Line data Source code
1 : /* pkdecrypt.c - public key decryption (well, acually using a secret key)
2 : * Copyright (C) 2001, 2003 Free Software Foundation, Inc.
3 : *
4 : * This file is part of GnuPG.
5 : *
6 : * GnuPG is free software; you can redistribute it and/or modify
7 : * it under the terms of the GNU General Public License as published by
8 : * the Free Software Foundation; either version 3 of the License, or
9 : * (at your option) any later version.
10 : *
11 : * GnuPG is distributed in the hope that it will be useful,
12 : * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 : * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 : * GNU General Public License for more details.
15 : *
16 : * You should have received a copy of the GNU General Public License
17 : * along with this program; if not, see <http://www.gnu.org/licenses/>.
18 : */
19 :
20 : #include <config.h>
21 : #include <errno.h>
22 : #include <stdio.h>
23 : #include <stdlib.h>
24 : #include <string.h>
25 : #include <ctype.h>
26 : #include <assert.h>
27 : #include <unistd.h>
28 : #include <sys/stat.h>
29 :
30 : #include "agent.h"
31 :
32 :
33 : /* DECRYPT the stuff in ciphertext which is expected to be a S-Exp.
34 : Try to get the key from CTRL and write the decoded stuff back to
35 : OUTFP. The padding information is stored at R_PADDING with -1
36 : for not known. */
37 : int
38 259 : agent_pkdecrypt (ctrl_t ctrl, const char *desc_text,
39 : const unsigned char *ciphertext, size_t ciphertextlen,
40 : membuf_t *outbuf, int *r_padding)
41 : {
42 259 : gcry_sexp_t s_skey = NULL, s_cipher = NULL, s_plain = NULL;
43 259 : unsigned char *shadow_info = NULL;
44 : int rc;
45 259 : char *buf = NULL;
46 : size_t len;
47 :
48 259 : *r_padding = -1;
49 :
50 259 : if (!ctrl->have_keygrip)
51 : {
52 0 : log_error ("speculative decryption not yet supported\n");
53 0 : rc = gpg_error (GPG_ERR_NO_SECKEY);
54 0 : goto leave;
55 : }
56 :
57 259 : rc = gcry_sexp_sscan (&s_cipher, NULL, (char*)ciphertext, ciphertextlen);
58 259 : if (rc)
59 : {
60 0 : log_error ("failed to convert ciphertext: %s\n", gpg_strerror (rc));
61 0 : rc = gpg_error (GPG_ERR_INV_DATA);
62 0 : goto leave;
63 : }
64 :
65 259 : if (DBG_CRYPTO)
66 : {
67 0 : log_printhex ("keygrip:", ctrl->keygrip, 20);
68 0 : log_printhex ("cipher: ", ciphertext, ciphertextlen);
69 : }
70 259 : rc = agent_key_from_file (ctrl, NULL, desc_text,
71 259 : ctrl->keygrip, &shadow_info,
72 : CACHE_MODE_NORMAL, NULL, &s_skey, NULL);
73 259 : if (rc)
74 : {
75 0 : if (gpg_err_code (rc) != GPG_ERR_NO_SECKEY)
76 0 : log_error ("failed to read the secret key\n");
77 0 : goto leave;
78 : }
79 :
80 259 : if (shadow_info)
81 : { /* divert operation to the smartcard */
82 :
83 0 : if (!gcry_sexp_canon_len (ciphertext, ciphertextlen, NULL, NULL))
84 : {
85 0 : rc = gpg_error (GPG_ERR_INV_SEXP);
86 0 : goto leave;
87 : }
88 :
89 0 : rc = divert_pkdecrypt (ctrl, ciphertext, shadow_info,
90 : &buf, &len, r_padding);
91 0 : if (rc)
92 : {
93 0 : log_error ("smartcard decryption failed: %s\n", gpg_strerror (rc));
94 0 : goto leave;
95 : }
96 :
97 0 : put_membuf_printf (outbuf, "(5:value%u:", (unsigned int)len);
98 0 : put_membuf (outbuf, buf, len);
99 0 : put_membuf (outbuf, ")", 2);
100 : }
101 : else
102 : { /* No smartcard, but a private key */
103 : /* if (DBG_CRYPTO ) */
104 : /* { */
105 : /* log_debug ("skey: "); */
106 : /* gcry_sexp_dump (s_skey); */
107 : /* } */
108 :
109 259 : rc = gcry_pk_decrypt (&s_plain, s_cipher, s_skey);
110 259 : if (rc)
111 : {
112 0 : log_error ("decryption failed: %s\n", gpg_strerror (rc));
113 0 : goto leave;
114 : }
115 :
116 259 : if (DBG_CRYPTO)
117 : {
118 0 : log_debug ("plain: ");
119 0 : gcry_sexp_dump (s_plain);
120 : }
121 259 : len = gcry_sexp_sprint (s_plain, GCRYSEXP_FMT_CANON, NULL, 0);
122 259 : assert (len);
123 259 : buf = xmalloc (len);
124 259 : len = gcry_sexp_sprint (s_plain, GCRYSEXP_FMT_CANON, buf, len);
125 259 : assert (len);
126 259 : if (*buf == '(')
127 24 : put_membuf (outbuf, buf, len);
128 : else
129 : {
130 : /* Old style libgcrypt: This is only an S-expression
131 : part. Turn it into a complete S-expression. */
132 235 : put_membuf (outbuf, "(5:value", 8);
133 235 : put_membuf (outbuf, buf, len);
134 235 : put_membuf (outbuf, ")", 2);
135 : }
136 : }
137 :
138 :
139 : leave:
140 259 : gcry_sexp_release (s_skey);
141 259 : gcry_sexp_release (s_plain);
142 259 : gcry_sexp_release (s_cipher);
143 259 : xfree (buf);
144 259 : xfree (shadow_info);
145 259 : return rc;
146 : }
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