Fix DER reading from stdin for BIO_f_readbuffer

Fixes #14559

The intitial implementation of the gets() function tried using the next bio's gets() function.
For a file BIO this returned incorrect data for binary data containing 0x00.
Just buffering all data during gets() did not work however since some
applications open and close the bio multiple times when dealing with pem
files containing multiple entries.. This does not work
when reading from stdin unless the data if buffered one byte at a time.

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/14599)

crypto/bio/bf_readbuff.c

@@ -57,7 +57,7 @@ static int readbuffer_new(BIO *bi)
     if (ctx == NULL)
         return 0;
     ctx->ibuf_size = DEFAULT_BUFFER_SIZE;
-    ctx->ibuf = OPENSSL_malloc(DEFAULT_BUFFER_SIZE);
+    ctx->ibuf = OPENSSL_zalloc(DEFAULT_BUFFER_SIZE);
     if (ctx->ibuf == NULL) {
         OPENSSL_free(ctx);
         return 0;
@@ -220,6 +220,7 @@ static int readbuffer_gets(BIO *b, char *buf, int size)
     BIO_F_BUFFER_CTX *ctx;
     int num = 0, num_chars, found_newline;
     char *p;
+    int i, j;
 
     if (size == 0)
         return 0;
@@ -227,42 +228,61 @@ static int readbuffer_gets(BIO *b, char *buf, int size)
     ctx = (BIO_F_BUFFER_CTX *)b->ptr;
     BIO_clear_retry_flags(b);
 
-    for (;;) {
-        if (ctx->ibuf_len > 0) {
-            p = &(ctx->ibuf[ctx->ibuf_off]);
-            found_newline = 0;
-            for (num_chars = 0;
-                 (num_chars < ctx->ibuf_len) && (num_chars < size);
-                 num_chars++) {
-                *(buf++) = p[num_chars];
-                if (p[num_chars] == '\n') {
-                    found_newline = 1;
-                    num_chars++;
-                    break;
-                }
+    /* If data is already buffered then use this first */
+    if (ctx->ibuf_len > 0) {
+        p = ctx->ibuf + ctx->ibuf_off;
+        found_newline = 0;
+        for (num_chars = 0;
+             (num_chars < ctx->ibuf_len) && (num_chars < size);
+             num_chars++) {
+            *buf++ = p[num_chars];
+            if (p[num_chars] == '\n') {
+                found_newline = 1;
+                num_chars++;
+                break;
             }
-            num += num_chars;
-            size -= num_chars;
-            ctx->ibuf_len -= num_chars;
-            ctx->ibuf_off += num_chars;
-            if (found_newline || size == 0) {
-                *buf = '\0';
-                return num;
-            }
-        } else {
-            /* read another line and resize if we have to */
-            if (!readbuffer_resize(ctx, size))
-                return 0;
-
-            /* Read another line from the next bio using BIO_gets */
-            num_chars = BIO_gets(b->next_bio, ctx->ibuf + ctx->ibuf_off,
-                                 1 + size);
-            if (num_chars <= 0) {
-                BIO_copy_next_retry(b);
-                *buf = '\0';
-                return num > 0 ? num : num_chars;
-            }
-            ctx->ibuf_len = num_chars;
+        }
+        num += num_chars;
+        size -= num_chars;
+        ctx->ibuf_len -= num_chars;
+        ctx->ibuf_off += num_chars;
+        if (found_newline || size == 0) {
+            *buf = '\0';
+            return num;
         }
     }
+    /*
+     * If there is no buffered data left then read any remaining data from the
+     * next bio.
+     */
+
+     /* Resize if we have to */
+     if (!readbuffer_resize(ctx, 1 + size))
+         return 0;
+     /*
+      * Read more data from the next bio using BIO_read_ex:
+      * Note we cannot use BIO_gets() here as it does not work on a
+      * binary stream that contains 0x00. (Since strlen() will stop at
+      * any 0x00 not at the last read '\n' in a FILE bio).
+      * Also note that some applications open and close the file bio
+      * multiple times and need to read the next available block when using
+      * stdin - so we need to READ one byte at a time!
+      */
+     p = ctx->ibuf + ctx->ibuf_off;
+     for (i = 0; i < size; ++i) {
+         j = BIO_read(b->next_bio, p, 1);
+         if (j <= 0) {
+             BIO_copy_next_retry(b);
+             *buf = '\0';
+             return num > 0 ? num : j;
+         }
+         *buf++ = *p;
+         num++;
+         ctx->ibuf_off++;
+         if (*p == '\n')
+             break;
+         ++p;
+     }
+     *buf = '\0';
+     return num;
 }

test/bio_readbuffer_test.c

@@ -0,0 +1,131 @@
+/*
+ * Copyright 2021 The OpenSSL Project Authors. All Rights Reserved.
+ *
+ * Licensed under the Apache License 2.0 (the "License").  You may not use
+ * this file except in compliance with the License.  You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
+ */
+
+#include <openssl/bio.h>
+#include "testutil.h"
+
+static const char *filename = NULL;
+
+/*
+ * Test that a BIO_f_readbuffer() with a BIO_new_file() behaves nicely if
+ * BIO_gets() and BIO_read_ex() are both called.
+ * Since the BIO_gets() calls buffer the reads, the BIO_read_ex() should
+ * still be able to read the buffered data if we seek back to the start.
+ *
+ * The following cases are tested using tstid:
+ * 0 : Just use BIO_read_ex().
+ * 1 : Try a few reads using BIO_gets() before using BIO_read_ex()
+ * 2 : Read the entire file using BIO_gets() before using BIO_read_ex().
+ */
+static int test_readbuffer_file_bio(int tstid)
+{
+    int ret = 0, len, partial;
+    BIO *in = NULL, *in_bio = NULL, *readbuf_bio = NULL;
+    char buf[255];
+    char expected[4096];
+    size_t readbytes = 0, bytes = 0, count = 0;
+
+    /* Open a file BIO and read all the data */
+    if (!TEST_ptr(in = BIO_new_file(filename, "r"))
+        || !TEST_int_eq(BIO_read_ex(in, expected, sizeof(expected),
+                                    &readbytes), 1)
+        || !TEST_int_lt(readbytes, sizeof(expected)))
+        goto err;
+    BIO_free(in);
+    in = NULL;
+
+    /* Create a new file bio that sits under a readbuffer BIO */
+    if (!TEST_ptr(readbuf_bio = BIO_new(BIO_f_readbuffer()))
+        || !TEST_ptr(in_bio = BIO_new_file(filename, "r")))
+        goto err;
+
+    in_bio = BIO_push(readbuf_bio, in_bio);
+    readbuf_bio = NULL;
+
+    if (!TEST_int_eq(BIO_tell(in_bio), 0))
+        goto err;
+
+    if (tstid != 0) {
+        partial = 4;
+        while (!BIO_eof(in_bio)) {
+            len = BIO_gets(in_bio, buf, sizeof(buf));
+            if (len == 0) {
+                if (!TEST_true(BIO_eof(in_bio)))
+                    goto err;
+            } else {
+                if (!TEST_int_gt(len, 0)
+                    || !TEST_int_le(len, (int)sizeof(buf) - 1))
+                    goto err;
+                if (!TEST_true(buf[len] == 0))
+                    goto err;
+                if (len > 1
+                    && !BIO_eof(in_bio)
+                    && len != ((int)sizeof(buf) - 1)
+                    && !TEST_true(buf[len - 1] == '\n'))
+                    goto err;
+            }
+            if (tstid == 1 && --partial == 0)
+                break;
+        }
+    }
+    if (!TEST_int_eq(BIO_seek(in_bio, 0), 1))
+        goto err;
+
+    len = 8; /* Do a small partial read to start with */
+    while (!BIO_eof(in_bio)) {
+        if (!TEST_int_eq(BIO_read_ex(in_bio, buf, len, &bytes), 1))
+            break;
+        if (!TEST_mem_eq(buf, bytes, expected + count, bytes))
+            goto err;
+        count += bytes;
+        len = sizeof(buf); /* fill the buffer on subsequent reads */
+    }
+    if (!TEST_int_eq(count, readbytes))
+        goto err;
+    ret = 1;
+err:
+    BIO_free(in);
+    BIO_free_all(in_bio);
+    BIO_free(readbuf_bio);
+    return ret;
+}
+
+typedef enum OPTION_choice {
+    OPT_ERR = -1,
+    OPT_EOF = 0,
+    OPT_TEST_ENUM
+} OPTION_CHOICE;
+
+const OPTIONS *test_get_options(void)
+{
+    static const OPTIONS test_options[] = {
+        OPT_TEST_OPTIONS_WITH_EXTRA_USAGE("file\n"),
+        { OPT_HELP_STR, 1, '-', "file\tFile to run tests on.\n" },
+        { NULL }
+    };
+    return test_options;
+}
+
+int setup_tests(void)
+{
+    OPTION_CHOICE o;
+
+    while ((o = opt_next()) != OPT_EOF) {
+        switch (o) {
+        case OPT_TEST_CASES:
+            break;
+        default:
+            return 0;
+        }
+    }
+    filename = test_get_argument(0);
+
+    ADD_ALL_TESTS(test_readbuffer_file_bio, 3);
+    return 1;
+}

test/build.info

@@ -57,7 +57,8 @@ IF[{- !$disabled{tests} -}]
           http_test servername_test ocspapitest fatalerrtest tls13ccstest \
           sysdefaulttest errtest ssl_ctx_test gosttest \
           context_internal_test aesgcmtest params_test evp_pkey_dparams_test \
-          keymgmt_internal_test hexstr_test provider_status_test defltfips_test
+          keymgmt_internal_test hexstr_test provider_status_test defltfips_test \
+          bio_readbuffer_test
 
   IF[{- !$disabled{'deprecated-3.0'} -}]
     PROGRAMS{noinst}=enginetest
@@ -307,6 +308,10 @@ IF[{- !$disabled{tests} -}]
   INCLUDE[bio_callback_test]=../include ../apps/include
   DEPEND[bio_callback_test]=../libcrypto libtestutil.a
 
+  SOURCE[bio_readbuffer_test]=bio_readbuffer_test.c
+  INCLUDE[bio_readbuffer_test]=../include ../apps/include
+  DEPEND[bio_readbuffer_test]=../libcrypto libtestutil.a
+
   SOURCE[bio_memleak_test]=bio_memleak_test.c
   INCLUDE[bio_memleak_test]=../include ../apps/include
   DEPEND[bio_memleak_test]=../libcrypto libtestutil.a

test/recipes/61-test_bio_readbuffer.t

@@ -0,0 +1,29 @@
+#! /usr/bin/env perl
+# Copyright 2021 The OpenSSL Project Authors. All Rights Reserved.
+#
+# Licensed under the Apache License 2.0 (the "License").  You may not use
+# this file except in compliance with the License.  You can obtain a copy
+# in the file LICENSE in the source distribution or at
+# https://www.openssl.org/source/license.html
+
+use strict;
+use warnings;
+
+use OpenSSL::Test qw(:DEFAULT srctop_file);
+
+setup('test_bio_readbuffer');
+
+my $pemfile = srctop_file("test", "certs", "leaf.pem");
+my $derfile = 'readbuffer_leaf.der';
+
+plan tests => 3;
+
+ok(run(app([ 'openssl', 'x509', '-inform', 'PEM', '-in', $pemfile,
+             '-outform', 'DER', '-out', $derfile])),
+   "Generate a DER certificate");
+
+ok(run(test(["bio_readbuffer_test", $derfile])),
+   "Running bio_readbuffer_test $derfile");
+
+ok(run(test(["bio_readbuffer_test", $pemfile])),
+   "Running bio_readbuffer_test $pemfile");