Don't assume GSSAPI result strings are null-terminated.

Our uses of gss_display_status() and gss_display_name() assumed
that the gss_buffer_desc strings returned by those functions are
null-terminated.  It appears that they generally are, given the
lack of field complaints up to now.  However, the available
documentation does not promise this, and some man pages
for gss_display_status() show examples that rely on the
gss_buffer_desc.length field instead of expecting null
termination.  Also, we now have a report that on some
implementations, clang's address sanitizer is of the opinion
that the byte after the specified length is undefined.

Hence, change the code to rely on the length field instead.

This might well be cosmetic rather than fixing any real bug, but
it's hard to be sure, so back-patch to all supported branches.
While here, also back-patch the v12 changes that made pg_GSS_error
deal honestly with multiple messages available from
gss_display_status.

Per report from Sudheer H R.

Discussion: https://postgr.es/m/5372B6D4-8276-42C0-B8FB-BD0918826FC3@tekenlight.com

diff --git a/src/backend/libpq/auth.c b/src/backend/libpq/auth.c
index 45dcd65afaf0788f4f29cd3538bae05490f78b04..a533786f0821e67efa4e76f59602f17619954d25 100644 (file)
--- a/src/backend/libpq/auth.c
+++ b/src/backend/libpq/auth.c
@@ -1193,6 +1193,7 @@ pg_GSS_checkauth(Port *port)
                min_stat,
                lmin_s;
    gss_buffer_desc gbuf;
+   char       *princ;
 
    /*
     * Get the name of the user that authenticated, and compare it to the pg
@@ -1206,18 +1207,27 @@ pg_GSS_checkauth(Port *port)
        return STATUS_ERROR;
    }
 
+   /*
+    * gbuf.value might not be null-terminated, so turn it into a regular
+    * null-terminated string.
+    */
+   princ = palloc(gbuf.length + 1);
+   memcpy(princ, gbuf.value, gbuf.length);
+   princ[gbuf.length] = '\0';
+   gss_release_buffer(&lmin_s, &gbuf);
+
    /*
     * Copy the original name of the authenticated principal into our backend
     * memory for display later.
     */
-   port->gss->princ = MemoryContextStrdup(TopMemoryContext, gbuf.value);
+   port->gss->princ = MemoryContextStrdup(TopMemoryContext, princ);
 
    /*
     * Split the username at the realm separator
     */
-   if (strchr(gbuf.value, '@'))
+   if (strchr(princ, '@'))
    {
-       char       *cp = strchr(gbuf.value, '@');
+       char       *cp = strchr(princ, '@');
 
        /*
         * If we are not going to include the realm in the username that is
@@ -1244,7 +1254,7 @@ pg_GSS_checkauth(Port *port)
                elog(DEBUG2,
                     "GSSAPI realm (%s) and configured realm (%s) don't match",
                     cp, port->hba->krb_realm);
-               gss_release_buffer(&lmin_s, &gbuf);
+               pfree(princ);
                return STATUS_ERROR;
            }
        }
@@ -1253,15 +1263,14 @@ pg_GSS_checkauth(Port *port)
    {
        elog(DEBUG2,
             "GSSAPI did not return realm but realm matching was requested");
-
-       gss_release_buffer(&lmin_s, &gbuf);
+       pfree(princ);
        return STATUS_ERROR;
    }
 
-   ret = check_usermap(port->hba->usermap, port->user_name, gbuf.value,
+   ret = check_usermap(port->hba->usermap, port->user_name, princ,
                        pg_krb_caseins_users);
 
-   gss_release_buffer(&lmin_s, &gbuf);
+   pfree(princ);
 
    return ret;
 }

diff --git a/src/backend/libpq/be-gssapi-common.c b/src/backend/libpq/be-gssapi-common.c
index be5d051c2027ad58e5cf8d5f49c1cff28872ae9b..3e2531c5f5e1c947313cd7db3edf0a8e1407e0ef 100644 (file)
--- a/src/backend/libpq/be-gssapi-common.c
+++ b/src/backend/libpq/be-gssapi-common.c
@@ -29,8 +29,6 @@ pg_GSS_error_int(char *s, size_t len, OM_uint32 stat, int type)
    OM_uint32   lmin_s,
                msg_ctx = 0;
 
-   s[0] = '\0';                /* just in case gss_display_status fails */
-
    do
    {
        if (gss_display_status(&lmin_s, stat, type, GSS_C_NO_OID,
@@ -43,16 +41,19 @@ pg_GSS_error_int(char *s, size_t len, OM_uint32 stat, int type)
            i++;
        }
        if (i < len)
-           strlcpy(s + i, gmsg.value, len - i);
+           memcpy(s + i, gmsg.value, Min(len - i, gmsg.length));
        i += gmsg.length;
        gss_release_buffer(&lmin_s, &gmsg);
    }
    while (msg_ctx);
 
-   if (i >= len)
+   /* add nul termination */
+   if (i < len)
+       s[i] = '\0';
+   else
    {
        elog(COMMERROR, "incomplete GSS error report");
-       s[len - 1] = '\0';      /* ensure string is nul-terminated */
+       s[len - 1] = '\0';
    }
 }
 

diff --git a/src/interfaces/libpq/fe-gssapi-common.c b/src/interfaces/libpq/fe-gssapi-common.c
index 6538a421c701d3e4bc099b318d761584c2534262..f87e7b2e31bd1d71fd8c58e88bafafe038fd7980 100644 (file)
--- a/src/interfaces/libpq/fe-gssapi-common.c
+++ b/src/interfaces/libpq/fe-gssapi-common.c
@@ -34,7 +34,8 @@ pg_GSS_error_int(PQExpBuffer str, OM_uint32 stat, int type)
        if (gss_display_status(&lmin_s, stat, type, GSS_C_NO_OID,
                               &msg_ctx, &lmsg) != GSS_S_COMPLETE)
            break;
-       appendPQExpBuffer(str, " %s", (char *) lmsg.value);
+       appendPQExpBufferChar(str, ' ');
+       appendBinaryPQExpBuffer(str, lmsg.value, lmsg.length);
        gss_release_buffer(&lmin_s, &lmsg);
    } while (msg_ctx);
 }