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+# Sign up to a homeserver
+
+This document describes the flow of registration to a homeserver. Examples come from the matrix.org homeserver, and the logs come from Riot-Android.
+
+Note that it contains bugs:
+ - "password" and "initial_device_display_name" values are sent a bit too much
+ - the first received "sessionId" is not reused
+ - The order of stages returned by the homeserver is not strictly followed
+
+Ref: https://matrix.org/docs/spec/client_server/latest#account-registration-and-management
+
+## Sign up flows
+
+### First step
+
+Client request the sign-up flows, once the homeserver is chosen by the user and its url is knwon (in the example it's https://matrix.org)
+
+> curl -X POST --data $'{"initial_device_display_name":"Mobile device","x_show_msisdn":true}' 'https://matrix.org/_matrix/client/r0/register'
+
+```json
+{
+  "initial_device_display_name": "Mobile device",
+  "x_show_msisdn": true
+}
+```
+
+401
+
+```json
+{
+  "session": "vwehdKMtkRedactedAMwgCACZ",
+  "flows": [
+    {
+      "stages": [
+        "m.login.recaptcha",
+        "m.login.terms",
+        "m.login.dummy"
+      ]
+    },
+    {
+      "stages": [
+        "m.login.recaptcha",
+        "m.login.terms",
+        "m.login.email.identity"
+      ]
+    }
+  ],
+  "params": {
+    "m.login.recaptcha": {
+      "public_key": "6LcgI54UAAAAAoREDACTEDoDdOocFpYVdjYBRe4zb"
+    },
+    "m.login.terms": {
+      "policies": {
+        "privacy_policy": {
+          "version": "1.0",
+          "en": {
+            "name": "Terms and Conditions",
+            "url": "https:\/\/matrix.org\/_matrix\/consent?v=1.0"
+          }
+        }
+      }
+    }
+  }
+}
+```
+
+### Step 1: entering user name and password
+
+The app is displaying a form with login and password. Only the login is sent for the first request
+
+> curl -X POST --data $'{"initial_device_display_name":"Mobile device","username":"alice"}' 'https://matrix.org/_matrix/client/r0/register'
+
+```json
+{
+  "initial_device_display_name": "Mobile device",
+  "username": "alice"
+}
+```
+
+401
+
+```json
+{
+  "session": "xptUYoREDACTEDogOWAGVnbJQ",
+  "flows": [
+    {
+      "stages": [
+        "m.login.recaptcha",
+        "m.login.terms",
+        "m.login.dummy"
+      ]
+    },
+    {
+      "stages": [
+        "m.login.recaptcha",
+        "m.login.terms",
+        "m.login.email.identity"
+      ]
+    }
+  ],
+  "params": {
+    "m.login.recaptcha": {
+      "public_key": "6LcgI54UAAAAAoREDACTEDoDdOocFpYVdjYBRe4zb"
+    },
+    "m.login.terms": {
+      "policies": {
+        "privacy_policy": {
+          "version": "1.0",
+          "en": {
+            "name": "Terms and Conditions",
+            "url": "https:\/\/matrix.org\/_matrix\/consent?v=1.0"
+          }
+        }
+      }
+    }
+  }
+}
+```
+
+#### If username already exists
+
+```json
+{
+  "errcode": "M_USER_IN_USE",
+  "error": "User ID already taken."
+}
+```
+
+### Step 2: entering email
+
+User is proposed to enter an email. We skip this step.
+
+> curl -X POST --data $'{"auth":{"session":"xptUYoREDACTEDogOWAGVnbJQ","type":"m.login.dummy"},"initial_device_display_name":"Mobile device","password":"azerty","username":"alice"}' 'https://matrix.org/_matrix/client/r0/register'
+
+```json
+{
+  "auth": {
+    "session": "xptUYoREDACTEDogOWAGVnbJQ",
+    "type": "m.login.dummy"
+  },
+  "initial_device_display_name": "Mobile device",
+  "password": "password_REDACTED",
+  "username":"alice"
+}
+```
+
+401
+
+```json
+{
+  "session": "xptUYoREDACTEDogOWAGVnbJQ",
+  "flows": [
+    {
+      "stages": [
+        "m.login.recaptcha",
+        "m.login.terms",
+        "m.login.dummy"
+      ]
+    },
+    {
+      "stages": [
+        "m.login.recaptcha",
+        "m.login.terms",
+        "m.login.email.identity"
+      ]
+    }
+  ],
+  "params": {
+    "m.login.recaptcha": {
+      "public_key": "6LcgI54UAAAAAoREDACTEDoDdOocFpYVdjYBRe4zb"
+    },
+    "m.login.terms": {
+      "policies": {
+        "privacy_policy": {
+          "version": "1.0",
+          "en": {
+            "name": "Terms and Conditions",
+            "url": "https:\/\/matrix.org\/_matrix\/consent?v=1.0"
+          }
+        }
+      }
+    }
+  },
+  "completed": [
+    "m.login.dummy"
+  ]
+}
+```
+
+### Step 2 bis: we enter an email
+
+> curl -X POST --data $'{"client_secret":"53e679ea-oRED-ACTED-92b8-3012c49c6cfa","email":"alice@yopmail.com","send_attempt":0}' 'https://matrix.org/_matrix/client/r0/register/email/requestToken'
+
+```json
+{
+  "client_secret": "53e679ea-oRED-ACTED-92b8-3012c49c6cfa",
+  "email": "alice@yopmail.com",
+  "send_attempt": 0
+}
+```
+
+200
+
+```json
+{
+  "sid": "qlBCREDACTEDEtgxD"
+}
+```
+
+And
+
+> curl -X POST --data $'{"auth":{"threepid_creds":{"client_secret":"53e679ea-oRED-ACTED-92b8-3012c49c6cfa","sid":"qlBCREDACTEDEtgxD"},"session":"xptUYoREDACTEDogOWAGVnbJQ","type":"m.login.email.identity"},"initial_device_display_name":"Mobile device","password":"password_REDACTED","username":"alice"}' 'https://matrix.org/_matrix/client/r0/register'
+
+```json
+{
+  "auth": {
+    "threepid_creds": {
+      "client_secret": "53e679ea-oRED-ACTED-92b8-3012c49c6cfa",
+      "sid": "qlBCREDACTEDEtgxD"
+    },
+    "session": "xptUYoREDACTEDogOWAGVnbJQ",
+    "type": "m.login.email.identity"
+  },
+  "initial_device_display_name": "Mobile device",
+  "password": "password_REDACTED",
+  "username": "alice"
+}
+```
+
+401
+
+```json
+{
+  "errcode": "M_UNAUTHORIZED",
+  "error": ""
+}
+```
+
+The app is now polling on 
+
+> curl -X POST --data $'{"auth":{"threepid_creds":{"client_secret":"53e679ea-oRED-ACTED-92b8-3012c49c6cfa","sid":"qlBCREDACTEDEtgxD"},"session":"xptUYoREDACTEDogOWAGVnbJQ","type":"m.login.email.identity"},"initial_device_display_name":"Mobile device","password":"password_REDACTED","username":"alice"}' 'https://matrix.org/_matrix/client/r0/register'
+
+```json
+{
+  "auth": {
+    "threepid_creds": {
+      "client_secret": "53e679ea-oRED-ACTED-92b8-3012c49c6cfa",
+      "sid": "qlBCREDACTEDEtgxD"
+    },
+    "session": "xptUYoREDACTEDogOWAGVnbJQ",
+    "type": "m.login.email.identity"
+  },
+  "initial_device_display_name": "Mobile device",
+  "password": "password_REDACTED",
+  "username": "alice"
+}
+```
+
+We click on the link received by email https://matrix.org/_matrix/client/unstable/registration/email/submit_token?token=vtQjQIZfwdoREDACTEDozrmKYSWlCXsJ&client_secret=53e679ea-oRED-ACTED-92b8-3012c49c6cfa&sid=qlBCREDACTEDEtgxD which contains:
+- A token vtQjQIZfwdoREDACTEDozrmKYSWlCXsJ
+- a client secret: 53e679ea-oRED-ACTED-92b8-3012c49c6cfa
+- A sid: qlBCREDACTEDEtgxD
+
+Once the link is clicked, the registration request (polling) returns a 401 with the following content:
+
+```json
+{
+  "session": "xptUYoREDACTEDogOWAGVnbJQ",
+  "flows": [
+    {
+      "stages": [
+        "m.login.recaptcha",
+        "m.login.terms",
+        "m.login.dummy"
+      ]
+    },
+    {
+      "stages": [
+        "m.login.recaptcha",
+        "m.login.terms",
+        "m.login.email.identity"
+      ]
+    }
+  ],
+  "params": {
+    "m.login.recaptcha": {
+      "public_key": "6LcgI54UAAAAAoREDACTEDoDdOocFpYVdjYBRe4zb"
+    },
+    "m.login.terms": {
+      "policies": {
+        "privacy_policy": {
+          "version": "1.0",
+          "en": {
+            "name": "Terms and Conditions",
+            "url": "https:\/\/matrix.org\/_matrix\/consent?v=1.0"
+          }
+        }
+      }
+    }
+  },
+  "completed": [
+    "m.login.email.identity"
+  ]
+}
+```
+
+### Step 3: Accepting T&C
+
+User is proposed to accept T&C and he accepts them
+
+> curl -X POST --data $'{"auth":{"session":"xptUYoREDACTEDogOWAGVnbJQ","type":"m.login.terms"},"initial_device_display_name":"Mobile device"}' 'https://matrix.org/_matrix/client/r0/register'
+
+```json
+{
+  "auth": {
+    "session": "xptUYoREDACTEDogOWAGVnbJQ",
+    "type": "m.login.terms"
+  },
+  "initial_device_display_name": "Mobile device"
+}
+```
+
+401
+
+```json
+{
+  "session": "xptUYoREDACTEDogOWAGVnbJQ",
+  "flows": [
+    {
+      "stages": [
+        "m.login.recaptcha",
+        "m.login.terms",
+        "m.login.dummy"
+      ]
+    },
+    {
+      "stages": [
+        "m.login.recaptcha",
+        "m.login.terms",
+        "m.login.email.identity"
+      ]
+    }
+  ],
+  "params": {
+    "m.login.recaptcha": {
+      "public_key": "6LcgI54UAAAAAoREDACTEDoDdOocFpYVdjYBRe4zb"
+    },
+    "m.login.terms": {
+      "policies": {
+        "privacy_policy": {
+          "version": "1.0",
+          "en": {
+            "name": "Terms and Conditions",
+            "url": "https:\/\/matrix.org\/_matrix\/consent?v=1.0"
+          }
+        }
+      }
+    }
+  },
+  "completed": [
+    "m.login.dummy",
+    "m.login.terms"
+  ]
+}
+```
+
+### Step 4: Captcha
+
+User is proposed to prove he is not a robot and he does it:
+
+> curl -X POST --data $'{"auth":{"response":"03AOLTBLSiGS9GhFDpAMblJ2nlXOmHXqAYJ5OvHCPUjiVLBef3k9snOYI_BDC32-t4D2jv-tpvkaiEI_uloobFd9RUTPpJ7con2hMddbKjSCYqXqcUQFhzhbcX6kw8uBnh2sbwBe80_ihrHGXEoACXQkL0ki1Q0uEtOeW20YBRjbNABsZPpLNZhGIWC0QVXnQ4FouAtZrl3gOAiyM-oG3cgP6M9pcANIAC_7T2P2amAHbtsTlSR9CsazNyS-rtDR9b5MywdtnWN9Aw8fTJb8cXQk_j7nvugMxzofPjSOrPKcr8h5OqPlpUCyxxnFtag6cuaPSUwh43D2L0E-ZX7djzaY2Yh_U2n6HegFNPOQ22CJmfrKwDlodmAfMPvAXyq77n3HpoREDACTEDo3830RHF4BfkGXUaZjctgg-A1mvC17hmQmQpkG7IhDqyw0onU-0vF_-ehCjq_CcQEDpS_O3uiHJaG5xGf-0rhLm57v_wA3deugbsZuO4uTuxZZycN_mKxZ97jlDVBetl9hc_5REPbhcT1w3uzTCSx7Q","session":"iLHmdwNlXZoREDACTEDoouwMi","type":"m.login.recaptcha"},"initial_device_display_name":"Mobile device"}' 'https://matrix.org/_matrix/client/r0/register'
+
+```json
+{
+  "auth": {
+    "response": "03AOLTBLSiGS9GhFDpAMblJ2nlXOmHXqAYJ5OvHCPUjiVLBef3k9snOYI_BDC32-t4D2jv-tpvkaiEI_uloobFd9RUTPpJ7con2hMddbKjSCYqXqcUQFhzhbcX6kw8uBnh2sbwBe80_ihrHGXEoACXQkL0ki1Q0uEtOeW20YBRjbNABsZPpLNZhGIWC0QVXnQ4FouAtZrl3gOAiyM-oG3cgP6M9pcANIAC_7T2P2amAHbtsTlSR9CsazNyS-rtDR9b5MywdtnWN9Aw8fTJb8cXQk_j7nvugMxzofPjSOrPKcr8h5OqPlpUCyxxnFtag6cuaPSUwh43D2L0E-ZX7djzaY2Yh_U2n6HegFNPOQ22CJmfrKwDlodmAfMPvAXyq77n3HpoREDACTEDo3830RHF4BfkGXUaZjctgg-A1mvC17hmQmQpkG7IhDqyw0onU-0vF_-ehCjq_CcQEDpS_O3uiHJaG5xGf-0rhLm57v_wA3deugbsZuO4uTuxZZycN_mKxZ97jlDVBetl9hc_5REPbhcT1w3uzTCSx7Q",
+    "session": "iLHmdwNlXZoREDACTEDoouwMi",
+    "type": "m.login.recaptcha"
+  },
+  "initial_device_display_name": "Mobile device"
+}
+```
+
+200
+
+```json
+{
+  "user_id": "@alice:matrix.org",
+  "home_server": "matrix.org",
+  "access_token": "MDAxOGxvY2F0aW9uIG1hdHJpeC5vcmcKMoREDACTEDo50aWZpZXIga2V5CjAwMTBjaWQgZ2VuID0gMQowMDI5Y2lkIHVzZXJfaWQgPSBAYmVub2l0eHh4eDptYXRoREDACTEDoCjAwMTZjaWQgdHlwZSA9IGFjY2VzcwowMDIxY2lkIG5vbmNlID0gNHVSVm00aVFDaWlKdoREDACTEDoJmc2lnbmF0dXJlIOmHnTLRfxiPjhrWhS-dThUX-qAzZktfRThzH1YyAsxaCg",
+  "device_id": "FLBAREDAJZ"
+}
+```
+
+The account is created!