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-rw-r--r--src/pluto/pem.c463
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diff --git a/src/pluto/pem.c b/src/pluto/pem.c
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+/* Loading of PEM encoded files with optional encryption
+ * Copyright (C) 2001-2004 Andreas Steffen, Zuercher Hochschule Winterthur
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version. See <http://www.fsf.org/copyleft/gpl.txt>.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * for more details.
+ *
+ * RCSID $Id: pem.c,v 1.4 2005/08/17 16:31:24 as Exp $
+ */
+
+/* decrypt a PEM encoded data block using DES-EDE3-CBC
+ * see RFC 1423 PEM: Algorithms, Modes and Identifiers
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <string.h>
+#include <stddef.h>
+#include <sys/types.h>
+
+#include <freeswan.h>
+#define HEADER_DES_LOCL_H /* stupid trick to force prototype decl in <des.h> */
+#include <libdes/des.h>
+
+#include "constants.h"
+#include "defs.h"
+#include "log.h"
+#include "md5.h"
+#include "whack.h"
+#include "pem.h"
+
+/*
+ * check the presence of a pattern in a character string
+ */
+static bool
+present(const char* pattern, chunk_t* ch)
+{
+ u_int pattern_len = strlen(pattern);
+
+ if (ch->len >= pattern_len && strncmp(ch->ptr, pattern, pattern_len) == 0)
+ {
+ ch->ptr += pattern_len;
+ ch->len -= pattern_len;
+ return TRUE;
+ }
+ return FALSE;
+}
+
+/*
+ * compare string with chunk
+ */
+static bool
+match(const char *pattern, const chunk_t *ch)
+{
+ return ch->len == strlen(pattern) &&
+ strncmp(pattern, ch->ptr, ch->len) == 0;
+}
+
+/*
+ * find a boundary of the form -----tag name-----
+ */
+static bool
+find_boundary(const char* tag, chunk_t *line)
+{
+ chunk_t name = empty_chunk;
+
+ if (!present("-----", line))
+ return FALSE;
+ if (!present(tag, line))
+ return FALSE;
+ if (*line->ptr != ' ')
+ return FALSE;
+ line->ptr++; line->len--;
+
+ /* extract name */
+ name.ptr = line->ptr;
+ while (line->len > 0)
+ {
+ if (present("-----", line))
+ {
+ DBG(DBG_PARSING,
+ DBG_log(" -----%s %.*s-----",
+ tag, (int)name.len, name.ptr);
+ )
+ return TRUE;
+ }
+ line->ptr++; line->len--; name.len++;
+ }
+ return FALSE;
+}
+
+/*
+ * eat whitespace
+ */
+static void
+eat_whitespace(chunk_t *src)
+{
+ while (src->len > 0 && (*src->ptr == ' ' || *src->ptr == '\t'))
+ {
+ src->ptr++; src->len--;
+ }
+}
+
+/*
+ * extracts a token ending with a given termination symbol
+ */
+static bool
+extract_token(chunk_t *token, char termination, chunk_t *src)
+{
+ u_char *eot = memchr(src->ptr, termination, src->len);
+
+ /* initialize empty token */
+ *token = empty_chunk;
+
+ if (eot == NULL) /* termination symbol not found */
+ return FALSE;
+
+ /* extract token */
+ token->ptr = src->ptr;
+ token->len = (u_int)(eot - src->ptr);
+
+ /* advance src pointer after termination symbol */
+ src->ptr = eot + 1;
+ src->len -= (token->len + 1);
+
+ return TRUE;
+}
+
+/*
+ * extracts a name: value pair from the PEM header
+ */
+static bool
+extract_parameter(chunk_t *name, chunk_t *value, chunk_t *line)
+{
+ DBG(DBG_PARSING,
+ DBG_log(" %.*s", (int)line->len, line->ptr);
+ )
+
+ /* extract name */
+ if (!extract_token(name,':', line))
+ return FALSE;
+
+ eat_whitespace(line);
+
+ /* extract value */
+ *value = *line;
+ return TRUE;
+}
+
+/*
+ * fetches a new line terminated by \n or \r\n
+ */
+static bool
+fetchline(chunk_t *src, chunk_t *line)
+{
+ if (src->len == 0) /* end of src reached */
+ return FALSE;
+
+ if (extract_token(line, '\n', src))
+ {
+ if (line->len > 0 && *(line->ptr + line->len -1) == '\r')
+ line->len--; /* remove optional \r */
+ }
+ else /*last line ends without newline */
+ {
+ *line = *src;
+ src->ptr += src->len;
+ src->len = 0;
+ }
+ return TRUE;
+}
+
+/*
+ * decrypts a DES-EDE-CBC encrypted data block
+ */
+static bool
+pem_decrypt_3des(chunk_t *blob, chunk_t *iv, const char *passphrase)
+{
+ MD5_CTX context;
+ u_char digest[MD5_DIGEST_SIZE];
+ u_char des_iv[DES_CBC_BLOCK_SIZE];
+ u_char key[24];
+ des_cblock *deskey = (des_cblock *)key;
+ des_key_schedule ks[3];
+ u_char padding, *last_padding_pos, *first_padding_pos;
+
+ /* Convert passphrase to 3des key */
+ MD5Init(&context);
+ MD5Update(&context, passphrase, strlen(passphrase));
+ MD5Update(&context, iv->ptr, iv->len);
+ MD5Final(digest, &context);
+
+ memcpy(key, digest, MD5_DIGEST_SIZE);
+
+ MD5Init(&context);
+ MD5Update(&context, digest, MD5_DIGEST_SIZE);
+ MD5Update(&context, passphrase, strlen(passphrase));
+ MD5Update(&context, iv->ptr, iv->len);
+ MD5Final(digest, &context);
+
+ memcpy(key + MD5_DIGEST_SIZE, digest, 24 - MD5_DIGEST_SIZE);
+
+ (void) des_set_key(&deskey[0], ks[0]);
+ (void) des_set_key(&deskey[1], ks[1]);
+ (void) des_set_key(&deskey[2], ks[2]);
+
+ /* decrypt data block */
+ memcpy(des_iv, iv->ptr, DES_CBC_BLOCK_SIZE);
+ des_ede3_cbc_encrypt((des_cblock *)blob->ptr, (des_cblock *)blob->ptr,
+ blob->len, ks[0], ks[1], ks[2], (des_cblock *)des_iv, FALSE);
+
+ /* determine amount of padding */
+ last_padding_pos = blob->ptr + blob->len - 1;
+ padding = *last_padding_pos;
+ first_padding_pos = (padding > blob->len)?
+ blob->ptr : last_padding_pos - padding;
+
+ /* check the padding pattern */
+ while (--last_padding_pos > first_padding_pos)
+ {
+ if (*last_padding_pos != padding)
+ return FALSE;
+ }
+
+ /* remove padding */
+ blob->len -= padding;
+ return TRUE;
+}
+
+/*
+ * optionally prompts for a passphrase before decryption
+ * currently we support DES-EDE3-CBC, only
+ */
+static err_t
+pem_decrypt(chunk_t *blob, chunk_t *iv, prompt_pass_t *pass, const char* label)
+{
+ DBG(DBG_CRYPT,
+ DBG_log(" decrypting file using 'DES-EDE3-CBC'");
+ )
+ if (iv->len != DES_CBC_BLOCK_SIZE)
+ return "size of DES-EDE3-CBC IV is not 8 bytes";
+
+ if (pass == NULL)
+ return "no passphrase available";
+
+ /* do we prompt for the passphrase? */
+ if (pass->prompt && pass->fd != NULL_FD)
+ {
+ int i;
+ chunk_t blob_copy;
+ err_t ugh = "invalid passphrase, too many trials";
+
+ whack_log(RC_ENTERSECRET, "need passphrase for '%s'", label);
+
+ for (i = 0; i < MAX_PROMPT_PASS_TRIALS; i++)
+ {
+ int n;
+
+ if (i > 0)
+ whack_log(RC_ENTERSECRET, "invalid passphrase, please try again");
+
+ n = read(pass->fd, pass->secret, PROMPT_PASS_LEN);
+
+ if (n == -1)
+ {
+ err_t ugh = "read(whackfd) failed";
+
+ whack_log(RC_LOG_SERIOUS,ugh);
+ return ugh;
+ }
+
+ pass->secret[n-1] = '\0';
+
+ if (strlen(pass->secret) == 0)
+ {
+ err_t ugh = "no passphrase entered, aborted";
+
+ whack_log(RC_LOG_SERIOUS, ugh);
+ return ugh;
+ }
+
+ clonetochunk(blob_copy, blob->ptr, blob->len, "blob copy");
+
+ if (pem_decrypt_3des(blob, iv, pass->secret))
+ {
+ whack_log(RC_SUCCESS, "valid passphrase");
+ pfree(blob_copy.ptr);
+ return NULL;
+ }
+
+ /* blob is useless after wrong decryption, restore the original */
+ pfree(blob->ptr);
+ *blob = blob_copy;
+ }
+ whack_log(RC_LOG_SERIOUS, ugh);
+ return ugh;
+ }
+ else
+ {
+ if (pem_decrypt_3des(blob, iv, pass->secret))
+ return NULL;
+ else
+ return "invalid passphrase";
+ }
+}
+
+/* Converts a PEM encoded file into its binary form
+ *
+ * RFC 1421 Privacy Enhancement for Electronic Mail, February 1993
+ * RFC 934 Message Encapsulation, January 1985
+ */
+err_t
+pemtobin(chunk_t *blob, prompt_pass_t *pass, const char* label, bool *pgp)
+{
+ typedef enum {
+ PEM_PRE = 0,
+ PEM_MSG = 1,
+ PEM_HEADER = 2,
+ PEM_BODY = 3,
+ PEM_POST = 4,
+ PEM_ABORT = 5
+ } state_t;
+
+ bool encrypted = FALSE;
+
+ state_t state = PEM_PRE;
+
+ chunk_t src = *blob;
+ chunk_t dst = *blob;
+ chunk_t line = empty_chunk;
+ chunk_t iv = empty_chunk;
+
+ u_char iv_buf[MAX_DIGEST_LEN];
+
+ /* zero size of converted blob */
+ dst.len = 0;
+
+ /* zero size of IV */
+ iv.ptr = iv_buf;
+ iv.len = 0;
+
+ while (fetchline(&src, &line))
+ {
+ if (state == PEM_PRE)
+ {
+ if (find_boundary("BEGIN", &line))
+ {
+ *pgp = FALSE;
+ state = PEM_MSG;
+ }
+ continue;
+ }
+ else
+ {
+ if (find_boundary("END", &line))
+ {
+ state = PEM_POST;
+ break;
+ }
+ if (state == PEM_MSG)
+ {
+ state = (memchr(line.ptr, ':', line.len) == NULL)?
+ PEM_BODY : PEM_HEADER;
+ }
+ if (state == PEM_HEADER)
+ {
+ chunk_t name = empty_chunk;
+ chunk_t value = empty_chunk;
+
+ /* an empty line separates HEADER and BODY */
+ if (line.len == 0)
+ {
+ state = PEM_BODY;
+ continue;
+ }
+
+ /* we are looking for a name: value pair */
+ if (!extract_parameter(&name, &value, &line))
+ continue;
+
+ if (match("Proc-Type", &name) && *value.ptr == '4')
+ encrypted = TRUE;
+ else if (match("DEK-Info", &name))
+ {
+ const char *ugh = NULL;
+ size_t len = 0;
+ chunk_t dek;
+
+ if (!extract_token(&dek, ',', &value))
+ dek = value;
+
+ /* we support DES-EDE3-CBC encrypted files, only */
+ if (!match("DES-EDE3-CBC", &dek))
+ return "we support DES-EDE3-CBC encrypted files, only";
+
+ eat_whitespace(&value);
+ ugh = ttodata(value.ptr, value.len, 16,
+ iv.ptr, MAX_DIGEST_LEN, &len);
+ if (ugh)
+ return "error in IV";
+
+ iv.len = len;
+ }
+ }
+ else /* state is PEM_BODY */
+ {
+ const char *ugh = NULL;
+ size_t len = 0;
+ chunk_t data;
+
+ /* remove any trailing whitespace */
+ if (!extract_token(&data ,' ', &line))
+ data = line;
+
+ /* check for PGP armor checksum */
+ if (*data.ptr == '=')
+ {
+ *pgp = TRUE;
+ data.ptr++;
+ data.len--;
+ DBG(DBG_PARSING,
+ DBG_log(" Armor checksum: %.*s", (int)data.len, data.ptr);
+ )
+ continue;
+ }
+
+ ugh = ttodata(data.ptr, data.len, 64,
+ dst.ptr, blob->len - dst.len, &len);
+ if (ugh)
+ {
+ DBG(DBG_PARSING,
+ DBG_log(" %s", ugh);
+ )
+ state = PEM_ABORT;
+ break;
+ }
+ else
+ {
+ dst.ptr += len;
+ dst.len += len;
+ }
+ }
+ }
+ }
+ /* set length to size of binary blob */
+ blob->len = dst.len;
+
+ if (state != PEM_POST)
+ return "file coded in unknown format, discarded";
+
+ if (encrypted)
+ return pem_decrypt(blob, &iv, pass, label);
+ else
+ return NULL;
+}
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