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gpg: Distinguish between missing and cleared key flags. 

* include/cipher.h (PUBKEY_USAGE_NONE): New.
* g10/getkey.c (parse_key_usage): Set new flag.
--

We do not want to use the default capabilities (derived from the
algorithm) if any key flags are given in a signature.  Thus if key
flags are used in any way, the default key capabilities are never
used.

This allows to create a key with key flags set to all zero so it can't
be used.  This better reflects common sense.
This commit is contained in:
Werner Koch 2013-03-15 15:46:03 +01:00
parent 76dc5c08dc
commit 4bde12206c
2 changed files with 13 additions and 2 deletions
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8
g10/getkey.c
View File

@ -1276,13 +1276,19 @@ parse_key_usage (PKT_signature * sig)
if (flags)
key_usage |= PUBKEY_USAGE_UNKNOWN;
if (!key_usage)
key_usage |= PUBKEY_USAGE_NONE;
}
else if (p) /* Key flags of length zero. */
key_usage |= PUBKEY_USAGE_NONE;
/* We set PUBKEY_USAGE_UNKNOWN to indicate that this key has a
capability that we do not handle. This serves to distinguish
between a zero key usage which we handle as the default
capabilities for that algorithm, and a usage that we do not
handle. */
handle. Likewise we use PUBKEY_USAGE_NONE to indicate that
key_flags have been given but they do not specify any usage. */
return key_usage;
}

7
include/cipher.h
View File

@ -54,9 +54,14 @@
#define PUBKEY_USAGE_SIG GCRY_PK_USAGE_SIGN /* Good for signatures. */
#define PUBKEY_USAGE_ENC GCRY_PK_USAGE_ENCR /* Good for encryption. */
#define PUBKEY_USAGE_CERT GCRY_PK_USAGE_CERT /* Also good to certify keys. */
#define PUBKEY_USAGE_CERT GCRY_PK_USAGE_CERT /* Also good to certify keys.*/
#define PUBKEY_USAGE_AUTH GCRY_PK_USAGE_AUTH /* Good for authentication. */
#define PUBKEY_USAGE_UNKNOWN GCRY_PK_USAGE_UNKN /* Unknown usage flag. */
#define PUBKEY_USAGE_NONE 256 /* No usage given. */
#if (GCRY_PK_USAGE_SIGN | GCRY_PK_USAGE_ENCR | GCRY_PK_USAGE_CERT \
| GCRY_PK_USAGE_AUTH | GCRY_PK_USAGE_UNKN) >= 256
# error Please choose another value for PUBKEY_USAGE_NONE
#endif
#define DIGEST_ALGO_MD5 /* 1 */ GCRY_MD_MD5
#define DIGEST_ALGO_SHA1 /* 2 */ GCRY_MD_SHA1