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Add function to extract key id from signatures

Browse Source 
This does not support all possibilities of RFC4880, but it does
cover every key currently used in Arch Linux.

Signed-off-by: Allan McRae <allan@archlinux.org>
This commit is contained in:
Allan McRae 2012-11-02 23:06:45 +10:00
parent 4ec6848f91
commit 05745089ac
2 changed files with 116 additions and 0 deletions
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113
lib/libalpm/signing.c
View File

@ -950,4 +950,117 @@ int SYMEXPORT alpm_siglist_cleanup(alpm_siglist_t *siglist)
return 0;
}
/**
* Extract the Issuer Key ID from a signature
* @param sig PGP signature
* @param len length of signature
* @param keys a pointer to storage for key IDs
* @return 0 on success, -1 on error
*/
int _alpm_extract_keyid(alpm_handle_t *handle, const char *identifier,
const unsigned char *sig, const size_t len, alpm_list_t **keys)
{
size_t pos, spos, blen, hlen, ulen, slen;
pos = 0;
while(pos < len) {
if(!(sig[pos] & 0x80)) {
_alpm_log(handle, ALPM_LOG_ERROR,
_("%s: signature format error"), identifier);
return -1;
}
if(sig[pos] & 0x40) {
/* "new" packet format is not supported */
_alpm_log(handle, ALPM_LOG_ERROR,
_("%s: unsupported signature format"), identifier);
return -1;
}
if(((sig[pos] & 0x3f) >> 2) != 2) {
/* signature is not a "Signature Packet" */
_alpm_log(handle, ALPM_LOG_ERROR,
_("%s: signature format error"), identifier);
return -1;
}
switch(sig[pos] & 0x03) {
case 0:
blen = sig[pos + 1];
pos = pos + 2;
break;
case 1:
blen = (sig[pos + 1] << 8) | sig[pos + 2];
pos = pos + 3;
break;
case 2:
blen = (sig[pos + 1] << 24) | (sig[pos + 2] << 16) | (sig[pos + 3] << 8) | sig[pos + 4];
pos = pos + 5;
break;
case 3:
/* partial body length not supported */
_alpm_log(handle, ALPM_LOG_ERROR,
_("%s: unsupported signature format"), identifier);
return -1;
}
if(sig[pos] != 4) {
/* only support version 4 signature packet format */
_alpm_log(handle, ALPM_LOG_ERROR,
_("%s: unsupported signature format"), identifier);
return -1;
}
if(sig[pos + 1] != 0x00) {
/* not a signature of a binary document */
_alpm_log(handle, ALPM_LOG_ERROR,
_("%s: signature format error"), identifier);
return -1;
}
pos = pos + 4;
hlen = (sig[pos] << 8) | sig[pos + 1];
pos = pos + hlen + 2;
ulen = (sig[pos] << 8) | sig[pos + 1];
pos = pos + 2;
spos = pos;
while(spos < pos + ulen) {
if(sig[spos] < 192) {
slen = sig[spos];
spos = spos + 1;
} else if(sig[spos] < 255) {
slen = (sig[spos] << 8) | sig[spos + 1];
spos = spos + 2;
} else {
slen = (sig[spos + 1] << 24) | (sig[spos + 2] << 16) | (sig[spos + 3] << 8) | sig[spos + 4];
spos = spos + 5;
}
if(sig[spos] == 16) {
/* issuer key ID */
char key[17];
size_t i;
for (i = 0; i < 8; i++) {
sprintf(&key[i * 2], "%02X", sig[spos + i + 1]);
}
*keys = alpm_list_add(*keys, strdup(key));
break;
}
spos = spos + slen;
}
pos = pos + (blen - hlen - 8);
}
return 0;
}
/* vim: set ts=2 sw=2 noet: */

3
lib/libalpm/signing.h
View File

@ -34,6 +34,9 @@ int _alpm_process_siglist(alpm_handle_t *handle, const char *identifier,
int _alpm_key_in_keychain(alpm_handle_t *handle, const char *fpr);
int _alpm_key_import(alpm_handle_t *handle, const char *fpr);
int _alpm_extract_keyid(alpm_handle_t *handle, const char *identifier,
const unsigned char *sig, const size_t len, alpm_list_t **keys);
#endif /* _ALPM_SIGNING_H */
/* vim: set ts=2 sw=2 noet: */