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/* pem.c
*
* Implements loading of files in the format specified by RFC 7468.
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#include "config.h"
#include "pem.h"
#include "file_wrappers.h"
#include "wtap-int.h"
#include <wsutil/buffer.h>
#include <glib.h>
#include <string.h>
/* 128 bytes should be enough to contain any line. Strictly speaking, 64 is
enough, but we provide some leeway to accomodate nonconformant producers and
trailing whitespace. The 2 extra bytes are for the trailing newline and NUL
terminator. */
#define MAX_LINE_LENGTH (128 + 2)
/* based on the `label` production in RFC 7468 */
#define RE_LABEL "([!-,.-~]([-\\s]?[!-,.-~])*)?"
struct pem_priv {
GRegex *re_blank_line;
GRegex *re_pre_eb;
GRegex *re_post_eb;
};
static char *read_complete_text_line(char line[MAX_LINE_LENGTH], FILE_T fh, int *err, gchar **err_info)
{
char *line_end;
if (!(line_end = file_getsp(line, MAX_LINE_LENGTH, fh))) {
*err = file_error(fh, err_info);
return NULL;
}
if (strlen(line) != (size_t)(line_end - line)) {
*err = WTAP_ERR_BAD_FILE;
*err_info = g_strdup("unexpected NUL inside a line");
return NULL;
}
if (line_end[-1] != '\n' && !file_eof(fh)) {
*err = WTAP_ERR_BAD_FILE;
*err_info = g_strdup("overlong line");
return NULL;
}
return line_end;
}
static gboolean pem_read_value(wtap *wth, FILE_T fh, wtap_rec *rec,
Buffer *buf, int *err, gchar **err_info)
{
struct pem_priv *priv = (struct pem_priv *)wth->priv;
char line[MAX_LINE_LENGTH];
// skip blank lines
do {
if (!read_complete_text_line(line, fh, err, err_info)) return FALSE;
} while (g_regex_match(priv->re_blank_line, line, (GRegexMatchFlags)0, NULL));
if (!g_regex_match(priv->re_pre_eb, line, (GRegexMatchFlags)0, NULL)) {
*err = WTAP_ERR_BAD_FILE;
*err_info = g_strdup("invalid pre-encapsulation boundary");
return FALSE;
}
gint base64_state = 0;
guint base64_save = 0;
ws_buffer_clean(buf);
for (; ; ) {
char *line_end = read_complete_text_line(line, fh, err, err_info);
if (!line_end) {
if (*err == 0) {
*err = WTAP_ERR_BAD_FILE;
*err_info = g_strdup("missing post-encapsulation boundary");
}
return FALSE;
}
if (g_regex_match(priv->re_post_eb, line, (GRegexMatchFlags)0, NULL))
break;
guchar decoded[(sizeof(line) / 4) * 3 + 3];
guint32 decoded_size = (guint32) g_base64_decode_step(
line, line_end - line, decoded, &base64_state, &base64_save);
if ((guint32)ws_buffer_length(buf) > G_MAXUINT32 - decoded_size) {
// we can't set the packet length if this happens
*err = WTAP_ERR_BAD_FILE;
*err_info = g_strdup("encoded value too large");
return FALSE;
}
ws_buffer_append(buf, decoded, decoded_size);
}
rec->rec_type = REC_TYPE_PACKET;
rec->presence_flags = 0;
rec->rec_header.packet_header.len =
rec->rec_header.packet_header.caplen =
(guint32)ws_buffer_length(buf);
return TRUE;
}
static gboolean pem_read(wtap *wth, int *err, gchar **err_info, gint64 *data_offset)
{
*data_offset = file_tell(wth->fh);
return pem_read_value(wth, wth->fh, &wth->rec, wth->rec_data, err, err_info);
}
static gboolean pem_seek_read(wtap *wth, gint64 seek_off, wtap_rec *rec,
Buffer *buf, int *err, gchar **err_info)
{
if (file_seek(wth->random_fh, seek_off, SEEK_SET, err) == -1)
return FALSE;
return pem_read_value(wth, wth->random_fh, rec, buf, err, err_info);
}
static void pem_close(wtap *wth)
{
struct pem_priv *priv = (struct pem_priv *)wth->priv;
g_regex_unref(priv->re_pre_eb);
g_regex_unref(priv->re_post_eb);
}
wtap_open_return_val pem_open(wtap *wth, int *err, gchar **err_info)
{
static const char expected_magic[] = "-----BEGIN ";
char actual_magic[sizeof(expected_magic) - 1];
if (!wtap_read_bytes(wth->fh, &actual_magic, sizeof(actual_magic), err, err_info)) {
if (*err == WTAP_ERR_SHORT_READ)
return WTAP_OPEN_NOT_MINE;
return WTAP_OPEN_ERROR;
}
if (memcmp(expected_magic, actual_magic, sizeof(actual_magic)) != 0)
return WTAP_OPEN_NOT_MINE;
if (file_seek(wth->fh, 0, SEEK_SET, err) == -1)
return WTAP_OPEN_ERROR;
wth->file_type_subtype = WTAP_FILE_TYPE_SUBTYPE_PEM;
wth->file_encap = WTAP_ENCAP_BER;
wth->snapshot_length = 0;
wth->file_tsprec = WTAP_TSPREC_SEC;
struct pem_priv *priv = g_new0(struct pem_priv, 1);
priv->re_blank_line = g_regex_new("^\\s*$", G_REGEX_RAW, (GRegexMatchFlags)0, NULL);
priv->re_pre_eb = g_regex_new("^-----BEGIN " RE_LABEL "-----\\s*$",
(GRegexCompileFlags)(G_REGEX_RAW | G_REGEX_NO_AUTO_CAPTURE),
(GRegexMatchFlags)0, NULL);
priv->re_post_eb = g_regex_new("^-----END " RE_LABEL "-----\\s*$",
(GRegexCompileFlags)(G_REGEX_RAW | G_REGEX_NO_AUTO_CAPTURE),
(GRegexMatchFlags)0, NULL);
wth->priv = priv;
wth->subtype_read = pem_read;
wth->subtype_seek_read = pem_seek_read;
wth->subtype_close = pem_close;
if (!priv->re_blank_line || !priv->re_pre_eb || !priv->re_post_eb) {
*err = WTAP_ERR_INTERNAL;
*err_info = g_strdup("failed to initialize reader");
return WTAP_OPEN_ERROR;
}
return WTAP_OPEN_MINE;
}
/*
* Editor modelines - http://www.wireshark.org/tools/modelines.html
*
* Local Variables:
* c-basic-offset: 4
* tab-width: 8
* indent-tabs-mode: nil
* End:
*
* vi: set shiftwidth=4 tabstop=8 expandtab:
* :indentSize=4:tabSize=8:noTabs=true:
*/
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