diff options
| -rw-r--r-- | src/basic/io-util.h | 9 | ||||
| -rw-r--r-- | src/coredump/coredump.c | 196 |
2 files changed, 192 insertions, 13 deletions
diff --git a/src/basic/io-util.h b/src/basic/io-util.h index 39728e06bc..3afb134266 100644 --- a/src/basic/io-util.h +++ b/src/basic/io-util.h @@ -91,7 +91,16 @@ struct iovec_wrapper *iovw_new(void); struct iovec_wrapper *iovw_free(struct iovec_wrapper *iovw); struct iovec_wrapper *iovw_free_free(struct iovec_wrapper *iovw); void iovw_free_contents(struct iovec_wrapper *iovw, bool free_vectors); + int iovw_put(struct iovec_wrapper *iovw, void *data, size_t len); +static inline int iovw_consume(struct iovec_wrapper *iovw, void *data, size_t len) { + /* Move data into iovw or free on error */ + int r = iovw_put(iovw, data, len); + if (r < 0) + free(data); + return r; +} + int iovw_put_string_field(struct iovec_wrapper *iovw, const char *field, const char *value); int iovw_put_string_field_free(struct iovec_wrapper *iovw, const char *field, char *value); void iovw_rebase(struct iovec_wrapper *iovw, char *old, char *new); diff --git a/src/coredump/coredump.c b/src/coredump/coredump.c index 9ce2b92ded..b6f3a2f256 100644 --- a/src/coredump/coredump.c +++ b/src/coredump/coredump.c @@ -4,6 +4,7 @@ #include <stdio.h> #include <sys/prctl.h> #include <sys/statvfs.h> +#include <sys/auxv.h> #include <sys/xattr.h> #include <unistd.h> @@ -107,6 +108,7 @@ enum { META_EXE = _META_MANDATORY_MAX, META_UNIT, + META_PROC_AUXV, _META_MAX }; @@ -121,10 +123,12 @@ static const char * const meta_field_names[_META_MAX] = { [META_COMM] = "COREDUMP_COMM=", [META_EXE] = "COREDUMP_EXE=", [META_UNIT] = "COREDUMP_UNIT=", + [META_PROC_AUXV] = "COREDUMP_PROC_AUXV=", }; typedef struct Context { const char *meta[_META_MAX]; + size_t meta_size[_META_MAX]; pid_t pid; bool is_pid1; bool is_journald; @@ -186,13 +190,16 @@ static uint64_t storage_size_max(void) { return 0; } -static int fix_acl(int fd, uid_t uid) { +static int fix_acl(int fd, uid_t uid, bool allow_user) { + assert(fd >= 0); + assert(uid_is_valid(uid)); #if HAVE_ACL int r; - assert(fd >= 0); - assert(uid_is_valid(uid)); + /* We don't allow users to read coredumps if the uid or capabilities were changed. */ + if (!allow_user) + return 0; if (uid_is_system(uid) || uid_is_dynamic(uid) || uid == UID_NOBODY) return 0; @@ -252,7 +259,8 @@ static int fix_permissions( const char *filename, const char *target, const Context *context, - uid_t uid) { + uid_t uid, + bool allow_user) { int r; @@ -262,7 +270,7 @@ static int fix_permissions( /* Ignore errors on these */ (void) fchmod(fd, 0640); - (void) fix_acl(fd, uid); + (void) fix_acl(fd, uid, allow_user); (void) fix_xattr(fd, context); r = fsync_full(fd); @@ -332,6 +340,153 @@ static int make_filename(const Context *context, char **ret) { return 0; } +static int parse_auxv64( + const uint64_t *auxv, + size_t size_bytes, + int *at_secure, + uid_t *uid, + uid_t *euid, + gid_t *gid, + gid_t *egid) { + + assert(auxv || size_bytes == 0); + + if (size_bytes % (2 * sizeof(uint64_t)) != 0) + return log_warning_errno(SYNTHETIC_ERRNO(EIO), "Incomplete auxv structure (%zu bytes).", size_bytes); + + size_t words = size_bytes / sizeof(uint64_t); + + /* Note that we set output variables even on error. */ + + for (size_t i = 0; i + 1 < words; i += 2) + switch (auxv[i]) { + case AT_SECURE: + *at_secure = auxv[i + 1] != 0; + break; + case AT_UID: + *uid = auxv[i + 1]; + break; + case AT_EUID: + *euid = auxv[i + 1]; + break; + case AT_GID: + *gid = auxv[i + 1]; + break; + case AT_EGID: + *egid = auxv[i + 1]; + break; + case AT_NULL: + if (auxv[i + 1] != 0) + goto error; + return 0; + } + error: + return log_warning_errno(SYNTHETIC_ERRNO(ENODATA), + "AT_NULL terminator not found, cannot parse auxv structure."); +} + +static int parse_auxv32( + const uint32_t *auxv, + size_t size_bytes, + int *at_secure, + uid_t *uid, + uid_t *euid, + gid_t *gid, + gid_t *egid) { + + assert(auxv || size_bytes == 0); + + size_t words = size_bytes / sizeof(uint32_t); + + if (size_bytes % (2 * sizeof(uint32_t)) != 0) + return log_warning_errno(SYNTHETIC_ERRNO(EIO), "Incomplete auxv structure (%zu bytes).", size_bytes); + + /* Note that we set output variables even on error. */ + + for (size_t i = 0; i + 1 < words; i += 2) + switch (auxv[i]) { + case AT_SECURE: + *at_secure = auxv[i + 1] != 0; + break; + case AT_UID: + *uid = auxv[i + 1]; + break; + case AT_EUID: + *euid = auxv[i + 1]; + break; + case AT_GID: + *gid = auxv[i + 1]; + break; + case AT_EGID: + *egid = auxv[i + 1]; + break; + case AT_NULL: + if (auxv[i + 1] != 0) + goto error; + return 0; + } + error: + return log_warning_errno(SYNTHETIC_ERRNO(ENODATA), + "AT_NULL terminator not found, cannot parse auxv structure."); +} + +static int grant_user_access(int core_fd, const Context *context) { + int at_secure = -1; + uid_t uid = UID_INVALID, euid = UID_INVALID; + uid_t gid = GID_INVALID, egid = GID_INVALID; + int r; + + assert(core_fd >= 0); + assert(context); + + if (!context->meta[META_PROC_AUXV]) + return log_warning_errno(SYNTHETIC_ERRNO(ENODATA), "No auxv data, not adjusting permissions."); + + uint8_t elf[EI_NIDENT]; + errno = 0; + if (pread(core_fd, &elf, sizeof(elf), 0) != sizeof(elf)) + return log_warning_errno(errno_or_else(EIO), + "Failed to pread from coredump fd: %s", STRERROR_OR_EOF(errno)); + + if (elf[EI_MAG0] != ELFMAG0 || + elf[EI_MAG1] != ELFMAG1 || + elf[EI_MAG2] != ELFMAG2 || + elf[EI_MAG3] != ELFMAG3 || + elf[EI_VERSION] != EV_CURRENT) + return log_info_errno(SYNTHETIC_ERRNO(EUCLEAN), + "Core file does not have ELF header, not adjusting permissions."); + if (!IN_SET(elf[EI_CLASS], ELFCLASS32, ELFCLASS64) || + !IN_SET(elf[EI_DATA], ELFDATA2LSB, ELFDATA2MSB)) + return log_info_errno(SYNTHETIC_ERRNO(EUCLEAN), + "Core file has strange ELF class, not adjusting permissions."); + + if ((elf[EI_DATA] == ELFDATA2LSB) != (__BYTE_ORDER == __LITTLE_ENDIAN)) + return log_info_errno(SYNTHETIC_ERRNO(EUCLEAN), + "Core file has non-native endianness, not adjusting permissions."); + + if (elf[EI_CLASS] == ELFCLASS64) + r = parse_auxv64((const uint64_t*) context->meta[META_PROC_AUXV], + context->meta_size[META_PROC_AUXV], + &at_secure, &uid, &euid, &gid, &egid); + else + r = parse_auxv32((const uint32_t*) context->meta[META_PROC_AUXV], + context->meta_size[META_PROC_AUXV], + &at_secure, &uid, &euid, &gid, &egid); + if (r < 0) + return r; + + /* We allow access if we got all the data and at_secure is not set and + * the uid/gid matches euid/egid. */ + bool ret = + at_secure == 0 && + uid != UID_INVALID && euid != UID_INVALID && uid == euid && + gid != GID_INVALID && egid != GID_INVALID && gid == egid; + log_debug("Will %s access (uid="UID_FMT " euid="UID_FMT " gid="GID_FMT " egid="GID_FMT " at_secure=%s)", + ret ? "permit" : "restrict", + uid, euid, gid, egid, yes_no(at_secure)); + return ret; +} + static int save_external_coredump( const Context *context, int input_fd, @@ -454,6 +609,8 @@ static int save_external_coredump( context->meta[META_ARGV_PID], context->meta[META_COMM]); truncated = r == 1; + bool allow_user = grant_user_access(fd, context) > 0; + #if HAVE_COMPRESSION if (arg_compress) { _cleanup_(unlink_and_freep) char *tmp_compressed = NULL; @@ -491,7 +648,7 @@ static int save_external_coredump( uncompressed_size += partial_uncompressed_size; } - r = fix_permissions(fd_compressed, tmp_compressed, fn_compressed, context, uid); + r = fix_permissions(fd_compressed, tmp_compressed, fn_compressed, context, uid, allow_user); if (r < 0) return r; @@ -518,7 +675,7 @@ static int save_external_coredump( "SIZE_LIMIT=%"PRIu64, max_size, "MESSAGE_ID=" SD_MESSAGE_TRUNCATED_CORE_STR); - r = fix_permissions(fd, tmp, fn, context, uid); + r = fix_permissions(fd, tmp, fn, context, uid, allow_user); if (r < 0) return log_error_errno(r, "Failed to fix permissions and finalize coredump %s into %s: %m", coredump_tmpfile_name(tmp), fn); @@ -766,7 +923,7 @@ static int change_uid_gid(const Context *context) { } static int submit_coredump( - Context *context, + const Context *context, struct iovec_wrapper *iovw, int input_fd) { @@ -945,16 +1102,15 @@ static int save_context(Context *context, const struct iovec_wrapper *iovw) { struct iovec *iovec = iovw->iovec + n; for (size_t i = 0; i < ELEMENTSOF(meta_field_names); i++) { - char *p; - /* Note that these strings are NUL terminated, because we made sure that a * trailing NUL byte is in the buffer, though not included in the iov_len * count (see process_socket() and gather_pid_metadata_*()) */ assert(((char*) iovec->iov_base)[iovec->iov_len] == 0); - p = startswith(iovec->iov_base, meta_field_names[i]); + const char *p = startswith(iovec->iov_base, meta_field_names[i]); if (p) { context->meta[i] = p; + context->meta_size[i] = iovec->iov_len - strlen(meta_field_names[i]); break; } } @@ -1191,6 +1347,7 @@ static int gather_pid_metadata(struct iovec_wrapper *iovw, Context *context) { uid_t owner_uid; pid_t pid; char *t; + size_t size; const char *p; int r; @@ -1255,13 +1412,26 @@ static int gather_pid_metadata(struct iovec_wrapper *iovw, Context *context) { (void) iovw_put_string_field_free(iovw, "COREDUMP_PROC_LIMITS=", t); p = procfs_file_alloca(pid, "cgroup"); - if (read_full_virtual_file(p, &t, NULL) >=0) + if (read_full_virtual_file(p, &t, NULL) >= 0) (void) iovw_put_string_field_free(iovw, "COREDUMP_PROC_CGROUP=", t); p = procfs_file_alloca(pid, "mountinfo"); - if (read_full_virtual_file(p, &t, NULL) >=0) + if (read_full_virtual_file(p, &t, NULL) >= 0) (void) iovw_put_string_field_free(iovw, "COREDUMP_PROC_MOUNTINFO=", t); + /* We attach /proc/auxv here. ELF coredumps also contain a note for this (NT_AUXV), see elf(5). */ + p = procfs_file_alloca(pid, "auxv"); + if (read_full_virtual_file(p, &t, &size) >= 0) { + char *buf = malloc(strlen("COREDUMP_PROC_AUXV=") + size + 1); + if (buf) { + /* Add a dummy terminator to make save_context() happy. */ + *((uint8_t*) mempcpy(stpcpy(buf, "COREDUMP_PROC_AUXV="), t, size)) = '\0'; + (void) iovw_consume(iovw, buf, size + strlen("COREDUMP_PROC_AUXV=")); + } + + free(t); + } + if (get_process_cwd(pid, &t) >= 0) (void) iovw_put_string_field_free(iovw, "COREDUMP_CWD=", t); |