                        continue;
+                if (maj <= 0)
+                        continue;
+
+                w++;
+                w += strspn(w, WHITESPACE);
+
+                if (fnmatch(name, w, 0) != 0)
+                        continue;
+
+                any = true;
+                (void) allow_list_device_pattern(prog, path, type, &maj, NULL, acc);
+        }
+
+        if (!any)
+                return log_debug_errno(SYNTHETIC_ERRNO(ENOENT),
+                                       "Device allow list pattern \"%s\" did not match anything.", name);
+
+        return 0;
+}
+
+int bpf_devices_allow_list_static(
+                BPFProgram *prog,
+                const char *path) {
+
+        static const char auto_devices[] =
+                "/dev/null\0" "rwm\0"
+                "/dev/zero\0" "rwm\0"
+                "/dev/full\0" "rwm\0"
+                "/dev/random\0" "rwm\0"
+                "/dev/urandom\0" "rwm\0"
+                "/dev/tty\0" "rwm\0"
+                "/dev/ptmx\0" "rwm\0"
+                /* Allow /run/systemd/inaccessible/{chr,blk} devices for mapping InaccessiblePaths */
+                "/run/systemd/inaccessible/chr\0" "rwm\0"
+                "/run/systemd/inaccessible/blk\0" "rwm\0";
+        int r = 0, k;
+
+        const char *node, *acc;
+        NULSTR_FOREACH_PAIR(node, acc, auto_devices) {
+                k = bpf_devices_allow_list_device(prog, path, node, acc);
+                if (r >= 0 && k < 0)
+                        r = k;
+        }
+
+        /* PTS (/dev/pts) devices may not be duplicated, but accessed */
+        k = bpf_devices_allow_list_major(prog, path, "pts", 'c', "rw");
+        if (r >= 0 && k < 0)
+                r = k;
+
+        return r;
+}