rassh

An SSH client for Android built around the real OpenSSH.
OpenSSH 10.6p1 and LibreSSL 4.4.0 running on a pseudo-terminal, an xterm compatible terminal emulator, and the keys a phone keyboard lacks.

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There is no SSH reimplementation: ssh, sftp, scp, ssh-agent, ssh-add and ssh-keygen are the OpenSSH programs, built with LibreSSL and upstream defaults, without distribution patches or a system-wide ssh_config, so what works with ssh on an OpenBSD box works here, ~/.ssh/config included, apart from agent forwarding and LocalCommand, see Agent and Key storage. FIDO security keys and PKCS#11 are left out, see Limitations. Once a fingerprint is enrolled, private keys are encrypted and unlocked with it.

Features

• OpenSSH programs - ssh, ssh-keygen, ssh-agent, ssh-add, scp and sftp from OpenSSH 10.6p1, built with LibreSSL 4.4.0
• Extra keys - two rows below the terminal, ESC / | - HOME ↑ END PGUP and TAB CTRL ALT ~ ← ↓ → PGDN. CTRL and ALT apply to the next key, typed or tapped, and ESC, TAB, HOME, END, arrows and page keys repeat while held
• Saved hosts - kept as Host blocks of ~/.ssh/config: host name, user, port, identity file, local, remote and dynamic forwards, plus any other ssh_config(5) option. Other blocks, Host *, Match and those naming several hosts included, and their comments are left untouched, the latter not listed, though their names are taken, the comments of an edited host stay among its other options, but not one ending its host name, user, port or identity file line. Further Host blocks of the same name only change with it: renaming the host renames them, deleting it deletes them. Renaming or deleting a host other hosts may reach through ProxyJump asks first, naming them, as ssh would then take its name for a plain host name there, without its block, every word of their ProxyJump values counting. ssh checks the file before it is saved, for each host its Host lines name and for a name they do not, like those of quick connect, since one bad line would stop them all: ssh reads every block, and an option a host's own IgnoreUnknown lets pass stops the others. Another host ssh refused already does not stop the change. A file changed during that check is not overwritten, nor a host changed or deleted elsewhere since its editor opened it. A config or known_hosts that is not UTF-8 is never rewritten: saving, deleting or moving a host, renaming a key, removing a changed host key or an Append import then stops with a message. One that is a link is rewritten in the file it names, and one linking to what the app cannot reach, a storage card removed for one, is neither read nor written, but a changed host key is only offered for removal from a known_hosts in ~/.ssh. Neither is read when over 1 MiB, which could take all the memory of the app, nor made so large by the app, an import or a save for one, nor is a vault over 16 MiB. A host with more than 16384 characters in one of the editor's fields, its other options for one, is edited in the local shell, the fields being that large at most. A checkbox attaches to the last tmux session or starts one, with RemoteCommand tmux a || tmux and RequestTTY yes. Another, under the identity file, makes ssh use only that key, and those other blocks such as Host * name, with IdentitiesOnly yes, without trying the other keys of the agent when the server refuses it. Common options, such as ServerAliveInterval, Compression, StrictHostKeyChecking or LogLevel, have a list of values each. Left at Default, an option writes no line, and the value shown next to Default is what ssh -G gives the saved host without it, from its other options, Host * blocks or ssh itself. A long press on a host opens its menu, dragging it then to another row moves its block in the file, but only past the blocks of other saved hosts: ssh takes the first value it finds, past a Host * or Match block the host would get other options. Nor does it move when its block or one it would pass has an IgnoreUnknown or Include line, as ssh skips an option it does not know only after an IgnoreUnknown line naming it, which an included file may hold
• Quick connect - plain ssh arguments, e.g. -p 2222 me@example.org or -J jump host, split into words and quoted as sh does, a # starting a word commenting out the rest of the line
• Local shell - from the menu, Android's own sh and toybox as the app user, in its home directory, with ssh, scp, sftp, ssh-add, ssh-agent and ssh-keygen first in PATH. It is given no agent, so only keys in clear are found there. With All files access it also reads and writes your files in shared storage, under /sdcard
• Encrypted keys - private keys live in a vault sealed by the Android Keystore and opened with a fingerprint, see Key storage
• Agent - each connection gets an ssh-agent of its own holding the unlocked keys while it logs in, so ssh, scp, sftp and ProxyJump hosts use them without writing them to disk, and one login emptying its agent cannot leave another without keys. ssh and the file browser remove the keys once logged in, scp, sftp and either of the first two reusing a ControlMaster connection after 60 seconds. Agent forwarding is off, as the server could use the keys while they are loaded. -A turns it on, but ssh only forwards the agent once logged in, when the keys have left it, so no vault key reaches the server. The agent also serves nothing to a connection ssh forwards with agent forwarding, so a jump host whose block sets ForwardAgent yes, read by its own ssh without the app's options, gets no key either. A host whose IdentityAgent is set, by a Host * block for one, uses that agent instead and gets no vault key
• Key management - generate ed25519, ecdsa, rsa or mldsa44-ed25519 keys, import, rename or delete private keys, create a missing public key or one ssh cannot load, show, copy or share public keys. Each key is listed with whether it is encrypted in the vault or in clear and, from its public key, its type, comment and SHA-256 fingerprint, as ssh prints it. OpenSSH 10.6 renamed the experimental ssh-mldsa44-ed25519@openssh.com keys, mldsa44-ed25519 keys made with older versions of rassh no longer load and must be generated again
• File browser - Browse files in the menu of a saved host: browse, download, upload, rename, delete files and empty folders and create folders over SFTP, through ssh, so the host's options, jump hosts and keys apply, but not its port forwards nor its LocalCommand, as with sftp, and it goes through a ControlMaster connection already running but never starts one for the host, whose sessions would end with it, though a jump host's ssh, which takes none of its options, follows its own ControlMaster setting. Tapping the path, or Go to folder in the menu, opens any folder, typed from the one shown, from /, or from ~, the folder the server started in. Files whose name starts with a dot are hidden, as by ls in sftp, until Show hidden files is ticked in the menu. Sort by, there too, lists by name, by size, largest first, or by date, newest first, folders always on top, links to them among the files. A tap opens a folder, or a link to one, and offers the actions of a file, a long press starts a selection, which taps add to or take from, to download several files into a folder picked once, skipping what is not a regular file, a folder for one, and listing at the end the files the server refused, delete several entries at once, counted in a dialog that can stop it, or rename one, which is how a folder, a link to one or a dangling link is renamed or deleted. A rename to a name in use is refused, unless only its case changes. Unlike a single file, such a download is not offered to resume once cut, as it says before starting. A transfer shows how much of the file is copied, out of its size when the server or the phone tells it. An upload first shows the names the files get on the server, as the app they come from gives them, those that exist there already and would be replaced too, one per line, with _ for a slash and for control, line break and bidi characters, which could hide or disguise another name, and a name over 255 bytes, empty, . or .. becomes upload, blanks around it trimmed. Files that would get the same name are refused, to upload one at a time. A file not shown as replaced, made on the server since or one of the upload on a server that ignores case, stops the upload instead. A transfer cut short by a lost connection, or by the browser going away, swiped from the recent apps for one, is offered to resume the next time the browser connects to that host, the last one cut short there only. A download goes on if the file did not change on the server and the one on the phone is a regular file it can append to that did not change, its size and time checked. Changed on the phone, it is left alone and the download stops, as it may be another file now. An upload goes on if the file on the phone is a regular file that did not change, its size, time and the SHA-256 of what was sent checked, and the server holds no more than was sent, nor less than all but its last 2 MiB. It writes again the last 2 MiB the server holds, as some of the 64 requests of 32 KiB in flight may not have landed. Otherwise the file starts again. A file of its name on the server that the upload could not have left, and the files after it that exist there by then, are replaced only once asked. A transfer stopped, also by closing its session from the terminal screen, or refused by the server is not offered: a download removes its partial file, an upload the file it created if the connection still works, but not one a resumed upload found there. Deleting or editing the host drops what was cut short, as does a Replace import, saving it unchanged does not. A transfer still running then and cut afterwards is offered again if the host kept its name, or dropped when the app starts again. A dropped download removes its partial file only if its size and time, when known, did not change since it was cut
• sftp and scp - from the menu of a saved host, working from shared storage with All files access, from the app's private directory without it
• Export and import - hosts, known host keys, keys and font size in one file sealed with a passphrase, see Moving to another phone
• Changed host keys - when ssh, sftp or the file browser is refused by a server whose key changed, a warning offers to remove the old key, then connecting again shows the fingerprint of the new one to confirm, unless StrictHostKeyChecking is accept-new, which takes it without asking, or yes, which refuses it: the warning says so, as does the message once it is removed when no pattern line is left. The host is resolved from the local configuration with ssh -G, so only the lines matching it are removed. From a line also naming other hosts only its name goes, with the addresses there when ssh checks the one it reaches, with CheckHostIP yes, no proxy and a HostName that is neither localhost nor a loopback address, which ssh never checks, nor another address unless a HostKeyAlias names the host off port 22, as it would refuse a new key differing from that one, or ask each time, and a pattern line is left, as other hosts may match it, unlike with ssh-keygen -R, which removes whole lines: the warning, or a message when nothing else can go, then says to edit known_hosts by hand, as ssh would still refuse the old key there. When ssh checks it the warning also says the address may keep the old key on another line, of its own, hashed for instance, or with another name of the same server, which nothing finds. Another name resolving to a loopback address is taken as checked. Nothing is offered for a jump host's key, nor for one in a file not directly in ~/.ssh. With a LogLevel below INFO nothing is offered, as the server could then print ssh's lines itself
• Sessions - several at once, kept alive by a foreground service and reached from its notification or from Sessions in the main menu. Opening a second one to the same saved host, with ssh, sftp or scp, or with the same quick connect text, asks first, offering to go back to the latest one, and a saved host with an ssh, sftp or scp session running says so in the list. Sessions reaching the same server, local shells included, show when they were opened, as do file browsers of the same host
• Terminal - 256 and 24 bit colors, alternate screen, scroll regions, wide characters, DEC line drawing, bracketed paste, reverse video, scrollback with a swipe or a fling, the swipe sending the arrow keys to full screen programs like vim or less, pinch to zoom, long press to select and copy. A paste, also one from the keyboard's clipboard, turns control characters other than tab and newline into spaces, more than xterm does by default, so that it cannot send ^C or end a bracketed paste. The keyboard is asked not to learn what is typed, passwords at ssh or sudo prompts included, nor what is typed in the app's own fields. A session ending inside a full screen program, a connection lost in tmux for one, goes back to the main screen and its history, followed by what the program's screen showed last, where ssh says why it ended
• Theme - light or dark like the phone, with its accent color, the terminal included. On the light background, the palette colors too pale to read on it, yellow or white for one, are darkened for text drawn on the screen's own background. Dark is true black, which turns OLED pixels off
• Font - DejaVu Sans Mono bundled, since some vendor themes swap the system monospace font for a proportional one
• Hardware keyboards - Esc, Tab and Shift-Tab, arrows, Home, End, Page Up and Down, Insert, Delete, F1 to F12, Ctrl and Alt, right Alt as AltGr and dead keys. With a layout such as Russian or Greek, Ctrl and Alt apply to the Latin letter of a key giving a non-Latin letter, not of one giving punctuation, as Q does in Greek

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Install

Download rassh-v<version>.apk from the latest release and install it. It needs Android 13 or newer on an arm64-v8a device.

Permission	Why
Internet	Connecting to servers
Local network	Reaching hosts on the LAN, asked on Android 17 and later
Notifications	Showing the notification of the open sessions, which stay open without it
Foreground service	Keeping sessions open in the background
Biometric	Unlocking the encrypted keys
Hide overlays	Hiding the windows of apps allowed to display over other apps while rassh shows, where a faint prompt could lead taps onto Delete or a host key removal. Screen dimmers, chat heads or a recorder's controls drawn that way go as well, on the whole display, until rassh leaves the screen
All files access	Reading and writing your files with sftp, scp and the local shell, asked each time sftp or scp starts without it, which can go on in the app's private directory instead

On Android 17 hosts on the LAN (RFC 1918, CGNAT and link-local addresses) cannot be reached without the local network permission. Hosts reached through a VPN or the mobile network, and port forwards on 127.0.0.1, do not need it.

Local and dynamic forwards listen on 127.0.0.1 and ::1 unless a bind address or GatewayPorts says otherwise, and Android shares those between all apps: while the connection is up, any app on the phone can use them, and a dynamic forward lets it reach whatever the server can.

rassh collects no data, see the privacy policy, also linked from the About dialog.

Key storage

Private keys are sealed in ~/.ssh/keys.vault, each with AES-256-GCM under a random vault key. The vault key is itself sealed by an AES key of the Android Keystore, kept in StrongBox when the phone has one that takes it, otherwise in the TEE, that only works after a strong biometric check and while the phone is unlocked. There is no PIN fallback.

• Until a fingerprint is enrolled, keys stay in clear in ~/.ssh. Once one is, at first start or later, the app asks whether enrolling a new fingerprint should destroy the keys. Destroying them stops someone who learns the PIN from adding a finger to use them, at the cost of every stored key. Android then destroys them too when every fingerprint is removed.
• Removing or resetting the screen lock always destroys them. Resetting the key storage then also removes their public keys and certificates.
• Private keys found in clear in ~/.ssh, existing, generated or imported, are moved into the vault after a fingerprint, once a public key ssh can load sits next to them, which Create public key makes again in place of one it cannot, if the vault has room and neither key is over 64 KiB, a larger public key being taken as missing. One named as a key of the vault never replaces it, it stays in clear unless it is the same key. Names hold up to 240 letters, digits, ., _ and - only, as they go into IdentityFile lines and the files of a key must fit the length of a file name, and neither end in .tmp nor take the name of another file there, config or known_hosts for instance: a key named otherwise, made in the local shell for instance, is listed with a note, stays out of the vault and stops exports until renamed. Nor can a key be given a name starting with a dot, or ending in .pub or -cert, those of the files that go with a key: one found named so, but for -cert, is not listed. A key that is a link stays in clear, the file it names would be left behind.
• Connecting, the file browser, sftp and scp ask for the fingerprint whenever the vault holds keys, then ssh-add loads the keys through pipes into an agent started for that connection alone, so the decrypted keys never touch the disk. ssh removes them from it as soon as it is logged in, through LocalCommand, which then takes the place of one set for the host, with PermitLocalCommand turned on: with EnableEscapeCommandline set, ! then runs a local command from the ~C command line as well. Otherwise, with scp, sftp, an ssh or the file browser reusing a ControlMaster connection, which does not log in itself, or a failed login, they leave it 60 seconds after the fingerprint, or when the screen turns off, and the agent ends with the connection. A login that takes longer, such as one waiting on a new host key to be confirmed, goes on without them. The Cancel button of the prompt, or an error such as too many attempts, connects without them, for password logins, while closing it with Back, leaving the app or turning the screen off connects nothing.

Public keys stay in clear next to the vault. For an IdentityFile whose private key is gone, ssh takes the public key next to it and finds the private one in the agent, so IdentityFile lines name vault keys as usual, and a certificate next to the key, <key>-cert.pub, is used too. Renaming or deleting a key in the app takes both along, and renaming also updates the IdentityFile and CertificateFile lines of ~/.ssh/config naming them. Lines naming the .pub of a vault key, as older versions wrote them, are pointed back at the key.

Root can read every file, but a copy of the vault reveals nothing: the Keystore key never leaves the TEE or StrongBox, and every use of it needs a fingerprint checked there. Keys still in clear are read directly. Root can also run code inside the app or the agent, so it can take the decrypted keys at the next fingerprint, or sign with them until they leave the agent. Keys on a phone where untrusted code ran as root should be treated as exposed and replaced.

A program running as the app can do the same without root. Anyone who had the phone unlocked in hand can start one from the local shell, and it keeps running as long as the app does. It can then read the keys ssh-add loads at the next fingerprint, or use them through the agent of the connection while they are in it. Before the fingerprint, connecting lists the programs of the app running outside the foreground of its sessions, such as those put in the background in the local shell, ssh -f or a ControlPersist connection, and offers to end them. One can still hide among the processes of an open session: when the phone was left unlocked out of your hands, close every session, or force-stop the app, before connecting.

Moving to another phone

Export, in the menu, writes ~/.ssh/config with its hosts, known_hosts, the keys of ~/.ssh with their public keys and certificates, and the font size to a file sealed with a passphrase of at least 12 characters, with AES-256-GCM under a key derived by PBKDF2-HMAC-SHA256 with 600,000 iterations, a dialog showing meanwhile, as while an import reads the file. Taking the keys out of the vault for it takes a fingerprint, but in the file they are only behind the passphrase: anyone getting the file can try passphrases offline, choose a long one. Android backup stays off, since the vault cannot leave the phone that made it. Files read through Include and keys kept outside ~/.ssh are not exported. A key named as early versions or the local shell allowed, with an @ for instance, must be renamed first, and an export stops at a key holding no private key in PEM form, naming it, as no import would take it. A certificate or public key without its private key is left out.

Import on the other phone first asks whether to append or replace, then reads the file, refusing it when one of its keys holds no private key in PEM form, and writes of a key only its PEM blocks, what ssh reads of it: any other line could make it a file ssh reads otherwise, a known_hosts the config names for one, as the key screen does with a key file. Of a public key or certificate only the first line shaped as ssh-keygen writes them is kept, past comments and blank lines, before any private key, and the file is left out when it has none, the key then has none yet:

• Append adds the Host blocks and keys whose names are not used yet, the known_hosts lines of hosts not known here yet, in known_hosts or known_hosts2, the files ssh reads by default, also through a hashed line, a pattern or a line of the other kind, key or @cert-authority, but not a @revoked line, as ssh would trust again an old key of one, removed here once changed, or a certificate a new authority signed, hashed and @revoked lines and comments as they are, but no key or @cert-authority line with a wildcard in a name not negated, which could match a host known here, and the font size if not set yet. Only Host blocks naming a single host are taken: global options, Match blocks and Host blocks with wildcards or several names are left out, as they could change the hosts already there, and so is a block holding an Include, whose file ssh reads for every host, one whose name holds a ~ or ^ or is . or .., one whose HostName, User, HostKeyAlias or ProxyJump holds a quote or another shell character, but a \ within a User, a blank, #, *, ?, !, ^, ~, a bracket in a HostName or User, a , in a HostName or HostKeyAlias, or a / but that of an ssh:// jump host, is . or .., starts with -, or has a jump user or host that is . or .., or a jump user, host or port starting with -, as the Match exec and Include lines here may take these values when ssh checks the result, and a block named as the HostName or a ProxyJump host of a host or a Host pattern there, as ssh reads the block of a jump host for it, and that of its HostName after a Match final or canonicalization, though not a name canonicalization makes by adding a domain. Every word of a ProxyJump value counts, a user or a port too, as a shell splits it for ssh, and no Host block comes in when such a value holds $, a backquote, ~, *, ?, { or }, which the shell would expand, or a word starting with -, which ssh would take as an option. A jump host named with % tokens or escapes, or reached through ProxyCommand, is not seen. ssh checks the result first, as when saving one, and nothing is imported if it refuses it: a host relying on a global IgnoreUnknown line left out would make it refuse them all. A host added whose key has the name of one already there uses that one, not the key of the file.
• Replace puts the whole ~/.ssh/config, known_hosts, the keys and the font size of the file in place of yours. They are written first, then what the file does not hold is removed, but for keys named in a way the app does not take, see Key storage, which stay.

Storing keys in the vault takes a fingerprint, cancelling it imports nothing, as does leaving the app while the file is read, since Android then closes the prompt, and an import that would put more than 64 keys in it stops before writing anything. Keys exported without their public key, or over 64 KiB, are written in clear, as they were, the former moving into the vault once their public key is made. On a phone without a fingerprint enrolled, all keys come in clear and move into the vault once one is. Only import files you made: the hosts of an export can run commands through ProxyCommand, LocalCommand or KnownHostsCommand, the config of a Replace import through Match exec too, which ssh runs as soon as a host is opened in the editor or saved, and its known_hosts decides which servers are trusted.

How it works

native/   build script for LibreSSL and OpenSSH, JNI pty helper
core/     terminal emulator, ssh_config editor, SFTP client and export format, plain Kotlin/JVM
app/      Android application
fastlane/ store descriptions, screenshots and changelogs, read by F-Droid

Programs	Android only lets an app execute files from its native library directory, so each program ships as lib<name>.so, e.g. libssh.so, extracted at install time
Home	$HOME is the app files directory, so ~/.ssh is private and excluded from backups and device transfers
PATH	~/bin holds links named after the programs and comes first in PATH: ssh finds itself there for ProxyJump, as do scp, sftp and ProxyCommand ssh -W lines
getpwuid	Bionic reports /data as the home of app users. The programs are linked with -Wl,--wrap=getpwuid and native/homedir.c answers $HOME
SSHFP	The resolver behind res_query() reaches no DNS server from an app, so VerifyHostKeyDNS found nothing. The programs are linked with -Wl,--wrap=res_query and native/dns.c sends the query to the system resolver with android_res_nquery(). It clears the authenticated data bit of the answer, which anyone answering on the network could set, as OpenBSD and glibc do by default: a fingerprint found shows as matching and ssh still asks
Files	The browser runs ssh -s host sftp with pipes as its standard input and output and speaks SFTP version 3 to it. ssh keeps the terminal for its messages and questions, shown while connecting
Patch	native/openssh-android.patch uses the OpenBSD libc explicit_bzero(), since bionic has neither it nor the bzero() function the portable fallback relies on, lets the SSHFP resolver code build without the state bionic keeps private, skips the setgid calls the Android seccomp filter kills, keeps no known_hosts.old when ssh rewrites the file for UpdateHostKeys, checking instead that the new file was fully written before it takes the place of the old one, and moves the ControlMaster socket into place with renameat2(), since Android refuses link() to apps. It also gives ssh-agent a -O no-forwarded option, which the app uses, serving nothing to a connection ssh binds as one it forwards for a server

Building

You need JDK 17 or later, the Android SDK with platform 37, and NDK r30. native/build.sh runs on x86_64 Linux and on macOS, where the NDK toolchain is.

export ANDROID_NDK_HOME=$ANDROID_HOME/ndk/30.0.16248370
native/build.sh
./gradlew :core:test :app:assembleDebug

native/build.sh downloads the LibreSSL and OpenSSH release tarballs from cdn.openbsd.org, checks their SHA-256 and builds them for arm64-v8a, or for the ABIs given as arguments: x86_64 for an emulator, which no release includes. The programs go to app/src/main/jniLibs, and their license files, shown in the About dialog, to app/src/main/assets/licenses.

The core tests include a fuzz test feeding the terminal random text, controls and escape sequences, 200 runs by default. A failure names the seed that replays it. The SFTP client tests run against /usr/lib/openssh/sftp-server, the Debian package openssh-sftp-server, and are skipped without it. For a longer search:

RASSH_FUZZ_RUNS=5000 ./gradlew :core:test --tests '*TerminalFuzzTest' --rerun

The workflow in .github/workflows/build.yml does the same, with lint and the release build, on every push and pull request, and keeps the APKs and the release app bundle as artifacts. A local release build is signed when RASSH_KEYSTORE_FILE names the keystore and the password and alias variables below are set. The workflow builds without the key. For pushes to main of this repository only, a job of its own, on another machine than the build and what it ran, signs the APK with apksigner and the bundle for Google Play with jarsigner, keeping them as the rassh-release and rassh-bundle artifacts. Those of forks, other branches and pull requests stay unsigned.

Releases

Bumping versionName in app/build.gradle.kts and pushing to main publishes a release tagged v<versionName> with the signed APK. Pushes whose version already has a release publish nothing. F-Droid takes the notes of a version from fastlane/metadata/android/en-US/changelogs/<versionCode>.txt, 500 characters at most.

Release APKs are signed with the key held in the repository secrets RASSH_KEYSTORE (base64 PKCS12 keystore), RASSH_KEYSTORE_PASSWORD, RASSH_KEY_ALIAS and RASSH_KEY_PASSWORD. Android only installs an update signed with the same key, so keep a copy of the keystore. The signing job stops when the APK or the bundle carries another certificate than the one the workflow names.

Compared with other clients

As of October 2026, from each project's own pages and sources.

	rassh	Termux + openssh	ConnectBot	Termius	Haven
SSH code	OpenSSH 10.6p1	OpenSSH 10.6p1	sshlib	proprietary	JSch, sshlib in preview
License	ISC	GPLv3	Apache-2.0	proprietary	AGPL-3.0
Hosts in ~/.ssh/config	yes	yes	no	no	no
Jump hosts	yes	yes	yes	yes	yes
Private keys	vault sealed by the Keystore, fingerprint on every use	files	encrypted, or kept in the Keystore	app vault, or kept in the Keystore	sealed by the Keystore
Signing inside the Keystore	none	none	RSA, ECDSA P-256, P-384, P-521	ECDSA P-256 (reported by users, not documented)	none
FIDO security keys	no	no	no	yes	yes
mosh	no	yes	yes	yes	yes
SFTP	file browser, command line	command line	no	file browser	file browser

rassh is the only one running OpenSSH behind an SSH interface, so ~/.ssh/config works as on a desktop, ProxyCommand and Match included, and new algorithms such as mldsa44-ed25519 keys come with OpenSSH. Termux has the same programs, as a general shell with keys in plain files. ConnectBot and Termius can keep keys in the Keystore that never leave it, but only RSA or ECDSA ones, no Ed25519 and no post-quantum keys. rassh keeps Ed25519 and mldsa44-ed25519 keys in a vault that is useless without the Keystore key and a fingerprint, so a copy of its files reveals nothing. They are decrypted only in memory, into the agent of the connection, until the login or for 60 seconds at most. JuiceSSH is no longer on Google Play.

Limitations

• No FIDO security keys and no PKCS#11
• No mosh
• No mouse reporting
• Combining characters are not rendered
• Screen readers such as TalkBack do not read the terminal output
• Saving a host writes its host name, user, port, identity file and forwards before its other options, and the common options, the tmux and the key-only lines after them, which changes the values that win when its block has an Include. Names used in included files are not checked when a host is added
• Keys, public keys and certificates are files in ~/.ssh: an Include whose pattern matches the name of one, made or imported, makes ssh read it as config and refuse the hosts it applies to
• The vault holds at most 64 keys, all loaded for each connection, and keys over 64 KiB stay out of it
• All files access (MANAGE_EXTERNAL_STORAGE) is restricted on Google Play to some app categories
• On Android 13 and 14, an app with a screen below rassh's in the same task, one rassh was opened from or a public key was shared to, can later start another one over rassh's, a fake prompt for one. From Android 15 the app asks Android to refuse that
• Android kills the programs apps start once more than 32 run on the phone (Android's default, phone makers may change it), those of apps in the background first, then the oldest: with many sessions open, the oldest end with status 137. Android 14 and later lift the limit with Disable child process restrictions in the developer options, Android 13 with adb shell settings put global settings_enable_monitor_phantom_procs false

License

ISC, see LICENSE. OpenSSH, LibreSSL, the Kotlin standard library and the DejaVu fonts keep their own licenses, which the About dialog shows.