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commit e6ae703ae597d798e310368d52b8f38ee11c6a73
Author: Greg Hudson <ghudson@mit.edu>
Date: Thu Jun 19 13:49:16 2014 -0400
Handle invalid RFC 1964 tokens [CVE-2014-4341...]
Detect the following cases which would otherwise cause invalid memory
accesses and/or integer underflow:
* An RFC 1964 token being processed by an RFC 4121-only context
[CVE-2014-4342]
* A header with fewer than 22 bytes after the token ID or an
incomplete checksum [CVE-2014-4341 CVE-2014-4342]
* A ciphertext shorter than the confounder [CVE-2014-4341]
* A declared padding length longer than the plaintext [CVE-2014-4341]
If we detect a bad pad byte, continue on to compute the checksum to
avoid creating a padding oracle, but treat the checksum as invalid
even if it compares equal.
CVE-2014-4341:
In MIT krb5, an unauthenticated remote attacker with the ability to
inject packets into a legitimately established GSSAPI application
session can cause a program crash due to invalid memory references
when attempting to read beyond the end of a buffer.
CVSSv2 Vector: AV:N/AC:M/Au:N/C:N/I:N/A:P/E:POC/RL:OF/RC:C
CVE-2014-4342:
In MIT krb5 releases krb5-1.7 and later, an unauthenticated remote
attacker with the ability to inject packets into a legitimately
established GSSAPI application session can cause a program crash due
to invalid memory references when reading beyond the end of a buffer
or by causing a null pointer dereference.
CVSSv2 Vector: AV:N/AC:M/Au:N/C:N/I:N/A:P/E:POC/RL:OF/RC:C
[tlyu@mit.edu: CVE summaries, CVSS]
(cherry picked from commit fb99962cbd063ac04c9a9d2cc7c75eab73f3533d)
ticket: 7949
version_fixed: 1.12.2
status: resolved
diff --git a/src/lib/gssapi/krb5/k5unseal.c b/src/lib/gssapi/krb5/k5unseal.c
index ca21d43..b65c83c 100644
--- a/src/lib/gssapi/krb5/k5unseal.c
+++ b/src/lib/gssapi/krb5/k5unseal.c
@@ -74,6 +74,7 @@ kg_unseal_v1(context, minor_status, ctx, ptr, bodysize, message_buffer,
int conflen = 0;
int signalg;
int sealalg;
+ int bad_pad = 0;
gss_buffer_desc token;
krb5_checksum cksum;
krb5_checksum md5cksum;
@@ -86,6 +87,7 @@ kg_unseal_v1(context, minor_status, ctx, ptr, bodysize, message_buffer,
krb5_ui_4 seqnum;
OM_uint32 retval;
size_t sumlen;
+ size_t padlen;
krb5_keyusage sign_usage = KG_USAGE_SIGN;
if (toktype == KG_TOK_SEAL_MSG) {
@@ -93,18 +95,23 @@ kg_unseal_v1(context, minor_status, ctx, ptr, bodysize, message_buffer,
message_buffer->value = NULL;
}
- /* get the sign and seal algorithms */
-
- signalg = ptr[0] + (ptr[1]<<8);
- sealalg = ptr[2] + (ptr[3]<<8);
-
/* Sanity checks */
- if ((ptr[4] != 0xff) || (ptr[5] != 0xff)) {
+ if (ctx->seq == NULL) {
+ /* ctx was established using a newer enctype, and cannot process RFC
+ * 1964 tokens. */
+ *minor_status = 0;
+ return GSS_S_DEFECTIVE_TOKEN;
+ }
+
+ if ((bodysize < 22) || (ptr[4] != 0xff) || (ptr[5] != 0xff)) {
*minor_status = 0;
return GSS_S_DEFECTIVE_TOKEN;
}
+ signalg = ptr[0] + (ptr[1]<<8);
+ sealalg = ptr[2] + (ptr[3]<<8);
+
if ((toktype != KG_TOK_SEAL_MSG) &&
(sealalg != 0xffff)) {
*minor_status = 0;
@@ -153,6 +160,11 @@ kg_unseal_v1(context, minor_status, ctx, ptr, bodysize, message_buffer,
return GSS_S_DEFECTIVE_TOKEN;
}
+ if ((size_t)bodysize < 14 + cksum_len) {
+ *minor_status = 0;
+ return GSS_S_DEFECTIVE_TOKEN;
+ }
+
/* get the token parameters */
if ((code = kg_get_seq_num(context, ctx->seq, ptr+14, ptr+6, &direction,
@@ -207,7 +219,20 @@ kg_unseal_v1(context, minor_status, ctx, ptr, bodysize, message_buffer,
plainlen = tmsglen;
conflen = kg_confounder_size(context, ctx->enc->keyblock.enctype);
- token.length = tmsglen - conflen - plain[tmsglen-1];
+ if (tmsglen < conflen) {
+ if (sealalg != 0xffff)
+ xfree(plain);
+ *minor_status = 0;
+ return(GSS_S_DEFECTIVE_TOKEN);
+ }
+ padlen = plain[tmsglen - 1];
+ if (tmsglen - conflen < padlen) {
+ /* Don't error out yet, to avoid padding oracle attacks. We will
+ * treat this as a checksum failure later on. */
+ padlen = 0;
+ bad_pad = 1;
+ }
+ token.length = tmsglen - conflen - padlen;
if (token.length) {
if ((token.value = (void *) gssalloc_malloc(token.length)) == NULL) {
@@ -403,7 +428,7 @@ kg_unseal_v1(context, minor_status, ctx, ptr, bodysize, message_buffer,
/* compare the computed checksum against the transmitted checksum */
- if (code) {
+ if (code || bad_pad) {
if (toktype == KG_TOK_SEAL_MSG)
gssalloc_free(token.value);
*minor_status = 0;
diff --git a/src/lib/gssapi/krb5/k5unsealiov.c b/src/lib/gssapi/krb5/k5unsealiov.c
index e34bda4..8d6a2da 100644
--- a/src/lib/gssapi/krb5/k5unsealiov.c
+++ b/src/lib/gssapi/krb5/k5unsealiov.c
@@ -69,7 +69,14 @@ kg_unseal_v1_iov(krb5_context context,
return GSS_S_DEFECTIVE_TOKEN;
}
- if (header->buffer.length < token_wrapper_len + 14) {
+ if (ctx->seq == NULL) {
+ /* ctx was established using a newer enctype, and cannot process RFC
+ * 1964 tokens. */
+ *minor_status = 0;
+ return GSS_S_DEFECTIVE_TOKEN;
+ }
+
+ if (header->buffer.length < token_wrapper_len + 22) {
*minor_status = 0;
return GSS_S_DEFECTIVE_TOKEN;
}
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