Fix a bug in NULL pointer bug when reading UDP channels #207
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
The udp_client_read function was not checking for a NULL pointer being returned by network_client_read_msg, causing a segmentation fault. After returning -1 from this function on error, it was also necessary to update channel_set_interactive to use the proper ssize_t type for the buf_len variable.
zeroSteiner
commented
Jan 28, 2021
Comment on lines
351
to
+355
| void *msg_buf = network_client_read_msg(ucc->nc, &msg_len); | ||
| if (msg_buf == NULL) { | ||
| errno = EIO; | ||
| return -1; | ||
| } |
There was a problem hiding this comment.
This was the core bug right here. Then we return -1 and check it appropriately in channel_set_interactive.
|
Confirmed fixed. Thanks! |
2 tasks
This pull request was closed.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
This fixes a segmentation fault where if in
udp_client_read,network_client_read_msgreturnsNULLit was not being checked before being passed tomemcpy. This lead to the Meterpreter session crashing.After fixing this issue, I noticed that
channel_set_interactivewas incorrectly using an unsigned value forbuf_lencausing it to not properly handle error statuses of-1. I updated that so it will only forward data tosend_write_requestwhen the value is a positive integer.You can reproduce this using the
enum_dnsmodule.Testing Steps
route add 0.0.0.0 -1auxiliary/gather/enum_dnsmodule, set the DOMAIN todigi.ninja(domain taken from auxiliary/gather/enum_dns - Auxiliary failed: NoMethodError undefined method `port' for #<Dnsruby::RR::IN::CNAME:0x000055891929efa8> metasploit-framework#13952)Example Output
Up to this point used the unpatched version. Between these two lines, I compiled my changes from this PR and re-ran the mettle binary.