I *always* forget svn add :(

1 files changed, 205 insertions, 0 deletions

diff --git a/networking/udhcp/domain_codec.c b/networking/udhcp/domain_codec.c
new file mode 100644
index 000000000..6e16ddedc
--- /dev/null
+++ b/networking/udhcp/domain_codec.c
@@ -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@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 */