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c-ares/docs/ares_process.3

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Avoid buffer overflow in RC4 loop comparison (#336) The rc4 function iterates over a buffer of size buffer_len who's maximum value is INT_MAX with a counter of type short that is not guaranteed to have maximum size INT_MAX. In circumstances where short is narrower than int and where buffer_len is larger than the maximum value of a short, it may be possible to loop infinitely as counter will overflow and never be greater than or equal to buffer_len. The solution is to make the comparison be between types of equal width. This commit defines counter as an int. Fix By: Fionn Fitzmaurice (@fionn)
4 years ago
.\"
.\" Copyright 1998 by the Massachusetts Institute of Technology.
.\"
.\" Permission to use, copy, modify, and distribute this
.\" software and its documentation for any purpose and without
.\" fee is hereby granted, provided that the above copyright
.\" notice appear in all copies and that both that copyright
.\" notice and this permission notice appear in supporting
.\" documentation, and that the name of M.I.T. not be used in
.\" advertising or publicity pertaining to distribution of the
.\" software without specific, written prior permission.
.\" M.I.T. makes no representations about the suitability of
.\" this software for any purpose. It is provided "as is"
.\" without express or implied warranty.
.\"
provide SPDX identifiers and a REUSE CI job to verify All files have their licence and copyright information clearly identifiable. If not in the file header, they are set separately in .reuse/dep5. All used license texts are provided in LICENSES/
2 years ago
.\" SPDX-License-Identifier: MIT
.\"
Avoid buffer overflow in RC4 loop comparison (#336) The rc4 function iterates over a buffer of size buffer_len who's maximum value is INT_MAX with a counter of type short that is not guaranteed to have maximum size INT_MAX. In circumstances where short is narrower than int and where buffer_len is larger than the maximum value of a short, it may be possible to loop infinitely as counter will overflow and never be greater than or equal to buffer_len. The solution is to make the comparison be between types of equal width. This commit defines counter as an int. Fix By: Fionn Fitzmaurice (@fionn)
4 years ago
.TH ARES_PROCESS 3 "25 July 1998"
.SH NAME
ares_process \- Process events for name resolution
.SH SYNOPSIS
.nf
#include <ares.h>
`ares_channel` -> `ares_channel_t *`: don't bury the pointer (#595) `ares_channel` is defined as `typedef struct ares_channeldata *ares_channel;`. The problem with this, is it embeds the pointer into the typedef, which means an `ares_channel` can never be declared as `const` as if you write `const ares_channel channel`, that expands to `struct ares_channeldata * const ares_channel` and not `const struct ares_channeldata *channel`. We will now typedef `ares_channel_t` as `typedef struct ares_channeldata ares_channel_t;`, so if you write `const ares_channel_t *channel`, it properly expands to `const struct ares_channeldata *channel`. We are maintaining the old typedef for API compatibility with existing integrations, and due to typedef expansion this should not even cause any compiler warnings for existing code. There are no ABI implications with this change. I could be convinced to keep existing public functions as `ares_channel` if a sufficient argument exists, but internally we really need make this change for modern best practices. This change will allow us to internally use `const ares_channel_t *` where appropriate. Whether or not we decide to change any public interfaces to use `const` may require further discussion on if there might be ABI implications (I don't think so, but I'm also not 100% sure what a compiler internally does with `const` when emitting machine code ... I think more likely ABI implications would occur going the opposite direction). FYI, This PR was done via a combination of sed and clang-format, the only manual code change was the addition of the new typedef, and a couple doc fixes :) Fix By: Brad House (@bradh352)
1 year ago
void ares_process(ares_channel_t *\fIchannel\fP,
Avoid buffer overflow in RC4 loop comparison (#336) The rc4 function iterates over a buffer of size buffer_len who's maximum value is INT_MAX with a counter of type short that is not guaranteed to have maximum size INT_MAX. In circumstances where short is narrower than int and where buffer_len is larger than the maximum value of a short, it may be possible to loop infinitely as counter will overflow and never be greater than or equal to buffer_len. The solution is to make the comparison be between types of equal width. This commit defines counter as an int. Fix By: Fionn Fitzmaurice (@fionn)
4 years ago
fd_set *\fIread_fds\fP,
fd_set *\fIwrite_fds\fP)
`ares_channel` -> `ares_channel_t *`: don't bury the pointer (#595) `ares_channel` is defined as `typedef struct ares_channeldata *ares_channel;`. The problem with this, is it embeds the pointer into the typedef, which means an `ares_channel` can never be declared as `const` as if you write `const ares_channel channel`, that expands to `struct ares_channeldata * const ares_channel` and not `const struct ares_channeldata *channel`. We will now typedef `ares_channel_t` as `typedef struct ares_channeldata ares_channel_t;`, so if you write `const ares_channel_t *channel`, it properly expands to `const struct ares_channeldata *channel`. We are maintaining the old typedef for API compatibility with existing integrations, and due to typedef expansion this should not even cause any compiler warnings for existing code. There are no ABI implications with this change. I could be convinced to keep existing public functions as `ares_channel` if a sufficient argument exists, but internally we really need make this change for modern best practices. This change will allow us to internally use `const ares_channel_t *` where appropriate. Whether or not we decide to change any public interfaces to use `const` may require further discussion on if there might be ABI implications (I don't think so, but I'm also not 100% sure what a compiler internally does with `const` when emitting machine code ... I think more likely ABI implications would occur going the opposite direction). FYI, This PR was done via a combination of sed and clang-format, the only manual code change was the addition of the new typedef, and a couple doc fixes :) Fix By: Brad House (@bradh352)
1 year ago
void ares_process_fd(ares_channel_t *\fIchannel\fP,
Avoid buffer overflow in RC4 loop comparison (#336) The rc4 function iterates over a buffer of size buffer_len who's maximum value is INT_MAX with a counter of type short that is not guaranteed to have maximum size INT_MAX. In circumstances where short is narrower than int and where buffer_len is larger than the maximum value of a short, it may be possible to loop infinitely as counter will overflow and never be greater than or equal to buffer_len. The solution is to make the comparison be between types of equal width. This commit defines counter as an int. Fix By: Fionn Fitzmaurice (@fionn)
4 years ago
ares_socket_t \fIread_fd\fP,
ares_socket_t \fIwrite_fd\fP)
.fi
.SH DESCRIPTION
The \fBares_process(3)\fP function handles input/output events and timeouts
associated with queries pending on the name service channel identified by
.IR channel .
The file descriptor sets pointed to by \fIread_fds\fP and \fIwrite_fds\fP
should have file descriptors set in them according to whether the file
descriptors specified by \fIares_fds(3)\fP are ready for reading and writing.
(The easiest way to determine this information is to invoke \fBselect(3)\fP
with a timeout no greater than the timeout given by \fIares_timeout(3)\fP).
The \fBares_process(3)\fP function will invoke callbacks for pending queries
if they complete successfully or fail.
\fBares_process_fd(3)\fP works the same way but acts and operates only on the
specific file descriptors (sockets) you pass in to the function. Use
ARES_SOCKET_BAD for "no action". This function is provided to allow users of
Fix typo in docs for ares_process_fd (#490) A single letter was missing Fix By: Brad Spencer (@b-spencer)
2 years ago
c-ares to avoid \fIselect(3)\fP in their applications and within c-ares.
Avoid buffer overflow in RC4 loop comparison (#336) The rc4 function iterates over a buffer of size buffer_len who's maximum value is INT_MAX with a counter of type short that is not guaranteed to have maximum size INT_MAX. In circumstances where short is narrower than int and where buffer_len is larger than the maximum value of a short, it may be possible to loop infinitely as counter will overflow and never be greater than or equal to buffer_len. The solution is to make the comparison be between types of equal width. This commit defines counter as an int. Fix By: Fionn Fitzmaurice (@fionn)
4 years ago
To only process possible timeout conditions without a socket event occurring,
one may pass NULL as the values for both \fIread_fds\fP and \fIwrite_fds\fP for
\fBares_process(3)\fP, or ARES_SOCKET_BAD for both \fIread_fd\fP and
\fIwrite_fd\fP for \fBares_process_fd(3)\fP.
.SH EXAMPLE
The following code fragment waits for all pending queries on a channel
to complete:
.nf
int nfds, count;
fd_set readers, writers;
struct timeval tv, *tvp;
while (1) {
FD_ZERO(&readers);
FD_ZERO(&writers);
nfds = ares_fds(channel, &readers, &writers);
if (nfds == 0)
break;
tvp = ares_timeout(channel, NULL, &tv);
count = select(nfds, &readers, &writers, NULL, tvp);
ares_process(channel, &readers, &writers);
}
.fi
.SH SEE ALSO
.BR ares_fds (3),
.BR ares_timeout (3)
.SH AUTHOR
Greg Hudson, MIT Information Systems
.br
Copyright 1998 by the Massachusetts Institute of Technology.