Support optional server certificate name checking. Bug 1479

[exim.git] / src / src / tls.c

diff --git a/src/src/tls.c b/src/src/tls.c
index 972785284b05c923c6b9d3ea6191a8cefd9f4b0c..b5ef965951ff3634471f7777438ebf2052877481 100644 (file)
--- a/src/src/tls.c
+++ b/src/src/tls.c
@@ -17,6 +17,7 @@ functions from the OpenSSL or GNU TLS libraries. */
 
 
 #include "exim.h"
+#include "transports/smtp.h"
 
 /* This module is compiled only when it is specifically requested in the
 build-time configuration. However, some compilers don't like compiling empty
@@ -85,6 +86,7 @@ return TRUE;
 
 #ifdef USE_GNUTLS
 #include "tls-gnu.c"
+#include "tlscert-gnu.c"
 
 #define ssl_xfer_buffer (state_server.xfer_buffer)
 #define ssl_xfer_buffer_lwm (state_server.xfer_buffer_lwm)
@@ -94,6 +96,7 @@ return TRUE;
 
 #else
 #include "tls-openssl.c"
+#include "tlscert-openssl.c"
 #endif
 
 
@@ -193,4 +196,140 @@ modify_variable(US"tls_sni",                  &dest_tsp->sni);
 #endif
 }
 
+/************************************************
+*      TLS certificate name operations         *
+************************************************/
+
+/* Convert an rfc4514 DN to an exim comma-sep list.
+Backslashed commas need to be replaced by doublecomma
+for Exim's list quoting.  We modify the given string
+inplace.
+*/
+
+static void
+dn_to_list(uschar * dn)
+{
+uschar * cp;
+for (cp = dn; *cp; cp++)
+  if (cp[0] == '\\' && cp[1] == ',')
+    *cp++ = ',';
+}
+
+
+/* Extract fields of a given type from an RFC4514-
+format Distinguished Name.  Return an Exim list.
+NOTE: We modify the supplied dn string during operation.
+
+Arguments:
+       dn      Distinguished Name string
+       mod     string containing optional list-sep and
+               field selector match, comma-separated
+Return:
+       allocated string with list of matching fields,
+       field type stripped
+*/
+
+uschar *
+tls_field_from_dn(uschar * dn, uschar * mod)
+{
+int insep = ',';
+uschar outsep = '\n';
+uschar * ele;
+uschar * match = NULL;
+int len;
+uschar * list = NULL;
+
+while (ele = string_nextinlist(&mod, &insep, NULL, 0))
+  if (ele[0] != '>')
+    match = ele;       /* field tag to match */
+  else if (ele[1])
+    outsep = ele[1];   /* nondefault separator */
+
+dn_to_list(dn);
+insep = ',';
+len = Ustrlen(match);
+while (ele = string_nextinlist(&dn, &insep, NULL, 0))
+  if (Ustrncmp(ele, match, len) == 0 && ele[len] == '=')
+    list = string_append_listele(list, outsep, ele+len+1);
+return list;
+}
+
+
+#ifdef EXPERIMENTAL_CERTNAMES
+/* Compare a domain name with a possibly-wildcarded name. Wildcards
+are restricted to a single one, as the first element of patterns
+having at least three dot-separated elements.  Case-independent.
+Return TRUE for a match
+*/
+static BOOL
+is_name_match(const uschar * name, const uschar * pat)
+{
+uschar * cp;
+return *pat == '*'             /* possible wildcard match */
+  ?    *++pat == '.'           /* starts star, dot              */
+    && !Ustrchr(++pat, '*')    /* has no more stars             */
+    && Ustrchr(pat, '.')       /* and has another dot.          */
+    && (cp = Ustrchr(name, '.'))/* The name has at least one dot */
+    && strcmpic(++cp, pat) == 0 /* and we only compare after it. */
+  :    !Ustrchr(pat+1, '*')
+    && strcmpic(name, pat) == 0;
+}
+
+/* Compare a list of names with the dnsname elements
+of the Subject Alternate Name, if any, and the
+Subject otherwise.
+
+Arguments:
+       namelist names to compare
+       cert     certificate
+
+Returns:
+       TRUE/FALSE
+*/
+
+BOOL
+tls_is_name_for_cert(uschar * namelist, void * cert)
+{
+uschar * altnames = tls_cert_subject_altname(cert, US"dns");
+uschar * subjdn;
+uschar * certname;
+int cmp_sep = 0;
+uschar * cmpname;
+
+if ((altnames = tls_cert_subject_altname(cert, US"dns")))
+  {
+  int alt_sep = '\n';
+  while (cmpname = string_nextinlist(&namelist, &cmp_sep, NULL, 0))
+    {
+    uschar * an = altnames;
+    while (certname = string_nextinlist(&an, &alt_sep, NULL, 0))
+      if (is_name_match(cmpname, certname))
+       return TRUE;
+    }
+  }
+
+else if ((subjdn = tls_cert_subject(cert, NULL)))
+  {
+  int sn_sep = ',';
+  uschar * sn;
+
+  dn_to_list(subjdn);
+  while (cmpname = string_nextinlist(&namelist, &cmp_sep, NULL, 0))
+    {
+    uschar * sn = subjdn;
+    while (certname = string_nextinlist(&sn, &sn_sep, NULL, 0))
+      if (  *certname++ == 'C'
+        && *certname++ == 'N'
+        && *certname++ == '='
+        && is_name_match(cmpname, certname)
+        )
+       return TRUE;
+    }
+  }
+return FALSE;
+}
+#endif
+
+/* vi: aw ai sw=2
+*/
 /* End of tls.c */