diff options
Diffstat (limited to 'libmisc/idmapping.c')
-rw-r--r-- | libmisc/idmapping.c | 223 |
1 files changed, 0 insertions, 223 deletions
diff --git a/libmisc/idmapping.c b/libmisc/idmapping.c deleted file mode 100644 index 30eb89f..0000000 --- a/libmisc/idmapping.c +++ /dev/null @@ -1,223 +0,0 @@ -/* - * SPDX-FileCopyrightText: 2013 Eric Biederman - * - * SPDX-License-Identifier: BSD-3-Clause - */ - -#include <config.h> -#include <sys/types.h> -#include <sys/stat.h> -#include <fcntl.h> -#include <limits.h> -#include <stdlib.h> -#include <stdio.h> -#include "prototypes.h" -#include "idmapping.h" -#if HAVE_SYS_CAPABILITY_H -#include <sys/prctl.h> -#include <sys/capability.h> -#endif -#include "shadowlog.h" - -struct map_range *get_map_ranges(int ranges, int argc, char **argv) -{ - struct map_range *mappings, *mapping; - int idx, argidx; - - if (ranges < 0 || argc < 0) { - fprintf(log_get_logfd(), "%s: error calculating number of arguments\n", log_get_progname()); - return NULL; - } - - if (ranges != ((argc + 2) / 3)) { - fprintf(log_get_logfd(), "%s: ranges: %u is wrong for argc: %d\n", log_get_progname(), ranges, argc); - return NULL; - } - - if ((ranges * 3) > argc) { - fprintf(log_get_logfd(), "ranges: %u argc: %d\n", - ranges, argc); - fprintf(log_get_logfd(), - _( "%s: Not enough arguments to form %u mappings\n"), - log_get_progname(), ranges); - return NULL; - } - - mappings = calloc(ranges, sizeof(*mappings)); - if (!mappings) { - fprintf(log_get_logfd(), _( "%s: Memory allocation failure\n"), - log_get_progname()); - exit(EXIT_FAILURE); - } - - /* Gather up the ranges from the command line */ - mapping = mappings; - for (idx = 0, argidx = 0; idx < ranges; idx++, argidx += 3, mapping++) { - if (!getulong(argv[argidx + 0], &mapping->upper)) { - free(mappings); - return NULL; - } - if (!getulong(argv[argidx + 1], &mapping->lower)) { - free(mappings); - return NULL; - } - if (!getulong(argv[argidx + 2], &mapping->count)) { - free(mappings); - return NULL; - } - if (ULONG_MAX - mapping->upper <= mapping->count || ULONG_MAX - mapping->lower <= mapping->count) { - fprintf(log_get_logfd(), _( "%s: subuid overflow detected.\n"), log_get_progname()); - exit(EXIT_FAILURE); - } - if (mapping->upper > UINT_MAX || - mapping->lower > UINT_MAX || - mapping->count > UINT_MAX) { - fprintf(log_get_logfd(), _( "%s: subuid overflow detected.\n"), log_get_progname()); - exit(EXIT_FAILURE); - } - if (mapping->lower + mapping->count > UINT_MAX || - mapping->upper + mapping->count > UINT_MAX) { - fprintf(log_get_logfd(), _( "%s: subuid overflow detected.\n"), log_get_progname()); - exit(EXIT_FAILURE); - } - if (mapping->lower + mapping->count < mapping->lower || - mapping->upper + mapping->count < mapping->upper) { - /* this one really shouldn't be possible given previous checks */ - fprintf(log_get_logfd(), _( "%s: subuid overflow detected.\n"), log_get_progname()); - exit(EXIT_FAILURE); - } - } - return mappings; -} - -/* Number of ascii digits needed to print any unsigned long in decimal. - * There are approximately 10 bits for every 3 decimal digits. - * So from bits to digits the formula is roundup((Number of bits)/10) * 3. - * For common sizes of integers this works out to: - * 2bytes --> 6 ascii estimate -> 65536 (5 real) - * 4bytes --> 12 ascii estimated -> 4294967296 (10 real) - * 8bytes --> 21 ascii estimated -> 18446744073709551616 (20 real) - * 16bytes --> 39 ascii estimated -> 340282366920938463463374607431768211456 (39 real) - */ -#define ULONG_DIGITS ((((sizeof(unsigned long) * CHAR_BIT) + 9)/10)*3) - -#if HAVE_SYS_CAPABILITY_H -static inline bool maps_lower_root(int cap, int ranges, const struct map_range *mappings) -{ - int idx; - const struct map_range *mapping; - - if (cap != CAP_SETUID) - return false; - - mapping = mappings; - for (idx = 0; idx < ranges; idx++, mapping++) { - if (mapping->lower == 0) - return true; - } - - return false; -} -#endif - -/* - * The ruid refers to the caller's uid and is used to reset the effective uid - * back to the callers real uid. - * This clutch mainly exists for setuid-based new{g,u}idmap binaries that are - * called in contexts where all capabilities other than the necessary - * CAP_SET{G,U}ID capabilities are dropped. Since the kernel will require - * assurance that the caller holds CAP_SYS_ADMIN over the target user namespace - * the only way it can confirm is in this case is if the effective uid is - * equivalent to the uid owning the target user namespace. - * Note, we only support this when a) new{g,u}idmap is not called by root and - * b) if the caller's uid and the uid retrieved via system appropriate means - * (shadow file or other) are identical. Specifically, this does not support - * when the root user calls the new{g,u}idmap binary for an unprivileged user. - * If this is wanted: use file capabilities! - */ -void write_mapping(int proc_dir_fd, int ranges, const struct map_range *mappings, - const char *map_file, uid_t ruid) -{ - int idx; - const struct map_range *mapping; - size_t bufsize; - char *buf, *pos; - int fd; - -#if HAVE_SYS_CAPABILITY_H - int cap; - struct __user_cap_header_struct hdr = {_LINUX_CAPABILITY_VERSION_3, 0}; - struct __user_cap_data_struct data[2] = {{0}}; - - if (strcmp(map_file, "uid_map") == 0) { - cap = CAP_SETUID; - } else if (strcmp(map_file, "gid_map") == 0) { - cap = CAP_SETGID; - } else { - fprintf(log_get_logfd(), _("%s: Invalid map file %s specified\n"), log_get_progname(), map_file); - exit(EXIT_FAILURE); - } - - /* Align setuid- and fscaps-based new{g,u}idmap behavior. */ - if (geteuid() == 0 && geteuid() != ruid) { - if (prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0) < 0) { - fprintf(log_get_logfd(), _("%s: Could not prctl(PR_SET_KEEPCAPS)\n"), log_get_progname()); - exit(EXIT_FAILURE); - } - - if (seteuid(ruid) < 0) { - fprintf(log_get_logfd(), _("%s: Could not seteuid to %d\n"), log_get_progname(), ruid); - exit(EXIT_FAILURE); - } - } - - /* Lockdown new{g,u}idmap by dropping all unneeded capabilities. */ - memset(data, 0, sizeof(data)); - data[0].effective = CAP_TO_MASK(cap); - /* - * When uid 0 from the ancestor userns is supposed to be mapped into - * the child userns we need to retain CAP_SETFCAP. - */ - if (maps_lower_root(cap, ranges, mappings)) - data[0].effective |= CAP_TO_MASK(CAP_SETFCAP); - data[0].permitted = data[0].effective; - if (capset(&hdr, data) < 0) { - fprintf(log_get_logfd(), _("%s: Could not set caps\n"), log_get_progname()); - exit(EXIT_FAILURE); - } -#endif - - bufsize = ranges * ((ULONG_DIGITS + 1) * 3); - pos = buf = xmalloc(bufsize); - - /* Build the mapping command */ - mapping = mappings; - for (idx = 0; idx < ranges; idx++, mapping++) { - /* Append this range to the string that will be written */ - int written = snprintf(pos, bufsize - (pos - buf), - "%lu %lu %lu\n", - mapping->upper, - mapping->lower, - mapping->count); - if ((written <= 0) || (written >= (bufsize - (pos - buf)))) { - fprintf(log_get_logfd(), _("%s: snprintf failed!\n"), log_get_progname()); - exit(EXIT_FAILURE); - } - pos += written; - } - - /* Write the mapping to the mapping file */ - fd = openat(proc_dir_fd, map_file, O_WRONLY); - if (fd < 0) { - fprintf(log_get_logfd(), _("%s: open of %s failed: %s\n"), - log_get_progname(), map_file, strerror(errno)); - exit(EXIT_FAILURE); - } - if (write(fd, buf, pos - buf) != (pos - buf)) { - fprintf(log_get_logfd(), _("%s: write to %s failed: %s\n"), - log_get_progname(), map_file, strerror(errno)); - exit(EXIT_FAILURE); - } - close(fd); - free(buf); -} |