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security: Check HMAC on FIPS fastpath input

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CVE-2026-32105: Add a check that the HMAC signature supplied with a
FIPS fastpath input PDU matches the calculated signature.
This commit is contained in:
matt335672
2026-03-10 18:03:39 +00:00
parent 90275daf6d
commit 2a411f7525
1 changed files with 56 additions and 31 deletions
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libxrdp/xrdp_sec.c
+56 -31
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@@ -832,6 +832,54 @@ xrdp_sec_hash_48(char *out, char *in, char *salt1, char *salt2, int salt)
ssl_md5_info_delete(md5_info);
}
/*****************************************************************************/
/* Output a uint32 into a buffer (little-endian) */
static void
buf_out_uint32(char *buffer, int value)
{
buffer[0] = (value) & 0xff;
buffer[1] = (value >> 8) & 0xff;
buffer[2] = (value >> 16) & 0xff;
buffer[3] = (value >> 24) & 0xff;
}
/*****************************************************************************/
/* Generate a MAC hash (5.2.3.1), using SHA1 for outgoing data */
static void
xrdp_sec_fips_sign(struct xrdp_sec *self, char *out, int out_len,
char *data, int data_len)
{
char buf[20];
char lenhdr[4];
buf_out_uint32(lenhdr, self->encrypt_use_count);
ssl_hmac_sha1_init(self->sign_fips_info, self->fips_sign_key, 20);
ssl_hmac_transform(self->sign_fips_info, data, data_len);
ssl_hmac_transform(self->sign_fips_info, lenhdr, 4);
ssl_hmac_complete(self->sign_fips_info, buf, 20);
g_memcpy(out, buf, out_len);
}
/*****************************************************************************/
/* Check a FIPS hash is valid */
static int
xrdp_sec_fips_check_sig(struct xrdp_sec *self, const char *sig, int sig_len,
char *data, int data_len)
{
char buf[20];
char lenhdr[4];
// Account for the decrypt operation which has just happened when
// creating the HMAC
buf_out_uint32(lenhdr, self->decrypt_use_count - 1);
ssl_hmac_sha1_init(self->sign_fips_info, self->fips_sign_key, 20);
ssl_hmac_transform(self->sign_fips_info, data, data_len);
ssl_hmac_transform(self->sign_fips_info, lenhdr, 4);
ssl_hmac_complete(self->sign_fips_info, buf, 20);
return memcmp(buf, sig, sig_len) == 0;
}
/*****************************************************************************/
static void
xrdp_sec_hash_16(char *out, char *in, char *salt1, char *salt2)
@@ -984,6 +1032,7 @@ xrdp_sec_recv_fastpath(struct xrdp_sec *self, struct stream *s)
int ver;
int len;
int pad;
const char *data_signature;
#ifndef USE_DEVEL_LOGGING
/* TODO: remove UNUSED_VAR once the `ver` variable is used for more than
@@ -1019,11 +1068,15 @@ xrdp_sec_recv_fastpath(struct xrdp_sec *self, struct stream *s)
}
/* remainder of TS_FP_INPUT_PDU */
in_uint8s(s, 8); /* dataSignature (8 bytes), skip for now */
LOG_DEVEL(LOG_LEVEL_TRACE, "CRYPT_LEVEL_FIPS - data len %d",
(int)(s->end - s->p));
in_uint8p(s, data_signature, 8);
xrdp_sec_fips_decrypt(self, s->p, (int)(s->end - s->p));
s->end -= pad;
if (!xrdp_sec_fips_check_sig(self, data_signature, 8,
s->p, (int)(s->end - s->p)))
{
LOG(LOG_LEVEL_ERROR, "MAC checksum error for FP-FIPS PDU");
return 1;
}
}
else
{
@@ -1215,34 +1268,6 @@ xrdp_sec_recv(struct xrdp_sec *self, struct stream *s, int *chan)
return 0;
}
/*****************************************************************************/
/* Output a uint32 into a buffer (little-endian) */
static void
buf_out_uint32(char *buffer, int value)
{
buffer[0] = (value) & 0xff;
buffer[1] = (value >> 8) & 0xff;
buffer[2] = (value >> 16) & 0xff;
buffer[3] = (value >> 24) & 0xff;
}
/*****************************************************************************/
/* Generate a MAC hash (5.2.3.1), using a combination of SHA1 and MD5 */
static void
xrdp_sec_fips_sign(struct xrdp_sec *self, char *out, int out_len,
char *data, int data_len)
{
char buf[20];
char lenhdr[4];
buf_out_uint32(lenhdr, self->encrypt_use_count);
ssl_hmac_sha1_init(self->sign_fips_info, self->fips_sign_key, 20);
ssl_hmac_transform(self->sign_fips_info, data, data_len);
ssl_hmac_transform(self->sign_fips_info, lenhdr, 4);
ssl_hmac_complete(self->sign_fips_info, buf, 20);
g_memcpy(out, buf, out_len);
}
/*****************************************************************************/
/* Generate a MAC hash (5.2.3.1), using a combination of SHA1 and MD5 */
static void