This does not support all possibilities of RFC4880, but it does
cover every key currently used in Arch Linux.
Signed-off-by: Allan McRae
---
lib/libalpm/signing.c | 100 ++++++++++++++++++++++++++++++++++++++++++++++++++
lib/libalpm/signing.h | 2 +
2 files changed, 102 insertions(+)
diff --git a/lib/libalpm/signing.c b/lib/libalpm/signing.c
index 9d56aba..6b13522 100644
--- a/lib/libalpm/signing.c
+++ b/lib/libalpm/signing.c
@@ -948,4 +948,104 @@ 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(const unsigned char *sig, size_t len, alpm_list_t **keys)
+{
+ size_t pos, spos, blen, hlen, ulen, slen;
+ pos = 0;
+
+ while(pos < len) {
+ if(!(sig[pos] & 0x80)) {
+ return -1;
+ }
+
+ if(sig[pos] & 0x40) {
+ // "new" packet format is not supported
+ return -1;
+ }
+
+ if(((sig[pos] & 0x3f) >> 2) != 2) {
+ // signature is not a "Signature Packet"
+ 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
+ return -1;
+ }
+
+ if(sig[pos] != 4) {
+ // only support version 4 signature packet format
+ return -1;
+ }
+
+ if(sig[pos + 1] != 0x00) {
+ // not a signature of a binary document
+ 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[16];
+ size_t i;
+ for (i = 0; i < 8; i++) {
+ sprintf(&key[i * 2], "%02hhX", 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: */
diff --git a/lib/libalpm/signing.h b/lib/libalpm/signing.h
index a78e4b7..6537ee3 100644
--- a/lib/libalpm/signing.h
+++ b/lib/libalpm/signing.h
@@ -34,6 +34,8 @@ 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(const unsigned char *sig, size_t len, alpm_list_t **keys);
+
#endif /* _ALPM_SIGNING_H */
/* vim: set ts=2 sw=2 noet: */
--
1.8.0