common: New function cmp_canon_sexp.

* common/sexputil.c (cmp_canon_sexp): New.
(cmp_canon_sexp_def_tcmp): New.
* common/t-sexputil.c (test_cmp_canon_sexp): Add a simple test.
--

To be used to fix
GnuPG-bug-id: 5061

Signed-off-by: Werner Koch <wk@gnupg.org>

common/sexputil.c

@@ -263,6 +263,96 @@ cmp_simple_canon_sexp (const unsigned char *a_orig,
 }
 
 
+
+/* Helper for cmp_canon_sexp.  */
+static int
+cmp_canon_sexp_def_tcmp (void *ctx, int depth,
+                         const unsigned char *aval, size_t alen,
+                         const unsigned char *bval, size_t blen)
+{
+  (void)ctx;
+  (void)depth;
+
+  if (alen > blen)
+    return 1;
+  else if (alen < blen)
+    return -1;
+  else
+    return memcmp (aval, bval, alen);
+}
+
+
+/* Compare the two canonical encoded s-expressions A with maximum
+ * length ALEN and B with maximum length BLEN.
+ *
+ * Returns 0 if they match.
+ *
+ * If TCMP is NULL, this is not different really different from a
+ * memcmp but does not consider any garbage after the last closing
+ * parentheses.
+ *
+ * If TCMP is not NULL, it is expected to be a function to compare the
+ * values of each token.  TCMP is called for each token while parsing
+ * the s-expressions until TCMP return a non-zero value.  Here the CTX
+ * receives the provided value TCMPCTX, DEPTH is the number of
+ * currently open parentheses and (AVAL,ALEN) and (BVAL,BLEN) the
+ * values of the current token.  TCMP needs to return zero to indicate
+ * that the tokens match.  */
+int
+cmp_canon_sexp (const unsigned char *a, size_t alen,
+                const unsigned char *b, size_t blen,
+                int (*tcmp)(void *ctx, int depth,
+                            const unsigned char *aval, size_t avallen,
+                            const unsigned char *bval, size_t bvallen),
+                void *tcmpctx)
+{
+  const unsigned char *a_buf, *a_tok;
+  const unsigned char *b_buf, *b_tok;
+  size_t a_buflen, a_toklen;
+  size_t b_buflen, b_toklen;
+  int a_depth, b_depth, ret;
+
+  if ((!a && !b) || (!alen && !blen))
+    return 0; /* Both are NULL, they are identical. */
+  if (!a || !b)
+    return !!a - !!b; /* One is NULL, they are not identical. */
+  if (*a != '(' || *b != '(')
+    log_bug ("invalid S-exp in %s\n", __func__);
+
+  if (!tcmp)
+    tcmp = cmp_canon_sexp_def_tcmp;
+
+  a_depth = 0;
+  a_buf = a;
+  a_buflen = alen;
+  b_depth = 0;
+  b_buf = b;
+  b_buflen = blen;
+
+  for (;;)
+    {
+      if (parse_sexp (&a_buf, &a_buflen, &a_depth, &a_tok, &a_toklen))
+        return -1;  /* A is invalid.  */
+      if (parse_sexp (&b_buf, &b_buflen, &b_depth, &b_tok, &b_toklen))
+        return -1;  /* B is invalid.  */
+      if (!a_depth && !b_depth)
+        return 0; /* End of both expressions - they match.  */
+      if (a_depth != b_depth)
+        return a_depth - b_depth; /* Not the same structure   */
+      if (!a_tok && !b_tok)
+        ; /* parens */
+      else if (a_tok && b_tok)
+        {
+          ret = tcmp (tcmpctx, a_depth, a_tok, a_toklen, b_tok, b_toklen);
+          if (ret)
+            return ret;  /* Mismatch */
+        }
+      else /* One has a paren other has not.  */
+        return !!a_tok - !!b_tok;
+    }
+}
+
+
 /* Create a simple S-expression from the hex string at LINE.  Returns
    a newly allocated buffer with that canonical encoded S-expression
    or NULL in case of an error.  On return the number of characters

common/t-sexputil.c

@@ -178,6 +178,107 @@ test_make_canon_sexp_from_rsa_pk (void)
 }
 
 
+
+/* Communiacation object for tcmp.  */
+struct tcmp_parm_s {
+  int curve_seen;
+};
+
+/* Helper for test_cmp_canon_sexp.  */
+static int
+tcmp1 (void *opaque, int depth,
+       const unsigned char *aval, size_t alen,
+       const unsigned char *bval, size_t blen)
+{
+  struct tcmp_parm_s *parm = opaque;
+
+  (void)depth;
+
+  if (parm->curve_seen)
+    {
+      /* Last token was "curve", canonicalize its argument.  */
+      parm->curve_seen = 0;
+
+      if (alen == 8 && !memcmp (aval, "nistp256", alen))
+        {
+          alen = 19;
+          aval = "1.2.840.10045.3.1.7";
+        }
+
+      if (blen == 8 && !memcmp (bval, "nistp256", blen))
+        {
+          blen = 19;
+          bval = "1.2.840.10045.3.1.7";
+        }
+    }
+  else if (alen == 5 && !memcmp (aval, "curve", 5))
+    parm->curve_seen = 1;
+  else
+    parm->curve_seen = 0;
+
+  if (alen > blen)
+    return 1;
+  else if (alen < blen)
+    return -1;
+  else
+    return memcmp (aval, bval, alen);
+}
+
+
+static void
+test_cmp_canon_sexp (void)
+{
+  struct {
+    unsigned char *a;
+    unsigned char *b;
+    int expected0;  /* Expected result without compare function.    */
+    int expected1;  /* Expected result with compare function tcmp1. */
+  }
+  tests[] = {
+  {
+   "(10:public-key(3:ecc(5:curve8:nistp256)(1:q10:qqqqqqqqqq)))",
+   "(10:public-key(3:ecc(5:curve8:nistp256)(1:q10:qqqqqqqqqq)))",
+   0, 0
+  },
+  {
+   "(10:public-key(3:ecc(5:curve19:1.2.840.10045.3.1.7)(1:q10:qqqqqqqqqq)))",
+   "(10:public-key(3:ecc(5:curve19:1.2.840.10045.3.1.7)(1:q10:qqqqqqqqqq)))",
+   0, 0
+  },
+  {
+   "(10:public-key(3:ecc(5:curve8:nistp256)(1:q10:qqqqqqqqqq)))",
+   "(10:public-key(3:ecc(5:curve19:1.2.840.10045.3.1.7)(1:q10:qqqqqqqqqq)))",
+   -1, 0
+  },
+  {
+   "(10:public-key(3:ecc(5:curve19:1.2.840.10045.3.1.7)(1:q10:qqqqqqqqqq)))",
+   "(10:public-key(3:ecc(5:curve8:nistp256)(1:q10:qqqqqqqqqq)))",
+   1, 0
+  },
+  {
+   NULL
+  }
+  };
+  struct tcmp_parm_s parm = {0};
+  int idx;
+  int res;
+
+  for (idx=0; tests[idx].a; idx++)
+    {
+      res = cmp_canon_sexp (tests[idx].a, strlen (tests[idx].a),
+                            tests[idx].b, strlen (tests[idx].b),
+                            NULL, NULL);
+      if (res != tests[idx].expected0)
+        fail (idx);
+      res = cmp_canon_sexp (tests[idx].a, strlen (tests[idx].a),
+                            tests[idx].b, strlen (tests[idx].b),
+                            tcmp1, &parm);
+      if (res != tests[idx].expected1)
+        fail (idx);
+    }
+}
+
+
 int
 main (int argc, char **argv)
 {
@@ -186,6 +287,7 @@ main (int argc, char **argv)
 
   test_hash_algo_from_sigval ();
   test_make_canon_sexp_from_rsa_pk ();
+  test_cmp_canon_sexp ();
 
   return 0;
 }

common/tlv.c

@@ -242,8 +242,8 @@ parse_ber_header (unsigned char const **buffer, size_t *size,
    returned as a pointer into the original buffer at TOK and TOKLEN.
    If a parentheses is the next token, TOK will be set to NULL.
    TOKLEN is checked to be within the bounds.  On error an error code
-   is returned and no pointer is not guaranteed to point to
+   is returned and pointers are not guaranteed to point to
-   a meaningful value.  DEPTH should be initialized to 0 and will
+   meaningful values.  DEPTH should be initialized to 0 and will
    reflect on return the actual depth of the tree. To detect the end
    of the S-expression it is advisable to check DEPTH after a
    successful return.

common/util.h

@@ -185,6 +185,12 @@ gpg_error_t make_canon_sexp_pad (gcry_sexp_t sexp, int secure,
 gpg_error_t keygrip_from_canon_sexp (const unsigned char *key, size_t keylen,
                                      unsigned char *grip);
 int cmp_simple_canon_sexp (const unsigned char *a, const unsigned char *b);
+int cmp_canon_sexp (const unsigned char *a, size_t alen,
+                    const unsigned char *b, size_t blen,
+                    int (*tcmp)(void *ctx, int depth,
+                                const unsigned char *aval, size_t avallen,
+                                const unsigned char *bval, size_t bvallen),
+                    void *tcmpctx);
 unsigned char *make_simple_sexp_from_hexstr (const char *line,
                                              size_t *nscanned);
 int hash_algo_from_sigval (const unsigned char *sigval);