+/* ----------------------------------------------------------------------
+ * Utility functions to compute SSH-2 fingerprints in a uniform way.
+ */
+char *ssh2_fingerprint_blob(const void *blob, int bloblen)
+{
+ unsigned char digest[16];
+ char fingerprint_str[16*3];
+ const char *algstr;
+ int alglen;
+ const struct ssh_signkey *alg;
+ int i;
+
+ /*
+ * The fingerprint hash itself is always just the MD5 of the blob.
+ */
+ MD5Simple(blob, bloblen, digest);
+ for (i = 0; i < 16; i++)
+ sprintf(fingerprint_str + i*3, "%02x%s", digest[i], i==15 ? "" : ":");
+
+ /*
+ * Identify the key algorithm, if possible.
+ */
+ alglen = toint(GET_32BIT((const unsigned char *)blob));
+ if (alglen > 0 && alglen < bloblen-4) {
+ algstr = (const char *)blob + 4;
+
+ /*
+ * If we can actually identify the algorithm as one we know
+ * about, get hold of the key's bit count too.
+ */
+ alg = find_pubkey_alg_len(alglen, algstr);
+ if (alg) {
+ int bits = alg->pubkey_bits(alg, blob, bloblen);
+ return dupprintf("%.*s %d %s", alglen, algstr,
+ bits, fingerprint_str);
+ } else {
+ return dupprintf("%.*s %s", alglen, algstr, fingerprint_str);
+ }
+ } else {
+ /*
+ * No algorithm available (which means a seriously confused
+ * key blob, but there we go). Return only the hash.
+ */
+ return dupstr(fingerprint_str);
+ }
+}
+
+char *ssh2_fingerprint(const struct ssh_signkey *alg, void *data)
+{
+ int len;
+ unsigned char *blob = alg->public_blob(data, &len);
+ char *ret = ssh2_fingerprint_blob(blob, len);
+ sfree(blob);
+ return ret;
+}
+