Package: release.debian.org Severity: normal Tags: bullseye User: release.debian....@packages.debian.org Usertags: pu X-Debbugs-Cc: libg...@packages.debian.org Control: affects -1 + src:libgit2
After fixing CVE-2023-22742 for LTS and ELTS, I'd like to see this CVE also fixed in stable, for consistency. The CVE is an inproper ssh certificate validation vulnerabilty, which allows man-in-the-middle attacks. [ Tests ] I've manually tested the patch (checking if git poperations still work using the ssh transport. Autopkgtests are green too. [ Risks ] Manual tests and test suite works ok. [ Checklist ] [X] *all* changes are documented in the d/changelog [X] I reviewed all changes and I approve them [X] attach debdiff against the package in (old)stable [X] the issue is verified as fixed in unstable [ Changes ] The change is a backport of the upstream fix: https://github.com/libgit2/libgit2/commit/cd6f679af401eda1f172402006ef8265f8bd58ea
diff -Nru libgit2-1.1.0+dfsg.1/debian/changelog libgit2-1.1.0+dfsg.1/debian/changelog --- libgit2-1.1.0+dfsg.1/debian/changelog 2021-01-06 18:28:58.000000000 +0100 +++ libgit2-1.1.0+dfsg.1/debian/changelog 2023-02-24 16:11:52.000000000 +0100 @@ -1,3 +1,10 @@ +libgit2 (1.1.0+dfsg.1-4+deb11u1) bullseye-security; urgency=high + + * Non-maintainer upload by the Security Team. + * Backport patch for CVE-2023-22742 (Closes: #1029368) + + -- Tobias Frost <t...@debian.org> Fri, 24 Feb 2023 16:11:52 +0100 + libgit2 (1.1.0+dfsg.1-4) unstable; urgency=medium * Source-only upload for migration. diff -Nru libgit2-1.1.0+dfsg.1/debian/patches/CVE-2023-22742.patch libgit2-1.1.0+dfsg.1/debian/patches/CVE-2023-22742.patch --- libgit2-1.1.0+dfsg.1/debian/patches/CVE-2023-22742.patch 1970-01-01 01:00:00.000000000 +0100 +++ libgit2-1.1.0+dfsg.1/debian/patches/CVE-2023-22742.patch 2023-02-24 16:11:52.000000000 +0100 @@ -0,0 +1,523 @@ +Description: CVE-2023-22742 - fails to verify SSH keys by default + CVE-Description: libgit2 is a cross-platform, linkable library + implementation of Git. When using an SSH remote with the optional libssh2 + backend, libgit2 does not perform certificate checking by default. Prior + versions of libgit2 require the caller to set the `certificate_check` field of + libgit2's `git_remote_callbacks` structure - if a certificate check callback is + not set, libgit2 does not perform any certificate checking. This means that by + default - without configuring a certificate check callback, clients will not + perform validation on the server SSH keys and may be subject to a + man-in-the-middle attack. + This is a backport of the upstream fix to the Debian stretch version. +Origin: https://github.com/libgit2/libgit2/pull/6449 +Bug-Debian: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1029368 +Forwarded: <URL|no|not-needed, useless if you have a Bug field, optional> +Last-Update: 2023-02-21 <YYYY-MM-DD, last update of the meta-information, optional> +--- +This patch header follows DEP-3: http://dep.debian.net/deps/dep3/ +--- a/src/transports/ssh.c ++++ b/src/transports/ssh.c +@@ -475,15 +475,122 @@ + return 0; + } + ++ ++#define KNOWN_HOSTS_FILE ".ssh/known_hosts" ++ ++/* ++ * Load the known_hosts file. ++ * ++ * Returns success but leaves the output NULL if we couldn't find the file. ++ */ ++static int load_known_hosts(LIBSSH2_KNOWNHOSTS **hosts, LIBSSH2_SESSION *session) ++{ ++ git_buf path = GIT_BUF_INIT; ++ LIBSSH2_KNOWNHOSTS *known_hosts = NULL; ++ int error; ++ char *home = getenv("HOME"); ++ ++ assert(hosts); ++ ++ if (!home) ++ return GIT_ENOTFOUND; ++ ++ ++ ++ if ((error = git_buf_join(&path, '/', home, KNOWN_HOSTS_FILE)) < 0) ++ goto out; ++ ++ if ((known_hosts = libssh2_knownhost_init(session)) == NULL) { ++ ssh_error(session, "error initializing known hosts"); ++ error = -1; ++ goto out; ++ } ++ ++ /* ++ * Try to read the file and consider not finding it as not trusting the ++ * host rather than an error. ++ */ ++ error = libssh2_knownhost_readfile(known_hosts, path.ptr, LIBSSH2_KNOWNHOST_FILE_OPENSSH); ++ if (error == LIBSSH2_ERROR_FILE) ++ error = 0; ++ if (error < 0) ++ ssh_error(session, "error reading known_hosts"); ++ ++out: ++ *hosts = known_hosts; ++ ++ git_buf_free(&path); ++ ++ return error; ++} ++ ++static const char *hostkey_type_to_string(int type) ++{ ++ switch (type) { ++ case LIBSSH2_KNOWNHOST_KEY_SSHRSA: ++ return "ssh-rsa"; ++ case LIBSSH2_KNOWNHOST_KEY_SSHDSS: ++ return "ssh-dss"; ++#ifdef LIBSSH2_KNOWNHOST_KEY_ECDSA_256 ++ case LIBSSH2_KNOWNHOST_KEY_ECDSA_256: ++ return "ecdsa-sha2-nistp256"; ++ case LIBSSH2_KNOWNHOST_KEY_ECDSA_384: ++ return "ecdsa-sha2-nistp384"; ++ case LIBSSH2_KNOWNHOST_KEY_ECDSA_521: ++ return "ecdsa-sha2-nistp521"; ++#endif ++#ifdef LIBSSH2_KNOWNHOST_KEY_ED25519 ++ case LIBSSH2_KNOWNHOST_KEY_ED25519: ++ return "ssh-ed25519"; ++#endif ++ } ++ ++ return NULL; ++} ++ ++/* ++ * We figure out what kind of key we want to ask the remote for by trying to ++ * look it up with a nonsense key and using that mismatch to figure out what key ++ * we do have stored for the host. ++ * ++ * Returns the string to pass to libssh2_session_method_pref or NULL if we were ++ * unable to find anything or an error happened. ++ */ ++static const char *find_hostkey_preference(LIBSSH2_KNOWNHOSTS *known_hosts, const char *hostname, int port) ++{ ++ struct libssh2_knownhost *host = NULL; ++ /* Specify no key type so we don't filter on that */ ++ int type = LIBSSH2_KNOWNHOST_TYPE_PLAIN | LIBSSH2_KNOWNHOST_KEYENC_RAW; ++ const char key = '\0'; ++ int error; ++ ++ /* ++ * In case of mismatch, we can find the type of key from known_hosts in ++ * the returned host's information as it means that an entry was found ++ * but our nonsense key obviously didn't match. ++ */ ++ error = libssh2_knownhost_checkp(known_hosts, hostname, port, &key, 1, type, &host); ++ if (error == LIBSSH2_KNOWNHOST_CHECK_MISMATCH) ++ return hostkey_type_to_string(host->typemask & LIBSSH2_KNOWNHOST_KEY_MASK); ++ ++ return NULL; ++} ++ + static int _git_ssh_session_create( + LIBSSH2_SESSION** session, ++ LIBSSH2_KNOWNHOSTS **hosts, ++ const char *hostname, ++ int port, + git_stream *io) + { + int rc = 0; + LIBSSH2_SESSION* s; ++ LIBSSH2_KNOWNHOSTS *known_hosts; + git_socket_stream *socket = GIT_CONTAINER_OF(io, git_socket_stream, parent); ++ const char *keytype = NULL; + + assert(session); ++ assert(hosts); + + s = libssh2_session_init(); + if (!s) { +@@ -491,21 +598,224 @@ + return -1; + } + ++ if ((rc = load_known_hosts(&known_hosts, s)) < 0) { ++ ssh_error(s, "error loading known_hosts"); ++ libssh2_session_free(s); ++ return -1; ++ } ++ ++ if ((keytype = find_hostkey_preference(known_hosts, hostname, port)) != NULL) { ++ do { ++ rc = libssh2_session_method_pref(s, LIBSSH2_METHOD_HOSTKEY, keytype); ++ } while (LIBSSH2_ERROR_EAGAIN == rc || LIBSSH2_ERROR_TIMEOUT == rc); ++ if (rc != LIBSSH2_ERROR_NONE) { ++ ssh_error(s, "failed to set hostkey preference"); ++ goto on_error; ++ } ++ } ++ + do { + rc = libssh2_session_handshake(s, socket->s); + } while (LIBSSH2_ERROR_EAGAIN == rc || LIBSSH2_ERROR_TIMEOUT == rc); + + if (rc != LIBSSH2_ERROR_NONE) { + ssh_error(s, "failed to start SSH session"); +- libssh2_session_free(s); +- return -1; ++ goto on_error; + } + + libssh2_session_set_blocking(s, 1); + + *session = s; ++ *hosts = known_hosts; + + return 0; ++ ++on_error: ++ libssh2_knownhost_free(known_hosts); ++ libssh2_session_free(s); ++ return -1; ++} ++ ++ ++/* ++ * Returns the typemask argument to pass to libssh2_knownhost_check{,p} based on ++ * the type of key that libssh2_session_hostkey returns. ++ */ ++static int fingerprint_type_mask(int keytype) ++{ ++ int mask = LIBSSH2_KNOWNHOST_TYPE_PLAIN | LIBSSH2_KNOWNHOST_KEYENC_RAW; ++ return mask; ++ ++ switch (keytype) { ++ case LIBSSH2_HOSTKEY_TYPE_RSA: ++ mask |= LIBSSH2_KNOWNHOST_KEY_SSHRSA; ++ break; ++ case LIBSSH2_HOSTKEY_TYPE_DSS: ++ mask |= LIBSSH2_KNOWNHOST_KEY_SSHDSS; ++ break; ++#ifdef LIBSSH2_HOSTKEY_TYPE_ECDSA_256 ++ case LIBSSH2_HOSTKEY_TYPE_ECDSA_256: ++ mask |= LIBSSH2_KNOWNHOST_KEY_ECDSA_256; ++ break; ++ case LIBSSH2_HOSTKEY_TYPE_ECDSA_384: ++ mask |= LIBSSH2_KNOWNHOST_KEY_ECDSA_384; ++ break; ++ case LIBSSH2_HOSTKEY_TYPE_ECDSA_521: ++ mask |= LIBSSH2_KNOWNHOST_KEY_ECDSA_521; ++ break; ++#endif ++#ifdef LIBSSH2_HOSTKEY_TYPE_ED25519 ++ case LIBSSH2_HOSTKEY_TYPE_ED25519: ++ mask |= LIBSSH2_KNOWNHOST_KEY_ED25519; ++ break; ++#endif ++ } ++ ++ return mask; ++} ++ ++/* ++ * Check the host against the user's known_hosts file. ++ * ++ * Returns 1/0 for valid/''not-valid or <0 for an error ++ */ ++static int check_against_known_hosts( ++ LIBSSH2_SESSION *session, ++ LIBSSH2_KNOWNHOSTS *known_hosts, ++ const char *hostname, ++ int port, ++ const char *key, ++ size_t key_len, ++ int key_type) ++{ ++ int check, typemask, ret = 0; ++ struct libssh2_knownhost *host = NULL; ++ ++ if (known_hosts == NULL) ++ return 0; ++ ++ typemask = fingerprint_type_mask(key_type); ++ check = libssh2_knownhost_checkp(known_hosts, hostname, port, key, key_len, typemask, &host); ++ if (check == LIBSSH2_KNOWNHOST_CHECK_FAILURE) { ++ ssh_error(session, "error checking for known host"); ++ return -1; ++ } ++ ++ ret = check == LIBSSH2_KNOWNHOST_CHECK_MATCH ? 1 : 0; ++ ++ return ret; ++} ++ ++/* ++ * Perform the check for the session's certificate against known hosts if ++ * possible and then ask the user if they have a callback. ++ * ++ * Returns 1/0 for valid/not-valid or <0 for an error ++ */ ++static int check_certificate( ++ LIBSSH2_SESSION *session, ++ LIBSSH2_KNOWNHOSTS *known_hosts, ++ git_transport_certificate_check_cb check_cb, ++ void *check_cb_payload, ++ const char *host, ++ int port) ++{ ++ git_cert_hostkey cert = {{ 0 }}; ++ const char *key; ++ size_t cert_len; ++ int cert_type, cert_valid = 0, error = 0; ++ ++ if ((key = libssh2_session_hostkey(session, &cert_len, &cert_type)) == NULL) { ++ ssh_error(session, "failed to retrieve hostkey"); ++ return -1; ++ } ++ ++ if ((cert_valid = check_against_known_hosts(session, known_hosts, host, port, key, cert_len, cert_type)) < 0) ++ return -1; ++ ++ cert.parent.cert_type = GIT_CERT_HOSTKEY_LIBSSH2; ++ if (key != NULL) { ++ cert.type |= GIT_CERT_SSH_RAW; ++ cert.hostkey = key; ++ cert.hostkey_len = cert_len; ++ switch (cert_type) { ++ case LIBSSH2_HOSTKEY_TYPE_RSA: ++ cert.raw_type = GIT_CERT_SSH_RAW_TYPE_RSA; ++ break; ++ case LIBSSH2_HOSTKEY_TYPE_DSS: ++ cert.raw_type = GIT_CERT_SSH_RAW_TYPE_DSS; ++ break; ++ ++#ifdef LIBSSH2_HOSTKEY_TYPE_ECDSA_256 ++ case LIBSSH2_HOSTKEY_TYPE_ECDSA_256: ++ cert.raw_type = GIT_CERT_SSH_RAW_TYPE_KEY_ECDSA_256; ++ break; ++ case LIBSSH2_HOSTKEY_TYPE_ECDSA_384: ++ cert.raw_type = GIT_CERT_SSH_RAW_TYPE_KEY_ECDSA_384; ++ break; ++ case LIBSSH2_KNOWNHOST_KEY_ECDSA_521: ++ cert.raw_type = GIT_CERT_SSH_RAW_TYPE_KEY_ECDSA_521; ++ break; ++#endif ++ ++#ifdef LIBSSH2_HOSTKEY_TYPE_ED25519 ++ case LIBSSH2_HOSTKEY_TYPE_ED25519: ++ cert.raw_type = GIT_CERT_SSH_RAW_TYPE_KEY_ED25519; ++ break; ++#endif ++ default: ++ cert.raw_type = GIT_CERT_SSH_RAW_TYPE_UNKNOWN; ++ } ++ } ++ ++#ifdef LIBSSH2_HOSTKEY_HASH_SHA256 ++ key = libssh2_hostkey_hash(session, LIBSSH2_HOSTKEY_HASH_SHA256); ++ if (key != NULL) { ++ cert.type |= GIT_CERT_SSH_SHA256; ++ memcpy(&cert.hash_sha256, key, 32); ++ } ++#endif ++ ++ key = libssh2_hostkey_hash(session, LIBSSH2_HOSTKEY_HASH_SHA1); ++ if (key != NULL) { ++ cert.type |= GIT_CERT_SSH_SHA1; ++ memcpy(&cert.hash_sha1, key, 20); ++ } ++ ++ key = libssh2_hostkey_hash(session, LIBSSH2_HOSTKEY_HASH_MD5); ++ if (key != NULL) { ++ cert.type |= GIT_CERT_SSH_MD5; ++ memcpy(&cert.hash_md5, key, 16); ++ } ++ ++ if (cert.type == 0) { ++ git_error_set(GITERR_SSH, "unable to get the host key"); ++ return -1; ++ } ++ ++ git_error_clear(); ++ error = 0; ++ if (!cert_valid) { ++ git_error_set(GITERR_SSH, "invalid or unknown remote ssh hostkey"); ++ error = GIT_ECERTIFICATE; ++ } ++ ++ if (check_cb != NULL) { ++ git_cert_hostkey *cert_ptr = &cert; ++ git_error_state previous_error = {0}; ++ ++ git_error_state_capture(&previous_error, error); ++ error = check_cb((git_cert *) cert_ptr, cert_valid, host, check_cb_payload); ++ if (error == GIT_PASSTHROUGH) { ++ error = git_error_state_restore(&previous_error); ++ } else if (error < 0 && !git_error_last()) { ++ git_error_set(GITERR_NET, "user canceled hostkey check"); ++ } ++ ++ git_error_state_free(&previous_error); ++ } ++ ++ return error; + } + + #define SSH_DEFAULT_PORT "22" +@@ -517,12 +827,13 @@ + git_smart_subtransport_stream **stream) + { + git_net_url urldata = GIT_NET_URL_INIT; +- int auth_methods, error = 0; ++ int auth_methods, error = 0, iport; + size_t i; + ssh_stream *s; + git_credential *cred = NULL; + LIBSSH2_SESSION* session=NULL; + LIBSSH2_CHANNEL* channel=NULL; ++ LIBSSH2_KNOWNHOSTS *known_hosts = NULL; + + t->current_stream = NULL; + +@@ -557,55 +868,20 @@ + (error = git_stream_connect(s->io)) < 0) + goto done; + +- if ((error = _git_ssh_session_create(&session, s->io)) < 0) +- goto done; +- +- if (t->owner->certificate_check_cb != NULL) { +- git_cert_hostkey cert = {{ 0 }}, *cert_ptr; +- const char *key; +- +- cert.parent.cert_type = GIT_CERT_HOSTKEY_LIBSSH2; +- +-#ifdef LIBSSH2_HOSTKEY_HASH_SHA256 +- key = libssh2_hostkey_hash(session, LIBSSH2_HOSTKEY_HASH_SHA256); +- if (key != NULL) { +- cert.type |= GIT_CERT_SSH_SHA256; +- memcpy(&cert.hash_sha256, key, 32); +- } +-#endif +- +- key = libssh2_hostkey_hash(session, LIBSSH2_HOSTKEY_HASH_SHA1); +- if (key != NULL) { +- cert.type |= GIT_CERT_SSH_SHA1; +- memcpy(&cert.hash_sha1, key, 20); +- } +- +- key = libssh2_hostkey_hash(session, LIBSSH2_HOSTKEY_HASH_MD5); +- if (key != NULL) { +- cert.type |= GIT_CERT_SSH_MD5; +- memcpy(&cert.hash_md5, key, 16); +- } +- +- if (cert.type == 0) { +- git_error_set(GIT_ERROR_SSH, "unable to get the host key"); +- error = -1; +- goto done; +- } +- +- /* We don't currently trust any hostkeys */ +- git_error_clear(); +- +- cert_ptr = &cert; ++ /* ++ * Try to parse the port as a number, if we can't then fall back to ++ * default. It would be nice if we could get the port that was resolved ++ * as part of the stream connection, but that's not something that's ++ * exposed. ++ */ ++ iport = atol(urldata.port); ++ if(iport == 0) iport = -1; + +- error = t->owner->certificate_check_cb((git_cert *) cert_ptr, 0, urldata.host, t->owner->message_cb_payload); +- +- if (error < 0 && error != GIT_PASSTHROUGH) { +- if (!git_error_last()) +- git_error_set(GIT_ERROR_NET, "user cancelled hostkey check"); ++ if ((error = _git_ssh_session_create(&session, &known_hosts, urldata.host, iport, s->io)) < 0) ++ goto done; + +- goto done; +- } +- } ++ if ((error = check_certificate(session, known_hosts, t->owner->certificate_check_cb, t->owner->message_cb_payload, urldata.host, iport)) < 0) ++ goto done; + + /* we need the username to ask for auth methods */ + if (!urldata.username) { +@@ -677,6 +953,9 @@ + if (error < 0) { + ssh_stream_free(*stream); + ++ if (known_hosts) ++ libssh2_knownhost_free(known_hosts); ++ + if (session) + libssh2_session_free(session); + } +--- a/include/git2/cert.h ++++ b/include/git2/cert.h +@@ -80,8 +80,29 @@ + GIT_CERT_SSH_SHA1 = (1 << 1), + /** SHA-256 is available */ + GIT_CERT_SSH_SHA256 = (1 << 2), ++ /** Raw hostkey is available */ ++ GIT_CERT_SSH_RAW = (1 << 3) + } git_cert_ssh_t; + ++ ++typedef enum { ++ /** The raw key is of an unknown type. */ ++ GIT_CERT_SSH_RAW_TYPE_UNKNOWN = 0, ++ /** The raw key is an RSA key. */ ++ GIT_CERT_SSH_RAW_TYPE_RSA = 1, ++ /** The raw key is a DSS key. */ ++ GIT_CERT_SSH_RAW_TYPE_DSS = 2, ++ /** The raw key is a ECDSA 256 key. */ ++ GIT_CERT_SSH_RAW_TYPE_KEY_ECDSA_256 = 3, ++ /** The raw key is a ECDSA 384 key. */ ++ GIT_CERT_SSH_RAW_TYPE_KEY_ECDSA_384 = 4, ++ /** The raw key is a ECDSA 521 key. */ ++ GIT_CERT_SSH_RAW_TYPE_KEY_ECDSA_521 = 5, ++ /** The raw key is a ED25519 key. */ ++ GIT_CERT_SSH_RAW_TYPE_KEY_ED25519 = 6 ++} git_cert_ssh_raw_type_t; ++ ++ + /** + * Hostkey information taken from libssh2 + */ +@@ -111,6 +132,28 @@ + * have the SHA-256 hash of the hostkey. + */ + unsigned char hash_sha256[32]; ++ ++ ++ /** ++ * Raw hostkey type. If `type` has `GIT_CERT_SSH_RAW` set, this will ++ * have the type of the raw hostkey. ++ */ ++ git_cert_ssh_raw_type_t raw_type; ++ ++ /** ++ * Pointer to the raw hostkey. If `type` has `GIT_CERT_SSH_RAW` set, ++ * this will have the raw contents of the hostkey. ++ */ ++ const char *hostkey; ++ ++ /** ++ * Raw hostkey length. If `type` has `GIT_CERT_SSH_RAW` set, this will ++ * have the length of the raw contents of the hostkey. ++ */ ++ size_t hostkey_len; ++ ++ ++ + } git_cert_hostkey; + + /** diff -Nru libgit2-1.1.0+dfsg.1/debian/patches/series libgit2-1.1.0+dfsg.1/debian/patches/series --- libgit2-1.1.0+dfsg.1/debian/patches/series 2020-12-06 23:46:54.000000000 +0100 +++ libgit2-1.1.0+dfsg.1/debian/patches/series 2023-02-24 13:05:26.000000000 +0100 @@ -1,2 +1,3 @@ disable-online-tests.patch enable-repro-builds.patch +CVE-2023-22742.patch
