This does not support all possibilities of RFC4880, but it does cover every key currently used in Arch Linux.
Signed-off-by: Allan McRae <[email protected]> --- 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
