Add compatibility function for older libkrb5

Before krb5 1.13 the krb5_salttype_to_string() function was returning
incorrect names (display names of some kind instead of the names
used by the rest of the library to map saltname to the salt type
integer number).
This patch adds a function that checks at runtime if we have a working
function and uses a fallback map updated to the salt types known up
to 1.12, this allows us to use the library provided function in
following releases where new salt types may emerge.

Signed-off-by: Simo Sorce <simo@redhat.com>
Reviewed-by: Milan Kubik <mkubik@redhat.com>

1 files changed, 60 insertions, 1 deletions

diff --git a/util/ipa_krb5.c b/util/ipa_krb5.c
index 65e10dd40..a27cd4a4e 100644
--- a/util/ipa_krb5.c
+++ b/util/ipa_krb5.c
@@ -1075,6 +1075,65 @@ int create_keys(krb5_context krbctx,
     return nkeys;
 }
 
+/* in older versions of libkrb5 the krb5_salttype_to_string() function is
+ * faulty and returns strings that do not match the expected format.
+ * Later version of krb5 were fixed to return the proper string.
+ * Do lazy detection the first time the function is invoked to determine
+ * if we can use the library provided function or if we have to use a
+ * fallback map which includes the salt types known up to krb5 1.12 (the
+ * fault is fixed upstream in 1.13). */
+static int ipa_salttype_to_string(krb5_int32 salttype,
+                                  char *buffer, size_t buflen)
+{
+    static int faulty_function = -1;
+
+    static const struct {
+        krb5_int32 salttype;
+        const char *name;
+    } fallback_map[] = {
+        { KRB5_KDB_SALTTYPE_NORMAL, "normal" },
+        { KRB5_KDB_SALTTYPE_V4, "v4" },
+        { KRB5_KDB_SALTTYPE_NOREALM, "norealm" },
+        { KRB5_KDB_SALTTYPE_ONLYREALM, "onlyrealm" },
+        { KRB5_KDB_SALTTYPE_SPECIAL, "special" },
+        { KRB5_KDB_SALTTYPE_AFS3, "afs3" },
+        { -1, NULL }
+    };
+
+    if (faulty_function == -1) {
+        /* haven't checked yet, let's find out */
+        char testbuf[100];
+        size_t len = 100;
+        int ret;
+
+        ret = krb5_salttype_to_string(KRB5_KDB_SALTTYPE_NORMAL, testbuf, len);
+        if (ret) return ret;
+
+        if (strcmp(buffer, "normal") == 0) {
+            faulty_function = 0;
+        } else {
+            faulty_function = 1;
+        }
+    }
+
+    if (faulty_function == 0) {
+        return krb5_salttype_to_string(salttype, buffer, buflen);
+    } else {
+        size_t len;
+        int i;
+        for (i = 0; fallback_map[i].name != NULL; i++) {
+            if (salttype == fallback_map[i].salttype) break;
+        }
+        if (fallback_map[i].name == NULL) return EINVAL;
+
+        len = strlen(fallback_map[i].name);
+        if (len >= buflen) return ENOMEM;
+
+        memcpy(buffer, fallback_map[i].name, len + 1);
+        return 0;
+    }
+}
+
 int ipa_kstuples_to_string(krb5_key_salt_tuple *kst, int n_kst, char **str)
 {
     char *buf = NULL;
@@ -1130,7 +1189,7 @@ int ipa_kstuples_to_string(krb5_key_salt_tuple *kst, int n_kst, char **str)
         buf[buf_cur + len] = ':';
         len++;
 
-        ret = krb5_salttype_to_string(kst[i].ks_salttype,
+        ret = ipa_salttype_to_string(kst[i].ks_salttype,
                                      &buf[buf_cur + len], buf_avail - len);
         if (ret == ENOMEM) {
             i--;