Re: [pacman-dev] [PATCH v3] Fallback to detached signatures during keyring check

On 06/01/20 at 11:45pm, Anatol Pomozov wrote:

Pacman has a 'key in keyring' verification step that makes sure the signatures have a valid keyid. Currently pacman parses embedded package signatures only.

Add a fallback to detached signatures. If embedded signature is missing then it tries to read corresponding *.sig file and get keyid from there.

Verification: debug: found cached pkg: /var/cache/pacman/pkg/glib-networking-2.64.3-1-x86_64.pkg.tar.zst debug: found detached signature /var/cache/pacman/pkg/glib-networking-2.64.3-1-x86_64.pkg.tar.zst.sig with size 310 debug: found signature key: A5E9288C4FA415FA debug: looking up key A5E9288C4FA415FA locally debug: key lookup success, key exists

Signed-off-by: Anatol Pomozov --- lib/libalpm/alpm.h | 11 +++++++++++ lib/libalpm/package.c | 34 ++++++++++++++++++++++++++++++++++ lib/libalpm/sync.c | 18 +++++++++--------- lib/libalpm/util.c | 37 +++++++++++++++++++++++++++++++++++++ lib/libalpm/util.h | 1 + 5 files changed, 92 insertions(+), 9 deletions(-)

diff --git a/lib/libalpm/alpm.h b/lib/libalpm/alpm.h index c6a13273..0ba57109 100644 --- a/lib/libalpm/alpm.h +++ b/lib/libalpm/alpm.h @@ -1403,6 +1403,17 @@ alpm_db_t *alpm_pkg_get_db(alpm_pkg_t *pkg); */ const char *alpm_pkg_get_base64_sig(alpm_pkg_t *pkg);

+/** Extracts package signature either from embedded package signature + * or if it is absent then reads data from detached signature file. + * @param pkg a pointer to package. + * @param sig output parameter for signature data. Callee function allocates + * a buffer needed for the signature data. Caller is responsible for + * freeing this buffer. + * @param sig_len output parameter for the signature data length. + * @return 0 on success, negative number on error.

alpm_errno_t values are positive.

+ */ +int alpm_pkg_get_sig(alpm_pkg_t *pkg, unsigned char **sig, size_t *sig_len); + /** Returns the method used to validate a package during install. * @param pkg a pointer to package * @return an enum member giving the validation method diff --git a/lib/libalpm/package.c b/lib/libalpm/package.c index 5c5fa073..1335b70e 100644 --- a/lib/libalpm/package.c +++ b/lib/libalpm/package.c @@ -268,6 +268,40 @@ const char SYMEXPORT *alpm_pkg_get_base64_sig(alpm_pkg_t *pkg) return pkg->base64_sig; }

+int SYMEXPORT alpm_pkg_get_sig(alpm_pkg_t *pkg, unsigned char **sig, size_t *sig_len) +{ + ASSERT(pkg != NULL, return -1); + + if(pkg->base64_sig) { + return alpm_decode_signature(pkg->base64_sig, sig, sig_len);

You're returning an error without setting pm_errno.

+ } else { + char *pkgpath, *sigpath; + alpm_errno_t err; + int ret = -1; + + pkgpath = _alpm_filecache_find(pkg->handle, pkg->filename); + if(!pkgpath) { + RET_ERR(pkg->handle, ALPM_ERR_PKG_NOT_FOUND, -1); + } + sigpath = _alpm_sigpath(pkg->handle, pkgpath); + if(!sigpath || _alpm_access(pkg->handle, NULL, sigpath, R_OK)) { + GOTO_ERR(pkg->handle, ALPM_ERR_SIG_MISSING, exit); + } + err = _alpm_read_file(sigpath, sig, sig_len); + if(err == ALPM_ERR_OK) { + _alpm_log(pkg->handle, ALPM_LOG_DEBUG, "found detached signature %s with size %ld\n", + sigpath, *sig_len); + } else { + GOTO_ERR(pkg->handle, err, exit); + } + ret = 0; +exit:

Change exit to cleanup; exit makes it look like you are terminating the program.

+ FREE(pkgpath); + FREE(sigpath); + return ret; + } +} + const char SYMEXPORT *alpm_pkg_get_arch(alpm_pkg_t *pkg) { ASSERT(pkg != NULL, return NULL); diff --git a/lib/libalpm/sync.c b/lib/libalpm/sync.c index 8c01ad95..9350793a 100644 --- a/lib/libalpm/sync.c +++ b/lib/libalpm/sync.c @@ -880,18 +880,18 @@ static int check_keyring(alpm_handle_t *handle) }

level = alpm_db_get_siglevel(alpm_pkg_get_db(pkg)); - if((level & ALPM_SIG_PACKAGE) && pkg->base64_sig) { - unsigned char *decoded_sigdata = NULL; - size_t data_len; - int decode_ret = alpm_decode_signature(pkg->base64_sig, - &decoded_sigdata, &data_len); - if(decode_ret == 0) { + if((level & ALPM_SIG_PACKAGE)) { + unsigned char *sig = NULL; + size_t sig_len; + int ret = alpm_pkg_get_sig(pkg, &sig, &sig_len); + if(ret == 0) { alpm_list_t *keys = NULL; - if(alpm_extract_keyid(handle, pkg->name, decoded_sigdata, - data_len, &keys) == 0) { + if(alpm_extract_keyid(handle, pkg->name, sig, + sig_len, &keys) == 0) { alpm_list_t *k; for(k = keys; k; k = k->next) { char *key = k->data; + _alpm_log(handle, ALPM_LOG_DEBUG, "found signature key: %s\n", key); if(!alpm_list_find(errors, key, key_cmp) && _alpm_key_in_keychain(handle, key) == 0) { keyinfo = malloc(sizeof(struct keyinfo_t)); @@ -905,8 +905,8 @@ static int check_keyring(alpm_handle_t *handle) } FREELIST(keys); } - free(decoded_sigdata); } + free(sig); } }

diff --git a/lib/libalpm/util.c b/lib/libalpm/util.c index 76728eb4..65a6f3df 100644 --- a/lib/libalpm/util.c +++ b/lib/libalpm/util.c @@ -1489,3 +1489,40 @@ void _alpm_alloc_fail(size_t size) { fprintf(stderr, "alloc failure: could not allocate %zu bytes\n", size); } + +/** This functions reads file content. + * + * Memory buffer is allocated by the callee function. It is responsibility + * of the caller to free the buffer. + * + * @param filepath filepath to read + * @param data pointer to output buffer + * @param data_len size of the output buffer + * @return error code for the operation + */ +alpm_errno_t _alpm_read_file(const char *filepath, unsigned char **data, size_t *data_len) +{ + struct stat st; + FILE *fp; + + if((fp = fopen(filepath, "rb")) == NULL) { + return -1;

-1 is not an alpm_errno_t.

+ } + + if(fstat(fileno(fp), &st) != 0) { + fclose(fp); + return ALPM_ERR_NOT_A_FILE; + } + *data_len = st.st_size; + + MALLOC(*data, *data_len, fclose(fp); return ALPM_ERR_MEMORY); + + if(fread(*data, *data_len, 1, fp) != 1) { + FREE(*data); + fclose(fp); + return ALPM_ERR_SYSTEM; + } + + fclose(fp); + return ALPM_ERR_OK; +} diff --git a/lib/libalpm/util.h b/lib/libalpm/util.h index 4fc6e718..03c8ed44 100644 --- a/lib/libalpm/util.h +++ b/lib/libalpm/util.h @@ -155,6 +155,7 @@ int _alpm_fnmatch_patterns(alpm_list_t *patterns, const char *string); int _alpm_fnmatch(const void *pattern, const void *string); void *_alpm_realloc(void **data, size_t *current, const size_t required); void *_alpm_greedy_grow(void **data, size_t *current, const size_t required); +alpm_errno_t _alpm_read_file(const char *filepath, unsigned char **data, size_t *data_len);

#ifndef HAVE_STRSEP char *strsep(char **, const char *); -- 2.27.0