Merge in nonce work I did at home

Conflicts:
	mcp/src/claim.cgi.c
	mcp/src/common.c
	mcp/src/in.tokend.c
	mcp/src/puzzler.cgi.c
	mcp/src/puzzles.cgi.c
	mcp/src/xxtea.c
	mcp/src/xxtea.h
This commit is contained in:
Neale Pickett 2010-09-23 18:30:40 -06:00
commit 8e25c9f074
15 changed files with 255 additions and 105 deletions

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@ -1,11 +1,15 @@
Ideas for puzzles Ideas for puzzles
================= =================
* Hide something in a .docx zip file * Hide something in a .docx zip file
* Bootable image with FreeDOS, Linux, Inferno? HURD?
* Bury puzzles in various weird locations within each OS
Network treasure hunt * Maybe put some in the boot loader, too
--------------------- * Perhaps have some sort of network puzzle as well
* DHCP option * Network treasure hunt
* Single TCP RST with token in payload * DHCP option
* Multiple TCP RST with different payloads * Single TCP RST with token in payload
* * Multiple TCP RST with different payloads
* PXE boot some sort of points-gathering client
* Init asks for a team hash, and starts awarding points
* Broken startup scripts, when fixed award more points
* Lots of remote exploits

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@ -12,7 +12,7 @@ $(PACKAGE): build
cp setup $(PKGDIR) cp setup $(PKGDIR)
find bin -not -name '*~' | cpio -p $(PKGDIR) find bin -not -name '*~' | cpio -p $(PKGDIR)
cp src/in.tokend src/pointscli $(PKGDIR)/bin cp src/in.tokend src/tokencli src/pointscli $(PKGDIR)/bin
find service -not -name '*~' -not -name '#*' | cpio -p $(PKGDIR) find service -not -name '*~' -not -name '#*' | cpio -p $(PKGDIR)

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@ -1,11 +1,14 @@
CFLAGS = -Wall -Werror CFLAGS = -Wall -Werror
TARGETS = in.tokend pointscli claim.cgi puzzler.cgi puzzles.cgi TARGETS = in.tokend tokencli claim.cgi
TARGETS += puzzler.cgi puzzles.cgi
TARGETS += pointscli
all: build all: build
build: $(TARGETS) build: $(TARGETS)
in.tokend: in.tokend.o xxtea.o common.o in.tokend: in.tokend.o arc4.o common.o
tokencli: tokencli.o arc4.o
pointscli: pointscli.o common.o pointscli: pointscli.o common.o
puzzles.cgi: puzzles.cgi.o common.o puzzles.cgi: puzzles.cgi.o common.o

59
mcp/src/arc4.c Normal file
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@ -0,0 +1,59 @@
#include <stdint.h>
#include <stdlib.h>
#include "arc4.h"
#define swap(a, b) do {int _swap=a; a=b, b=_swap;} while (0)
struct arc4_ctx {
uint8_t S[256];
uint8_t i;
uint8_t j;
};
void
arc4_init(struct arc4_ctx *ctx, uint8_t const *key, size_t keylen)
{
int i;
int j = 0;
for (i = 0; i < 256; i += 1) {
ctx->S[i] = i;
}
for (i = 0; i < 256; i += 1) {
j = (j + ctx->S[i] + key[i % keylen]) % 256;
swap(ctx->S[i], ctx->S[j]);
}
ctx->i = 0;
ctx->j = 0;
}
uint8_t
arc4_pad(struct arc4_ctx *ctx)
{
ctx->i = (ctx->i + 1) % 256;
ctx->j = (ctx->j + ctx->S[ctx->i]) % 256;
swap(ctx->S[ctx->i], ctx->S[ctx->j]);
return ctx->S[(ctx->S[ctx->i] + ctx->S[ctx->j]) % 256];
}
void
arc4_crypt(struct arc4_ctx *ctx,
uint8_t *obuf, uint8_t const *ibuf, size_t buflen)
{
size_t k;
for (k = 0; k < buflen; k += 1) {
obuf[k] = ibuf[k] ^ arc4_pad(ctx);
}
}
void
arc4_crypt_buffer(uint8_t const *key, size_t keylen,
uint8_t *buf, size_t buflen)
{
struct arc4_ctx ctx;
arc4_init(&ctx, key, keylen);
arc4_crypt(&ctx, buf, buf, buflen);
}

16
mcp/src/arc4.h Normal file
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@ -0,0 +1,16 @@
#ifndef __ARC4_H__
#define __ARC4_H__
#include <stdint.h>
#include <stdlib.h>
struct arc4_ctx;
void arc4_init(struct arc4_ctx *ctx, uint8_t const *key, size_t keylen);
uint8_t arc4_pad(struct arc4_ctx *ctx);
void arc4_crypt(struct arc4_ctx *ctx,
uint8_t *obuf, uint8_t const *ibuf, size_t buflen);
void arc4_crypt_buffer(uint8_t const *key, size_t keylen,
uint8_t *buf, size_t buflen);
#endif

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@ -64,7 +64,7 @@ main(int argc, char *argv[])
category[i] = '\0'; category[i] = '\0';
{ {
char line[TEAM_MAX + TOKEN_MAX + 1]; char line[200];
my_snprintf(line, sizeof(line), my_snprintf(line, sizeof(line),
"%s %s", team, token); "%s %s", team, token);

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@ -282,6 +282,29 @@ fgrepx(char const *needle, char const *filename)
return found; return found;
} }
int32_t
my_random()
{
static int urandom = -2;
int len;
int32_t ret;
if (-2 == urandom) {
urandom = open("/dev/urandom", O_RDONLY);
srandom(time(NULL) * getpid());
}
if (-1 == urandom) {
return (int32_t)random();
}
len = read(urandom, &ret, sizeof(ret));
if (len != sizeof(ret)) {
return (int32_t)random();
}
return ret;
}
int int
my_snprintf(char *buf, size_t buflen, char *fmt, ...) my_snprintf(char *buf, size_t buflen, char *fmt, ...)
{ {

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@ -2,6 +2,7 @@
#define __COMMON_H__ #define __COMMON_H__
#include <stddef.h> #include <stddef.h>
#include <stdint.h>
#define TEAM_MAX 40 #define TEAM_MAX 40
#define CAT_MAX 40 #define CAT_MAX 40
@ -17,6 +18,7 @@ void cgi_error(char *fmt, ...);
int fgrepx(char const *needle, char const *filename); int fgrepx(char const *needle, char const *filename);
int32_t my_random();
int my_snprintf(char *buf, size_t buflen, char *fmt, ...); int my_snprintf(char *buf, size_t buflen, char *fmt, ...);
char *state_path(char const *fmt, ...); char *state_path(char const *fmt, ...);
char *package_path(char const *fmt, ...); char *package_path(char const *fmt, ...);

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@ -9,8 +9,9 @@
#include <stddef.h> #include <stddef.h>
#include <string.h> #include <string.h>
#include <ctype.h> #include <ctype.h>
#include <sysexits.h>
#include "common.h" #include "common.h"
#include "xxtea.h" #include "arc4.h"
#define itokenlen 3 #define itokenlen 3
@ -73,17 +74,15 @@ main(int argc, char *argv[])
size_t servicelen; size_t servicelen;
char token[80]; char token[80];
size_t tokenlen; size_t tokenlen;
uint32_t key[4]; uint8_t key[256];
size_t keylen;
/* Seed the random number generator. This ought to be unpredictable
enough for a contest. */
srand((int)time(NULL) * (int)getpid());
/* Read service name. */ /* Read service name. */
{ {
ssize_t len; ssize_t len;
len = read(0, service, sizeof(service) - 1); len = read(0, service, sizeof(service));
if (0 >= len) return 0;
for (servicelen = 0; for (servicelen = 0;
(servicelen < len) && isalnum(service[servicelen]); (servicelen < len) && isalnum(service[servicelen]);
servicelen += 1); servicelen += 1);
@ -92,34 +91,45 @@ main(int argc, char *argv[])
/* Read in that service's key. */ /* Read in that service's key. */
{ {
int fd; int fd;
size_t len; int ret;
fd = open(state_path("token.keys/%.*s", (int)servicelen, service), O_RDONLY); fd = open(state_path("token.keys/%.*s", (int)servicelen, service), O_RDONLY);
if (-1 == fd) { if (-1 == fd) {
write(1, "!nosvc", 6); perror("Open key");
return 0; return 0;
} }
len = read(fd, &key, 16); ret = read(fd, &key, sizeof(key));
close(fd); if (-1 == ret) {
perror("Read key");
return 0;
}
keylen = (size_t)ret;
if (16 != len) { close(fd);
write(1, "!shortkey", 9); }
/* Send a nonce, expect it back encrypted */
{
int32_t nonce = my_random();
int32_t enonce = 0;
write(1, &nonce, sizeof(nonce));
arc4_crypt_buffer(key, keylen, (uint8_t *)&nonce, sizeof(nonce));
read(0, &enonce, sizeof(enonce));
if (nonce != enonce) {
write(1, ":<", 2);
return 0; return 0;
} }
} }
/* Create the token. */ /* Create the token. */
{ {
uint8_t crap[itokenlen]; int32_t crap = my_random();
char digest[bubblebabble_len(itokenlen)]; char digest[bubblebabble_len(itokenlen)];
int i;
/* Digest some random junk. */ /* Digest some random junk. */
for (i = 0; i < itokenlen; i += 1) { bubblebabble(digest, (char *)&crap, itokenlen);
crap[i] = (uint8_t)random();
}
bubblebabble(digest, (char *)crap, itokenlen);
/* Append digest to service name. */ /* Append digest to service name. */
tokenlen = (size_t)snprintf(token, sizeof(token), tokenlen = (size_t)snprintf(token, sizeof(token),
@ -158,19 +168,14 @@ main(int argc, char *argv[])
} }
} }
/* Encrypt the token. Note that now tokenlen is in uint32_ts, not /* Encrypt the token. */
chars! Also remember that token must be big enough to hold a
multiple of 4 chars, since tea will go ahead and jumble them up for
you. If the compiler aligns words this shouldn't be a problem. */
{ {
tokenlen = (tokenlen + (tokenlen % sizeof(uint32_t))) / sizeof(uint32_t); arc4_crypt_buffer(key, keylen, (uint8_t *)token, tokenlen);
tea_encode(key, (uint32_t *)token, tokenlen);
} }
/* Send it back. If there's an error here, it's okay. Better to have /* Send it back. If there's an error here, it's okay. Better to have
unclaimed tokens than unclaimable ones. */ unclaimed tokens than unclaimable ones. */
write(1, token, tokenlen * sizeof(uint32_t)); write(1, token, tokenlen);
return 0; return 0;
} }

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@ -67,7 +67,7 @@ main(int argc, char *argv[])
} }
{ {
char line[TEAM_MAX + CAT_MAX + sizeof(points_str) + 2]; char line[200];
my_snprintf(line, sizeof(line), my_snprintf(line, sizeof(line),
"%s %s %ld", team, category, points); "%s %s %ld", team, category, points);

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@ -19,11 +19,12 @@ longcmp(long *a, long *b)
#define PUZZLES_MAX 100 #define PUZZLES_MAX 100
/** Keeps track of the most points yet awarded in each category */ /** Keeps track of the most points yet awarded in each category */
int ncats = 0;
struct { struct {
char cat[CAT_MAX]; char cat[CAT_MAX];
long points; long points;
} points_by_cat[PUZZLES_MAX]; } points_by_cat[PUZZLES_MAX];
int ncats = 0;
size_t size_t
read_until_char(FILE *f, char *buf, size_t buflen, char delim) read_until_char(FILE *f, char *buf, size_t buflen, char delim)
@ -70,8 +71,6 @@ main(int argc, char *argv[])
read_until_char(f, points_str, sizeof(points_str), '\n'); read_until_char(f, points_str, sizeof(points_str), '\n');
points = atol(points_str); points = atol(points_str);
printf("%s %ld\n", cat, points);
for (i = 0; i < ncats; i += 1) { for (i = 0; i < ncats; i += 1) {
if (0 == strcmp(cat, points_by_cat[i].cat)) break; if (0 == strcmp(cat, points_by_cat[i].cat)) break;
} }

92
mcp/src/tokencli.c Normal file
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@ -0,0 +1,92 @@
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>
#include <sysexits.h>
#include <stdio.h>
#include "arc4.h"
/* I don't feel compelled to put all the TCP client code in here
* when it's so simple to run this with netcat or ucspi. Plus, using
* stdin and stdout makes it simpler to test.
*/
int
read_key(char *filename, uint8_t *key, size_t *keylen)
{
int fd = open(filename, O_RDONLY);
int len;
if (-1 == fd) {
perror("open");
return EX_NOINPUT;
}
len = read(fd, key, *keylen);
if (-1 == len) {
perror("read");
return EX_NOINPUT;
}
*keylen = (size_t)len;
return 0;
}
int
main(int argc, char *argv[]) {
uint8_t skey[200];
size_t skeylen = sizeof(skey);
char token[200];
size_t tokenlen;
int ret;
if (argc != 3) {
fprintf(stderr, "Usage: %s SERVICE SERVICEKEY 3>TOKENFILE\n", argv[0]);
fprintf(stderr, "\n");
fprintf(stderr, "SERVICEKEY is a filenames.\n");
fprintf(stderr, "Tokens are written to file descriptor 3.\n");
return EX_USAGE;
}
/* read in keys */
ret = read_key(argv[2], skey, &skeylen);
if (0 != ret) return ret;
/* write service name */
write(1, argv[1], strlen(argv[1]));
/* read nonce, send back encrypted version */
{
uint8_t nonce[80];
int noncelen;
noncelen = read(0, nonce, sizeof(nonce));
if (0 >= noncelen) {
perror("read");
return EX_IOERR;
}
arc4_crypt_buffer(skey, skeylen, nonce, (size_t)noncelen);
write(1, nonce, (size_t)noncelen);
}
/* read token */
{
int len;
len = read(0, token, sizeof(token));
if (0 >= len) {
perror("read");
return EX_IOERR;
}
tokenlen = (size_t)len;
}
/* decrypt it */
arc4_crypt_buffer(skey, skeylen, (uint8_t *)token, tokenlen);
/* write it to fd 3 */
write(3, token, tokenlen);
return 0;
}

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@ -1,51 +0,0 @@
#include <stdint.h>
#include <stddef.h>
#define DELTA 0x9e3779b9
#define MX ((z>>5^y<<2) + (y>>3^z<<4)) ^ ((sum^y) + (k[(p&3)^e] ^ z));
void
btea(uint32_t *v, int n, uint32_t const k[4])
{
uint32_t y, z, sum;
unsigned p, rounds, e;
if (n > 1) { /* Coding Part */
rounds = 6 + 52/n;
sum = 0;
z = v[n-1];
do {
sum += DELTA;
e = (sum >> 2) & 3;
for (p=0; p<n-1; p++)
y = v[p+1], z = v[p] += MX;
y = v[0];
z = v[n-1] += MX;
} while (--rounds);
} else if (n < -1) { /* Decoding Part */
n = -n;
rounds = 6 + 52/n;
sum = rounds*DELTA;
y = v[0];
do {
e = (sum >> 2) & 3;
for (p=n-1; p>0; p--)
z = v[p-1], y = v[p] -= MX;
z = v[n-1];
y = v[0] -= MX;
} while ((sum -= DELTA) != 0);
}
}
void
tea_encode(uint32_t const key[4], uint32_t *buf, size_t buflen)
{
btea(buf, buflen, key);
}
void
tea_decode(uint32_t const key[4], uint32_t *buf, size_t buflen)
{
btea(buf, -buflen, key);
}

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@ -1,2 +0,0 @@
void tea_encode(uint32_t const key[4], uint32_t *buf, size_t buflen);
void tea_decode(uint32_t const key[4], uint32_t *buf, size_t buflen);

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@ -88,8 +88,8 @@ fi
mkdir -p $CTF_BASE/token.keys mkdir -p $CTF_BASE/token.keys
echo -n '0123456789abcdef' > $CTF_BASE/token.keys/tokencat echo -n '0123456789abcdef' > $CTF_BASE/token.keys/tokencat
# in.tokend uses a random number generator mkfifo $CTF_BASE/nancy
echo -n 'tokencat' | src/in.tokend > /dev/null src/tokencli tokencat $CTF_BASE/token.keys/tokencat < $CTF_BASE/nancy 3>$CTF_BASE/t | src/in.tokend > $CTF_BASE/nancy
if ! grep -q 'tokencat:x....-....x' $CTF_BASE/tokens.db; then if ! grep -q 'tokencat:x....-....x' $CTF_BASE/tokens.db; then
die "in.tokend didn't write to database" die "in.tokend didn't write to database"
@ -103,11 +103,11 @@ if src/claim.cgi t=$hash k=tokencat:xanax-xanax | grep -q success; then
die "claim.cgi gave points for a bogus token" die "claim.cgi gave points for a bogus token"
fi fi
if ! src/claim.cgi t=$hash k=$(cat $CTF_BASE/tokens.db) | grep -q success; then if ! src/claim.cgi t=$hash k=$(cat $CTF_BASE/t) | grep -q success; then
die "claim.cgi didn't give me any points" die "claim.cgi didn't give me any points"
fi fi
if src/claim.cgi t=$hash k=$(cat $CTF_BASE/tokens.db) | grep -q success; then if src/claim.cgi t=$hash k=$(cat $CTF_BASE/t) | grep -q success; then
die "claim.cgi gave me points twice for the same token" die "claim.cgi gave me points twice for the same token"
fi fi