From 97c26c1924b076ef23ebe4381558e8aa025712b2 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 16:54:37 +0200 Subject: Adding upstream version 1:4.13+dfsg1. Signed-off-by: Daniel Baumann --- libmisc/idmapping.c | 223 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 223 insertions(+) create mode 100644 libmisc/idmapping.c (limited to 'libmisc/idmapping.c') diff --git a/libmisc/idmapping.c b/libmisc/idmapping.c new file mode 100644 index 0000000..30eb89f --- /dev/null +++ b/libmisc/idmapping.c @@ -0,0 +1,223 @@ +/* + * SPDX-FileCopyrightText: 2013 Eric Biederman + * + * SPDX-License-Identifier: BSD-3-Clause + */ + +#include +#include +#include +#include +#include +#include +#include +#include "prototypes.h" +#include "idmapping.h" +#if HAVE_SYS_CAPABILITY_H +#include +#include +#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); +} -- cgit v1.2.3