CVE-2009-0844 SPNEGO can read beyond buffer end

SPNEGO can read beyond the end of a buffer if the claimed DER length
exceeds the number of bytes in the input buffer. This can lead to
crash or information disclosure.

Thanks to Apple for reporting this vulnerability and providing
patches.

ticket: 6443
tags: pullup
target_version: 1.7

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@22174 dc483132-0cff-0310-8789-dd5450dbe970

1 files changed, 24 insertions, 27 deletions

diff --git a/src/lib/gssapi/spnego/spnego_mech.c b/src/lib/gssapi/spnego/spnego_mech.c
index 2fc6f7158..06a653e47 100644
--- a/src/lib/gssapi/spnego/spnego_mech.c
+++ b/src/lib/gssapi/spnego/spnego_mech.c
@@ -83,8 +83,8 @@ typedef const gss_OID_desc *gss_OID_const;
 
 /* der routines defined in libgss */
 extern unsigned int gssint_der_length_size(OM_uint32);
-extern int gssint_get_der_length(unsigned char **, OM_uint32, OM_uint32*);
-extern int gssint_put_der_length(OM_uint32, unsigned char **, OM_uint32);
+extern int gssint_get_der_length(unsigned char **, OM_uint32, unsigned int*);
+extern int gssint_put_der_length(OM_uint32, unsigned char **, unsigned int);
 
 
 /* private routines for spnego_mechanism */
@@ -2390,22 +2390,16 @@ static gss_buffer_t
 get_input_token(unsigned char **buff_in, unsigned int buff_length)
 {
 	gss_buffer_t input_token;
-	unsigned int bytes;
+	unsigned int len;
 
-	if (**buff_in != OCTET_STRING)
+	if (g_get_tag_and_length(buff_in, OCTET_STRING, buff_length, &len) < 0)
 		return (NULL);
 
-	(*buff_in)++;
 	input_token = (gss_buffer_t)malloc(sizeof (gss_buffer_desc));
-
 	if (input_token == NULL)
 		return (NULL);
 
-	input_token->length = gssint_get_der_length(buff_in, buff_length, &bytes);
-	if ((int)input_token->length == -1) {
-		free(input_token);
-		return (NULL);
-	}
+	input_token->length = len;
 	input_token->value = malloc(input_token->length);
 
 	if (input_token->value == NULL) {
@@ -2457,8 +2451,8 @@ get_mech_set(OM_uint32 *minor_status, unsigned char **buff_in,
 {
 	gss_OID_set returned_mechSet;
 	OM_uint32 major_status;
-	OM_uint32 length;
-	OM_uint32 bytes;
+	int length;
+	unsigned int bytes;
 	OM_uint32 set_length;
 	unsigned char		*start;
 	int i;
@@ -2470,23 +2464,26 @@ get_mech_set(OM_uint32 *minor_status, unsigned char **buff_in,
 	(*buff_in)++;
 
 	length = gssint_get_der_length(buff_in, buff_length, &bytes);
+	if (length < 0 || buff_length - bytes < (unsigned int)length)
+		return NULL;
 
 	major_status = gss_create_empty_oid_set(minor_status,
 						&returned_mechSet);
 	if (major_status != GSS_S_COMPLETE)
 		return (NULL);
 
-	for (set_length = 0, i = 0; set_length < length; i++) {
+	for (set_length = 0, i = 0; set_length < (unsigned int)length; i++) {
 		gss_OID_desc *temp = get_mech_oid(minor_status, buff_in,
 			buff_length - (*buff_in - start));
-		if (temp != NULL) {
-		    major_status = gss_add_oid_set_member(minor_status,
-					temp, &returned_mechSet);
-		    if (major_status == GSS_S_COMPLETE) {
+		if (temp == NULL)
+			break;
+
+		major_status = gss_add_oid_set_member(minor_status,
+						      temp, &returned_mechSet);
+		if (major_status == GSS_S_COMPLETE) {
 			set_length += returned_mechSet->elements[i].length +2;
 			if (generic_gss_release_oid(minor_status, &temp))
-			    map_errcode(minor_status);
-		    }
+				map_errcode(minor_status);
 		}
 	}
 
@@ -2665,7 +2662,7 @@ get_negTokenResp(OM_uint32 *minor_status,
 		return GSS_S_DEFECTIVE_TOKEN;
 	if (*ptr++ == SEQUENCE) {
 		tmplen = gssint_get_der_length(&ptr, REMAIN, &bytes);
-		if (tmplen < 0)
+		if (tmplen < 0 || REMAIN < (unsigned int)tmplen)
 			return GSS_S_DEFECTIVE_TOKEN;
 	}
 	if (REMAIN < 1)
@@ -2675,7 +2672,7 @@ get_negTokenResp(OM_uint32 *minor_status,
 
 	if (tag == CONTEXT) {
 		tmplen = gssint_get_der_length(&ptr, REMAIN, &bytes);
-		if (tmplen < 0)
+		if (tmplen < 0 || REMAIN < (unsigned int)tmplen)
 			return GSS_S_DEFECTIVE_TOKEN;
 
 		if (g_get_tag_and_length(&ptr, ENUMERATED,
@@ -2696,7 +2693,7 @@ get_negTokenResp(OM_uint32 *minor_status,
 	}
 	if (tag == (CONTEXT | 0x01)) {
 		tmplen = gssint_get_der_length(&ptr, REMAIN, &bytes);
-		if (tmplen < 0)
+		if (tmplen < 0 || REMAIN < (unsigned int)tmplen)
 			return GSS_S_DEFECTIVE_TOKEN;
 
 		*supportedMech = get_mech_oid(minor_status, &ptr, REMAIN);
@@ -2710,7 +2707,7 @@ get_negTokenResp(OM_uint32 *minor_status,
 	}
 	if (tag == (CONTEXT | 0x02)) {
 		tmplen = gssint_get_der_length(&ptr, REMAIN, &bytes);
-		if (tmplen < 0)
+		if (tmplen < 0 || REMAIN < (unsigned int)tmplen)
 			return GSS_S_DEFECTIVE_TOKEN;
 
 		*responseToken = get_input_token(&ptr, REMAIN);
@@ -2724,7 +2721,7 @@ get_negTokenResp(OM_uint32 *minor_status,
 	}
 	if (tag == (CONTEXT | 0x03)) {
 		tmplen = gssint_get_der_length(&ptr, REMAIN, &bytes);
-		if (tmplen < 0)
+		if (tmplen < 0 || REMAIN < (unsigned int)tmplen)
 			return GSS_S_DEFECTIVE_TOKEN;
 
 		*mechListMIC = get_input_token(&ptr, REMAIN);
@@ -3269,7 +3266,7 @@ g_get_tag_and_length(unsigned char **buf, int tag,
 	unsigned char *ptr = *buf;
 	int ret = -1; /* pessimists, assume failure ! */
 	unsigned int encoded_len;
-	unsigned int tmplen = 0;
+	int tmplen = 0;
 
 	*outlen = 0;
 	if (buflen > 1 && *ptr == tag) {
@@ -3278,7 +3275,7 @@ g_get_tag_and_length(unsigned char **buf, int tag,
 						&encoded_len);
 		if (tmplen < 0) {
 			ret = -1;
-		} else if (tmplen > buflen - (ptr - *buf)) {
+		} else if ((unsigned int)tmplen > buflen - (ptr - *buf)) {
 			ret = -1;
 		} else
 			ret = 0;