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agent: Do not overwrite a key file by a shadow key file.

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* agent/findkey.c: Remove assert.h and use log_assert all over the
file.
(fname_from_keygrip): Add arg for_new.
(is_shadowed_key): New.
(agent_write_private_key): Rewrite to use read, write to new file,
rename pattern.  Ignore attempts to overwrite a regular key file by a
shadow key file.
(read_key_file): Move all cleanup code to the end of the function.
--

GnuPG-bug-id: 6386
I am not shure whether we should allow overwriting with FORCE set.
This commit is contained in:
Werner Koch 2023-03-14 10:09:41 +01:00
parent 4f754caad8
commit b28d9ff865
No known key found for this signature in database
GPG Key ID: E3FDFF218E45B72B
1 changed files with 130 additions and 161 deletions
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291
agent/findkey.c
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@ -27,10 +27,8 @@
#include <string.h>
#include <ctype.h>
#include <fcntl.h>
#include <assert.h>
#include <unistd.h>
#include <sys/stat.h>
#include <assert.h>
#include <npth.h> /* (we use pth_sleep) */
#include "agent.h"
@ -42,6 +40,12 @@
#define O_BINARY 0
#endif
static gpg_error_t read_key_file (const unsigned char *grip,
gcry_sexp_t *result, nvc_t *r_keymeta);
static gpg_error_t is_shadowed_key (gcry_sexp_t s_skey);
/* Helper to pass data to the check callback of the unprotect function. */
struct try_unprotect_arg_s
{
@ -53,15 +57,16 @@ struct try_unprotect_arg_s
};
/* Return the file name for the 20 byte keygrip GRIP. Return NULL on
* error. */
/* Return the file name for the 20 byte keygrip GRIP. With FOR_NEW
* create a file name for later renaming to the actual name. Return
* NULL on error. */
static char *
fname_from_keygrip (const unsigned char *grip)
fname_from_keygrip (const unsigned char *grip, int for_new)
{
char hexgrip[40+4+1];
char hexgrip[40+4+4+1];
bin2hex (grip, 20, hexgrip);
strcpy (hexgrip+40, ".key");
strcpy (hexgrip+40, for_new? ".key.tmp" : ".key");
return make_filename_try (gnupg_homedir (), GNUPG_PRIVATE_KEYS_DIR,
hexgrip, NULL);
@ -70,8 +75,8 @@ fname_from_keygrip (const unsigned char *grip)
/* Write the S-expression formatted key (BUFFER,LENGTH) to our key
* storage. With FORCE passed as true an existing key with the given
* GRIP will get overwritten. If SERIALNO and KEYREF are given a
* Token line is added to the key if the extended format is used. If
* GRIP will be overwritten. If SERIALNO and KEYREF are given a Token
* line is added to the key if the extended format is used. If
* TIMESTAMP is not zero and the key doies not yet exists it will be
* recorded as creation date. */
int
@ -82,115 +87,40 @@ agent_write_private_key (const unsigned char *grip,
time_t timestamp)
{
gpg_error_t err;
char *fname;
char *oldfname = NULL;
char *fname = NULL;
estream_t fp;
int update, newkey;
int newkey = 0;
nvc_t pk = NULL;
gcry_sexp_t key = NULL;
int is_regular;
int remove = 0;
char *token0 = NULL;
char *token = NULL;
char *dispserialno_buffer = NULL;
char **tokenfields = NULL;
int blocksigs = 0;
fname = fname_from_keygrip (grip);
if (!fname)
oldfname = fname_from_keygrip (grip, 0);
if (!oldfname)
return out_of_core ();
/* FIXME: Write to a temp file first so that write failures during
key updates won't lead to a key loss. */
if (!force && !gnupg_access (fname, F_OK))
err = read_key_file (grip, &key, &pk);
if (err)
{
log_error ("secret key file '%s' already exists\n", fname);
xfree (fname);
return gpg_error (GPG_ERR_EEXIST);
}
fp = es_fopen (fname, force? "rb+,mode=-rw" : "wbx,mode=-rw");
if (!fp)
{
gpg_error_t tmperr = gpg_error_from_syserror ();
if (force && gpg_err_code (tmperr) == GPG_ERR_ENOENT)
{
fp = es_fopen (fname, "wbx,mode=-rw");
if (!fp)
tmperr = gpg_error_from_syserror ();
}
if (!fp)
{
log_error ("can't create '%s': %s\n", fname, gpg_strerror (tmperr));
xfree (fname);
return tmperr;
}
update = 0;
newkey = 1;
}
else if (force)
{
gpg_error_t rc;
char first;
/* See if an existing key is in extended format. */
if (es_fread (&first, 1, 1, fp) != 1)
{
rc = gpg_error_from_syserror ();
log_error ("error reading first byte from '%s': %s\n",
fname, strerror (errno));
xfree (fname);
es_fclose (fp);
return rc;
}
rc = es_fseek (fp, 0, SEEK_SET);
if (rc)
{
log_error ("error seeking in '%s': %s\n", fname, strerror (errno));
xfree (fname);
es_fclose (fp);
return rc;
}
if (first == '(')
{
/* Key is still in the old format - force it into extended
* format. We do not request an update here because an
* existing key is not yet in extended key format and no
* extended infos are yet available. */
update = 0;
newkey = 0;
}
if (gpg_err_code (err) == GPG_ERR_ENOENT)
newkey = 1;
else
{
/* Key is already in the extended format. */
update = 1;
newkey = 0;
}
}
else
{
/* The key file did not exist: we assume this is a new key and
* write the Created: entry. */
update = 0;
newkey = 1;
}
if (update)
{
int lineno = 0;
err = nvc_parse_private_key (&pk, &lineno, fp);
if (err && gpg_err_code (err) != GPG_ERR_ENOENT)
{
log_error ("error parsing '%s' line %d: %s\n",
fname, lineno, gpg_strerror (err));
log_error ("can't open '%s': %s\n", oldfname, gpg_strerror (err));
goto leave;
}
}
else
if (!pk)
{
/* Key is still in the old format or does not exist - create a
* new container. */
pk = nvc_new_private_key ();
if (!pk)
{
@ -198,10 +128,13 @@ agent_write_private_key (const unsigned char *grip,
goto leave;
}
}
es_clearerr (fp);
/* Check whether we already have a regular key. */
is_regular = (key && gpg_err_code (is_shadowed_key (key)) != GPG_ERR_TRUE);
/* Turn (BUFFER,LENGTH) into a gcrypt s-expression and set it into
* our name value container. */
gcry_sexp_release (key);
err = gcry_sexp_sscan (&key, NULL, buffer, length);
if (err)
goto leave;
@ -209,6 +142,22 @@ agent_write_private_key (const unsigned char *grip,
if (err)
goto leave;
/* Check that we do not update a regular key with a shadow key. */
if (is_regular && gpg_err_code (is_shadowed_key (key)) == GPG_ERR_TRUE)
{
log_info ("updating regular key file '%s'"
" by a shadow key inhibited\n", oldfname);
err = 0; /* Simply ignore the error. */
goto leave;
}
/* Check that we update a regular key only in force mode. */
if (is_regular && !force)
{
log_error ("secret key file '%s' already exists\n", oldfname);
err = gpg_error (GPG_ERR_EEXIST);
goto leave;
}
/* If requested write a Token line. */
if (serialno && keyref)
{
@ -283,10 +232,14 @@ agent_write_private_key (const unsigned char *grip,
goto leave;
}
/* Back to start and write. */
err = es_fseek (fp, 0, SEEK_SET);
if (err)
goto leave;
/* Create a temporary file for writing. */
fname = fname_from_keygrip (grip, 1);
fp = fname ? es_fopen (fname, "wbx,mode=-rw") : NULL;
if (!fp)
{
log_error ("can't create '%s': %s\n", fname, gpg_strerror (err));
goto leave;
}
err = nvc_write (pk, fp);
if (!err)
@ -298,14 +251,6 @@ agent_write_private_key (const unsigned char *grip,
goto leave;
}
if (ftruncate (es_fileno (fp), es_ftello (fp)))
{
err = gpg_error_from_syserror ();
log_error ("error truncating '%s': %s\n", fname, gpg_strerror (err));
remove = 1;
goto leave;
}
if (es_fclose (fp))
{
err = gpg_error_from_syserror ();
@ -313,16 +258,27 @@ agent_write_private_key (const unsigned char *grip,
remove = 1;
goto leave;
}
else
fp = NULL;
fp = NULL;
err = gnupg_rename_file (fname, oldfname, &blocksigs);
if (err)
{
err = gpg_error_from_syserror ();
log_error ("error renaming '%s': %s\n", fname, gpg_strerror (err));
remove = 1;
goto leave;
}
bump_key_eventcounter ();
leave:
if (blocksigs)
gnupg_unblock_all_signals ();
es_fclose (fp);
if (remove)
if (remove && fname)
gnupg_remove (fname);
xfree (fname);
xfree (oldfname);
xfree (token);
xfree (token0);
xfree (dispserialno_buffer);
@ -345,7 +301,7 @@ try_unprotect_cb (struct pin_entry_info_s *pi)
gnupg_isotime_t now, protected_at, tmptime;
char *desc = NULL;
assert (!arg->unprotected_key);
log_assert (!arg->unprotected_key);
arg->change_required = 0;
err = agent_unprotect (ctrl, arg->protected_key, pi->pin, protected_at,
@ -722,7 +678,7 @@ unprotect (ctrl_t ctrl, const char *cache_nonce, const char *desc_text,
}
else
{
assert (arg.unprotected_key);
log_assert (arg.unprotected_key);
if (arg.change_required)
{
/* The callback told as that the user should change their
@ -730,7 +686,7 @@ unprotect (ctrl_t ctrl, const char *cache_nonce, const char *desc_text,
size_t canlen, erroff;
gcry_sexp_t s_skey;
assert (arg.unprotected_key);
log_assert (arg.unprotected_key);
canlen = gcry_sexp_canon_len (arg.unprotected_key, 0, NULL, NULL);
rc = gcry_sexp_sscan (&s_skey, &erroff,
(char*)arg.unprotected_key, canlen);
@ -774,17 +730,17 @@ unprotect (ctrl_t ctrl, const char *cache_nonce, const char *desc_text,
/* Read the key identified by GRIP from the private key directory and
* return it as an gcrypt S-expression object in RESULT. If R_KEYMETA
* is not NULl and the extended key format is used, the meta data
* items are stored there. However the "Key:" item is removed from
* it. On failure returns an error code and stores NULL at RESULT. */
* is not NULL, the meta data items are stored there. However the
* "Key:" item is removed. Returns an error code and stores NULL at
* RESULT. */
static gpg_error_t
read_key_file (const unsigned char *grip, gcry_sexp_t *result, nvc_t *r_keymeta)
{
gpg_error_t err;
char *fname;
estream_t fp;
estream_t fp = NULL;
struct stat st;
unsigned char *buf;
unsigned char *buf = NULL;
size_t buflen, erroff;
gcry_sexp_t s_skey;
char first;
@ -793,15 +749,19 @@ read_key_file (const unsigned char *grip, gcry_sexp_t *result, nvc_t *r_keymeta)
if (r_keymeta)
*r_keymeta = NULL;
fname = fname_from_keygrip (grip);
fp = fname? es_fopen (fname, "rb") : NULL;
fname = fname_from_keygrip (grip, 0);
if (!fname)
{
err = gpg_error_from_syserror ();
goto leave;
}
fp = es_fopen (fname, "rb");
if (!fp)
{
err = gpg_error_from_syserror ();
if (gpg_err_code (err) != GPG_ERR_ENOENT)
log_error ("can't open '%s': %s\n", fname, gpg_strerror (err));
xfree (fname);
return err;
goto leave;
}
if (es_fread (&first, 1, 1, fp) != 1)
@ -809,18 +769,14 @@ read_key_file (const unsigned char *grip, gcry_sexp_t *result, nvc_t *r_keymeta)
err = gpg_error_from_syserror ();
log_error ("error reading first byte from '%s': %s\n",
fname, gpg_strerror (err));
xfree (fname);
es_fclose (fp);
return err;
goto leave;
}
if (es_fseek (fp, 0, SEEK_SET))
{
err = gpg_error_from_syserror ();
log_error ("error seeking in '%s': %s\n", fname, gpg_strerror (err));
xfree (fname);
es_fclose (fp);
return err;
goto leave;
}
if (first != '(')
@ -830,8 +786,6 @@ read_key_file (const unsigned char *grip, gcry_sexp_t *result, nvc_t *r_keymeta)
int line;
err = nvc_parse_private_key (&pk, &line, fp);
es_fclose (fp);
if (err)
log_error ("error parsing '%s' line %d: %s\n",
fname, line, gpg_strerror (err));
@ -849,17 +803,14 @@ read_key_file (const unsigned char *grip, gcry_sexp_t *result, nvc_t *r_keymeta)
*r_keymeta = pk;
else
nvc_release (pk);
xfree (fname);
return err;
goto leave;
}
if (fstat (es_fileno (fp), &st))
{
err = gpg_error_from_syserror ();
log_error ("can't stat '%s': %s\n", fname, gpg_strerror (err));
xfree (fname);
es_fclose (fp);
return err;
goto leave;
}
buflen = st.st_size;
@ -869,11 +820,7 @@ read_key_file (const unsigned char *grip, gcry_sexp_t *result, nvc_t *r_keymeta)
err = gpg_error_from_syserror ();
log_error ("error allocating %zu bytes for '%s': %s\n",
buflen, fname, gpg_strerror (err));
xfree (fname);
es_fclose (fp);
xfree (buf);
return err;
goto leave;
}
if (es_fread (buf, buflen, 1, fp) != 1)
@ -881,25 +828,24 @@ read_key_file (const unsigned char *grip, gcry_sexp_t *result, nvc_t *r_keymeta)
err = gpg_error_from_syserror ();
log_error ("error reading %zu bytes from '%s': %s\n",
buflen, fname, gpg_strerror (err));
xfree (fname);
es_fclose (fp);
xfree (buf);
return err;
goto leave;
}
/* Convert the file into a gcrypt S-expression object. */
err = gcry_sexp_sscan (&s_skey, &erroff, (char*)buf, buflen);
xfree (fname);
es_fclose (fp);
xfree (buf);
if (err)
{
log_error ("failed to build S-Exp (off=%u): %s\n",
(unsigned int)erroff, gpg_strerror (err));
return err;
goto leave;
}
*result = s_skey;
return 0;
leave:
es_fclose (fp);
xfree (fname);
xfree (buf);
return err;
}
@ -1270,6 +1216,29 @@ agent_is_eddsa_key (gcry_sexp_t s_key)
}
/* This function returns GPG_ERR_TRUE if S_SKEY represents a shadowed
* key. 0 is return for other key types. Any other error may occur
* if S_SKEY is not valid. */
static gpg_error_t
is_shadowed_key (gcry_sexp_t s_skey)
{
gpg_error_t err;
unsigned char *buf;
size_t buflen;
err = make_canon_sexp (s_skey, &buf, &buflen);
if (err)
return err;
if (agent_private_key_type (buf) == PRIVATE_KEY_SHADOWED)
err = gpg_error (GPG_ERR_TRUE);
wipememory (buf, buflen);
xfree (buf);
return err;
}
/* Return the key for the keygrip GRIP. The result is stored at
RESULT. This function extracts the key from the private key
database and returns it as an S-expression object as it is. On
@ -1376,7 +1345,7 @@ agent_public_key_from_file (ctrl_t ctrl,
such a task. After all that is what we do in protect.c. Need
to find common patterns and write a straightformward API to use
them. */
assert (sizeof (size_t) <= sizeof (void*));
log_assert (sizeof (size_t) <= sizeof (void*));
format = xtrymalloc (15+4+7*npkey+10+15+1+1);
if (!format)
@ -1401,14 +1370,14 @@ agent_public_key_from_file (ctrl_t ctrl,
*p++ = '(';
*p++ = *s++;
p = stpcpy (p, " %m)");
assert (argidx < DIM (args));
log_assert (argidx < DIM (args));
args[argidx++] = &array[idx];
}
*p++ = ')';
if (uri)
{
p = stpcpy (p, "(uri %b)");
assert (argidx+1 < DIM (args));
log_assert (argidx+1 < DIM (args));
uri_intlen = (int)uri_length;
args[argidx++] = (void *)&uri_intlen;
args[argidx++] = (void *)&uri;
@ -1416,14 +1385,14 @@ agent_public_key_from_file (ctrl_t ctrl,
if (comment)
{
p = stpcpy (p, "(comment %b)");
assert (argidx+1 < DIM (args));
log_assert (argidx+1 < DIM (args));
comment_intlen = (int)comment_length;
args[argidx++] = (void *)&comment_intlen;
args[argidx++] = (void*)&comment;
}
*p++ = ')';
*p = 0;
assert (argidx < DIM (args));
log_assert (argidx < DIM (args));
args[argidx] = NULL;
err = gcry_sexp_build_array (&list, NULL, format, args);
@ -1520,7 +1489,7 @@ agent_key_info_from_file (ctrl_t ctrl, const unsigned char *grip,
if (!err)
{
n = gcry_sexp_canon_len (s, 0, NULL, NULL);
assert (n);
log_assert (n);
*r_shadow_info = xtrymalloc (n);
if (!*r_shadow_info)
err = gpg_error_from_syserror ();