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Date: Mon, 31 Jul 2017 21:19:55 +0530
From: Dhiru Kholia <dhiru.kholia@...il.com>
To: oss-security@...ts.openwall.com
Subject: Potential security bugs in "eapmd5pass" software (3 CVE IDs)

Summary
-------

This report describes 4 bugs in the eapmd5pass software package as shipped with
Kali Linux. Bug 1 is a regular functionality related bug. The other 3 bugs are
memory safety bugs that can be triggered remotely.

I found these bugs with the help of libFuzzer.

The worst case security impact of these three memory safety bugs seems to be
limited to a remote denial of service (eapmd5pass crash and loss of intended
functionality) under certain circumstances.

Reproducers are available at https://github.com/kholia/reproducers URL.


Steps to reproduce
------------------

http://www.willhackforsushi.com/?page_id=67

https://tools.kali.org/wireless-attacks/eapmd5pass

Add "-fsanitize=address" to Makefile and build eapmd5pass.

After building eapmd5pass with "make", ensure that ASan is enabled.

$ ldd ./eapmd5pass | grep asan
	libasan.so.3 => /lib64/libasan.so.3 (0x00007fc7e85a5000)


Bug 1
-----

$ ./eapmd5pass -r brad.eaptest.cap -w wordlist
eapmd5pass - Dictionary attack against EAP-MD5
Error placing pcap interface in non-blocking mode.
pcap_setnonblock: No such file or directory

It seems eapmd5pass has a non-security bug which causes it to fail to process
.pcap files. Here is a patch to fix this problem,

diff --git a/eapmd5pass.c b/eapmd5pass.c
index 10b2a48..7ee51bb 100644
--- a/eapmd5pass.c
+++ b/eapmd5pass.c
@@ -684,7 +684,7 @@ int main(int argc, char *argv[])
        }

        /* Set non-blocking */
-       if (pcap_setnonblock(p, PCAP_DONOTBLOCK, errbuf) != 0) {
+       if (!strlen(pcapfile) > 0 && pcap_setnonblock(p, PCAP_DONOTBLOCK, errbuf) != 0) {
                fprintf(stderr, "Error placing pcap interface in non-blocking "
                        "mode.\n");
                perror("pcap_setnonblock");


After applying this patch,

$ ./eapmd5pass -r brad.eaptest.cap -w wordlist
eapmd5pass - Dictionary attack against EAP-MD5
Collected all data necessary to attack password for "brad-foundstone", starting attack.
User password is "bradtest".
1 passwords in 0.00 seconds: 4424.78 passwords/second.


Bug 2
-----

$ ./eapmd5pass -r crash-4c384505c65c675a6a821f2a2f25ea967ec2a8c0 -w wordlist

==22182==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x6310000147ff at pc 0x000000403a7c bp 0x7ffe04164960 sp 0x7ffe04164950
READ of size 1 at 0x6310000147ff thread T0
    #0 0x403a7b in assess_packet /fuzzing/eapmd5pass-orig/eapmd5pass.c:134
    #1 0x7f13f28ec87c in pcap_offline_read (/lib64/libpcap.so.1+0x2187c)
    #2 0x401c4b in main /fuzzing/eapmd5pass-orig/eapmd5pass.c:734
    #3 0x7f13f20c8730 in __libc_start_main (/lib64/libc.so.6+0x20730)
    #4 0x402018 in _start (/fuzzing/eapmd5pass-orig/eapmd5pass+0x402018)

The "offset" variable is -2 and "if (dot11->u1.fc.from_ds == 1 && dot11->u1.fc.to_ds == 1)" line is dereferencing out-of-bounds memory.

Here is a fix for ignoring invalid "offset" values,

diff --git a/eapmd5pass.c b/eapmd5pass.c
index 10b2a48..7a7d900 100644
--- a/eapmd5pass.c
+++ b/eapmd5pass.c
@@ -115,6 +115,9 @@ void assess_packet(char *user, struct pcap_pkthdr *h, u_int8_t *pkt)

        dot11buf = (pkt + offset);

+       if (offset < 0)
+               return;
+
        pcount++; /* Global packet counter */
        if (__verbosity > 2) {
                printf("Checking Frame: %ld....\n",pcount);


Affected Component: Function "assess_packet" in eapmd5pass.c

Affected Product Code Base: eapmd5pass - 1.4

Attack Type: Remote

Impact Denial of Service: true

Attack Vectors: Network: processing crafted network traffic, Local: opening a crafted .pcap file.

The Common Vulnerabilities and Exposures (CVE) project has assigned the ID
CVE-2017-11668 to this issue.

Summary: An out-of-bounds read flaw related to eapmd5pass.c:134 was found in
the way eapmd5pass handled processing of network packets. A remote attacker
could potentially use this flaw to crash the eapmd5pass process under certain
circumstances by generating specially crafted network traffic.


Bug 3
-----

$ ./eapmd5pass -r crash-9a3774d38a5959db160a2564c1487c57f2b336b9 -w wordlist
=================================================================
==22237==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x60200000efe8 at pc 0x000000403e45 bp 0x7ffd6b32b6c0 sp 0x7ffd6b32b6b0
READ of size 1 at 0x60200000efe8 thread T0
    #0 0x403e44 in assess_packet /fuzzing/eapmd5pass-orig/eapmd5pass.c:211
    #1 0x7f9d6c67b87c in pcap_offline_read (/lib64/libpcap.so.1+0x2187c)
    #2 0x401c4b in main /fuzzing/eapmd5pass-orig/eapmd5pass.c:737
    #3 0x7f9d6be57730 in __libc_start_main (/lib64/libc.so.6+0x20730)
    #4 0x402018 in _start (/fuzzing/eapmd5pass-orig/eapmd5pass+0x402018)


This invalid read occurs on "if (dot2hdr->dsap != IEEE8022_SNAP ||
dot2hdr->ssap != IEEE8022_SNAP)" line. The packet length is too small, and it
isn't validated before the packet is consumed.

Here is a patch to fix this problem,

index 10b2a48..b125e53 100644
--- a/eapmd5pass.c
+++ b/eapmd5pass.c
@@ -115,6 +115,13 @@ void assess_packet(char *user, struct pcap_pkthdr *h, u_int8_t *pkt)

        dot11buf = (pkt + offset);

+       /* Check minimum packet length */
+       if (offset + sizeof(struct dot11hdr) > h->caplen)
+               return;
+
        pcount++; /* Global packet counter */
        if (__verbosity > 2) {
                printf("Checking Frame: %ld....\n",pcount);

Affected Component: Function "assess_packet" in eapmd5pass.c

Note: Similar validation checks should be added at other places in this function.

The Common Vulnerabilities and Exposures (CVE) project has assigned the ID
CVE-2017-11669 to this issue. This issue is different from CVE-2017-11668 (Bug
2).

Summary: An out-of-bounds read flaw related to eapmd5pass.c:211 was found in
the way eapmd5pass handled processing of network packets. A remote attacker
could potentially use this flaw to crash the eapmd5pass process under certain
circumstances by generating specially crafted network traffic.


Bug 4
-----

$ ./eapmd5pass -r crash-1717d491a7b9beba422fe919d524ab973fbe7266 -w wordlist
==23135==ERROR: AddressSanitizer: negative-size-param: (size=-1)
    #0 0x7f9185d1b31b  (/lib64/libasan.so.3+0x5f31b)
    #1 0x402a4f in extract_eapusername /fuzzing/eapmd5pass-orig/eapmd5pass.c:459
    #2 0x403f25 in extract_eapusername /fuzzing/eapmd5pass-orig/eapmd5pass.c:441
    #3 0x403f25 in assess_packet /fuzzing/eapmd5pass-orig/eapmd5pass.c:284
    #4 0x7f9185a9987c in pcap_offline_read (/lib64/libpcap.so.1+0x2187c)
    #5 0x401c4b in main /fuzzing/eapmd5pass-orig/eapmd5pass.c:744
    #6 0x7f9185275730 in __libc_start_main (/lib64/libc.so.6+0x20730)
    #7 0x402018 in _start (/fuzzing/eapmd5pass-orig/eapmd5pass+0x402018)


This crash occurs in "memcpy(em->username, (eap+5), usernamelen)" line.
"usernamelen" is negative at this point in the execution flow.  This bug can be
reliably used to crash eapmd5pass (non-ASan and ASan builds) remotely.

Here is a patch to fix this problem,

diff --git a/eapmd5pass.c b/eapmd5pass.c
index 10b2a48..b643d9b 100644
--- a/eapmd5pass.c
@@ -444,6 +454,9 @@ int extract_eapusername(uint8_t *eap, int len, struct eapmd5pass_data *em)
        /* 5 bytes for EAP header information without identity information */
        usernamelen = (eaplen - 5);

+       if (usernamelen < 0)
+               return 1;
+
        usernamelen = (eaplen > sizeof(em->username))
                        ? sizeof(em->username) : usernamelen;
        memcpy(em->username, (eap+5), usernamelen);


Affected Component: Function "extract_eapusername" in eapmd5pass.c

The Common Vulnerabilities and Exposures (CVE) project has assigned the ID
CVE-2017-11670 to this issue.

Summary: An out-of-bounds read and write flaw was found in the way eapmd5pass
handled network traffic. A remote attacker could potentially use this flaw to
crash the eapmd5pass process by generating specially crafted network traffic.

-- 
Dhiru

View attachment "combined-fixes.diff" of type "text/plain" (2369 bytes)

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