[Nagiosplug-devel] [Nagiosplug-help] check_smtp doesn't read whole lines
Holger Weiss
holger at CIS.FU-Berlin.DE
Fri Aug 3 20:47:40 CEST 2007
[ Please follow up to <nagiosplug-devel at lists.sourceforge.net> and Chris. ]
* Chris Adams <cmadams at hiwaay.net> [2007-08-01 19:59]:
> For some unknown network reason, I'm getting the SMTP banner line split
> into multiple packets between a certain client/server combination. This
> breaks trying to do anything beyond a simple "look for the banner" check
> with check_smtp, because it isn't reading correctly. It reads a packet
> and treats it as a single response, instead of reading whole lines.
Yes, that's clearly a check_smtp bug. (Unfortunately, other plugins
suffer from that problem, too.) I had fixing this on my mental TODO
list for a while but didn't get around to it so far. I've attached a
quick`n'dirty patch against check_smtp.c from the 1.4.9 release which
should fix your problem. Hopefully, someone else or myself will get
around to implementing a proper fix before the next release, otherwise
I'll probably commit this patch for the moment.
> The HELO/EHLO response handling is also broken in that it reads only a
> packet instead of properly handling multi-line SMTP responses.
This should be fixed by the patch, too.
Thanks, Holger
--
PGP fingerprint: F1F0 9071 8084 A426 DD59 9839 59D3 F3A1 B8B5 D3DE
-------------- next part --------------
Index: check_smtp.c
===================================================================
--- check_smtp.c (revision 1769)
+++ check_smtp.c (working copy)
@@ -40,6 +40,8 @@
const char *copyright = "2000-2006";
const char *email = "nagiosplug-devel at lists.sourceforge.net";
+#include <ctype.h>
+
#include "common.h"
#include "netutils.h"
#include "utils.h"
@@ -74,6 +76,8 @@
int validate_arguments (void);
void print_help (void);
void print_usage (void);
+int recvline(char *, size_t);
+int recvlines(char *, size_t);
int my_close(void);
#include "regex.h"
@@ -115,7 +119,6 @@
enum {
TCP_PROTOCOL = 1,
UDP_PROTOCOL = 2,
- MAXBUF = 1024
};
/* written by lauri alanko */
@@ -221,7 +224,7 @@
/* watch for the SMTP connection string and */
/* return a WARNING status if we couldn't read any data */
- if (recv (sd, buffer, MAX_INPUT_BUFFER - 1, 0) == -1) {
+ if (recvlines(buffer, MAX_INPUT_BUFFER) <= 0) {
printf (_("recv() failed\n"));
result = STATE_WARNING;
}
@@ -245,11 +248,10 @@
send(sd, helocmd, strlen(helocmd), 0);
/* allow for response to helo command to reach us */
- if(read (sd, buffer, MAXBUF - 1) < 0){
+ if (recvlines(buffer, MAX_INPUT_BUFFER) <= 0) {
printf (_("recv() failed\n"));
return STATE_WARNING;
} else if(use_ehlo){
- buffer[MAXBUF-1]='\0';
if(strstr(buffer, "250 STARTTLS") != NULL ||
strstr(buffer, "250-STARTTLS") != NULL){
supports_tls=TRUE;
@@ -267,7 +269,7 @@
/* send the STARTTLS command */
send(sd, SMTP_STARTTLS, strlen(SMTP_STARTTLS), 0);
- recv(sd,buffer, MAX_INPUT_BUFFER-1, 0); /* wait for it */
+ recvlines(buffer, MAX_INPUT_BUFFER); /* wait for it */
if (!strstr (buffer, server_expect)) {
printf (_("Server does not support STARTTLS\n"));
send (sd, SMTP_QUIT, strlen (SMTP_QUIT), 0);
@@ -301,13 +303,12 @@
}
if (verbose)
printf(_("sent %s"), helocmd);
- if ((n = my_recv(buffer, MAX_INPUT_BUFFER - 1)) <= 0) {
+ if ((n = recvlines(buffer, MAX_INPUT_BUFFER)) <= 0) {
printf("%s\n", _("SMTP UNKNOWN - Cannot read EHLO response via TLS."));
my_close();
return STATE_UNKNOWN;
}
if (verbose) {
- buffer[n] = '\0';
printf("%s", buffer);
}
@@ -336,16 +337,14 @@
*/
if (smtp_use_dummycmd) {
my_send(cmd_str, strlen(cmd_str));
- my_recv(buffer, MAX_INPUT_BUFFER-1);
- if (verbose)
+ if (recvlines(buffer, MAX_INPUT_BUFFER) >= 1 && verbose)
printf("%s", buffer);
}
while (n < ncommands) {
asprintf (&cmd_str, "%s%s", commands[n], "\r\n");
my_send(cmd_str, strlen(cmd_str));
- my_recv(buffer, MAX_INPUT_BUFFER-1);
- if (verbose)
+ if (recvlines(buffer, MAX_INPUT_BUFFER) >= 1 && verbose)
printf("%s", buffer);
strip (buffer);
if (n < nresponses) {
@@ -394,12 +393,11 @@
if (verbose)
printf (_("sent %s\n"), "AUTH LOGIN");
- if((ret = my_recv(buffer, MAXBUF - 1)) < 0){
+ if ((ret = recvlines(buffer, MAX_INPUT_BUFFER)) <= 0) {
asprintf(&error_msg, _("recv() failed after AUTH LOGIN, "));
result = STATE_WARNING;
break;
}
- buffer[ret] = 0;
if (verbose)
printf (_("received %s\n"), buffer);
@@ -416,12 +414,11 @@
if (verbose)
printf (_("sent %s\n"), abuf);
- if ((ret = my_recv(buffer, MAX_INPUT_BUFFER-1)) == -1) {
+ if ((ret = recvlines(buffer, MAX_INPUT_BUFFER)) <= 0) {
result = STATE_CRITICAL;
asprintf(&error_msg, _("recv() failed after sending authuser, "));
break;
}
- buffer[ret] = 0;
if (verbose) {
printf (_("received %s\n"), buffer);
}
@@ -437,12 +434,11 @@
if (verbose) {
printf (_("sent %s\n"), abuf);
}
- if ((ret = my_recv(buffer, MAX_INPUT_BUFFER-1)) == -1) {
+ if ((ret = recvlines(buffer, MAX_INPUT_BUFFER)) <= 0) {
result = STATE_CRITICAL;
asprintf(&error_msg, _("recv() failed after sending authpass, "));
break;
}
- buffer[ret] = 0;
if (verbose) {
printf (_("received %s\n"), buffer);
}
@@ -700,6 +696,65 @@
}
+/*
+ * Receive one line, copy it into buf and nul-terminate it. Returns the
+ * number of bytes written to buf (including the '\0') or 0 on EOF or <0 on
+ * error.
+ *
+ * TODO: Reading one byte at a time is very inefficient. Replace this by a
+ * function which buffers the data, move that to netutils.c and change
+ * check_smtp and other plugins to use that. Also, remove (\r)\n.
+ */
+int
+recvline(char *buf, size_t bufsize)
+{
+ int result;
+ unsigned i;
+
+ for (i = result = 0; i < bufsize - 1; i++) {
+ if ((result = my_recv(&buf[i], 1)) != 1)
+ break;
+ if (buf[i] == '\n') {
+ buf[++i] = '\0';
+ return i;
+ }
+ }
+ return (result == 1 || i == 0) ? -2 : result; /* -2 if out of space */
+}
+
+
+/*
+ * Receive one or more lines, copy them into buf and nul-terminate it. Returns
+ * the number of bytes written to buf (including the '\0') or 0 on EOF or <0 on
+ * error. Works for all protocols which format multiline replies as follows:
+ *
+ * ``The format for multiline replies requires that every line, except the last,
+ * begin with the reply code, followed immediately by a hyphen, `-' (also known
+ * as minus), followed by text. The last line will begin with the reply code,
+ * followed immediately by <SP>, optionally some text, and <CRLF>. As noted
+ * above, servers SHOULD send the <SP> if subsequent text is not sent, but
+ * clients MUST be prepared for it to be omitted.'' (RFC 2821, 4.2.1)
+ *
+ * TODO: Move this to netutils.c. Also, remove \r and possibly the final \n.
+ */
+int
+recvlines(char *buf, size_t bufsize)
+{
+ int result;
+ unsigned i;
+
+ for (i = 0; /* forever */; i += result - 1)
+ if (!((result = recvline(buf + i, bufsize - i)) > 3 &&
+ isdigit(buf[i]) &&
+ isdigit(buf[i + 1]) &&
+ isdigit(buf[i + 2]) &&
+ buf[i + 3] == '-'))
+ break;
+
+ return (result <= 0) ? result : result + (int)i;
+}
+
+
int
my_close (void)
{
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