svn commit: trunk/busybox/networking/udhcp
vda at busybox.net
vda at busybox.net
Tue Feb 27 22:39:19 UTC 2007
Author: vda
Date: 2007-02-27 14:39:19 -0800 (Tue, 27 Feb 2007)
New Revision: 17982
Log:
I *always* forget svn add :(
Added:
trunk/busybox/networking/udhcp/domain_codec.c
Changeset:
Added: trunk/busybox/networking/udhcp/domain_codec.c
===================================================================
--- trunk/busybox/networking/udhcp/domain_codec.c (rev 0)
+++ trunk/busybox/networking/udhcp/domain_codec.c 2007-02-27 22:39:19 UTC (rev 17982)
@@ -0,0 +1,205 @@
+/* vi: set sw=4 ts=4: */
+
+/* RFC1035 domain compression routines (C) 2007 Gabriel Somlo <somlo at cmu.edu>
+ *
+ * Loosely based on the isc-dhcpd implementation by dhankins at isc.org
+ *
+ * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
+ */
+
+#if ENABLE_FEATURE_RFC3397
+
+#include "common.h"
+#include "options.h"
+
+#define NS_MAXDNAME 1025 /* max domain name length */
+#define NS_MAXCDNAME 255 /* max compressed domain name length */
+#define NS_MAXLABEL 63 /* max label length */
+#define NS_MAXDNSRCH 6 /* max domains in search path */
+#define NS_CMPRSFLGS 0xc0 /* name compression pointer flag */
+
+
+/* expand a RFC1035-compressed list of domain names "cstr", of length "clen";
+ * returns a newly allocated string containing the space-separated domains,
+ * prefixed with the contents of string pre, or NULL if an error occurs.
+ */
+char *dname_dec(const uint8_t *cstr, int clen, const char *pre)
+{
+ const uint8_t *c;
+ int crtpos, retpos, depth, plen = 0, len = 0;
+ char *dst = NULL;
+
+ if (!cstr)
+ return NULL;
+
+ if (pre)
+ plen = strlen(pre);
+
+ /* We make two passes over the cstr string. First, we compute
+ * how long the resulting string would be. Then we allocate a
+ * new buffer of the required length, and fill it in with the
+ * expanded content. The advantage of this approach is not
+ * having to deal with requiring callers to supply their own
+ * buffer, then having to check if it's sufficiently large, etc.
+ */
+
+ while (!dst) {
+
+ if (len > 0) { /* second pass? allocate dst buffer and copy pre */
+ dst = xmalloc(len + plen);
+ memcpy(dst, pre, plen);
+ }
+
+ crtpos = retpos = depth = len = 0;
+
+ while (crtpos < clen) {
+ c = cstr + crtpos;
+
+ if ((*c & NS_CMPRSFLGS) != 0) { /* pointer */
+ if (crtpos + 2 > clen) /* no offset to jump to? abort */
+ return NULL;
+ if (retpos == 0) /* toplevel? save return spot */
+ retpos = crtpos + 2;
+ depth++;
+ crtpos = ((*c & 0x3f) << 8) | (*(c + 1) & 0xff); /* jump */
+ } else if (*c) { /* label */
+ if (crtpos + *c + 1 > clen) /* label too long? abort */
+ return NULL;
+ if (dst)
+ memcpy(dst + plen + len, c + 1, *c);
+ len += *c + 1;
+ crtpos += *c + 1;
+ if (dst)
+ *(dst + plen + len - 1) = '.';
+ } else { /* null: end of current domain name */
+ if (retpos == 0) { /* toplevel? keep going */
+ crtpos++;
+ } else { /* return to toplevel saved spot */
+ crtpos = retpos;
+ retpos = depth = 0;
+ }
+ if (dst)
+ *(dst + plen + len - 1) = ' ';
+ }
+
+ if (depth > NS_MAXDNSRCH || /* too many jumps? abort, it's a loop */
+ len > NS_MAXDNAME * NS_MAXDNSRCH) /* result too long? abort */
+ return NULL;
+ }
+
+ if (!len) /* expanded string has 0 length? abort */
+ return NULL;
+
+ if (dst)
+ *(dst + plen + len - 1) = '\0';
+ }
+
+ return dst;
+}
+
+/* Convert a domain name (src) from human-readable "foo.blah.com" format into
+ * RFC1035 encoding "\003foo\004blah\003com\000". Return allocated string, or
+ * NULL if an error occurs.
+ */
+static uint8_t *convert_dname(const char *src)
+{
+ uint8_t c, *res, *lp, *rp;
+ int len;
+
+ res = xmalloc(strlen(src) + 2);
+ rp = lp = res;
+ rp++;
+
+ for (;;) {
+ c = (uint8_t)*src++;
+ if (c == '.' || c == '\0') { /* end of label */
+ len = rp - lp - 1;
+ /* label too long, too short, or two '.'s in a row? abort */
+ if (len > NS_MAXLABEL || len == 0 || (c == '.' && *src == '.')) {
+ free(res);
+ return NULL;
+ }
+ *lp = len;
+ lp = rp++;
+ if (c == '\0' || *src == '\0') /* end of dname */
+ break;
+ } else {
+ if (c >= 0x41 && c <= 0x5A) /* uppercase? convert to lower */
+ c += 0x20;
+ *rp++ = c;
+ }
+ }
+
+ *lp = 0;
+ if (rp - res > NS_MAXCDNAME) { /* dname too long? abort */
+ free(res);
+ return NULL;
+ }
+ return res;
+}
+
+/* returns the offset within cstr at which dname can be found, or -1
+ */
+static int find_offset(const uint8_t *cstr, int clen, const uint8_t *dname)
+{
+ const uint8_t *c, *d;
+ int off, inc;
+
+ /* find all labels in cstr */
+ off = 0;
+ while (off < clen) {
+ c = cstr + off;
+
+ if ((*c & NS_CMPRSFLGS) != 0) { /* pointer, skip */
+ off += 2;
+ } else if (*c) { /* label, try matching dname */
+ inc = *c + 1;
+ d = dname;
+ while (*c == *d && memcmp(c + 1, d + 1, *c) == 0) {
+ if (*c == 0) /* match, return offset */
+ return off;
+ d += *c + 1;
+ c += *c + 1;
+ if ((*c & NS_CMPRSFLGS) != 0) /* pointer, jump */
+ c = cstr + (((*c & 0x3f) << 8) | (*(c + 1) & 0xff));
+ }
+ off += inc;
+ } else { /* null, skip */
+ off++;
+ }
+ }
+
+ return -1;
+}
+
+/* computes string to be appended to cstr so that src would be added to
+ * the compression (best case, it's a 2-byte pointer to some offset within
+ * cstr; worst case, it's all of src, converted to rfc3011 format).
+ * The computed string is returned directly; its length is returned via retlen;
+ * NULL and 0, respectively, are returned if an error occurs.
+ */
+uint8_t *dname_enc(const uint8_t *cstr, int clen, const char *src, int *retlen)
+{
+ uint8_t *d, *dname;
+ int off;
+
+ dname = convert_dname(src);
+ if (dname == NULL) {
+ *retlen = 0;
+ return NULL;
+ }
+
+ for (d = dname; *d != 0; d += *d + 1) {
+ off = find_offset(cstr, clen, d);
+ if (off >= 0) { /* found a match, add pointer and terminate string */
+ *d++ = NS_CMPRSFLGS;
+ *d = off;
+ break;
+ }
+ }
+
+ *retlen = d - dname + 1;
+ return dname;
+}
+
+#endif /* ENABLE_FEATURE_RFC3397 */
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